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1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
75394189 DSH |
5 | EVP_DigestVerifyInit, EVP_DigestVerifyUpdate, EVP_DigestVerifyFinal, |
6 | EVP_DigestVerify - EVP signature verification functions | |
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7 | |
8 | =head1 SYNOPSIS | |
9 | ||
10 | #include <openssl/evp.h> | |
11 | ||
12 | int EVP_DigestVerifyInit(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx, | |
e9b77246 | 13 | const EVP_MD *type, ENGINE *e, EVP_PKEY *pkey); |
8bdce8d1 | 14 | int EVP_DigestVerifyUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt); |
75394189 DSH |
15 | int EVP_DigestVerifyFinal(EVP_MD_CTX *ctx, const unsigned char *sig, |
16 | size_t siglen); | |
17 | int EVP_DigestVerify(EVP_MD_CTX *ctx, const unsigned char *sigret, | |
18 | size_t siglen, const unsigned char *tbs, size_t tbslen); | |
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19 | |
20 | =head1 DESCRIPTION | |
21 | ||
22 | The EVP signature routines are a high level interface to digital signatures. | |
23 | ||
24 | EVP_DigestVerifyInit() sets up verification context B<ctx> to use digest | |
0c714ba2 | 25 | B<type> from ENGINE B<e> and public key B<pkey>. B<ctx> must be created |
f097e875 | 26 | with EVP_MD_CTX_new() before calling this function. If B<pctx> is not NULL, the |
29cf84c6 | 27 | EVP_PKEY_CTX of the verification operation will be written to B<*pctx>: this |
f097e875 | 28 | can be used to set alternative verification options. Note that any existing |
675f4cee PY |
29 | value in B<*pctx> is overwritten. The EVP_PKEY_CTX value returned must not be freed |
30 | directly by the application if B<ctx> is not assigned an EVP_PKEY_CTX value before | |
4045f688 NT |
31 | being passed to EVP_DigestVerifyInit() (which means the EVP_PKEY_CTX is created |
32 | inside EVP_DigestVerifyInit() and it will be freed automatically when the | |
f097e875 | 33 | EVP_MD_CTX is freed). |
29cf84c6 | 34 | |
a5c83db4 | 35 | No B<EVP_PKEY_CTX> will be created by EVP_DigestSignInit() if the passed B<ctx> |
ca7c9828 | 36 | has already been assigned one via L<EVP_MD_CTX_set_pkey_ctx(3)>. See also L<SM2(7)>. |
675f4cee | 37 | |
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38 | EVP_DigestVerifyUpdate() hashes B<cnt> bytes of data at B<d> into the |
39 | verification context B<ctx>. This function can be called several times on the | |
40 | same B<ctx> to include additional data. This function is currently implemented | |
41 | using a macro. | |
42 | ||
43 | EVP_DigestVerifyFinal() verifies the data in B<ctx> against the signature in | |
44 | B<sig> of length B<siglen>. | |
45 | ||
27b138e9 | 46 | EVP_DigestVerify() verifies B<tbslen> bytes at B<tbs> against the signature |
75394189 DSH |
47 | in B<sig> of length B<siglen>. |
48 | ||
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49 | =head1 RETURN VALUES |
50 | ||
51 | EVP_DigestVerifyInit() and EVP_DigestVerifyUpdate() return 1 for success and 0 | |
c03726ca | 52 | for failure. |
29cf84c6 | 53 | |
75394189 DSH |
54 | EVP_DigestVerifyFinal() and EVP_DigestVerify() return 1 for success; any other |
55 | value indicates failure. A return value of zero indicates that the signature | |
56 | did not verify successfully (that is, B<tbs> did not match the original data or | |
57 | the signature had an invalid form), while other values indicate a more serious | |
58 | error (and sometimes also indicate an invalid signature form). | |
29cf84c6 | 59 | |
9b86974e | 60 | The error codes can be obtained from L<ERR_get_error(3)>. |
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61 | |
62 | =head1 NOTES | |
63 | ||
64 | The B<EVP> interface to digital signatures should almost always be used in | |
65 | preference to the low level interfaces. This is because the code then becomes | |
66 | transparent to the algorithm used and much more flexible. | |
67 | ||
27b138e9 | 68 | EVP_DigestVerify() is a one shot operation which verifies a single block of |
74e78361 DSH |
69 | data in one function. For algorithms that support streaming it is equivalent |
70 | to calling EVP_DigestVerifyUpdate() and EVP_DigestVerifyFinal(). For | |
71 | algorithms which do not support streaming (e.g. PureEdDSA) it is the only way | |
72 | to verify data. | |
75394189 | 73 | |
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74 | In previous versions of OpenSSL there was a link between message digest types |
75 | and public key algorithms. This meant that "clone" digests such as EVP_dss1() | |
76 | needed to be used to sign using SHA1 and DSA. This is no longer necessary and | |
77 | the use of clone digest is now discouraged. | |
78 | ||
f987a4dd DMSP |
79 | For some key types and parameters the random number generator must be seeded. |
80 | If the automatic seeding or reseeding of the OpenSSL CSPRNG fails due to | |
81 | external circumstances (see L<RAND(7)>), the operation will fail. | |
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82 | |
83 | The call to EVP_DigestVerifyFinal() internally finalizes a copy of the digest | |
2dd8cb3b | 84 | context. This means that EVP_VerifyUpdate() and EVP_VerifyFinal() can |
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85 | be called later to digest and verify additional data. |
86 | ||
fa332bba | 87 | Since only a copy of the digest context is ever finalized, the context must |
c12a2d27 | 88 | be cleaned up after use by calling EVP_MD_CTX_free() or a memory leak |
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89 | will occur. |
90 | ||
91 | =head1 SEE ALSO | |
92 | ||
9b86974e | 93 | L<EVP_DigestSignInit(3)>, |
73fb82b7 | 94 | L<EVP_DigestInit(3)>, |
b97fdb57 RL |
95 | L<evp(7)>, L<HMAC(3)>, L<MD2(3)>, |
96 | L<MD5(3)>, L<MDC2(3)>, L<RIPEMD160(3)>, | |
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97 | L<SHA1(3)>, L<dgst(1)>, |
98 | L<RAND(7)> | |
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99 | |
100 | =head1 HISTORY | |
101 | ||
1bc74519 | 102 | EVP_DigestVerifyInit(), EVP_DigestVerifyUpdate() and EVP_DigestVerifyFinal() |
df75c2bf | 103 | were added in OpenSSL 1.0.0. |
29cf84c6 | 104 | |
e2f92610 RS |
105 | =head1 COPYRIGHT |
106 | ||
35fd9953 | 107 | Copyright 2006-2019 The OpenSSL Project Authors. All Rights Reserved. |
e2f92610 RS |
108 | |
109 | Licensed under the OpenSSL license (the "License"). You may not use | |
110 | this file except in compliance with the License. You can obtain a copy | |
111 | in the file LICENSE in the source distribution or at | |
112 | L<https://www.openssl.org/source/license.html>. | |
113 | ||
114 | =cut |