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1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
0e521004 | 5 | EVP_PKEY_sign_init, EVP_PKEY_sign |
11031468 | 6 | - sign using a public key algorithm |
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7 | |
8 | =head1 SYNOPSIS | |
9 | ||
10 | #include <openssl/evp.h> | |
11 | ||
12 | int EVP_PKEY_sign_init(EVP_PKEY_CTX *ctx); | |
13 | int EVP_PKEY_sign(EVP_PKEY_CTX *ctx, | |
e9b77246 BB |
14 | unsigned char *sig, size_t *siglen, |
15 | const unsigned char *tbs, size_t tbslen); | |
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16 | |
17 | =head1 DESCRIPTION | |
18 | ||
0e521004 RL |
19 | EVP_PKEY_sign_init() initializes a public key algorithm context I<ctx> for |
20 | signing using the algorithm given when the context was created | |
21 | using L<EVP_PKEY_CTX_new(3)> or variants thereof. The algorithm is used to | |
22 | fetch a B<EVP_SIGNATURE> method implicitly, see L<provider(7)/Implicit fetch> | |
8c1cbc72 | 23 | for more information about implicit fetches. |
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24 | |
25 | The EVP_PKEY_sign() function performs a public key signing operation | |
0e521004 RL |
26 | using I<ctx>. The data to be signed is specified using the I<tbs> and |
27 | I<tbslen> parameters. If I<sig> is NULL then the maximum size of the output | |
28 | buffer is written to the I<siglen> parameter. If I<sig> is not NULL then | |
29 | before the call the I<siglen> parameter should contain the length of the | |
30 | I<sig> buffer, if the call is successful the signature is written to | |
31 | I<sig> and the amount of data written to I<siglen>. | |
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32 | |
33 | =head1 NOTES | |
34 | ||
d64c533a EK |
35 | EVP_PKEY_sign() does not hash the data to be signed, and therefore is |
36 | normally used to sign digests. For signing arbitrary messages, see the | |
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37 | L<EVP_DigestSignInit(3)> and |
38 | L<EVP_SignInit(3)> signing interfaces instead. | |
d64c533a | 39 | |
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40 | After the call to EVP_PKEY_sign_init() algorithm specific control |
41 | operations can be performed to set any appropriate parameters for the | |
9b86974e | 42 | operation (see L<EVP_PKEY_CTX_ctrl(3)>). |
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43 | |
44 | The function EVP_PKEY_sign() can be called more than once on the same | |
45 | context if several operations are performed using the same parameters. | |
46 | ||
47 | =head1 RETURN VALUES | |
48 | ||
49 | EVP_PKEY_sign_init() and EVP_PKEY_sign() return 1 for success and 0 | |
50 | or a negative value for failure. In particular a return value of -2 | |
51 | indicates the operation is not supported by the public key algorithm. | |
52 | ||
cda77422 | 53 | =head1 EXAMPLES |
ba544377 | 54 | |
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55 | Sign data using RSA with PKCS#1 padding and SHA256 digest: |
56 | ||
57 | #include <openssl/evp.h> | |
58 | #include <openssl/rsa.h> | |
59 | ||
60 | EVP_PKEY_CTX *ctx; | |
d64c533a | 61 | /* md is a SHA-256 digest in this example. */ |
43636910 | 62 | unsigned char *md, *sig; |
d64c533a | 63 | size_t mdlen = 32, siglen; |
43636910 | 64 | EVP_PKEY *signing_key; |
d64c533a EK |
65 | |
66 | /* | |
67 | * NB: assumes signing_key and md are set up before the next | |
68 | * step. signing_key must be an RSA private key and md must | |
69 | * point to the SHA-256 digest to be signed. | |
43636910 | 70 | */ |
d64c533a | 71 | ctx = EVP_PKEY_CTX_new(signing_key, NULL /* no engine */); |
43636910 | 72 | if (!ctx) |
2947af32 | 73 | /* Error occurred */ |
43636910 | 74 | if (EVP_PKEY_sign_init(ctx) <= 0) |
2947af32 | 75 | /* Error */ |
43636910 | 76 | if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0) |
2947af32 | 77 | /* Error */ |
43636910 | 78 | if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0) |
2947af32 | 79 | /* Error */ |
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80 | |
81 | /* Determine buffer length */ | |
82 | if (EVP_PKEY_sign(ctx, NULL, &siglen, md, mdlen) <= 0) | |
2947af32 | 83 | /* Error */ |
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84 | |
85 | sig = OPENSSL_malloc(siglen); | |
86 | ||
87 | if (!sig) | |
2947af32 | 88 | /* malloc failure */ |
1bc74519 | 89 | |
43636910 | 90 | if (EVP_PKEY_sign(ctx, sig, &siglen, md, mdlen) <= 0) |
2947af32 | 91 | /* Error */ |
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92 | |
93 | /* Signature is siglen bytes written to buffer sig */ | |
ba544377 | 94 | |
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95 | |
96 | =head1 SEE ALSO | |
97 | ||
9b86974e RS |
98 | L<EVP_PKEY_CTX_new(3)>, |
99 | L<EVP_PKEY_CTX_ctrl(3)>, | |
100 | L<EVP_PKEY_encrypt(3)>, | |
101 | L<EVP_PKEY_decrypt(3)>, | |
102 | L<EVP_PKEY_verify(3)>, | |
103 | L<EVP_PKEY_verify_recover(3)>, | |
1bc74519 | 104 | L<EVP_PKEY_derive(3)> |
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105 | |
106 | =head1 HISTORY | |
107 | ||
fc5ecadd | 108 | These functions were added in OpenSSL 1.0.0. |
ba544377 | 109 | |
e2f92610 RS |
110 | =head1 COPYRIGHT |
111 | ||
33388b44 | 112 | Copyright 2006-2020 The OpenSSL Project Authors. All Rights Reserved. |
e2f92610 | 113 | |
4746f25a | 114 | Licensed under the Apache License 2.0 (the "License"). You may not use |
e2f92610 RS |
115 | this file except in compliance with the License. You can obtain a copy |
116 | in the file LICENSE in the source distribution or at | |
117 | L<https://www.openssl.org/source/license.html>. | |
118 | ||
119 | =cut |