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diff --git a/openssl/FAQ b/openssl/FAQ index 0e008cbdd..b34e1091c 100644 --- a/openssl/FAQ +++ b/openssl/FAQ @@ -1,1025 +1,1025 @@ -OpenSSL - Frequently Asked Questions --------------------------------------- - -[MISC] Miscellaneous questions - -* Which is the current version of OpenSSL? -* Where is the documentation? -* How can I contact the OpenSSL developers? -* Where can I get a compiled version of OpenSSL? -* Why aren't tools like 'autoconf' and 'libtool' used? -* What is an 'engine' version? -* How do I check the authenticity of the OpenSSL distribution? - -[LEGAL] Legal questions - -* Do I need patent licenses to use OpenSSL? -* Can I use OpenSSL with GPL software? - -[USER] Questions on using the OpenSSL applications - -* Why do I get a "PRNG not seeded" error message? -* Why do I get an "unable to write 'random state'" error message? -* How do I create certificates or certificate requests? -* Why can't I create certificate requests? -* Why does <SSL program> fail with a certificate verify error? -* Why can I only use weak ciphers when I connect to a server using OpenSSL? -* How can I create DSA certificates? -* Why can't I make an SSL connection using a DSA certificate? -* How can I remove the passphrase on a private key? -* Why can't I use OpenSSL certificates with SSL client authentication? -* Why does my browser give a warning about a mismatched hostname? -* How do I install a CA certificate into a browser? -* Why is OpenSSL x509 DN output not conformant to RFC2253? -* What is a "128 bit certificate"? Can I create one with OpenSSL? -* Why does OpenSSL set the authority key identifier extension incorrectly? -* How can I set up a bundle of commercial root CA certificates? - -[BUILD] Questions about building and testing OpenSSL - -* Why does the linker complain about undefined symbols? -* Why does the OpenSSL test fail with "bc: command not found"? -* Why does the OpenSSL test fail with "bc: 1 no implemented"? -* Why does the OpenSSL test fail with "bc: stack empty"? -* Why does the OpenSSL compilation fail on Alpha Tru64 Unix? -* Why does the OpenSSL compilation fail with "ar: command not found"? -* Why does the OpenSSL compilation fail on Win32 with VC++? -* What is special about OpenSSL on Redhat? -* Why does the OpenSSL compilation fail on MacOS X? -* Why does the OpenSSL test suite fail on MacOS X? -* Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]? -* Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"? -* Why does the OpenSSL test suite fail in sha512t on x86 CPU? -* Why does compiler fail to compile sha512.c? -* Test suite still fails, what to do? -* I think I've found a bug, what should I do? -* I'm SURE I've found a bug, how do I report it? -* I've found a security issue, how do I report it? - -[PROG] Questions about programming with OpenSSL - -* Is OpenSSL thread-safe? -* I've compiled a program under Windows and it crashes: why? -* How do I read or write a DER encoded buffer using the ASN1 functions? -* OpenSSL uses DER but I need BER format: does OpenSSL support BER? -* I've tried using <M_some_evil_pkcs12_macro> and I get errors why? -* I've called <some function> and it fails, why? -* I just get a load of numbers for the error output, what do they mean? -* Why do I get errors about unknown algorithms? -* Why can't the OpenSSH configure script detect OpenSSL? -* Can I use OpenSSL's SSL library with non-blocking I/O? -* Why doesn't my server application receive a client certificate? -* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier? -* I think I've detected a memory leak, is this a bug? -* Why does Valgrind complain about the use of uninitialized data? -* Why doesn't a memory BIO work when a file does? -* Where are the declarations and implementations of d2i_X509() etc? - -=============================================================================== - -[MISC] ======================================================================== - -* Which is the current version of OpenSSL? - -The current version is available from <URL: http://www.openssl.org>. -OpenSSL 1.0.0d was released on Feb 8th, 2011. - -In addition to the current stable release, you can also access daily -snapshots of the OpenSSL development version at <URL: -ftp://ftp.openssl.org/snapshot/>, or get it by anonymous CVS access. - - -* Where is the documentation? - -OpenSSL is a library that provides cryptographic functionality to -applications such as secure web servers. Be sure to read the -documentation of the application you want to use. The INSTALL file -explains how to install this library. - -OpenSSL includes a command line utility that can be used to perform a -variety of cryptographic functions. It is described in the openssl(1) -manpage. Documentation for developers is currently being written. Many -manual pages are available; overviews over libcrypto and -libssl are given in the crypto(3) and ssl(3) manpages. - -The OpenSSL manpages are installed in /usr/local/ssl/man/ (or a -different directory if you specified one as described in INSTALL). -In addition, you can read the most current versions at -<URL: http://www.openssl.org/docs/>. Note that the online documents refer -to the very latest development versions of OpenSSL and may include features -not present in released versions. If in doubt refer to the documentation -that came with the version of OpenSSL you are using. - -For information on parts of libcrypto that are not yet documented, you -might want to read Ariel Glenn's documentation on SSLeay 0.9, OpenSSL's -predecessor, at <URL: http://www.columbia.edu/~ariel/ssleay/>. Much -of this still applies to OpenSSL. - -There is some documentation about certificate extensions and PKCS#12 -in doc/openssl.txt - -The original SSLeay documentation is included in OpenSSL as -doc/ssleay.txt. It may be useful when none of the other resources -help, but please note that it reflects the obsolete version SSLeay -0.6.6. - - -* How can I contact the OpenSSL developers? - -The README file describes how to submit bug reports and patches to -OpenSSL. Information on the OpenSSL mailing lists is available from -<URL: http://www.openssl.org>. - - -* Where can I get a compiled version of OpenSSL? - -You can finder pointers to binary distributions in -<URL: http://www.openssl.org/related/binaries.html> . - -Some applications that use OpenSSL are distributed in binary form. -When using such an application, you don't need to install OpenSSL -yourself; the application will include the required parts (e.g. DLLs). - -If you want to build OpenSSL on a Windows system and you don't have -a C compiler, read the "Mingw32" section of INSTALL.W32 for information -on how to obtain and install the free GNU C compiler. - -A number of Linux and *BSD distributions include OpenSSL. - - -* Why aren't tools like 'autoconf' and 'libtool' used? - -autoconf will probably be used in future OpenSSL versions. If it was -less Unix-centric, it might have been used much earlier. - -* What is an 'engine' version? - -With version 0.9.6 OpenSSL was extended to interface to external crypto -hardware. This was realized in a special release '0.9.6-engine'. With -version 0.9.7 the changes were merged into the main development line, -so that the special release is no longer necessary. - -* How do I check the authenticity of the OpenSSL distribution? - -We provide MD5 digests and ASC signatures of each tarball. -Use MD5 to check that a tarball from a mirror site is identical: - - md5sum TARBALL | awk '{print $1;}' | cmp - TARBALL.md5 - -You can check authenticity using pgp or gpg. You need the OpenSSL team -member public key used to sign it (download it from a key server, see a -list of keys at <URL: http://www.openssl.org/about/>). Then -just do: - - pgp TARBALL.asc - -[LEGAL] ======================================================================= - -* Do I need patent licenses to use OpenSSL? - -The patents section of the README file lists patents that may apply to -you if you want to use OpenSSL. For information on intellectual -property rights, please consult a lawyer. The OpenSSL team does not -offer legal advice. - -You can configure OpenSSL so as not to use IDEA, MDC2 and RC5 by using - ./config no-idea no-mdc2 no-rc5 - - -* Can I use OpenSSL with GPL software? - -On many systems including the major Linux and BSD distributions, yes (the -GPL does not place restrictions on using libraries that are part of the -normal operating system distribution). - -On other systems, the situation is less clear. Some GPL software copyright -holders claim that you infringe on their rights if you use OpenSSL with -their software on operating systems that don't normally include OpenSSL. - -If you develop open source software that uses OpenSSL, you may find it -useful to choose an other license than the GPL, or state explicitly that -"This program is released under the GPL with the additional exemption that -compiling, linking, and/or using OpenSSL is allowed." If you are using -GPL software developed by others, you may want to ask the copyright holder -for permission to use their software with OpenSSL. - - -[USER] ======================================================================== - -* Why do I get a "PRNG not seeded" error message? - -Cryptographic software needs a source of unpredictable data to work -correctly. Many open source operating systems provide a "randomness -device" (/dev/urandom or /dev/random) that serves this purpose. -All OpenSSL versions try to use /dev/urandom by default; starting with -version 0.9.7, OpenSSL also tries /dev/random if /dev/urandom is not -available. - -On other systems, applications have to call the RAND_add() or -RAND_seed() function with appropriate data before generating keys or -performing public key encryption. (These functions initialize the -pseudo-random number generator, PRNG.) Some broken applications do -not do this. As of version 0.9.5, the OpenSSL functions that need -randomness report an error if the random number generator has not been -seeded with at least 128 bits of randomness. If this error occurs and -is not discussed in the documentation of the application you are -using, please contact the author of that application; it is likely -that it never worked correctly. OpenSSL 0.9.5 and later make the -error visible by refusing to perform potentially insecure encryption. - -If you are using Solaris 8, you can add /dev/urandom and /dev/random -devices by installing patch 112438 (Sparc) or 112439 (x86), which are -available via the Patchfinder at <URL: http://sunsolve.sun.com> -(Solaris 9 includes these devices by default). For /dev/random support -for earlier Solaris versions, see Sun's statement at -<URL: http://sunsolve.sun.com/pub-cgi/retrieve.pl?doc=fsrdb/27606&zone_32=SUNWski> -(the SUNWski package is available in patch 105710). - -On systems without /dev/urandom and /dev/random, it is a good idea to -use the Entropy Gathering Demon (EGD); see the RAND_egd() manpage for -details. Starting with version 0.9.7, OpenSSL will automatically look -for an EGD socket at /var/run/egd-pool, /dev/egd-pool, /etc/egd-pool and -/etc/entropy. - -Most components of the openssl command line utility automatically try -to seed the random number generator from a file. The name of the -default seeding file is determined as follows: If environment variable -RANDFILE is set, then it names the seeding file. Otherwise if -environment variable HOME is set, then the seeding file is $HOME/.rnd. -If neither RANDFILE nor HOME is set, versions up to OpenSSL 0.9.6 will -use file .rnd in the current directory while OpenSSL 0.9.6a uses no -default seeding file at all. OpenSSL 0.9.6b and later will behave -similarly to 0.9.6a, but will use a default of "C:\" for HOME on -Windows systems if the environment variable has not been set. - -If the default seeding file does not exist or is too short, the "PRNG -not seeded" error message may