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1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
64cee65e | 5 | EVP_PKEY_sign_init, EVP_PKEY_sign - sign using a public key algorithm |
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6 | |
7 | =head1 SYNOPSIS | |
8 | ||
9 | #include <openssl/evp.h> | |
10 | ||
11 | int EVP_PKEY_sign_init(EVP_PKEY_CTX *ctx); | |
12 | int EVP_PKEY_sign(EVP_PKEY_CTX *ctx, | |
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13 | unsigned char *sig, size_t *siglen, |
14 | const unsigned char *tbs, size_t tbslen); | |
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15 | |
16 | =head1 DESCRIPTION | |
17 | ||
18 | The EVP_PKEY_sign_init() function initializes a public key algorithm | |
19 | context using key B<pkey> for a signing operation. | |
20 | ||
21 | The EVP_PKEY_sign() function performs a public key signing operation | |
22 | using B<ctx>. The data to be signed is specified using the B<tbs> and | |
23 | B<tbslen> parameters. If B<sig> is B<NULL> then the maximum size of the output | |
24 | buffer is written to the B<siglen> parameter. If B<sig> is not B<NULL> then | |
25 | before the call the B<siglen> parameter should contain the length of the | |
26 | B<sig> buffer, if the call is successful the signature is written to | |
27 | B<sig> and the amount of data written to B<siglen>. | |
28 | ||
29 | =head1 NOTES | |
30 | ||
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31 | EVP_PKEY_sign() does not hash the data to be signed, and therefore is |
32 | normally used to sign digests. For signing arbitrary messages, see the | |
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33 | L<EVP_DigestSignInit(3)> and |
34 | L<EVP_SignInit(3)> signing interfaces instead. | |
d64c533a | 35 | |
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36 | After the call to EVP_PKEY_sign_init() algorithm specific control |
37 | operations can be performed to set any appropriate parameters for the | |
9b86974e | 38 | operation (see L<EVP_PKEY_CTX_ctrl(3)>). |
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39 | |
40 | The function EVP_PKEY_sign() can be called more than once on the same | |
41 | context if several operations are performed using the same parameters. | |
42 | ||
43 | =head1 RETURN VALUES | |
44 | ||
45 | EVP_PKEY_sign_init() and EVP_PKEY_sign() return 1 for success and 0 | |
46 | or a negative value for failure. In particular a return value of -2 | |
47 | indicates the operation is not supported by the public key algorithm. | |
48 | ||
49 | =head1 EXAMPLE | |
50 | ||
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51 | Sign data using RSA with PKCS#1 padding and SHA256 digest: |
52 | ||
53 | #include <openssl/evp.h> | |
54 | #include <openssl/rsa.h> | |
55 | ||
56 | EVP_PKEY_CTX *ctx; | |
d64c533a | 57 | /* md is a SHA-256 digest in this example. */ |
43636910 | 58 | unsigned char *md, *sig; |
d64c533a | 59 | size_t mdlen = 32, siglen; |
43636910 | 60 | EVP_PKEY *signing_key; |
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61 | |
62 | /* | |
63 | * NB: assumes signing_key and md are set up before the next | |
64 | * step. signing_key must be an RSA private key and md must | |
65 | * point to the SHA-256 digest to be signed. | |
43636910 | 66 | */ |
d64c533a | 67 | ctx = EVP_PKEY_CTX_new(signing_key, NULL /* no engine */); |
43636910 | 68 | if (!ctx) |
2947af32 | 69 | /* Error occurred */ |
43636910 | 70 | if (EVP_PKEY_sign_init(ctx) <= 0) |
2947af32 | 71 | /* Error */ |
43636910 | 72 | if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0) |
2947af32 | 73 | /* Error */ |
43636910 | 74 | if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0) |
2947af32 | 75 | /* Error */ |
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76 | |
77 | /* Determine buffer length */ | |
78 | if (EVP_PKEY_sign(ctx, NULL, &siglen, md, mdlen) <= 0) | |
2947af32 | 79 | /* Error */ |
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80 | |
81 | sig = OPENSSL_malloc(siglen); | |
82 | ||
83 | if (!sig) | |
2947af32 | 84 | /* malloc failure */ |
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43636910 | 86 | if (EVP_PKEY_sign(ctx, sig, &siglen, md, mdlen) <= 0) |
2947af32 | 87 | /* Error */ |
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88 | |
89 | /* Signature is siglen bytes written to buffer sig */ | |
ba544377 | 90 | |
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91 | |
92 | =head1 SEE ALSO | |
93 | ||
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94 | L<EVP_PKEY_CTX_new(3)>, |
95 | L<EVP_PKEY_CTX_ctrl(3)>, | |
96 | L<EVP_PKEY_encrypt(3)>, | |
97 | L<EVP_PKEY_decrypt(3)>, | |
98 | L<EVP_PKEY_verify(3)>, | |
99 | L<EVP_PKEY_verify_recover(3)>, | |
1bc74519 | 100 | L<EVP_PKEY_derive(3)> |
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101 | |
102 | =head1 HISTORY | |
103 | ||
fb552ac6 | 104 | These functions were first added to OpenSSL 1.0.0. |
ba544377 | 105 | |
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106 | =head1 COPYRIGHT |
107 | ||
108 | Copyright 2006-2016 The OpenSSL Project Authors. All Rights Reserved. | |
109 | ||
110 | Licensed under the OpenSSL license (the "License"). You may not use | |
111 | this file except in compliance with the License. You can obtain a copy | |
112 | in the file LICENSE in the source distribution or at | |
113 | L<https://www.openssl.org/source/license.html>. | |
114 | ||
115 | =cut |