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Diffstat (limited to 'openssl/doc/crypto/PKCS7_verify.pod')
| -rw-r--r-- | openssl/doc/crypto/PKCS7_verify.pod | 116 |
1 files changed, 116 insertions, 0 deletions
diff --git a/openssl/doc/crypto/PKCS7_verify.pod b/openssl/doc/crypto/PKCS7_verify.pod new file mode 100644 index 000000000..3490b5dc8 --- /dev/null +++ b/openssl/doc/crypto/PKCS7_verify.pod @@ -0,0 +1,116 @@ +=pod + +=head1 NAME + +PKCS7_verify - verify a PKCS#7 signedData structure + +=head1 SYNOPSIS + +int PKCS7_verify(PKCS7 *p7, STACK_OF(X509) *certs, X509_STORE *store, BIO *indata, BIO *out, int flags); + +STACK_OF(X509) *PKCS7_get0_signers(PKCS7 *p7, STACK_OF(X509) *certs, int flags); + +=head1 DESCRIPTION + +PKCS7_verify() verifies a PKCS#7 signedData structure. B<p7> is the PKCS7 +structure to verify. B<certs> is a set of certificates in which to search for +the signer's certificate. B<store> is a trusted certficate store (used for +chain verification). B<indata> is the signed data if the content is not +present in B<p7> (that is it is detached). The content is written to B<out> +if it is not NULL. + +B<flags> is an optional set of flags, which can be used to modify the verify +operation. + +PKCS7_get0_signers() retrieves the signer's certificates from B<p7>, it does +B<not> check their validity or whether any signatures are valid. The B<certs> +and B<flags> parameters have the same meanings as in PKCS7_verify(). + +=head1 VERIFY PROCESS + +Normally the verify process proceeds as follows. + +Initially some sanity checks are performed on B<p7>. The type of B<p7> must +be signedData. There must be at least one signature on the data and if +the content is detached B<indata> cannot be B<NULL>. + +An attempt is made to locate all the signer's certificates, first looking in +the B<certs> parameter (if it is not B<NULL>) and then looking in any certificates +contained in the B<p7> structure itself. If any signer's certificates cannot be +located the operation fails. + +Each signer's certificate is chain verified using the B<smimesign> purpose and +the supplied trusted certificate store. Any internal certificates in the message +are used as untrusted CAs. If any chain verify fails an error code is returned. + +Finally the signed content is read (and written to B<out> is it is not NULL) and +the signature's checked. + +If all signature's verify correctly then the function is successful. + +Any of the following flags (ored together) can be passed in the B<flags> parameter +to change the default verify behaviour. Only the flag B<PKCS7_NOINTERN> is +meaningful to PKCS7_get0_signers(). + +If B<PKCS7_NOINTERN> is set the certificates in the message itself are not +searched when locating the signer's certificate. This means that all the signers +certificates must be in the B<certs> parameter. + +If the B<PKCS7_TEXT> flag is set MIME headers for type B<text/plain> are deleted +from the content. If the content is not of type B<text/plain> then an error is +returned. + +If B<PKCS7_NOVERIFY> is set the signer's certificates are not chain verified. + +If B<PKCS7_NOCHAIN> is set then the certificates contained in the message are +not used as untrusted CAs. This means that the whole verify chain (apart from +the signer's certificate) must be contained in the trusted store. + +If B<PKCS7_NOSIGS> is set then the signatures on the data are not checked. + +=head1 NOTES + +One application of B<PKCS7_NOINTERN> is to only accept messages signed by +a small number of certificates. The acceptable certificates would be passed +in the B<certs> parameter. In this case if the signer is not one of the +certificates supplied in B<certs> then the verify will fail because the +signer cannot be found. + +Care should be taken when modifying the default verify behaviour, for example +setting B<PKCS7_NOVERIFY|PKCS7_NOSIGS> will totally disable all verification +and any signed message will be considered valid. This combination is however +useful if one merely wishes to write the content to B<out> and its validity +is not considered important. + +Chain verification should arguably be performed using the signing time rather +than the current time. However since the signing time is supplied by the +signer it cannot be trusted without additional evidence (such as a trusted +timestamp). + +=head1 RETURN VALUES + +PKCS7_verify() returns 1 for a successful verification and zero or a negative +value if an error occurs. + +PKCS7_get0_signers() returns all signers or B<NULL> if an error occurred. + +The error can be obtained from L<ERR_get_error(3)|ERR_get_error(3)> + +=head1 BUGS + +The trusted certificate store is not searched for the signers certificate, +this is primarily due to the inadequacies of the current B<X509_STORE> +functionality. + +The lack of single pass processing and need to hold all data in memory as +mentioned in PKCS7_sign() also applies to PKCS7_verify(). + +=head1 SEE ALSO + +L<ERR_get_error(3)|ERR_get_error(3)>, L<PKCS7_sign(3)|PKCS7_sign(3)> + +=head1 HISTORY + +PKCS7_verify() was added to OpenSSL 0.9.5 + +=cut |