occur. - -The openssl command line utility will write back a new state to the -default seeding file (and create this file if necessary) unless -there was no sufficient seeding. - -Pointing $RANDFILE to an Entropy Gathering Daemon socket does not work. -Use the "-rand" option of the OpenSSL command line tools instead. -The $RANDFILE environment variable and $HOME/.rnd are only used by the -OpenSSL command line tools. Applications using the OpenSSL library -provide their own configuration options to specify the entropy source, -please check out the documentation coming the with application. - - -* Why do I get an "unable to write 'random state'" error message? - - -Sometimes the openssl command line utility does not abort with -a "PRNG not seeded" error message, but complains that it is -"unable to write 'random state'". This message refers to the -default seeding file (see previous answer). A possible reason -is that no default filename is known because neither RANDFILE -nor HOME is set. (Versions up to 0.9.6 used file ".rnd" in the -current directory in this case, but this has changed with 0.9.6a.) - - -* How do I create certificates or certificate requests? - -Check out the CA.pl(1) manual page. This provides a simple wrapper round -the 'req', 'verify', 'ca' and 'pkcs12' utilities. For finer control check -out the manual pages for the individual utilities and the certificate -extensions documentation (currently in doc/openssl.txt). - - -* Why can't I create certificate requests? - -You typically get the error: - - unable to find 'distinguished_name' in config - problems making Certificate Request - -This is because it can't find the configuration file. Check out the -DIAGNOSTICS section of req(1) for more information. - - -* Why does <SSL program> fail with a certificate verify error? - -This problem is usually indicated by log messages saying something like -"unable to get local issuer certificate" or "self signed certificate". -When a certificate is verified its root CA must be "trusted" by OpenSSL -this typically means that the CA certificate must be placed in a directory -or file and the relevant program configured to read it. The OpenSSL program -'verify' behaves in a similar way and issues similar error messages: check -the verify(1) program manual page for more information. - - -* Why can I only use weak ciphers when I connect to a server using OpenSSL? - -This is almost certainly because you are using an old "export grade" browser -which only supports weak encryption. Upgrade your browser to support 128 bit -ciphers. - - -* How can I create DSA certificates? - -Check the CA.pl(1) manual page for a DSA certificate example. - - -* Why can't I make an SSL connection to a server using a DSA certificate? - -Typically you'll see a message saying there are no shared ciphers when -the same setup works fine with an RSA certificate. There are two possible -causes. The client may not support connections to DSA servers most web -browsers (including Netscape and MSIE) only support connections to servers -supporting RSA cipher suites. The other cause is that a set of DH parameters -has not been supplied to the server. DH parameters can be created with the -dhparam(1) command and loaded using the SSL_CTX_set_tmp_dh() for example: -check the source to s_server in apps/s_server.c for an example. - - -* How can I remove the passphrase on a private key? - -Firstly you should be really *really* sure you want to do this. Leaving -a private key unencrypted is a major security risk. If you decide that -you do have to do this check the EXAMPLES sections of the rsa(1) and -dsa(1) manual pages. - - -* Why can't I use OpenSSL certificates with SSL client authentication? - -What will typically happen is that when a server requests authentication -it will either not include your certificate or tell you that you have -no client certificates (Netscape) or present you with an empty list box -(MSIE). The reason for this is that when a server requests a client -certificate it includes a list of CAs names which it will accept. Browsers -will only let you select certificates from the list on the grounds that -there is little point presenting a certificate which the server will -reject. - -The solution is to add the relevant CA certificate to your servers "trusted -CA list". How you do this depends on the server software in uses. You can -print out the servers list of acceptable CAs using the OpenSSL s_client tool: - -openssl s_client -connect www.some.host:443 -prexit - -If your server only requests certificates on certain URLs then you may need -to manually issue an HTTP GET command to get the list when s_client connects: - -GET /some/page/needing/a/certificate.html - -If your CA does not appear in the list then this confirms the problem. - - -* Why does my browser give a warning about a mismatched hostname? - -Browsers expect the server's hostname to match the value in the commonName -(CN) field of the certificate. If it does not then you get a warning. - - -* How do I install a CA certificate into a browser? - -The usual way is to send the DER encoded certificate to the browser as -MIME type application/x-x509-ca-cert, for example by clicking on an appropriate -link. On MSIE certain extensions such as .der or .cacert may also work, or you -can import the certificate using the certificate import wizard. - -You can convert a certificate to DER form using the command: - -openssl x509 -in ca.pem -outform DER -out ca.der - -Occasionally someone suggests using a command such as: - -openssl pkcs12 -export -out cacert.p12 -in cacert.pem -inkey cakey.pem - -DO NOT DO THIS! This command will give away your CAs private key and -reduces its security to zero: allowing anyone to forge certificates in -whatever name they choose. - -* Why is OpenSSL x509 DN output not conformant to RFC2253? - -The ways to print out the oneline format of the DN (Distinguished Name) have -been extended in version 0.9.7 of OpenSSL. Using the new X509_NAME_print_ex() -interface, the "-nameopt" option could be introduded. See the manual -page of the "openssl x509" commandline tool for details. The old behaviour -has however been left as default for the sake of compatibility. - -* What is a "128 bit certificate"? Can I create one with OpenSSL? - -The term "128 bit certificate" is a highly misleading marketing term. It does -*not* refer to the size of the public key in the certificate! A certificate -containing a 128 bit RSA key would have negligible security. - -There were various other names such as "magic certificates", "SGC -certificates", "step up certificates" etc. - -You can't generally create such a certificate using OpenSSL but there is no -need to any more. Nowadays web browsers using unrestricted strong encryption -are generally available. - -When there were tight restrictions on the export of strong encryption -software from the US only weak encryption algorithms could be freely exported -(initially 40 bit and then 56 bit). It was widely recognised that this was -inadequate. A relaxation of the rules allowed the use of strong encryption but -only to an authorised server. - -Two slighly different techniques were developed to support this, one used by -Netscape was called "step up", the other used by MSIE was called "Server Gated -Cryptography" (SGC). When a browser initially connected to a server it would -check to see if the certificate contained certain extensions and was issued by -an authorised authority. If these test succeeded it would reconnect using -strong encryption. - -Only certain (initially one) certificate authorities could issue the -certificates and they generally cost more than ordinary certificates. - -Although OpenSSL can create certificates containing the appropriate extensions -the certificate would not come from a permitted authority and so would not -be recognized. - -The export laws were later changed to allow almost unrestricted use of strong -encryption so these certificates are now obsolete. - - -* Why does OpenSSL set the authority key identifier (AKID) extension incorrectly? - -It doesn't: this extension is often the cause of confusion. - -Consider a certificate chain A->B->C so that A signs B and B signs C. Suppose -certificate C contains AKID. - -The purpose of this extension is to identify the authority certificate B. This -can be done either by including the subject key identifier of B or its issuer -name and serial number. - -In this latter case because it is identifying certifcate B it must contain the -issuer name and serial number of B. - -It is often wrongly assumed that it should contain the subject name of B. If it -did this would be redundant information because it would duplicate the issuer -name of C. - - -* How can I set up a bundle of commercial root CA certificates? - -The OpenSSL software is shipped without any root CA certificate as the -OpenSSL project does not have any policy on including or excluding -any specific CA and does not intend to set up such a policy. Deciding -about which CAs to support is up to application developers or -administrators. - -Other projects do have other policies so you can for example extract the CA -bundle used by Mozilla and/or modssl as described in this article: - - <URL: http://www.mail-archive.com/modssl-users@modssl.org/msg16980.html> - - -[BUILD] ======================================================================= - -* Why does the linker complain about undefined symbols? - -Maybe the compilation was interrupted, and make doesn't notice that -something is missing. Run "make clean; make". - -If you used ./Configure instead of ./config, make sure that you -selected the right target. File formats may differ slightly between -OS versions (for example sparcv8/sparcv9, or a.out/elf). - -In case you get errors about the following symbols, use the config -option "no-asm", as described in INSTALL: - - BF_cbc_encrypt, BF_decrypt, BF_encrypt, CAST_cbc_encrypt, - CAST_decrypt, CAST_encrypt, RC4, RC5_32_cbc_encrypt, RC5_32_decrypt, - RC5_32_encrypt, bn_add_words, bn_div_words, bn_mul_add_words, - bn_mul_comba4, bn_mul_comba8, bn_mul_words, bn_sqr_comba4, - bn_sqr_comba8, bn_sqr_words, bn_sub_words, des_decrypt3, - des_ede3_cbc_encrypt, des_encrypt, des_encrypt2, des_encrypt3, - des_ncbc_encrypt, md5_block_asm_host_order, sha1_block_asm_data_order - -If none of these helps, you may want to try using the current snapshot. -If the problem persists, please submit a bug report. - - -* Why does the OpenSSL test fail with "bc: command not found"? - -You didn't install "bc", the Unix calculator. If you want to run the -tests, get GNU bc from ftp://ftp.gnu.org or from your OS distributor. - - -* Why does the OpenSSL test fail with "bc: 1 no implemented"? - -On some SCO installations or versions, bc has a bug that gets triggered -when you run the test suite (using "make test"). The message returned is -"bc: 1 not implemented". - -The best way to deal with this is to find another implementation of bc -and compile/install it. GNU bc (see <URL: http://www.gnu.org/software/software.html> -for download instructions) can be safely used, for example. - - -* Why does the OpenSSL test fail with "bc: stack empty"? - -On some DG/ux versions, bc seems to have a too small stack for calculations -that the OpenSSL bntest throws at it. This gets triggered when you run the -test suite (using "make test"). The message returned is "bc: stack empty". - -The best way to deal with this is to find another implementation of bc -and compile/install it. GNU bc (see <URL: http://www.gnu.org/software/software.html> -for download instructions) can be safely used, for example. - - -* Why does the OpenSSL compilation fail on Alpha Tru64 Unix? - -On some Alpha installations running Tru64 Unix and Compaq C, the compilation -of crypto/sha/sha_dgst.c fails with the message 'Fatal: Insufficient virtual -memory to continue compilation.' As far as the tests have shown, this