5 CMS_verify, CMS_get0_signers - verify a CMS SignedData structure
9 #include <openssl/cms.h>
11 int CMS_verify(CMS_ContentInfo *cms, STACK_OF(X509) *certs, X509_STORE *store,
12 BIO *indata, BIO *out, unsigned int flags);
14 STACK_OF(X509) *CMS_get0_signers(CMS_ContentInfo *cms);
18 CMS_verify() verifies a CMS SignedData structure. B<cms> is the CMS_ContentInfo
19 structure to verify. B<certs> is a set of certificates in which to search for
20 the signing certificate(s). B<store> is a trusted certificate store used for
21 chain verification. B<indata> is the detached content if the content is not
22 present in B<cms>. The content is written to B<out> if it is not NULL.
24 B<flags> is an optional set of flags, which can be used to modify the verify
27 CMS_get0_signers() retrieves the signing certificate(s) from B<cms>, it may only
28 be called after a successful CMS_verify() operation.
32 Normally the verify process proceeds as follows.
34 Initially some sanity checks are performed on B<cms>. The type of B<cms> must
35 be SignedData. There must be at least one signature on the data and if
36 the content is detached B<indata> cannot be B<NULL>.
38 An attempt is made to locate all the signing certificate(s), first looking in
39 the B<certs> parameter (if it is not NULL) and then looking in any
40 certificates contained in the B<cms> structure itself. If any signing
41 certificate cannot be located the operation fails.
43 Each signing certificate is chain verified using the B<smimesign> purpose and
44 the supplied trusted certificate store. Any internal certificates in the message
45 are used as untrusted CAs. If CRL checking is enabled in B<store> any internal
46 CRLs are used in addition to attempting to look them up in B<store>. If any
47 chain verify fails an error code is returned.
49 Finally the signed content is read (and written to B<out> if it is not NULL)
50 and the signature's checked.
52 If all signature's verify correctly then the function is successful.
54 Any of the following flags (ored together) can be passed in the B<flags>
55 parameter to change the default verify behaviour.
57 If B<CMS_NOINTERN> is set the certificates in the message itself are not
58 searched when locating the signing certificate(s). This means that all the
59 signing certificates must be in the B<certs> parameter.
61 If B<CMS_NOCRL> is set and CRL checking is enabled in B<store> then any
62 CRLs in the message itself are ignored.
64 If the B<CMS_TEXT> flag is set MIME headers for type B<text/plain> are deleted
65 from the content. If the content is not of type B<text/plain> then an error is
68 If B<CMS_NO_SIGNER_CERT_VERIFY> is set the signing certificates are not
69 verified, unless CMS_CADES flag is also set.
71 If B<CMS_NO_ATTR_VERIFY> is set the signed attributes signature is not
72 verified, unless CMS_CADES flag is also set.
74 If B<CMS_CADES> is set, each signer certificate is checked against the
75 "ESS signing-certificate" extension added in the signed attributes of the
78 If B<CMS_NO_CONTENT_VERIFY> is set then the content digest is not checked.
82 One application of B<CMS_NOINTERN> is to only accept messages signed by
83 a small number of certificates. The acceptable certificates would be passed
84 in the B<certs> parameter. In this case if the signer is not one of the
85 certificates supplied in B<certs> then the verify will fail because the
86 signer cannot be found.
88 In some cases the standard techniques for looking up and validating
89 certificates are not appropriate: for example an application may wish to
90 lookup certificates in a database or perform customised verification. This
91 can be achieved by setting and verifying the signers certificates manually
92 using the signed data utility functions.
94 Care should be taken when modifying the default verify behaviour, for example
95 setting B<CMS_NO_CONTENT_VERIFY> will totally disable all content verification
96 and any modified content will be considered valid. This combination is however
97 useful if one merely wishes to write the content to B<out> and its validity
98 is not considered important.
100 Chain verification should arguably be performed using the signing time rather
101 than the current time. However, since the signing time is supplied by the
102 signer it cannot be trusted without additional evidence (such as a trusted
107 CMS_verify() returns 1 for a successful verification and zero if an error
110 CMS_get0_signers() returns all signers or NULL if an error occurred.
112 The error can be obtained from L<ERR_get_error(3)>
116 The trusted certificate store is not searched for the signing certificate,
117 this is primarily due to the inadequacies of the current B<X509_STORE>
120 The lack of single pass processing means that the signed content must all
121 be held in memory if it is not detached.
125 L<ERR_get_error(3)>, L<CMS_sign(3)>
129 Copyright 2008-2020 The OpenSSL Project Authors. All Rights Reserved.
131 Licensed under the Apache License 2.0 (the "License"). You may not use
132 this file except in compliance with the License. You can obtain a copy
133 in the file LICENSE in the source distribution or at
134 L<https://www.openssl.org/source/license.html>.