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Diffstat (limited to 'openssl/doc/crypto/EVP_DigestInit.pod')
| -rw-r--r-- | openssl/doc/crypto/EVP_DigestInit.pod | 256 |
1 files changed, 256 insertions, 0 deletions
diff --git a/openssl/doc/crypto/EVP_DigestInit.pod b/openssl/doc/crypto/EVP_DigestInit.pod new file mode 100644 index 000000000..130cd7f60 --- /dev/null +++ b/openssl/doc/crypto/EVP_DigestInit.pod @@ -0,0 +1,256 @@ +=pod + +=head1 NAME + +EVP_MD_CTX_init, EVP_MD_CTX_create, EVP_DigestInit_ex, EVP_DigestUpdate, +EVP_DigestFinal_ex, EVP_MD_CTX_cleanup, EVP_MD_CTX_destroy, EVP_MAX_MD_SIZE, +EVP_MD_CTX_copy_ex, EVP_MD_CTX_copy, EVP_MD_type, EVP_MD_pkey_type, EVP_MD_size, +EVP_MD_block_size, EVP_MD_CTX_md, EVP_MD_CTX_size, EVP_MD_CTX_block_size, EVP_MD_CTX_type, +EVP_md_null, EVP_md2, EVP_md5, EVP_sha, EVP_sha1, EVP_dss, EVP_dss1, EVP_mdc2, +EVP_ripemd160, EVP_get_digestbyname, EVP_get_digestbynid, EVP_get_digestbyobj - +EVP digest routines + +=head1 SYNOPSIS + + #include <openssl/evp.h> + + void EVP_MD_CTX_init(EVP_MD_CTX *ctx); + EVP_MD_CTX *EVP_MD_CTX_create(void); + + int EVP_DigestInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl); + int EVP_DigestUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt); + int EVP_DigestFinal_ex(EVP_MD_CTX *ctx, unsigned char *md, + unsigned int *s); + + int EVP_MD_CTX_cleanup(EVP_MD_CTX *ctx); + void EVP_MD_CTX_destroy(EVP_MD_CTX *ctx); + + int EVP_MD_CTX_copy_ex(EVP_MD_CTX *out,const EVP_MD_CTX *in); + + int EVP_DigestInit(EVP_MD_CTX *ctx, const EVP_MD *type); + int EVP_DigestFinal(EVP_MD_CTX *ctx, unsigned char *md, + unsigned int *s); + + int EVP_MD_CTX_copy(EVP_MD_CTX *out,EVP_MD_CTX *in); + + #define EVP_MAX_MD_SIZE (16+20) /* The SSLv3 md5+sha1 type */ + + + #define EVP_MD_type(e) ((e)->type) + #define EVP_MD_pkey_type(e) ((e)->pkey_type) + #define EVP_MD_size(e) ((e)->md_size) + #define EVP_MD_block_size(e) ((e)->block_size) + + #define EVP_MD_CTX_md(e) (e)->digest) + #define EVP_MD_CTX_size(e) EVP_MD_size((e)->digest) + #define EVP_MD_CTX_block_size(e) EVP_MD_block_size((e)->digest) + #define EVP_MD_CTX_type(e) EVP_MD_type((e)->digest) + + const EVP_MD *EVP_md_null(void); + const EVP_MD *EVP_md2(void); + const EVP_MD *EVP_md5(void); + const EVP_MD *EVP_sha(void); + const EVP_MD *EVP_sha1(void); + const EVP_MD *EVP_dss(void); + const EVP_MD *EVP_dss1(void); + const EVP_MD *EVP_mdc2(void); + const EVP_MD *EVP_ripemd160(void); + + const EVP_MD *EVP_get_digestbyname(const char *name); + #define EVP_get_digestbynid(a) EVP_get_digestbyname(OBJ_nid2sn(a)) + #define EVP_get_digestbyobj(a) EVP_get_digestbynid(OBJ_obj2nid(a)) + +=head1 DESCRIPTION + +The EVP digest routines are a high level interface to message digests. + +EVP_MD_CTX_init() initializes digest contet B<ctx>. + +EVP_MD_CTX_create() allocates, initializes and returns a digest contet. + +EVP_DigestInit_ex() sets up digest context B<ctx> to use a digest +B<type> from ENGINE B<impl>. B<ctx> must be initialized before calling this +function. B<type> will typically be supplied by a functionsuch as EVP_sha1(). +If B<impl> is NULL then the default implementation of digest B<type> is used. + +EVP_DigestUpdate() hashes B<cnt> bytes of data at B<d> into the +digest context B<ctx>. This function can be called several times on the +same B<ctx> to hash additional data. + +EVP_DigestFinal_ex() retrieves the digest value from B<ctx> and places +it