1=pod 2 3=head1 NAME 4 5PKCS7_verify, PKCS7_get0_signers - verify a PKCS#7 signedData structure 6 7=head1 SYNOPSIS 8 9 #include <openssl/pkcs7.h> 10 11 int PKCS7_verify(PKCS7 *p7, STACK_OF(X509) *certs, X509_STORE *store, 12 BIO *indata, BIO *out, int flags); 13 14 STACK_OF(X509) *PKCS7_get0_signers(PKCS7 *p7, STACK_OF(X509) *certs, int flags); 15 16=head1 DESCRIPTION 17 18PKCS7_verify() verifies a PKCS#7 signedData structure. B<p7> is the PKCS7 19structure to verify. B<certs> is a set of certificates in which to search for 20the signer's certificate. B<store> is a trusted certificate store (used for 21chain verification). B<indata> is the signed data if the content is not 22present in B<p7> (that is it is detached). The content is written to B<out> 23if it is not NULL. 24 25B<flags> is an optional set of flags, which can be used to modify the verify 26operation. 27 28PKCS7_get0_signers() retrieves the signer's certificates from B<p7>, it does 29B<not> check their validity or whether any signatures are valid. The B<certs> 30and B<flags> parameters have the same meanings as in PKCS7_verify(). 31 32=head1 VERIFY PROCESS 33 34Normally the verify process proceeds as follows. 35 36Initially some sanity checks are performed on B<p7>. The type of B<p7> must 37be signedData. There must be at least one signature on the data and if 38the content is detached B<indata> cannot be B<NULL>. If the content is 39not detached and B<indata> is not B<NULL>, then the structure has both 40embedded and external content. To treat this as an error, use the flag 41B<PKCS7_NO_DUAL_CONTENT>. 42The default behavior allows this, for compatibility with older 43versions of OpenSSL. 44 45An attempt is made to locate all the signer's certificates, first looking in 46the B<certs> parameter (if it is not B<NULL>) and then looking in any certificates 47contained in the B<p7> structure itself. If any signer's certificates cannot be 48located the operation fails. 49 50Each signer's certificate is chain verified using the B<smimesign> purpose and 51the supplied trusted certificate store. Any internal certificates in the message 52are used as untrusted CAs. If any chain verify fails an error code is returned. 53 54Finally the signed content is read (and written to B<out> is it is not NULL) and 55the signature's checked. 56 57If all signature's verify correctly then the function is successful. 58 59Any of the following flags (ored together) can be passed in the B<flags> parameter 60to change the default verify behaviour. Only the flag B<PKCS7_NOINTERN> is 61meaningful to PKCS7_get0_signers(). 62 63If B<PKCS7_NOINTERN> is set the certificates in the message itself are not 64searched when locating the signer's certificate. This means that all the signers 65certificates must be in the B<certs> parameter. 66 67If the B<PKCS7_TEXT> flag is set MIME headers for type B<text/plain> are deleted 68from the content. If the content is not of type B<text/plain> then an error is 69returned. 70 71If B<PKCS7_NOVERIFY> is set the signer's certificates are not chain verified. 72 73If B<PKCS7_NOCHAIN> is set then the certificates contained in the message are 74not used as untrusted CAs. This means that the whole verify chain (apart from 75the signer's certificate) must be contained in the trusted store. 76 77If B<PKCS7_NOSIGS> is set then the signatures on the data are not checked. 78 79=head1 NOTES 80 81One application of B<PKCS7_NOINTERN> is to only accept messages signed by 82a small number of certificates. The acceptable certificates would be passed 83in the B<certs> parameter. In this case if the signer is not one of the 84certificates supplied in B<certs> then the verify will fail because the 85signer cannot be found. 86 87Care should be taken when modifying the default verify behaviour, for example 88setting B<PKCS7_NOVERIFY|PKCS7_NOSIGS> will totally disable all verification 89and any signed message will be considered valid. This combination is however 90useful if one merely wishes to write the content to B<out> and its validity 91is not considered important. 92 93Chain verification should arguably be performed using the signing time rather 94than the current time. However, since the signing time is supplied by the 95signer it cannot be trusted without additional evidence (such as a trusted 96timestamp). 97 98=head1 RETURN VALUES 99 100PKCS7_verify() returns one for a successful verification and zero 101if an error occurs. 102 103PKCS7_get0_signers() returns all signers or B<NULL> if an error occurred. 104 105The error can be obtained from L<ERR_get_error(3)> 106 107=head1 BUGS 108 109The trusted certificate store is not searched for the signers certificate, 110this is primarily due to the inadequacies of the current B<X509_STORE> 111functionality. 112 113The lack of single pass processing and need to hold all data in memory as 114mentioned in PKCS7_sign() also applies to PKCS7_verify(). 115 116=head1 SEE ALSO 117 118L<ERR_get_error(3)>, L<PKCS7_sign(3)> 119 120=head1 COPYRIGHT 121 122Copyright 2002-2020 The OpenSSL Project Authors. All Rights Reserved. 123 124Licensed under the OpenSSL license (the "License"). You may not use 125this file except in compliance with the License. You can obtain a copy 126in the file LICENSE in the source distribution or at 127L<https://www.openssl.org/source/license.html>. 128 129=cut 130