5 PKCS7_verify, PKCS7_get0_signers - verify a PKCS#7 signedData structure
9 #include <openssl/pkcs7.h>
11 int PKCS7_verify(PKCS7 *p7, STACK_OF(X509) *certs, X509_STORE *store, BIO *indata, BIO *out, int flags);
13 STACK_OF(X509) *PKCS7_get0_signers(PKCS7 *p7, STACK_OF(X509) *certs, int flags);
17 PKCS7_verify() verifies a PKCS#7 signedData structure. B<p7> is the PKCS7
18 structure to verify. B<certs> is a set of certificates in which to search for
19 the signer's certificate. B<store> is a trusted certificate store (used for
20 chain verification). B<indata> is the signed data if the content is not
21 present in B<p7> (that is it is detached). The content is written to B<out>
24 B<flags> is an optional set of flags, which can be used to modify the verify
27 PKCS7_get0_signers() retrieves the signer's certificates from B<p7>, it does
28 B<not> check their validity or whether any signatures are valid. The B<certs>
29 and B<flags> parameters have the same meanings as in PKCS7_verify().
33 Normally the verify process proceeds as follows.
35 Initially some sanity checks are performed on B<p7>. The type of B<p7> must
36 be signedData. There must be at least one signature on the data and if
37 the content is detached B<indata> cannot be B<NULL>. If the content is
38 not detached and B<indata> is not B<NULL>, then the structure has both
39 embedded and external content. To treat this as an error, use the flag
40 B<PKCS7_NO_DUAL_CONTENT>.
41 The default behavior allows this, for compatibility with older
44 An attempt is made to locate all the signer's certificates, first looking in
45 the B<certs> parameter (if it is not B<NULL>) and then looking in any certificates
46 contained in the B<p7> structure itself. If any signer's certificates cannot be
47 located the operation fails.
49 Each signer's certificate is chain verified using the B<smimesign> purpose and
50 the supplied trusted certificate store. Any internal certificates in the message
51 are used as untrusted CAs. If any chain verify fails an error code is returned.
53 Finally the signed content is read (and written to B<out> is it is not NULL) and
54 the signature's checked.
56 If all signature's verify correctly then the function is successful.
58 Any of the following flags (ored together) can be passed in the B<flags> parameter
59 to change the default verify behaviour. Only the flag B<PKCS7_NOINTERN> is
60 meaningful to PKCS7_get0_signers().
62 If B<PKCS7_NOINTERN> is set the certificates in the message itself are not
63 searched when locating the signer's certificate. This means that all the signers
64 certificates must be in the B<certs> parameter.
66 If the B<PKCS7_TEXT> flag is set MIME headers for type B<text/plain> are deleted
67 from the content. If the content is not of type B<text/plain> then an error is
70 If B<PKCS7_NOVERIFY> is set the signer's certificates are not chain verified.
72 If B<PKCS7_NOCHAIN> is set then the certificates contained in the message are
73 not used as untrusted CAs. This means that the whole verify chain (apart from
74 the signer's certificate) must be contained in the trusted store.
76 If B<PKCS7_NOSIGS> is set then the signatures on the data are not checked.
80 One application of B<PKCS7_NOINTERN> is to only accept messages signed by
81 a small number of certificates. The acceptable certificates would be passed
82 in the B<certs> parameter. In this case if the signer is not one of the
83 certificates supplied in B<certs> then the verify will fail because the
84 signer cannot be found.
86 Care should be taken when modifying the default verify behaviour, for example
87 setting B<PKCS7_NOVERIFY|PKCS7_NOSIGS> will totally disable all verification
88 and any signed message will be considered valid. This combination is however
89 useful if one merely wishes to write the content to B<out> and its validity
90 is not considered important.
92 Chain verification should arguably be performed using the signing time rather
93 than the current time. However since the signing time is supplied by the
94 signer it cannot be trusted without additional evidence (such as a trusted
99 PKCS7_verify() returns one for a successful verification and zero
102 PKCS7_get0_signers() returns all signers or B<NULL> if an error occurred.
104 The error can be obtained from L<ERR_get_error(3)>
108 The trusted certificate store is not searched for the signers certificate,
109 this is primarily due to the inadequacies of the current B<X509_STORE>
112 The lack of single pass processing and need to hold all data in memory as
113 mentioned in PKCS7_sign() also applies to PKCS7_verify().
117 L<ERR_get_error(3)>, L<PKCS7_sign(3)>
121 Copyright 2002-2016 The OpenSSL Project Authors. All Rights Reserved.
123 Licensed under the OpenSSL license (the "License"). You may not use
124 this file except in compliance with the License. You can obtain a copy
125 in the file LICENSE in the source distribution or at
126 L<https://www.openssl.org/source/license.html>.