1CMS_VERIFY(3ossl) OpenSSL CMS_VERIFY(3ossl)
2
6 CMS_verify, CMS_get0_signers - verify a CMS SignedData structure
7
9 #include <openssl/cms.h>
10 int CMS_verify(CMS_ContentInfo *cms, STACK_OF(X509) *certs, X509_STORE *store,
12 BIO *indata, BIO *out, unsigned int flags);
13 STACK_OF(X509) *CMS_get0_signers(CMS_ContentInfo *cms);
15
17 CMS_verify() is very similar to PKCS7_verify(3). It verifies a CMS
18 SignedData structure contained in a structure of type CMS_ContentInfo.
19 cms points to the CMS_ContentInfo structure to verify. The optional
20 certs parameter refers to a set of certificates in which to search for
21 signing certificates. cms may contain extra untrusted CA certificates
22 that may be used for chain building as well as CRLs that may be used
23 for certificate validation. store may be NULL or point to the trusted
24 certificate store to use for chain verification. indata refers to the
25 signed data if the content is detached from cms. Otherwise indata
26 should be NULL and the signed data must be in cms. The content is
27 written to the BIO out unless it is NULL. flags is an optional set of
28 flags, which can be used to modify the operation.
29 CMS_get0_signers() retrieves the signing certificate(s) from cms, it
31 may only be called after a successful CMS_verify() operation.
32
34 Normally the verify process proceeds as follows.
35 Initially some sanity checks are performed on cms. The type of cms must
37 be SignedData. There must be at least one signature on the data and if
38 the content is detached indata cannot be NULL.
39 An attempt is made to locate all the signing certificate(s), first
41 looking in the certs parameter (if it is not NULL) and then looking in
42 any certificates contained in the cms structure unless CMS_NOINTERN is
43 set. If any signing certificate cannot be located the operation fails.
44 Each signing certificate is chain verified using the smimesign purpose
46 and using the trusted certificate store store if supplied. Any
47 internal certificates in the message, which may have been added using
48 CMS_add1_cert(3), are used as untrusted CAs. If CRL checking is
49 enabled in store and CMS_NOCRL is not set, any internal CRLs, which may
50 have been added using CMS_add1_crl(3), are used in addition to
51 attempting to look them up in store. If store is not NULL and any
52 chain verify fails an error code is returned.
53 Finally the signed content is read (and written to out unless it is
55 NULL) and the signature is checked.
56 If all signatures verify correctly then the function is successful.
58 Any of the following flags (ored together) can be passed in the flags
60 parameter to change the default verify behaviour.
61 If CMS_NOINTERN is set the certificates in the message itself are not
63 searched when locating the signing certificate(s). This means that all
64 the signing certificates must be in the certs parameter.
65 If CMS_NOCRL is set and CRL checking is enabled in store then any CRLs
67 in the message itself are ignored.
68 If the CMS_TEXT flag is set MIME headers for type text/plain are
70 deleted from the content. If the content is not of type text/plain then
71 an error is returned.
72 If CMS_NO_SIGNER_CERT_VERIFY is set the signing certificates are not
74 chain verified, unless CMS_CADES flag is also set.
75 If CMS_NO_ATTR_VERIFY is set the signed attributes signature is not
77 verified, unless CMS_CADES flag is also set.
78 If CMS_CADES is set, each signer certificate is checked against the ESS
80 signingCertificate or ESS signingCertificateV2 extension that is
81 required in the signed attributes of the signature.
82 If CMS_NO_CONTENT_VERIFY is set then the content digest is not checked.
84
86 One application of CMS_NOINTERN is to only accept messages signed by a
87 small number of certificates. The acceptable certificates would be
88 passed in the certs parameter. In this case if the signer certificate
89 is not one of the certificates supplied in certs then the verify will
90 fail because the signer cannot be found.
91 In some cases the standard techniques for looking up and validating
93 certificates are not appropriate: for example an application may wish
94 to lookup certificates in a database or perform customised
95 verification. This can be achieved by setting and verifying the signer
96 certificates manually using the signed data utility functions.
97 Care should be taken when modifying the default verify behaviour, for
99 example setting CMS_NO_CONTENT_VERIFY will totally disable all content
100 verification and any modified content will be considered valid. This
101 combination is however useful if one merely wishes to write the content
102 to out and its validity is not considered important.
103 Chain verification should arguably be performed using the signing time
105 rather than the current time. However, since the signing time is
106 supplied by the signer it cannot be trusted without additional evidence
107 (such as a trusted timestamp).
108
110 CMS_verify() returns 1 for a successful verification and 0 if an error
111 occurred.
112 CMS_get0_signers() returns all signers or NULL if an error occurred.
114 The error can be obtained from ERR_get_error(3)
116
118 The trusted certificate store is not searched for the signing
119 certificate. This is primarily due to the inadequacies of the current
120 X509_STORE functionality.
121 The lack of single pass processing means that the signed content must
123 all be held in memory if it is not detached.
124
126 PKCS7_verify(3), CMS_add1_cert(3), CMS_add1_crl(3),
127 OSSL_ESS_check_signing_certs(3), ERR_get_error(3), CMS_sign(3)
128
130 Copyright 2008-2022 The OpenSSL Project Authors. All Rights Reserved.
131 Licensed under the Apache License 2.0 (the "License"). You may not use
133 this file except in compliance with the License. You can obtain a copy
134 in the file LICENSE in the source distribution or at
135 <https://www.openssl.org/source/license.html>.
1363.1.1 2023-08-31 CMS_VERIFY(3ossl)