may be -a compiler bug. What happens is that it eats up a lot of resident memory -to build something, probably a table. The problem is clearly in the -optimization code, because if one eliminates optimization completely (-O0), -the compilation goes through (and the compiler consumes about 2MB of resident -memory instead of 240MB or whatever one's limit is currently). - -There are three options to solve this problem: - -1. set your current data segment size soft limit higher. Experience shows -that about 241000 kbytes seems to be enough on an AlphaServer DS10. You do -this with the command 'ulimit -Sd nnnnnn', where 'nnnnnn' is the number of -kbytes to set the limit to. - -2. If you have a hard limit that is lower than what you need and you can't -get it changed, you can compile all of OpenSSL with -O0 as optimization -level. This is however not a very nice thing to do for those who expect to -get the best result from OpenSSL. A bit more complicated solution is the -following: - ------ snip:start ----- - make DIRS=crypto SDIRS=sha "`grep '^CFLAG=' Makefile.ssl | \ - sed -e 's/ -O[0-9] / -O0 /'`" - rm `ls crypto/*.o crypto/sha/*.o | grep -v 'sha_dgst\.o'` - make ------ snip:end ----- - -This will only compile sha_dgst.c with -O0, the rest with the optimization -level chosen by the configuration process. When the above is done, do the -test and installation and you're set. - -3. Reconfigure the toolkit with no-sha0 option to leave out SHA0. It -should not be used and is not used in SSL/TLS nor any other recognized -protocol in either case. - - -* Why does the OpenSSL compilation fail with "ar: command not found"? - -Getting this message is quite usual on Solaris 2, because Sun has hidden -away 'ar' and other development commands in directories that aren't in -$PATH by default. One of those directories is '/usr/ccs/bin'. The -quickest way to fix this is to do the following (it assumes you use sh -or any sh-compatible shell): - ------ snip:start ----- - PATH=${PATH}:/usr/ccs/bin; export PATH ------ snip:end ----- - -and then redo the compilation. What you should really do is make sure -'/usr/ccs/bin' is permanently in your $PATH, for example through your -'.profile' (again, assuming you use a sh-compatible shell). - - -* Why does the OpenSSL compilation fail on Win32 with VC++? - -Sometimes, you may get reports from VC++ command line (cl) that it -can't find standard include files like stdio.h and other weirdnesses. -One possible cause is that the environment isn't correctly set up. -To solve that problem for VC++ versions up to 6, one should run -VCVARS32.BAT which is found in the 'bin' subdirectory of the VC++ -installation directory (somewhere under 'Program Files'). For VC++ -version 7 (and up?), which is also called VS.NET, the file is called -VSVARS32.BAT instead. -This needs to be done prior to running NMAKE, and the changes are only -valid for the current DOS session. - - -* What is special about OpenSSL on Redhat? - -Red Hat Linux (release 7.0 and later) include a preinstalled limited -version of OpenSSL. For patent reasons, support for IDEA, RC5 and MDC2 -is disabled in this version. The same may apply to other Linux distributions. -Users may therefore wish to install more or all of the features left out. - -To do this you MUST ensure that you do not overwrite the openssl that is in -/usr/bin on your Red Hat machine. Several packages depend on this file, -including sendmail and ssh. /usr/local/bin is a good alternative choice. The -libraries that come with Red Hat 7.0 onwards have different names and so are -not affected. (eg For Red Hat 7.2 they are /lib/libssl.so.0.9.6b and -/lib/libcrypto.so.0.9.6b with symlinks /lib/libssl.so.2 and -/lib/libcrypto.so.2 respectively). - -Please note that we have been advised by Red Hat attempting to recompile the -openssl rpm with all the cryptography enabled will not work. All other -packages depend on the original Red Hat supplied openssl package. It is also -worth noting that due to the way Red Hat supplies its packages, updates to -openssl on each distribution never change the package version, only the -build number. For example, on Red Hat 7.1, the latest openssl package has -version number 0.9.6 and build number 9 even though it contains all the -relevant updates in packages up to and including 0.9.6b. - -A possible way around this is to persuade Red Hat to produce a non-US -version of Red Hat Linux. - -FYI: Patent numbers and expiry dates of US patents: -MDC-2: 4,908,861 13/03/2007 -IDEA: 5,214,703 25/05/2010 -RC5: 5,724,428 03/03/2015 - - -* Why does the OpenSSL compilation fail on MacOS X? - -If the failure happens when trying to build the "openssl" binary, with -a large number of undefined symbols, it's very probable that you have -OpenSSL 0.9.6b delivered with the operating system (you can find out by -running '/usr/bin/openssl version') and that you were trying to build -OpenSSL 0.9.7 or newer. The problem is that the loader ('ld') in -MacOS X has a misfeature that's quite difficult to go around. -Look in the file PROBLEMS for a more detailed explanation and for possible -solutions. - - -* Why does the OpenSSL test suite fail on MacOS X? - -If the failure happens when running 'make test' and the RC4 test fails, -it's very probable that you have OpenSSL 0.9.6b delivered with the -operating system (you can find out by running '/usr/bin/openssl version') -and that you were trying to build OpenSSL 0.9.6d. The problem is that -the loader ('ld') in MacOS X has a misfeature that's quite difficult to -go around and has linked the programs "openssl" and the test programs -with /usr/lib/libcrypto.dylib and /usr/lib/libssl.dylib instead of the -libraries you just built. -Look in the file PROBLEMS for a more detailed explanation and for possible -solutions. - -* Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]? - -Failure in BN_sqr test is most likely caused by a failure to configure the -toolkit for current platform or lack of support for the platform in question. -Run './config -t' and './apps/openssl version -p'. Do these platform -identifiers match? If they don't, then you most likely failed to run -./config and you're hereby advised to do so before filing a bug report. -If ./config itself fails to run, then it's most likely problem with your -local environment and you should turn to your system administrator (or -similar). If identifiers match (and/or no alternative identifier is -suggested by ./config script), then the platform is unsupported. There might -or might not be a workaround. Most notably on SPARC64 platforms with GNU -C compiler you should be able to produce a working build by running -'./config -m32'. I understand that -m32 might not be what you want/need, -but the build should be operational. For further details turn to -<openssl-dev@openssl.org>. - -* Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"? - -As of 0.9.7 assembler routines were overhauled for position independence -of the machine code, which is essential for shared library support. For -some reason OpenBSD is equipped with an out-of-date GNU assembler which -finds the new code offensive. To work around the problem, configure with -no-asm (and sacrifice a great deal of performance) or patch your assembler -according to <URL: http://www.openssl.org/~appro/gas-1.92.3.OpenBSD.patch>. -For your convenience a pre-compiled replacement binary is provided at -<URL: http://www.openssl.org/~appro/gas-1.92.3.static.aout.bin>. -Reportedly elder *BSD a.out platforms also suffer from this problem and -remedy should be same. Provided binary is statically linked and should be -working across wider range of *BSD branches, not just OpenBSD. - -* Why does the OpenSSL test suite fail in sha512t on x86 CPU? - -If the test program in question fails withs SIGILL, Illegal Instruction -exception, then you more than likely to run SSE2-capable CPU, such as -Intel P4, under control of kernel which does not support SSE2 -instruction extentions. See accompanying INSTALL file and -OPENSSL_ia32cap(3) documentation page for further information. - -* Why does compiler fail to compile sha512.c? - -OpenSSL SHA-512 implementation depends on compiler support for 64-bit -integer type. Few elder compilers [ULTRIX cc, SCO compiler to mention a -couple] lack support for this and therefore are incapable of compiling -the module in question. The recommendation is to disable SHA-512 by -adding no-sha512 to ./config [or ./Configure] command line. Another -possible alternative might be to switch to GCC. - -* Test suite still fails, what to do? - -Another common reason for failure to complete some particular test is -simply bad code generated by a buggy component in toolchain or deficiency -in run-time environment. There are few cases documented in PROBLEMS file, -consult it for possible workaround before you beat the drum. Even if you -don't find solution or even mention there, do reserve for possibility of -a compiler bug. Compiler bugs might appear in rather bizarre ways, they -never make sense, and tend to emerge when you least expect them. In order -to identify one, drop optimization level, e.g. by editing CFLAG line in -top-level Makefile, recompile and re-run the test. - -* I think I've found a bug, what should I do? - -If you are a new user then it is quite likely you haven't found a bug and -something is happening you aren't familiar with. Check this FAQ, the associated -documentation and the mailing lists for similar queries. If you are still -unsure whether it is a bug or not submit a query to the openssl-users mailing -list. - - -* I'm SURE I've found a bug, how do I report it? - -Bug reports with no security implications should be sent to the request -tracker. This can be done by mailing the report to <rt@openssl.org> (or its -alias <openssl-bugs@openssl.org>), please note that messages sent to the -request tracker also appear in the public openssl-dev mailing list. - -The report should be in plain text. Any patches should be sent as -plain text attachments because some mailers corrupt patches sent inline. -If your issue affects multiple versions of OpenSSL check any patches apply -cleanly and, if possible include patches to each affected version. - -The report should be given a meaningful subject line briefly summarising the -issue. Just "bug in OpenSSL" or "bug in OpenSSL 0.9.8n" is not very helpful. - -By sending reports to the request tracker the bug can then be given a priority -and assigned to the appropriate maintainer. The history of discussions can be -accessed and if the issue has been addressed or a reason why not. If patches -are only sent to openssl-dev they can be mislaid if a team member has to -wade through months of old messages to review the discussion. - -See also <URL: http://www.openssl.org/support/rt.html> - - -* I've found a security issue, how do I report it? - -If you think your bug has security implications then please send it to -openssl-security@openssl.org if you don't get a prompt reply at least -acknowledging receipt then resend or mail it directly to one of the -more active team members (e.g. Steve). - -[PROG] ======================================================================== - -* Is OpenSSL thread-safe? - -Yes (with limitations: an SSL connection may not concurrently be used -by multiple threads). On Windows and many Unix systems, OpenSSL -automatically uses the multi-threaded versions of the standard -libraries. If your platform is not one of these, consult the INSTALL -file. - -Multi-threaded applications must provide two callback functions to -OpenSSL by calling CRYPTO_set_locking_callback() and -CRYPTO_set_id_callback(), for all versions of OpenSSL up to and -including 0.9.8[abc...]