1=pod 2 3=head1 NAME 4 5PKCS7_verify - verify a PKCS#7 signedData structure 6 7=head1 SYNOPSIS 8 9int PKCS7_verify(PKCS7 *p7, STACK_OF(X509) *certs, X509_STORE *store, BIO *indata, BIO *out, int flags); 10 11int PKCS7_get0_signers(PKCS7 *p7, STACK_OF(X509) *certs, int flags); 12 13=head1 DESCRIPTION 14 15PKCS7_verify() verifies a PKCS#7 signedData structure. B<p7> is the PKCS7 16structure to verify. B<certs> is a set of certificates in which to search for 17the signer's certificate. B<store> is a trusted certficate store (used for 18chain verification). B<indata> is the signed data if the content is not 19present in B<p7> (that is it is detached). The content is written to B<out> 20if it is not NULL. 21 22B<flags> is an optional set of flags, which can be used to modify the verify 23operation. 24 25PKCS7_get0_signers() retrieves the signer's certificates from B<p7>, it does 26B<not> check their validity or whether any signatures are valid. The B<certs> 27and B<flags> parameters have the same meanings as in PKCS7_verify(). 28 29=head1 VERIFY PROCESS 30 31Normally the verify process proceeds as follows. 32 33Initially some sanity checks are performed on B<p7>. The type of B<p7> must 34be signedData. There must be at least one signature on the data and if 35the content is detached B<indata> cannot be B<NULL>. 36 37An attempt is made to locate all the signer's certificates, first looking in 38the B<certs> parameter (if it is not B<NULL>) and then looking in any certificates 39contained in the B<p7> structure itself. If any signer's certificates cannot be 40located the operation fails. 41 42Each signer's certificate is chain verified using the B<smimesign> purpose and 43the supplied trusted certificate store. Any internal certificates in the message 44are used as untrusted CAs. If any chain verify fails an error code is returned. 45 46Finally the signed content is read (and written to B<out> is it is not NULL) and 47the signature's checked. 48 49If all signature's verify correctly then the function is successful. 50 51Any of the following flags (ored together) can be passed in the B<flags> parameter 52to change the default verify behaviour. Only the flag B<PKCS7_NOINTERN> is 53meaningful to PKCS7_get0_signers(). 54 55If B<PKCS7_NOINTERN> is set the certificates in the message itself are not 56searched when locating the signer's certificate. This means that all the signers 57certificates must be in the B<certs> parameter. 58 59If the B<PKCS7_TEXT> flag is set MIME headers for type B<text/plain> are deleted 60from the content. If the content is not of type B<text/plain> then an error is 61returned. 62 63If B<PKCS7_NOVERIFY> is set the signer's certificates are not chain verified. 64 65If B<PKCS7_NOCHAIN> is set then the certificates contained in the message are 66not used as untrusted CAs. This means that the whole verify chain (apart from 67the signer's certificate) must be contained in the trusted store. 68 69If B<PKCS7_NOSIGS> is set then the signatures on the data are not checked. 70 71=head1 NOTES 72 73One application of B<PKCS7_NOINTERN> is to only accept messages signed by 74a small number of certificates. The acceptable certificates would be passed 75in the B<certs> parameter. In this case if the signer is not one of the 76certificates supplied in B<certs> then the verify will fail because the 77signer cannot be found. 78 79Care should be taken when modifying the default verify behaviour, for example 80setting B<PKCS7_NOVERIFY|PKCS7_NOSIGS> will totally disable all verification 81and any signed message will be considered valid. This combination is however 82useful if one merely wishes to write the content to B<out> and its validity 83is not considered important. 84 85Chain verification should arguably be performed using the signing time rather 86than the current time. However since the signing time is supplied by the 87signer it cannot be trusted without additional evidence (such as a trusted 88timestamp). 89 90=head1 RETURN VALUES 91 92PKCS7_verify() returns 1 for a successful verification and zero or a negative 93value if an error occurs. 94 95PKCS7_get0_signers() returns all signers or B<NULL> if an error occurred. 96 97The error can be obtained from L<ERR_get_error(3)|ERR_get_error(3)> 98 99=head1 BUGS 100 101The trusted certificate store is not searched for the signers certificate, 102this is primarily due to the inadequacies of the current B<X509_STORE> 103functionality. 104 105The lack of single pass processing and need to hold all data in memory as 106mentioned in PKCS7_sign() also applies to PKCS7_verify(). 107 108=head1 SEE ALSO 109 110L<ERR_get_error(3)|ERR_get_error(3)>, L<PKCS7_sign(3)|PKCS7_sign(3)> 111 112=head1 HISTORY 113 114PKCS7_verify() was added to OpenSSL 0.9.5 115 116=cut 117