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1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
75394189 DSH |
5 | EVP_DigestSignInit, EVP_DigestSignUpdate, EVP_DigestSignFinal, |
6 | EVP_DigestSign - EVP signing functions | |
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7 | |
8 | =head1 SYNOPSIS | |
9 | ||
10 | #include <openssl/evp.h> | |
11 | ||
12 | int EVP_DigestSignInit(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx, | |
1bc74519 | 13 | const EVP_MD *type, ENGINE *e, EVP_PKEY *pkey); |
8bdce8d1 | 14 | int EVP_DigestSignUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt); |
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15 | int EVP_DigestSignFinal(EVP_MD_CTX *ctx, unsigned char *sig, size_t *siglen); |
16 | ||
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17 | int EVP_DigestSign(EVP_MD_CTX *ctx, unsigned char *sigret, |
18 | size_t *siglen, const unsigned char *tbs, | |
19 | size_t tbslen); | |
20 | ||
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21 | =head1 DESCRIPTION |
22 | ||
23 | The EVP signature routines are a high level interface to digital signatures. | |
24 | ||
25 | EVP_DigestSignInit() sets up signing context B<ctx> to use digest B<type> from | |
0c714ba2 | 26 | ENGINE B<e> and private key B<pkey>. B<ctx> must be created with |
25191fff | 27 | EVP_MD_CTX_new() before calling this function. If B<pctx> is not NULL the |
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28 | EVP_PKEY_CTX of the signing operation will be written to B<*pctx>: this can |
29 | be used to set alternative signing options. | |
30 | ||
31 | EVP_DigestSignUpdate() hashes B<cnt> bytes of data at B<d> into the | |
32 | signature context B<ctx>. This function can be called several times on the | |
33 | same B<ctx> to include additional data. This function is currently implemented | |
186bb907 | 34 | using a macro. |
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35 | |
36 | EVP_DigestSignFinal() signs the data in B<ctx> places the signature in B<sig>. | |
37 | If B<sig> is B<NULL> then the maximum size of the output buffer is written to | |
38 | the B<siglen> parameter. If B<sig> is not B<NULL> then before the call the | |
39 | B<siglen> parameter should contain the length of the B<sig> buffer, if the | |
40 | call is successful the signature is written to B<sig> and the amount of data | |
41 | written to B<siglen>. | |
42 | ||
75394189 | 43 | EVP_DigestSign() signs B<tbslen> bytes of data at B<tbs> and places the |
27b138e9 | 44 | signature in B<sig> and its length in B<siglen> in a similar way to |
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45 | EVP_DigestSignFinal(). |
46 | ||
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47 | =head1 RETURN VALUES |
48 | ||
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49 | EVP_DigestSignInit(), EVP_DigestSignUpdate(), EVP_DigestSignaFinal() and |
50 | EVP_DigestSign() return 1 for success and 0 or a negative value for failure. In | |
51 | particular a return value of -2 indicates the operation is not supported by the | |
52 | public key algorithm. | |
29cf84c6 | 53 | |
9b86974e | 54 | The error codes can be obtained from L<ERR_get_error(3)>. |
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55 | |
56 | =head1 NOTES | |
57 | ||
58 | The B<EVP> interface to digital signatures should almost always be used in | |
59 | preference to the low level interfaces. This is because the code then becomes | |
60 | transparent to the algorithm used and much more flexible. | |
61 | ||
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62 | EVP_DigestSign() is a one shot operation which signs a single block of data |
63 | in one function. For algorithms that support streaming it is equivalent to | |
64 | calling EVP_DigestSignUpdate() and EVP_DigestSignFinal(). For algorithms which | |
65 | do not support streaming (e.g. PureEdDSA) it is the only way to sign data. | |
75394189 | 66 | |
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67 | In previous versions of OpenSSL there was a link between message digest types |
68 | and public key algorithms. This meant that "clone" digests such as EVP_dss1() | |
69 | needed to be used to sign using SHA1 and DSA. This is no longer necessary and | |
70 | the use of clone digest is now discouraged. | |
71 | ||
72 | For some key types and parameters the random number generator must be seeded | |
1bc74519 | 73 | or the operation will fail. |
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74 | |
75 | The call to EVP_DigestSignFinal() internally finalizes a copy of the digest | |
76 | context. This means that calls to EVP_DigestSignUpdate() and | |
77 | EVP_DigestSignFinal() can be called later to digest and sign additional data. | |
78 | ||
79 | Since only a copy of the digest context is ever finalized the context must | |
80 | be cleaned up after use by calling EVP_MD_CTX_cleanup() or a memory leak | |
81 | will occur. | |
82 | ||
83 | The use of EVP_PKEY_size() with these functions is discouraged because some | |
84 | signature operations may have a signature length which depends on the | |
85 | parameters set. As a result EVP_PKEY_size() would have to return a value | |
86 | which indicates the maximum possible signature for any set of parameters. | |
87 | ||
88 | =head1 SEE ALSO | |
89 | ||
9b86974e | 90 | L<EVP_DigestVerifyInit(3)>, |
73fb82b7 | 91 | L<EVP_DigestInit(3)>, |
b97fdb57 RL |
92 | L<evp(7)>, L<HMAC(3)>, L<MD2(3)>, |
93 | L<MD5(3)>, L<MDC2(3)>, L<RIPEMD160(3)>, | |
94 | L<SHA1(3)>, L<dgst(1)> | |
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95 | |
96 | =head1 HISTORY | |
97 | ||
1bc74519 | 98 | EVP_DigestSignInit(), EVP_DigestSignUpdate() and EVP_DigestSignFinal() |
fb552ac6 | 99 | were first added to OpenSSL 1.0.0. |
29cf84c6 | 100 | |
e2f92610 RS |
101 | =head1 COPYRIGHT |
102 | ||
73fb82b7 | 103 | Copyright 2006-2017 The OpenSSL Project Authors. All Rights Reserved. |
e2f92610 RS |
104 | |
105 | Licensed under the OpenSSL license (the "License"). You may not use | |
106 | this file except in compliance with the License. You can obtain a copy | |
107 | in the file LICENSE in the source distribution or at | |
108 | L<https://www.openssl.org/source/license.html>. | |
109 | ||
110 | =cut |