. As of version 1.0.0, CRYPTO_set_id_callback() -and associated APIs are deprecated by CRYPTO_THREADID_set_callback() -and friends. This is described in the threads(3) manpage. - -* I've compiled a program under Windows and it crashes: why? - -This is usually because you've missed the comment in INSTALL.W32. -Your application must link against the same version of the Win32 -C-Runtime against which your openssl libraries were linked. The -default version for OpenSSL is /MD - "Multithreaded DLL". - -If you are using Microsoft Visual C++'s IDE (Visual Studio), in -many cases, your new project most likely defaulted to "Debug -Singlethreaded" - /ML. This is NOT interchangeable with /MD and your -program will crash, typically on the first BIO related read or write -operation. - -For each of the six possible link stage configurations within Win32, -your application must link against the same by which OpenSSL was -built. If you are using MS Visual C++ (Studio) this can be changed -by: - - 1. Select Settings... from the Project Menu. - 2. Select the C/C++ Tab. - 3. Select "Code Generation from the "Category" drop down list box - 4. Select the Appropriate library (see table below) from the "Use - run-time library" drop down list box. Perform this step for both - your debug and release versions of your application (look at the - top left of the settings panel to change between the two) - - Single Threaded /ML - MS VC++ often defaults to - this for the release - version of a new project. - Debug Single Threaded /MLd - MS VC++ often defaults to - this for the debug version - of a new project. - Multithreaded /MT - Debug Multithreaded /MTd - Multithreaded DLL /MD - OpenSSL defaults to this. - Debug Multithreaded DLL /MDd - -Note that debug and release libraries are NOT interchangeable. If you -built OpenSSL with /MD your application must use /MD and cannot use /MDd. - -As per 0.9.8 the above limitation is eliminated for .DLLs. OpenSSL -.DLLs compiled with some specific run-time option [we insist on the -default /MD] can be deployed with application compiled with different -option or even different compiler. But there is a catch! Instead of -re-compiling OpenSSL toolkit, as you would have to with prior versions, -you have to compile small C snippet with compiler and/or options of -your choice. The snippet gets installed as -<install-root>/include/openssl/applink.c and should be either added to -your application project or simply #include-d in one [and only one] -of your application source files. Failure to link this shim module -into your application manifests itself as fatal "no OPENSSL_Applink" -run-time error. An explicit reminder is due that in this situation -[mixing compiler options] it is as important to add CRYPTO_malloc_init -prior first call to OpenSSL. - -* How do I read or write a DER encoded buffer using the ASN1 functions? - -You have two options. You can either use a memory BIO in conjunction -with the i2d_*_bio() or d2i_*_bio() functions or you can use the -i2d_*(), d2i_*() functions directly. Since these are often the -cause of grief here are some code fragments using PKCS7 as an example: - - unsigned char *buf, *p; - int len; - - len = i2d_PKCS7(p7, NULL); - buf = OPENSSL_malloc(len); /* or Malloc, error checking omitted */ - p = buf; - i2d_PKCS7(p7, &p); - -At this point buf contains the len bytes of the DER encoding of -p7. - -The opposite assumes we already have len bytes in buf: - - unsigned char *p; - p = buf; - p7 = d2i_PKCS7(NULL, &p, len); - -At this point p7 contains a valid PKCS7 structure of NULL if an error -occurred. If an error occurred ERR_print_errors(bio) should give more -information. - -The reason for the temporary variable 'p' is that the ASN1 functions -increment the passed pointer so it is ready to read or write the next -structure. This is often a cause of problems: without the temporary -variable the buffer pointer is changed to point just after the data -that has been read or written. This may well be uninitialized data -and attempts to free the buffer will have unpredictable results -because it no longer points to the same address. - - -* OpenSSL uses DER but I need BER format: does OpenSSL support BER? - -The short answer is yes, because DER is a special case of BER and OpenSSL -ASN1 decoders can process BER. - -The longer answer is that ASN1 structures can be encoded in a number of -different ways. One set of ways is the Basic Encoding Rules (BER) with various -permissible encodings. A restriction of BER is the Distinguished Encoding -Rules (DER): these uniquely specify how a given structure is encoded. - -Therefore, because DER is a special case of BER, DER is an acceptable encoding -for BER. - - -* I've tried using <M_some_evil_pkcs12_macro> and I get errors why? - -This usually happens when you try compiling something using the PKCS#12 -macros with a C++ compiler. There is hardly ever any need to use the -PKCS#12 macros in a program, it is much easier to parse and create -PKCS#12 files using the PKCS12_parse() and PKCS12_create() functions -documented in doc/openssl.txt and with examples in demos/pkcs12. The -'pkcs12' application has to use the macros because it prints out -debugging information. - - -* I've called <some function> and it fails, why? - -Before submitting a report or asking in one of the mailing lists, you -should try to determine the cause. In particular, you should call -ERR_print_errors() or ERR_print_errors_fp() after the failed call -and see if the message helps. Note that the problem may occur earlier -than you think -- you should check for errors after every call where -it is possible, otherwise the actual problem may be hidden because -some OpenSSL functions clear the error state. - - -* I just get a load of numbers for the error output, what do they mean? - -The actual format is described in the ERR_print_errors() manual page. -You should call the function ERR_load_crypto_strings() before hand and -the message will be output in text form. If you can't do this (for example -it is a pre-compiled binary) you can use the errstr utility on the error -code itself (the hex digits after the second colon). - - -* Why do I get errors about unknown algorithms? - -The cause is forgetting to load OpenSSL's table of algorithms with -OpenSSL_add_all_algorithms(). See the manual page for more information. This -can cause several problems such as being unable to read in an encrypted -PEM file, unable to decrypt a PKCS#12 file or signature failure when -verifying certificates. - -* Why can't the OpenSSH configure script detect OpenSSL? - -Several reasons for problems with the automatic detection exist. -OpenSSH requires at least version 0.9.5a of the OpenSSL libraries. -Sometimes the distribution has installed an older version in the system -locations that is detected instead of a new one installed. The OpenSSL -library might have been compiled for another CPU or another mode (32/64 bits). -Permissions might be wrong. - -The general answer is to check the config.log file generated when running -the OpenSSH configure script. It should contain the detailed information -on why the OpenSSL library was not detected or considered incompatible. - - -* Can I use OpenSSL's SSL library with non-blocking I/O? - -Yes; make sure to read the SSL_get_error(3) manual page! - -A pitfall to avoid: Don't assume that SSL_read() will just read from -the underlying transport or that SSL_write() will just write to it -- -it is also possible that SSL_write() cannot do any useful work until -there is data to read, or that SSL_read() cannot do anything until it -is possible to send data. One reason for this is that the peer may -request a new TLS/SSL handshake at any time during the protocol, -requiring a bi-directional message exchange; both SSL_read() and -SSL_write() will try to continue any pending handshake. - - -* Why doesn't my server application receive a client certificate? - -Due to the TLS protocol definition, a client will only send a certificate, -if explicitly asked by the server. Use the SSL_VERIFY_PEER flag of the -SSL_CTX_set_verify() function to enable the use of client certificates. - - -* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier? - -For OpenSSL 0.9.7 the OID table was extended and corrected. In earlier -versions, uniqueIdentifier was incorrectly used for X.509 certificates. -The correct name according to RFC2256 (LDAP) is x500UniqueIdentifier. -Change your code to use the new name when compiling against OpenSSL 0.9.7. - - -* I think I've detected a memory leak, is this a bug? - -In most cases the cause of an apparent memory leak is an OpenSSL internal table -that is allocated when an application starts up. Since such tables do not grow -in size over time they are harmless. - -These internal tables can be freed up when an application closes using various -functions. Currently these include following: - -Thread-local cleanup functions: - - ERR_remove_state() - -Application-global cleanup functions that are aware of usage (and therefore -thread-safe): - - ENGINE_cleanup() and CONF_modules_unload() - -"Brutal" (thread-unsafe) Application-global cleanup functions: - - ERR_free_strings(), EVP_cleanup() and CRYPTO_cleanup_all_ex_data(). - - -* Why does Valgrind complain about the use of uninitialized data? - -When OpenSSL's PRNG routines are called to generate random numbers the supplied -buffer contents are mixed into the entropy pool: so it technically does not -matter whether the buffer is initialized at this point or not. Valgrind (and -other test tools) will complain about this. When using Valgrind, make sure the -OpenSSL library has been compiled with the PURIFY macro defined (-DPURIFY) -to get rid of these warnings. - - -* Why doesn't a memory BIO work when a file does? - -This can occur in several cases for example reading an S/MIME email message. -The reason is that a memory BIO can do one of two things when all the data -has been read from it. - -The default behaviour is to indicate that no more data is available and that -the call should be retried, this is to allow the application to fill up the BIO -again if necessary. - -Alternatively it can indicate that no more data is available and that EOF has -been reached. - -If a memory BIO is to behave in the same way as a file this second behaviour -is needed. This must be done by calling: - - BIO_set_mem_eof_return(bio, 0); - -See the manual pages for more details. - - -* Where are the declarations and implementations of d2i_X509() etc? - -These are defined and implemented by macros of the form: - - - DECLARE_ASN1_FUNCTIONS(X509) and IMPLEMENT_ASN1_FUNCTIONS(X509) - -The implementation passes an ASN1 "template" defining the structure into an -ASN1 interpreter using generalised functions such as ASN1_item_d2i(). - - -=============================================================================== +OpenSSL - Frequently Asked Questions
+--------------------------------------
+
+[MISC] Miscellaneous questions
+
+* Which is the current version of OpenSSL?
+* Where is the documentation?
+* How can I contact the OpenSSL developers?
+* Where can I get a compiled version of OpenSSL?
+* Why aren't tools like 'autoconf' and 'libtool' used?
+* What is an 'engine' version?
+* How do I check the authenticity of the OpenSSL distribution?
+
+[LEGAL] Legal questions
+
+* Do I need patent licenses to use OpenSSL?
+* Can I use OpenSSL with GPL software?
+
+[USER] Questions on using the OpenSSL applications
+
+* Why do I get a "PRNG not seeded" error message?
+* Why do I get an "unable to write 'random state'" error message?
+* How do I create certificates or certificate requests?
+* Why can't I create certificate requests?
+* Why does <SSL program> fail with a certificate verify error?
+* Why can I only use weak ciphers when I connect to a server using OpenSSL?
+* How can I create DSA certificates?
+* Why can't I make an SSL connection using a DSA certificate?
+* How can I remove the passphrase on a private key?
+* Why can't I use OpenSSL certificates with SSL client authentication?
+* Why does my browser give a warning about a mismatched hostname?
+* How do I install a CA certificate into a browser?
