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1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
aafbe1cc | 5 | PKCS7_verify, PKCS7_get0_signers - verify a PKCS#7 signedData structure |
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6 | |
7 | =head1 SYNOPSIS | |
8 | ||
c264592d | 9 | #include <openssl/pkcs7.h> |
7e9db7ce | 10 | |
c264592d UM |
11 | int PKCS7_verify(PKCS7 *p7, STACK_OF(X509) *certs, X509_STORE *store, BIO *indata, BIO *out, int flags); |
12 | ||
13 | STACK_OF(X509) *PKCS7_get0_signers(PKCS7 *p7, STACK_OF(X509) *certs, int flags); | |
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14 | |
15 | =head1 DESCRIPTION | |
16 | ||
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 certficate 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> | |
22 | if it is not NULL. | |
23 | ||
24 | B<flags> is an optional set of flags, which can be used to modify the verify | |
25 | operation. | |
26 | ||
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(). | |
30 | ||
31 | =head1 VERIFY PROCESS | |
32 | ||
33 | Normally the verify process proceeds as follows. | |
34 | ||
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>. | |
38 | ||
39 | An attempt is made to locate all the signer's certificates, first looking in | |
40 | the B<certs> parameter (if it is not B<NULL>) and then looking in any certificates | |
41 | contained in the B<p7> structure itself. If any signer's certificates cannot be | |
42 | located the operation fails. | |
43 | ||
44 | Each signer's certificate is chain verified using the B<smimesign> purpose and | |
45 | the supplied trusted certificate store. Any internal certificates in the message | |
46 | are used as untrusted CAs. If any chain verify fails an error code is returned. | |
47 | ||
48 | Finally the signed content is read (and written to B<out> is it is not NULL) and | |
49 | the signature's checked. | |
50 | ||
51 | If all signature's verify correctly then the function is successful. | |
52 | ||
53 | Any of the following flags (ored together) can be passed in the B<flags> parameter | |
54 | to change the default verify behaviour. Only the flag B<PKCS7_NOINTERN> is | |
55 | meaningful to PKCS7_get0_signers(). | |
56 | ||
57 | If B<PKCS7_NOINTERN> is set the certificates in the message itself are not | |
58 | searched when locating the signer's certificate. This means that all the signers | |
59 | certificates must be in the B<certs> parameter. | |
60 | ||
61 | If the B<PKCS7_TEXT> flag is set MIME headers for type B<text/plain> are deleted | |
62 | from the content. If the content is not of type B<text/plain> then an error is | |
63 | returned. | |
64 | ||
65 | If B<PKCS7_NOVERIFY> is set the signer's certificates are not chain verified. | |
66 | ||
67 | If B<PKCS7_NOCHAIN> is set then the certificates contained in the message are | |
68 | not used as untrusted CAs. This means that the whole verify chain (apart from | |
69 | the signer's certificate) must be contained in the trusted store. | |
70 | ||
71 | If B<PKCS7_NOSIGS> is set then the signatures on the data are not checked. | |
72 | ||
73 | =head1 NOTES | |
74 | ||
75 | One application of B<PKCS7_NOINTERN> is to only accept messages signed by | |
76 | a small number of certificates. The acceptable certificates would be passed | |
77 | in the B<certs> parameter. In this case if the signer is not one of the | |
78 | certificates supplied in B<certs> then the verify will fail because the | |
79 | signer cannot be found. | |
80 | ||
81 | Care should be taken when modifying the default verify behaviour, for example | |
82 | setting B<PKCS7_NOVERIFY|PKCS7_NOSIGS> will totally disable all verification | |
83 | and any signed message will be considered valid. This combination is however | |
84 | useful if one merely wishes to write the content to B<out> and its validity | |
85 | is not considered important. | |
86 | ||
87 | Chain verification should arguably be performed using the signing time rather | |
88 | than the current time. However since the signing time is supplied by the | |
89 | signer it cannot be trusted without additional evidence (such as a trusted | |
90 | timestamp). | |
91 | ||
92 | =head1 RETURN VALUES | |
93 | ||
94 | PKCS7_verify() returns 1 for a successful verification and zero or a negative | |
95 | value if an error occurs. | |
96 | ||
97 | PKCS7_get0_signers() returns all signers or B<NULL> if an error occurred. | |
98 | ||
99 | The error can be obtained from L<ERR_get_error(3)|ERR_get_error(3)> | |
100 | ||
101 | =head1 BUGS | |
102 | ||
103 | The trusted certificate store is not searched for the signers certificate, | |
104 | this is primarily due to the inadequacies of the current B<X509_STORE> | |
105 | functionality. | |
106 | ||
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107 | The lack of single pass processing and need to hold all data in memory as |
108 | mentioned in PKCS7_sign() also applies to PKCS7_verify(). | |
109 | ||
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110 | =head1 SEE ALSO |
111 | ||
112 | L<ERR_get_error(3)|ERR_get_error(3)>, L<PKCS7_sign(3)|PKCS7_sign(3)> | |
113 | ||
114 | =head1 HISTORY | |
115 | ||
4e1b50e2 | 116 | PKCS7_verify() was added to OpenSSL 0.9.5 |
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117 | |
118 | =cut |