in B<md>. If the B<s> parameter is not NULL then the number of +bytes of data written (i.e. the length of the digest) will be written +to the integer at B<s>, at most B<EVP_MAX_MD_SIZE> bytes will be written. +After calling EVP_DigestFinal_ex() no additional calls to EVP_DigestUpdate() +can be made, but EVP_DigestInit_ex() can be called to initialize a new +digest operation. + +EVP_MD_CTX_cleanup() cleans up digest context B<ctx>, it should be called +after a digest context is no longer needed. + +EVP_MD_CTX_destroy() cleans up digest context B<ctx> and frees up the +space allocated to it, it should be called only on a context created +using EVP_MD_CTX_create(). + +EVP_MD_CTX_copy_ex() can be used to copy the message digest state from +B<in> to B<out>. This is useful if large amounts of data are to be +hashed which only differ in the last few bytes. B<out> must be initialized +before calling this function. + +EVP_DigestInit() behaves in the same way as EVP_DigestInit_ex() except +the passed context B<ctx> does not have to be initialized, and it always +uses the default digest implementation. + +EVP_DigestFinal() is similar to EVP_DigestFinal_ex() except the digest +contet B<ctx> is automatically cleaned up. + +EVP_MD_CTX_copy() is similar to EVP_MD_CTX_copy_ex() except the destination +B<out> does not have to be initialized. + +EVP_MD_size() and EVP_MD_CTX_size() return the size of the message digest +when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure, i.e. the size of the +hash. + +EVP_MD_block_size() and EVP_MD_CTX_block_size() return the block size of the +message digest when passed an B<EVP_MD> or an B<EVP_MD_CTX> structure. + +EVP_MD_type() and EVP_MD_CTX_type() return the NID of the OBJECT IDENTIFIER +representing the given message digest when passed an B<EVP_MD> structure. +For example EVP_MD_type(EVP_sha1()) returns B<NID_sha1>. This function is +normally used when setting ASN1 OIDs. + +EVP_MD_CTX_md() returns the B<EVP_MD> structure corresponding to the passed +B<EVP_MD_CTX>. + +EVP_MD_pkey_type() returns the NID of the public key signing algorithm associated +with this digest. For example EVP_sha1() is associated with RSA so this will +return B<NID_sha1WithRSAEncryption>. This "link" between digests and signature +algorithms may not be retained in future versions of OpenSSL. + +EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), EVP_mdc2() and EVP_ripemd160() +return B<EVP_MD> structures for the MD2, MD5, SHA, SHA1, MDC2 and RIPEMD160 digest +algorithms respectively. The associated signature algorithm is RSA in each case. + +EVP_dss() and EVP_dss1() return B<EVP_MD> structures for SHA and SHA1 digest +algorithms but using DSS (DSA) for the signature algorithm. + +EVP_md_null() is a "null" message digest that does nothing: i.e. the hash it +returns is of zero length. + +EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj() +return an B<EVP_MD> structure when passed a digest name, a digest NID or +an ASN1_OBJECT structure respectively. The digest table must be initialized +using, for example, OpenSSL_add_all_digests() for these functions to work. + +=head1 RETURN VALUES + +EVP_DigestInit_ex(), EVP_DigestUpdate() and EVP_DigestFinal_ex() return 1 for +success and 0 for failure. + +EVP_MD_CTX_copy_ex() returns 1 if successful or 0 for failure. + +EVP_MD_type(), EVP_MD_pkey_type() and EVP_MD_type() return the NID of the +corresponding OBJECT IDENTIFIER or NID_undef if none exists. + +EVP_MD_size(), EVP_MD_block_size(), EVP_MD_CTX_size(e), EVP_MD_size(), +EVP_MD_CTX_block_size() and EVP_MD_block_size() return the digest or block +size in bytes. + +EVP_md_null(), EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), EVP_dss(), +EVP_dss1(), EVP_mdc2() and EVP_ripemd160() return pointers to the +corresponding EVP_MD structures. + +EVP_get_digestbyname(), EVP_get_digestbynid() and EVP_get_digestbyobj() +return either an B<EVP_MD> structure or NULL if an error occurs. + +=head1 NOTES + +The B<EVP> interface to message digests should almost always be used in +preference to the low level interfaces. This is because the code then becomes +transparent to the digest used and much more flexible. + +SHA1 is the digest of choice for new applications. The other digest algorithms +are still in common use. + +For most applications the B<impl> parameter to EVP_DigestInit_ex() will be +set to NULL to use the default digest implementation. + +The functions EVP_DigestInit(), EVP_DigestFinal() and EVP_MD_CTX_copy() are +obsolete but are retained to maintain compatibility with existing code. New +applications should use EVP_DigestInit_ex(), EVP_DigestFinal_ex() and +EVP_MD_CTX_copy_ex() because they can efficiently reuse a digest context +instead of initializing and cleaning it up on each call and allow non default +implementations of digests to be specified. + +In OpenSSL 0.9.7 and later if digest contexts are not cleaned up after use +memory leaks will occur. + +=head1 EXAMPLE + +This example digests the data "Test Message\n" and "Hello World\n", using the +digest name passed on the command line. + + #include <stdio.h> + #include <openssl/evp.h> + + main(int argc, char *argv[]) + { + EVP_MD_CTX mdctx; + const EVP_MD *md; + char mess1[] = "Test Message\n"; + char mess2[] = "Hello World\n"; + unsigned char md_value[EVP_MAX_MD_SIZE]; + int md_len, i; + + OpenSSL_add_all_digests(); + + if(!argv[1]) { + printf("Usage: mdtest digestname\n"); + exit(1); + } + + md = EVP_get_digestbyname(argv[1]); + + if(!md) { + printf("Unknown message digest %s\n", argv[1]); + exit(1); + } + + EVP_MD_CTX_init(&mdctx); + EVP_DigestInit_ex(&mdctx, md, NULL); + EVP_DigestUpdate(&mdctx, mess1, strlen(mess1)); + EVP_DigestUpdate(&mdctx, mess2, strlen(mess2)); + EVP_DigestFinal_ex(&mdctx, md_value, &md_len); + EVP_MD_CTX_cleanup(&mdctx); + + printf("Digest is: "); + for(i = 0; i < md_len; i++) printf("%02x", md_value[i]); + printf("\n"); + } + +=head1 BUGS + +The link between digests and signing algorithms results in a situation where +EVP_sha1() must be used with RSA and EVP_dss1() must be used with DSS +even though they are identical digests. + +=head1 SEE ALSO + +L<evp(3)|evp(3)>, L<hmac(3)|hmac(3)>, L<md2(3)|md2(3)>, +L<md5(3)|md5(3)>, L<mdc2(3)|mdc2(3)>, L<ripemd(3)|ripemd(3)>, +L<sha(3)|sha(3)>, L<dgst(1)|dgst(1)> + +=head1 HISTORY + +EVP_DigestInit(), EVP_DigestUpdate() and EVP_DigestFinal() are +available in all versions of SSLeay and OpenSSL. + +EVP_MD_CTX_init(), EVP_MD_CTX_create(), EVP_MD_CTX_copy_ex(), +EVP_MD_CTX_cleanup(), EVP_MD_CTX_destroy(), EVP_DigestInit_ex() +and EVP_DigestFinal_ex() were added in OpenSSL 0.9.7. + +EVP_md_null(), EVP_md2(), EVP_md5(), EVP_sha(), EVP_sha1(), +EVP_dss(), EVP_dss1(), EVP_mdc2() and EVP_ripemd160() were +changed to return truely const EVP_MD * in OpenSSL 0.9.7. + +=cut |