+* Why is OpenSSL x509 DN output not conformant to RFC2253?
+* What is a "128 bit certificate"? Can I create one with OpenSSL?
+* Why does OpenSSL set the authority key identifier extension incorrectly?
+* How can I set up a bundle of commercial root CA certificates?
+
+[BUILD] Questions about building and testing OpenSSL
+
+* Why does the linker complain about undefined symbols?
+* Why does the OpenSSL test fail with "bc: command not found"?
+* Why does the OpenSSL test fail with "bc: 1 no implemented"?
+* Why does the OpenSSL test fail with "bc: stack empty"?
+* Why does the OpenSSL compilation fail on Alpha Tru64 Unix?
+* Why does the OpenSSL compilation fail with "ar: command not found"?
+* Why does the OpenSSL compilation fail on Win32 with VC++?
+* What is special about OpenSSL on Redhat?
+* Why does the OpenSSL compilation fail on MacOS X?
+* Why does the OpenSSL test suite fail on MacOS X?
+* Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]?
+* Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"?
+* Why does the OpenSSL test suite fail in sha512t on x86 CPU?
+* Why does compiler fail to compile sha512.c?
+* Test suite still fails, what to do?
+* I think I've found a bug, what should I do?
+* I'm SURE I've found a bug, how do I report it?
+* I've found a security issue, how do I report it?
+
+[PROG] Questions about programming with OpenSSL
+
+* Is OpenSSL thread-safe?
+* I've compiled a program under Windows and it crashes: why?
+* How do I read or write a DER encoded buffer using the ASN1 functions?
+* OpenSSL uses DER but I need BER format: does OpenSSL support BER?
+* I've tried using <M_some_evil_pkcs12_macro> and I get errors why?
+* I've called <some function> and it fails, why?
+* I just get a load of numbers for the error output, what do they mean?
+* Why do I get errors about unknown algorithms?
+* Why can't the OpenSSH configure script detect OpenSSL?
+* Can I use OpenSSL's SSL library with non-blocking I/O?
+* Why doesn't my server application receive a client certificate?
+* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier?
+* I think I've detected a memory leak, is this a bug?
+* Why does Valgrind complain about the use of uninitialized data?
+* Why doesn't a memory BIO work when a file does?
+* Where are the declarations and implementations of d2i_X509() etc?
+
+===============================================================================
+
+[MISC] ========================================================================
+
+* Which is the current version of OpenSSL?
+
+The current version is available from <URL: http://www.openssl.org>.
+OpenSSL 1.0.0d was released on Feb 8th, 2011.
+
+In addition to the current stable release, you can also access daily
+snapshots of the OpenSSL development version at <URL:
+ftp://ftp.openssl.org/snapshot/>, or get it by anonymous CVS access.
+
+
+* Where is the documentation?
+
+OpenSSL is a library that provides cryptographic functionality to
+applications such as secure web servers. Be sure to read the
+documentation of the application you want to use. The INSTALL file
+explains how to install this library.
+
+OpenSSL includes a command line utility that can be used to perform a
+variety of cryptographic functions. It is described in the openssl(1)
+manpage. Documentation for developers is currently being written. Many
+manual pages are available; overviews over libcrypto and
+libssl are given in the crypto(3) and ssl(3) manpages.
+
+The OpenSSL manpages are installed in /usr/local/ssl/man/ (or a
+different directory if you specified one as described in INSTALL).
+In addition, you can read the most current versions at
+<URL: http://www.openssl.org/docs/>. Note that the online documents refer
+to the very latest development versions of OpenSSL and may include features
+not present in released versions. If in doubt refer to the documentation
+that came with the version of OpenSSL you are using.
+
+For information on parts of libcrypto that are not yet documented, you
+might want to read Ariel Glenn's documentation on SSLeay 0.9, OpenSSL's
+predecessor, at <URL: http://www.columbia.edu/~ariel/ssleay/>. Much
+of this still applies to OpenSSL.
+
+There is some documentation about certificate extensions and PKCS#12
+in doc/openssl.txt
+
+The original SSLeay documentation is included in OpenSSL as
+doc/ssleay.txt. It may be useful when none of the other resources
+help, but please note that it reflects the obsolete version SSLeay
+0.6.6.
+
+
+* How can I contact the OpenSSL developers?
+
+The README file describes how to submit bug reports and patches to
+OpenSSL. Information on the OpenSSL mailing lists is available from
+<URL: http://www.openssl.org>.
+
+
+* Where can I get a compiled version of OpenSSL?
+
+You can finder pointers to binary distributions in
+<URL: http://www.openssl.org/related/binaries.html> .
+
+Some applications that use OpenSSL are distributed in binary form.
+When using such an application, you don't need to install OpenSSL
+yourself; the application will include the required parts (e.g. DLLs).
+
+If you want to build OpenSSL on a Windows system and you don't have
+a C compiler, read the "Mingw32" section of INSTALL.W32 for information
+on how to obtain and install the free GNU C compiler.
+
+A number of Linux and *BSD distributions include OpenSSL.
+
+
+* Why aren't tools like 'autoconf' and 'libtool' used?
+
+autoconf will probably be used in future OpenSSL versions. If it was
+less Unix-centric, it might have been used much earlier.
+
+* What is an 'engine' version?
+
+With version 0.9.6 OpenSSL was extended to interface to external crypto
+hardware. This was realized in a special release '0.9.6-engine'. With
+version 0.9.7 the changes were merged into the main development line,
+so that the special release is no longer necessary.
+
+* How do I check the authenticity of the OpenSSL distribution?
+
+We provide MD5 digests and ASC signatures of each tarball.
+Use MD5 to check that a tarball from a mirror site is identical:
+
+ md5sum TARBALL | awk '{print $1;}' | cmp - TARBALL.md5
+
+You can check authenticity using pgp or gpg. You need the OpenSSL team
+member public key used to sign it (download it from a key server, see a
+list of keys at <URL: http://www.openssl.org/about/>). Then
+just do:
+
+ pgp TARBALL.asc
+
+[LEGAL] =======================================================================
+
+* Do I need patent licenses to use OpenSSL?
+
+The patents section of the README file lists patents that may apply to
+you if you want to use OpenSSL. For information on intellectual
+property rights, please consult a lawyer. The OpenSSL team does not
+offer legal advice.
+
+You can configure OpenSSL so as not to use IDEA, MDC2 and RC5 by using
+ ./config no-idea no-mdc2 no-rc5
+
+
+* Can I use OpenSSL with GPL software?
+
+On many systems including the major Linux and BSD distributions, yes (the
+GPL does not place restrictions on using libraries that are part of the
+normal operating system distribution).
+
+On other systems, the situation is less clear. Some GPL software copyright
+holders claim that you infringe on their rights if you use OpenSSL with
+their software on operating systems that don't normally include OpenSSL.
+
+If you develop open source software that uses OpenSSL, you may find it
+useful to choose an other license than the GPL, or state explicitly that
+"This program is released under the GPL with the additional exemption that
+compiling, linking, and/or using OpenSSL is allowed." If you are using
+GPL software developed by others, you may want to ask the copyright holder
+for permission to use their software with OpenSSL.
+
+
+[USER] ========================================================================
+
+* Why do I get a "PRNG not seeded" error message?
+
+Cryptographic software needs a source of unpredictable data to work
+correctly. Many open source operating systems provide a "randomness
+device" (/dev/urandom or /dev/random) that serves this purpose.
+All OpenSSL versions try to use /dev/urandom by default; starting with
+version 0.9.7, OpenSSL also tries /dev/random if /dev/urandom is not
+available.
+
+On other systems, applications have to call the RAND_add() or
+RAND_seed() function with appropriate data before generating keys or
+performing public key encryption. (These functions initialize the
+pseudo-random number generator, PRNG.) Some broken applications do
+not do this. As of version 0.9.5, the OpenSSL functions that need
+randomness report an error if the random number generator has not been
+seeded with at least 128 bits of randomness. If this error occurs and
+is not discussed in the documentation of the application you are
+using, please contact the author of that application; it is likely
+that it never worked correctly. OpenSSL 0.9.5 and later make the
+error visible by refusing to perform potentially insecure encryption.
+
+If you are using Solaris 8, you can add /dev/urandom and /dev/random
+devices by installing patch 112438 (Sparc) or 112439 (x86), which are
+available via the Patchfinder at <URL: http://sunsolve.sun.com>
+(Solaris 9 includes these devices by default). For /dev/random support
+for earlier Solaris versions, see Sun's statement at
+<URL: http://sunsolve.sun.com/pub-cgi/retrieve.pl?doc=fsrdb/27606&zone_32=SUNWski>
+(the SUNWski package is available in patch 105710).
+
+On systems without /dev/urandom and /dev/random, it is a good idea to
+use the Entropy Gathering Demon (EGD); see the RAND_egd() manpage for
+details. Starting with version 0.9.7, OpenSSL will automatically look
+for an EGD socket at /var/run/egd-pool, /dev/egd-pool, /etc/egd-pool and
+/etc/entropy.
+
+Most components of the openssl command line utility automatically try
+to seed the random number generator from a file. The name of the
+default seeding file is determined as follows: If environment variable
+RANDFILE is set, then it names the seeding file. Otherwise if
+environment variable HOME is set, then the seeding file is $HOME/.rnd.
+If neither RANDFILE nor HOME is set, versions up to OpenSSL 0.9.6 will
+use file .rnd in the current directory while OpenSSL 0.9.6a uses no
+default seeding file at all. OpenSSL 0.9.6b and later will behave
+similarly to 0.9.6a, but will use a default of "C:\" for HOME on
+Windows systems if the environment variable has not been set.
+
+If the default seeding file does not exist or is too short, the "PRNG
+not seeded" error message may occur.
+
+The openssl command line utility will write back a new state to the
+default seeding file (and create this file if necessary) unless
+there was no sufficient seeding.
+
+Pointing $RANDFILE to an Entropy Gathering Daemon socket does not work.
+Use the "-rand" option of the OpenSSL command line tools instead.
+The $RANDFILE environment variable and $HOME/.rnd are only used by the
+OpenSSL command line tools. Applications using the OpenSSL library
+provide their own configuration options to specify the entropy source,
+please check out the documentation coming the with application.
+
+
+* Why do I get an "unable to write 'random state'" error message?
+
+
+Sometimes the openssl command line utility does not abort with
+a "PRNG not seeded" error message, but complains that it is
+"unable to write 'random state'". This message refers to the
+default seeding file (see previous answer). A possible reason
+is that no default filename is known because neither RANDFILE
+nor HOME is set. (Versions up to 0.9.6 used file ".rnd" in the
+current directory in this case, but this has changed with 0.9.6a.)
+
+
+* How do I create certificates or certificate requests?
+
+Check out the CA.pl(1) manual page. This provides a simple wrapper round
+the 'req', 'verify', 'ca' and 'pkcs12' utilities. For finer control check
+out the manual pages for the individual utilities and the certificate
+extensions documentation (currently in doc/openssl.txt).
+
+
+* Why can't I create certificate requests?
+
+You typically get the error:
+
+ unable to find 'distinguished_name' in config
+ problems making Certificate Request
+
+This is because it can't find the configuration file. Check out the
+DIAGNOSTICS section of req(1) for more information.
+
+
+* Why does <SSL program> fail with a certificate verify error?
+
+This problem is usually indicated by log messages saying something like
+"unable to get local issuer certificate" or "self signed certificate".
+When a certificate is verified its root CA must be "trusted" by OpenSSL
+this typically means that the CA certificate must be placed in a directory
+or file and the relevant program configured to read it. The OpenSSL program
+'verify' behaves in a similar way and issues similar error messages: check
+the verify(1) program manual page for more information.
+
+
+* Why can I only use weak ciphers when I connect to a server using OpenSSL?
+
+This is almost certainly because you are using an old "export grade" browser
+which only supports weak encryption. Upgrade your browser to support 128 bit
+ciphers.
+
+
+* How can I create DSA certificates?
+
+Check the CA.pl(1) manual page for a DSA certificate example.
+
+
+* Why can't I make an SSL connection to a server using a DSA certificate?
+
+Typically you'll see a message saying there are no shared ciphers when
+the same setup works fine with an RSA certificate. There are two possible
+causes. The client may not support connections to DSA servers most web
+browsers (including Netscape and MSIE) only support connections to servers
+supporting RSA cipher suites. The other cause is that a set of DH parameters
+has not been supplied to the server. DH parameters can be created with the
+dhparam(1) command and loaded using the SSL_CTX_set_tmp_dh() for example:
+check the source to s_server in apps/s_server.c for an example.
+
+
+* How can I remove the passphrase on a private key?
+
+Firstly you should be really *really* sure you want to do this. Leaving
+a private key unencrypted is a major security risk. If you decide that
+you do have to do this check the EXAMPLES sections of the rsa(1) and
+dsa(1) manual pages.
+
+
+* Why can't I use OpenSSL certificates with SSL client authentication?
+
+What will typically happen is that when a server requests authentication
+it will either not include your certificate or tell you that you have
+no client certificates (Netscape) or present you with an empty list box
+(MSIE). The reason for this is that when a server requests a client
+certificate it includes a list of CAs names which it will accept. Browsers
+will only let you select certificates from the list on the grounds that
+there is little point presenting a certificate which the server will
+reject.
+
+The solution is to add the relevant CA certificate to your servers "trusted
+CA list". How you do this depends on the server software in uses. You can
+print out the servers list of acceptable CAs using the OpenSSL s_client tool:
+
+openssl s_client -connect www.some.host:443 -prexit
+
+If your server only requests certificates on certain URLs then you may need
+to manually issue an HTTP GET command to get the list when s_client connects:
+
+GET /some/page/needing/a/certificate.html
+
+If your CA does not appear in the list then this confirms the problem.
+
+
+* Why does my browser give a warning about a mismatched hostname?
+
+Browsers expect the server's hostname to match the value in the commonName
+(CN) field of the certificate. If it does not then you get a warning.
+
+
+* How do I install a CA certificate into a browser?
+
+The usual way is to send the DER encoded certificate to the browser as
+MIME type application/x-x509-ca-cert, for example by clicking on an appropriate
+link. On MSIE certain extensions such as .der or .cacert may also work, or you
+can import the certificate using the certificate import wizard.
+
+You can convert a certificate to DER form using the command:
+
+openssl x509 -in ca.pem -outform DER -out ca.der
+
+Occasionally someone suggests using a command such as:
+
+openssl pkcs12 -export -out cacert.p12 -in cacert.pem -inkey cakey.pem
+
+DO NOT DO THIS! This command will give away your CAs private key and
+reduces its security to zero: allowing anyone to forge certificates in
+whatever name they choose.
+
+* Why is OpenSSL x509 DN output not conformant to RFC2253?
+
+The ways to print out the oneline format of the DN (Distinguished Name) have
+been extended in version 0.9.7 of OpenSSL. Using the new X509_NAME_print_ex()
+interface, the "-nameopt" option could be introduded. See the manual
+page of the "openssl x509" commandline tool for details. The old behaviour
+has however been left as default for the sake of compatibility.
+
+* What is a "128 bit certificate"? Can I create one with OpenSSL?
+
+The term "128 bit certificate" is a highly misleading marketing term. It does
+*not* refer to the size of the public key in the certificate! A certificate
+containing a 128 bit RSA key would have negligible security.
+
+There were various other names such as "magic certificates", "SGC
+certificates", "step up certificates" etc.
+
+You can't generally create such a certificate using OpenSSL but there is no
+need to any more. Nowadays web browsers using unrestricted strong encryption
+are generally available.
+
+When there were tight restrictions on the export of strong encryption
+software from the US only weak encryption algorithms could be freely exported
+(initially 40 bit and then 56 bit). It was widely recognised that this was
+inadequate. A relaxation of the rules allowed the use of strong encryption but
+only to an authorised server.
+
+Two slighly different techniques were developed to support this, one used by
+Netscape was called "step up", the other used by MSIE was called "Server Gated
+Cryptography" (SGC). When a browser initially connected to a server it would
+check to see if the certificate contained certain extensions and was issued by
+an authorised authority. If these test succeeded it would reconnect using
+strong encryption.
+
+Only certain (initially one) certificate authorities could issue the
+certificates and they generally cost more than ordinary certificates.
+
+Although OpenSSL can create certificates containing the appropriate extensions
+the certificate would not come from a permitted authority and so would not
+be recognized.
+
+The export laws were later changed to allow almost unrestricted use of strong
+encryption so these certificates are now obsolete.
+
+
+* Why does OpenSSL set the authority key identifier (AKID) extension incorrectly?
+
+It doesn't: this extension is often the cause of confusion.
+
+Consider a certificate chain A->B->C so that A signs B and B signs C. Suppose
+certificate C contains AKID.
+
+The purpose of this extension is to identify the authority certificate B. This
+can be done either by including the subject key identifier of B or its issuer
+name and serial number.
+
+In this latter case because it is identifying certifcate B it must contain the
+issuer name and serial number of B.
+
+It is often wrongly assumed that it should contain the subject name of B. If it
+did this would be redundant information because it would duplicate the issuer
+name of C.
+
+
+* How can I set up a bundle of commercial root CA certificates?
+
+The OpenSSL software is shipped without any root CA certificate as the
+OpenSSL project does not have any policy on including or excluding
+any specific CA and does not intend to set up such a policy. Deciding
+about which CAs to support is up to application developers or
+administrators.
+
+Other projects do have other policies so you can for example extract the CA
+bundle used by Mozilla and/or modssl as described in this article:
+
+ <URL: http://www.mail-archive.com/modssl-users@modssl.org/msg16980.html>
+
+
+[BUILD] =======================================================================
+
+* Why does the linker complain about undefined symbols?
+
+Maybe the compilation was interrupted, and make doesn't notice that
+something is missing. Run "make clean; make".
+
+If you used ./Configure instead of ./config, make sure that you
+selected the right target. File formats may differ slightly between
+OS versions (for example sparcv8/sparcv9, or a.out/elf).
+
+In case you get errors about the following symbols, use the config
+option "no-asm", as described in INSTALL:
+
+ BF_cbc_encrypt, BF_decrypt, BF_encrypt, CAST_cbc_encrypt,
+ CAST_decrypt, CAST_encrypt, RC4, RC5_32_cbc_encrypt, RC5_32_decrypt,
+ RC5_32_encrypt, bn_add_words, bn_div_words, bn_mul_add_words,
+ bn_mul_comba4, bn_mul_comba8, bn_mul_words, bn_sqr_comba4,
+ bn_sqr_comba8, bn_sqr_words, bn_sub_words, des_decrypt3,
+ des_ede3_cbc_encrypt, des_encrypt, des_encrypt2, des_encrypt3,
+ des_ncbc_encrypt, md5_block_asm_host_order, sha1_block_asm_data_order
+
+If none of these helps, you may want to try using the current snapshot.
+If the problem persists, please submit a bug report.
+
+
+* Why does the OpenSSL test fail with "bc: command not found"?
+
+You didn't install "bc", the Unix calculator. If you want to run the
+tests, get GNU bc from ftp://ftp.gnu.org or from your OS distributor.
+
+
+* Why does the OpenSSL test fail with "bc: 1 no implemented"?
+
+On some SCO installations or versions, bc has a bug that gets triggered
+when you run the test suite (using "make test"). The message returned is
+"bc: 1 not implemented".
+
+The best way to deal with this is to find another implementation of bc
+and compile/install it. GNU bc (see <URL: http://www.gnu.org/software/software.html>
+for download instructions) can be safely used, for example.
+
+
+* Why does the OpenSSL test fail with "bc: stack empty"?
+
+On some DG/ux versions, bc seems to have a too small stack for calculations
+that the OpenSSL bntest throws at it. This gets triggered when you run the
+test suite (using "make test"). The message returned is "bc: stack empty".
+
+The best way to deal with this is to find another implementation of bc
+and compile/install it. GNU bc (see <URL: http://www.gnu.org/software/software.html>
+for download instructions) can be safely used, for example.
+
+
+* Why does the OpenSSL compilation fail on Alpha Tru64 Unix?
+
+On some Alpha installations running Tru64 Unix and Compaq C, the compilation
+of crypto/sha/sha_dgst.c fails with the message 'Fatal: Insufficient virtual
+memory to continue compilation.' As far as the tests have shown, this may be
+a compiler bug. What happens is that it eats up a lot of resident memory
+to build something, probably a table. The problem is clearly in the
+optimization code, because if one eliminates optimization completely (-O0),
+the compilation goes through (and the compiler consumes about 2MB of resident
+memory instead of 240MB or whatever one's limit is currently).
+
+There are three options to solve this problem:
+
+1. set your current data segment size soft limit higher. Experience shows
+that about 241000 kbytes seems to be enough on an AlphaServer DS10. You do
+this with the command 'ulimit -Sd nnnnnn', where 'nnnnnn' is the number of
+kbytes to set the limit to.
+
+2. If you have a hard limit that is lower than what you need and you can't
+get it changed, you can compile all of OpenSSL with -O0 as optimization
+level. This is however not a very nice thing to do for those who expect to
+get the best result from OpenSSL. A bit more complicated solution is the
+following:
+
+----- snip:start -----
+ make DIRS=crypto SDIRS=sha "`grep '^CFLAG=' Makefile.ssl | \
+ sed -e 's/ -O[0-9] / -O0 /'`"
+ rm `ls crypto/*.o crypto/sha/*.o | grep -v 'sha_dgst\.o'`
+ make
+----- snip:end -----
+
+This will only compile sha_dgst.c with -O0, the rest with the optimization
+level chosen by the configuration process. When the above is done, do the
+test and installation and you're set.
+
+3. Reconfigure the toolkit with no-sha0 option to leave out SHA0. It
+should not be used and is not used in SSL/TLS nor any other recognized
+protocol in either case.
+
+
+* Why does the OpenSSL compilation fail with "ar: command not found"?
+
+Getting this message is quite usual on Solaris 2, because Sun has hidden
+away 'ar' and other development commands in directories that aren't in
+$PATH by default. One of those directories is '/usr/ccs/bin'. The
+quickest way to fix this is to do the following (it assumes you use sh
+or any sh-compatible shell):
+
+----- snip:start -----
+ PATH=${PATH}:/usr/ccs/bin; export PATH
+----- snip:end -----
+
+and then redo the compilation. What you should really do is make sure
+'/usr/ccs/bin' is permanently in your $PATH, for example through your
+'.profile' (again, assuming you use a sh-compatible shell).
+
+
+* Why does the OpenSSL compilation fail on Win32 with VC++?
+
+Sometimes, you may get reports from VC++ command line (cl) that it
+can't find standard include files like stdio.h and other weirdnesses.
+One possible cause is that the environment isn't correctly set up.
+To solve that problem for VC++ versions up to 6, one should run
+VCVARS32.BAT which is found in the 'bin' subdirectory of the VC++
+installation directory (somewhere under 'Program Files'). For VC++
+version 7 (and up?), which is also called VS.NET, the file is called
+VSVARS32.BAT instead.
+This needs to be done prior to running NMAKE, and the changes are only
+valid for the current DOS session.
+
+
+* What is special about OpenSSL on Redhat?
+
+Red Hat Linux (release 7.0 and later) include a preinstalled limited
+version of OpenSSL. For patent reasons, support for IDEA, RC5 and MDC2
+is disabled in this version. The same may apply to other Linux distributions.
+Users may therefore wish to install more or all of the features left out.
+
+To do this you MUST ensure that you do not overwrite the openssl that is in
+/usr/bin on your Red Hat machine. Several packages depend on this file,
+including sendmail and ssh. /usr/local/bin is a good alternative choice. The
+libraries that come with Red Hat 7.0 onwards have different names and so are
+not affected. (eg For Red Hat 7.2 they are /lib/libssl.so.0.9.6b and
+/lib/libcrypto.so.0.9.6b with symlinks /lib/libssl.so.2 and
+/lib/libcrypto.so.2 respectively).
+
+Please note that we have been advised by Red Hat attempting to recompile the
+openssl rpm with all the cryptography enabled will not work. All other
+packages depend on the original Red Hat supplied openssl package. It is also
+worth noting that due to the way Red Hat supplies its packages, updates to
+openssl on each distribution never change the package version, only the
+build number. For example, on Red Hat 7.1, the latest openssl package has
+version number 0.9.6 and build number 9 even though it contains all the
+relevant updates in packages up to and including 0.9.6b.
+
+A possible way around this is to persuade Red Hat to produce a non-US
+version of Red Hat Linux.
+
+FYI: Patent numbers and expiry dates of US patents:
+MDC-2: 4,908,861 13/03/2007
+IDEA: 5,214,703 25/05/2010
+RC5: 5,724,428 03/03/2015
+
+
+* Why does the OpenSSL compilation fail on MacOS X?
+
+If the failure happens when trying to build the "openssl" binary, with
+a large number of undefined symbols, it's very probable that you have
+OpenSSL 0.9.6b delivered with the operating system (you can find out by
+running '/usr/bin/openssl version') and that you were trying to build
+OpenSSL 0.9.7 or newer. The problem is that the loader ('ld') in
+MacOS X has a misfeature that's quite difficult to go around.
+Look in the file PROBLEMS for a more detailed explanation and for possible
+solutions.
+
+
+* Why does the OpenSSL test suite fail on MacOS X?
+
+If the failure happens when running 'make test' and the RC4 test fails,
+it's very probable that you have OpenSSL 0.9.6b delivered with the
+operating system (you can find out by running '/usr/bin/openssl version')
+and that you were trying to build OpenSSL 0.9.6d. The problem is that
+the loader ('ld') in MacOS X has a misfeature that's quite difficult to
+go around and has linked the programs "openssl" and the test programs
+with /usr/lib/libcrypto.dylib and /usr/lib/libssl.dylib instead of the
+libraries you just built.
+Look in the file PROBLEMS for a more detailed explanation and for possible
+solutions.
+
+* Why does the OpenSSL test suite fail in BN_sqr test [on a 64-bit platform]?
+
+Failure in BN_sqr test is most likely caused by a failure to configure the
+toolkit for current platform or lack of support for the platform in question.
+Run './config -t' and './apps/openssl version -p'. Do these platform
+identifiers match? If they don't, then you most likely failed to run
+./config and you're hereby advised to do so before filing a bug report.
+If ./config itself fails to run, then it's most likely problem with your
+local environment and you should turn to your system administrator (or
+similar). If identifiers match (and/or no alternative identifier is
+suggested by ./config script), then the platform is unsupported. There might
+or might not be a workaround. Most notably on SPARC64 platforms with GNU
+C compiler you should be able to produce a working build by running
+'./config -m32'. I understand that -m32 might not be what you want/need,
+but the build should be operational. For further details turn to
+<openssl-dev@openssl.org>.
+
+* Why does OpenBSD-i386 build fail on des-586.s with "Unimplemented segment type"?
+
+As of 0.9.7 assembler routines were overhauled for position independence
+of the machine code, which is essential for shared library support. For
+some reason OpenBSD is equipped with an out-of-date GNU assembler which
+finds the new code offensive. To work around the problem, configure with
+no-asm (and sacrifice a great deal of performance) or patch your assembler
+according to <URL: http://www.openssl.org/~appro/gas-1.92.3.OpenBSD.patch>.
+For your convenience a pre-compiled replacement binary is provided at
+<URL: http://www.openssl.org/~appro/gas-1.92.3.static.aout.bin>.
+Reportedly elder *BSD a.out platforms also suffer from this problem and
+remedy should be same. Provided binary is statically linked and should be
+working across wider range of *BSD branches, not just OpenBSD.
+
+* Why does the OpenSSL test suite fail in sha512t on x86 CPU?
+
+If the test program in question fails withs SIGILL, Illegal Instruction
+exception, then you more than likely to run SSE2-capable CPU, such as
+Intel P4, under control of kernel which does not support SSE2
+instruction extentions. See accompanying INSTALL file and
+OPENSSL_ia32cap(3) documentation page for further information.
+
+* Why does compiler fail to compile sha512.c?
+
+OpenSSL SHA-512 implementation depends on compiler support for 64-bit
+integer type. Few elder compilers [ULTRIX cc, SCO compiler to mention a
+couple] lack support for this and therefore are incapable of compiling
+the module in question. The recommendation is to disable SHA-512 by
+adding no-sha512 to ./config [or ./Configure] command line. Another
+possible alternative might be to switch to GCC.
+
+* Test suite still fails, what to do?
+
+Another common reason for failure to complete some particular test is
+simply bad code generated by a buggy component in toolchain or deficiency
+in run-time environment. There are few cases documented in PROBLEMS file,
+consult it for possible workaround before you beat the drum. Even if you
+don't find solution or even mention there, do reserve for possibility of
+a compiler bug. Compiler bugs might appear in rather bizarre ways, they
+never make sense, and tend to emerge when you least expect them. In order
+to identify one, drop optimization level, e.g. by editing CFLAG line in
+top-level Makefile, recompile and re-run the test.
+
+* I think I've found a bug, what should I do?
+
+If you are a new user then it is quite likely you haven't found a bug and
+something is happening you aren't familiar with. Check this FAQ, the associated
+documentation and the mailing lists for similar queries. If you are still
+unsure whether it is a bug or not submit a query to the openssl-users mailing
+list.
+
+
+* I'm SURE I've found a bug, how do I report it?
+
+Bug reports with no security implications should be sent to the request
+tracker. This can be done by mailing the report to <rt@openssl.org> (or its
+alias <openssl-bugs@openssl.org>), please note that messages sent to the
+request tracker also appear in the public openssl-dev mailing list.
+
+The report should be in plain text. Any patches should be sent as
+plain text attachments because some mailers corrupt patches sent inline.
+If your issue affects multiple versions of OpenSSL check any patches apply
+cleanly and, if possible include patches to each affected version.
+
+The report should be given a meaningful subject line briefly summarising the
+issue. Just "bug in OpenSSL" or "bug in OpenSSL 0.9.8n" is not very helpful.
+
+By sending reports to the request tracker the bug can then be given a priority
+and assigned to the appropriate maintainer. The history of discussions can be
+accessed and if the issue has been addressed or a reason why not. If patches
+are only sent to openssl-dev they can be mislaid if a team member has to
+wade through months of old messages to review the discussion.
+
+See also <URL: http://www.openssl.org/support/rt.html>
+
+
+* I've found a security issue, how do I report it?
+
+If you think your bug has security implications then please send it to
+openssl-security@openssl.org if you don't get a prompt reply at least
+acknowledging receipt then resend or mail it directly to one of the
+more active team members (e.g. Steve).
+
+[PROG] ========================================================================
+
+* Is OpenSSL thread-safe?
+
+Yes (with limitations: an SSL connection may not concurrently be used
+by multiple threads). On Windows and many Unix systems, OpenSSL
+automatically uses the multi-threaded versions of the standard
+libraries. If your platform is not one of these, consult the INSTALL
+file.
+
+Multi-threaded applications must provide two callback functions to
+OpenSSL by calling CRYPTO_set_locking_callback() and
+CRYPTO_set_id_callback(), for all versions of OpenSSL up to and
+including 0.9.8[abc...]. As of version 1.0.0, CRYPTO_set_id_callback()
+and associated APIs are deprecated by CRYPTO_THREADID_set_callback()
+and friends. This is described in the threads(3) manpage.
+
+* I've compiled a program under Windows and it crashes: why?
+
+This is usually because you've missed the comment in INSTALL.W32.
+Your application must link against the same version of the Win32
+C-Runtime against which your openssl libraries were linked. The
+default version for OpenSSL is /MD - "Multithreaded DLL".
+
+If you are using Microsoft Visual C++'s IDE (Visual Studio), in
+many cases, your new project most likely defaulted to "Debug
+Singlethreaded" - /ML. This is NOT interchangeable with /MD and your
+program will crash, typically on the first BIO related read or write
+operation.
+
+For each of the six possible link stage configurations within Win32,
+your application must link against the same by which OpenSSL was
+built. If you are using MS Visual C++ (Studio) this can be changed
+by:
+
+ 1. Select Settings... from the Project Menu.
+ 2. Select the C/C++ Tab.
+ 3. Select "Code Generation from the "Category" drop down list box
+ 4. Select the Appropriate library (see table below) from the "Use
+ run-time library" drop down list box. Perform this step for both
+ your debug and release versions of your application (look at the
+ top left of the settings panel to change between the two)
+
+ Single Threaded /ML - MS VC++ often defaults to
+ this for the release
+ version of a new project.
+ Debug Single Threaded /MLd - MS VC++ often defaults to
+ this for the debug version
+ of a new project.
+ Multithreaded /MT
+ Debug Multithreaded /MTd
+ Multithreaded DLL /MD - OpenSSL defaults to this.
+ Debug Multithreaded DLL /MDd
+
+Note that debug and release libraries are NOT interchangeable. If you
+built OpenSSL with /MD your application must use /MD and cannot use /MDd.
+
+As per 0.9.8 the above limitation is eliminated for .DLLs. OpenSSL
+.DLLs compiled with some specific run-time option [we insist on the
+default /MD] can be deployed with application compiled with different
+option or even different compiler. But there is a catch! Instead of
+re-compiling OpenSSL toolkit, as you would have to with prior versions,
+you have to compile small C snippet with compiler and/or options of
+your choice. The snippet gets installed as
+<install-root>/include/openssl/applink.c and should be either added to
+your application project or simply #include-d in one [and only one]
+of your application source files. Failure to link this shim module
+into your application manifests itself as fatal "no OPENSSL_Applink"
+run-time error. An explicit reminder is due that in this situation
+[mixing compiler options] it is as important to add CRYPTO_malloc_init
+prior first call to OpenSSL.
+
+* How do I read or write a DER encoded buffer using the ASN1 functions?
+
+You have two options. You can either use a memory BIO in conjunction
+with the i2d_*_bio() or d2i_*_bio() functions or you can use the
+i2d_*(), d2i_*() functions directly. Since these are often the
+cause of grief here are some code fragments using PKCS7 as an example:
+
+ unsigned char *buf, *p;
+ int len;
+
+ len = i2d_PKCS7(p7, NULL);
+ buf = OPENSSL_malloc(len); /* or Malloc, error checking omitted */
+ p = buf;
+ i2d_PKCS7(p7, &p);
+
+At this point buf contains the len bytes of the DER encoding of
+p7.
+
+The opposite assumes we already have len bytes in buf:
+
+ unsigned char *p;
+ p = buf;
+ p7 = d2i_PKCS7(NULL, &p, len);
+
+At this point p7 contains a valid PKCS7 structure of NULL if an error
+occurred. If an error occurred ERR_print_errors(bio) should give more
+information.
+
+The reason for the temporary variable 'p' is that the ASN1 functions
+increment the passed pointer so it is ready to read or write the next
+structure. This is often a cause of problems: without the temporary
+variable the buffer pointer is changed to point just after the data
+that has been read or written. This may well be uninitialized data
+and attempts to free the buffer will have unpredictable results
+because it no longer points to the same address.
+
+
+* OpenSSL uses DER but I need BER format: does OpenSSL support BER?
+
+The short answer is yes, because DER is a special case of BER and OpenSSL
+ASN1 decoders can process BER.
+
+The longer answer is that ASN1 structures can be encoded in a number of
+different ways. One set of ways is the Basic Encoding Rules (BER) with various
+permissible encodings. A restriction of BER is the Distinguished Encoding
+Rules (DER): these uniquely specify how a given structure is encoded.
+
+Therefore, because DER is a special case of BER, DER is an acceptable encoding
+for BER.
+
+
+* I've tried using <M_some_evil_pkcs12_macro> and I get errors why?
+
+This usually happens when you try compiling something using the PKCS#12
+macros with a C++ compiler. There is hardly ever any need to use the
+PKCS#12 macros in a program, it is much easier to parse and create
+PKCS#12 files using the PKCS12_parse() and PKCS12_create() functions
+documented in doc/openssl.txt and with examples in demos/pkcs12. The
+'pkcs12' application has to use the macros because it prints out
+debugging information.
+
+
+* I've called <some function> and it fails, why?
+
+Before submitting a report or asking in one of the mailing lists, you
+should try to determine the cause. In particular, you should call
+ERR_print_errors() or ERR_print_errors_fp() after the failed call
+and see if the message helps. Note that the problem may occur earlier
+than you think -- you should check for errors after every call where
+it is possible, otherwise the actual problem may be hidden because
+some OpenSSL functions clear the error state.
+
+
+* I just get a load of numbers for the error output, what do they mean?
+
+The actual format is described in the ERR_print_errors() manual page.
+You should call the function ERR_load_crypto_strings() before hand and
+the message will be output in text form. If you can't do this (for example
+it is a pre-compiled binary) you can use the errstr utility on the error
+code itself (the hex digits after the second colon).
+
+
+* Why do I get errors about unknown algorithms?
+
+The cause is forgetting to load OpenSSL's table of algorithms with
+OpenSSL_add_all_algorithms(). See the manual page for more information. This
+can cause several problems such as being unable to read in an encrypted
+PEM file, unable to decrypt a PKCS#12 file or signature failure when
+verifying certificates.
+
+* Why can't the OpenSSH configure script detect OpenSSL?
+
+Several reasons for problems with the automatic detection exist.
+OpenSSH requires at least version 0.9.5a of the OpenSSL libraries.
+Sometimes the distribution has installed an older version in the system
+locations that is detected instead of a new one installed. The OpenSSL
+library might have been compiled for another CPU or another mode (32/64 bits).
+Permissions might be wrong.
+
+The general answer is to check the config.log file generated when running
+the OpenSSH configure script. It should contain the detailed information
+on why the OpenSSL library was not detected or considered incompatible.
+
+
+* Can I use OpenSSL's SSL library with non-blocking I/O?
+
+Yes; make sure to read the SSL_get_error(3) manual page!
+
+A pitfall to avoid: Don't assume that SSL_read() will just read from
+the underlying transport or that SSL_write() will just write to it --
+it is also possible that SSL_write() cannot do any useful work until
+there is data to read, or that SSL_read() cannot do anything until it
+is possible to send data. One reason for this is that the peer may
+request a new TLS/SSL handshake at any time during the protocol,
+requiring a bi-directional message exchange; both SSL_read() and
+SSL_write() will try to continue any pending handshake.
+
+
+* Why doesn't my server application receive a client certificate?
+
+Due to the TLS protocol definition, a client will only send a certificate,
+if explicitly asked by the server. Use the SSL_VERIFY_PEER flag of the
+SSL_CTX_set_verify() function to enable the use of client certificates.
+
+
+* Why does compilation fail due to an undefined symbol NID_uniqueIdentifier?
+
+For OpenSSL 0.9.7 the OID table was extended and corrected. In earlier
+versions, uniqueIdentifier was incorrectly used for X.509 certificates.
+The correct name according to RFC2256 (LDAP) is x500UniqueIdentifier.
+Change your code to use the new name when compiling against OpenSSL 0.9.7.
+
+
+* I think I've detected a memory leak, is this a bug?
+
+In most cases the cause of an apparent memory leak is an OpenSSL internal table
+that is allocated when an application starts up. Since such tables do not grow
+in size over time they are harmless.
+
+These internal tables can be freed up when an application closes using various
+functions. Currently these include following:
+
+Thread-local cleanup functions:
+
+ ERR_remove_state()
+
+Application-global cleanup functions that are aware of usage (and therefore
+thread-safe):
+
+ ENGINE_cleanup() and CONF_modules_unload()
+
+"Brutal" (thread-unsafe) Application-global cleanup functions:
+
+ ERR_free_strings(), EVP_cleanup() and CRYPTO_cleanup_all_ex_data().
+
+
+* Why does Valgrind complain about the use of uninitialized data?
+
+When OpenSSL's PRNG routines are called to generate random numbers the supplied
+buffer contents are mixed into the entropy pool: so it technically does not
+matter whether the buffer is initialized at this point or not. Valgrind (and
+other test tools) will complain about this. When using Valgrind, make sure the
+OpenSSL library has been compiled with the PURIFY macro defined (-DPURIFY)
+to get rid of these warnings.
+
+
+* Why doesn't a memory BIO work when a file does?
+
+This can occur in several cases for example reading an S/MIME email message.
+The reason is that a memory BIO can do one of two things when all the data
+has been read from it.
+
+The default behaviour is to indicate that no more data is available and that
+the call should be retried, this is to allow the application to fill up the BIO
+again if necessary.
+
+Alternatively it can indicate that no more data is available and that EOF has
+been reached.
+
+If a memory BIO is to behave in the same way as a file this second behaviour
+is needed. This must be done by calling:
+
+ BIO_set_mem_eof_return(bio, 0);
+
+See the manual pages for more details.
+
+
+* Where are the declarations and implementations of d2i_X509() etc?
+
+These are defined and implemented by macros of the form:
+
+
+ DECLARE_ASN1_FUNCTIONS(X509) and IMPLEMENT_ASN1_FUNCTIONS(X509)
+
+The implementation passes an ASN1 "template" defining the structure into an
+ASN1 interpreter using generalised functions such as ASN1_item_d2i().
+
+
+===============================================================================
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