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1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
ee22fca5 | 5 | EVP_PKEY_sign_init, EVP_PKEY_sign_init_ex, EVP_PKEY_sign |
11031468 | 6 | - sign using a public key algorithm |
ba544377 DSH |
7 | |
8 | =head1 SYNOPSIS | |
9 | ||
10 | #include <openssl/evp.h> | |
11 | ||
12 | int EVP_PKEY_sign_init(EVP_PKEY_CTX *ctx); | |
ee22fca5 | 13 | int EVP_PKEY_sign_init_ex(EVP_PKEY_CTX *ctx, const OSSL_PARAM params[]); |
ba544377 | 14 | int EVP_PKEY_sign(EVP_PKEY_CTX *ctx, |
e9b77246 BB |
15 | unsigned char *sig, size_t *siglen, |
16 | const unsigned char *tbs, size_t tbslen); | |
ba544377 DSH |
17 | |
18 | =head1 DESCRIPTION | |
19 | ||
0e521004 RL |
20 | EVP_PKEY_sign_init() initializes a public key algorithm context I<ctx> for |
21 | signing using the algorithm given when the context was created | |
22 | using L<EVP_PKEY_CTX_new(3)> or variants thereof. The algorithm is used to | |
23 | fetch a B<EVP_SIGNATURE> method implicitly, see L<provider(7)/Implicit fetch> | |
8c1cbc72 | 24 | for more information about implicit fetches. |
ba544377 | 25 | |
ee22fca5 P |
26 | EVP_PKEY_sign_init_ex() is the same as EVP_PKEY_sign_init() but additionally |
27 | sets the passed parameters I<params> on the context before returning. | |
28 | ||
ba544377 | 29 | The EVP_PKEY_sign() function performs a public key signing operation |
0e521004 RL |
30 | using I<ctx>. The data to be signed is specified using the I<tbs> and |
31 | I<tbslen> parameters. If I<sig> is NULL then the maximum size of the output | |
32 | buffer is written to the I<siglen> parameter. If I<sig> is not NULL then | |
33 | before the call the I<siglen> parameter should contain the length of the | |
34 | I<sig> buffer, if the call is successful the signature is written to | |
35 | I<sig> and the amount of data written to I<siglen>. | |
ba544377 DSH |
36 | |
37 | =head1 NOTES | |
38 | ||
d64c533a EK |
39 | EVP_PKEY_sign() does not hash the data to be signed, and therefore is |
40 | normally used to sign digests. For signing arbitrary messages, see the | |
9b86974e RS |
41 | L<EVP_DigestSignInit(3)> and |
42 | L<EVP_SignInit(3)> signing interfaces instead. | |
d64c533a | 43 | |
ba544377 DSH |
44 | After the call to EVP_PKEY_sign_init() algorithm specific control |
45 | operations can be performed to set any appropriate parameters for the | |
9b86974e | 46 | operation (see L<EVP_PKEY_CTX_ctrl(3)>). |
ba544377 DSH |
47 | |
48 | The function EVP_PKEY_sign() can be called more than once on the same | |
49 | context if several operations are performed using the same parameters. | |
50 | ||
51 | =head1 RETURN VALUES | |
52 | ||
53 | EVP_PKEY_sign_init() and EVP_PKEY_sign() return 1 for success and 0 | |
54 | or a negative value for failure. In particular a return value of -2 | |
55 | indicates the operation is not supported by the public key algorithm. | |
56 | ||
cda77422 | 57 | =head1 EXAMPLES |
ba544377 | 58 | |
43636910 DSH |
59 | Sign data using RSA with PKCS#1 padding and SHA256 digest: |
60 | ||
61 | #include <openssl/evp.h> | |
62 | #include <openssl/rsa.h> | |
63 | ||
64 | EVP_PKEY_CTX *ctx; | |
d64c533a | 65 | /* md is a SHA-256 digest in this example. */ |
43636910 | 66 | unsigned char *md, *sig; |
d64c533a | 67 | size_t mdlen = 32, siglen; |
43636910 | 68 | EVP_PKEY *signing_key; |
d64c533a EK |
69 | |
70 | /* | |
71 | * NB: assumes signing_key and md are set up before the next | |
72 | * step. signing_key must be an RSA private key and md must | |
73 | * point to the SHA-256 digest to be signed. | |
43636910 | 74 | */ |
d64c533a | 75 | ctx = EVP_PKEY_CTX_new(signing_key, NULL /* no engine */); |
43636910 | 76 | if (!ctx) |
2947af32 | 77 | /* Error occurred */ |
43636910 | 78 | if (EVP_PKEY_sign_init(ctx) <= 0) |
2947af32 | 79 | /* Error */ |
43636910 | 80 | if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0) |
2947af32 | 81 | /* Error */ |
43636910 | 82 | if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0) |
2947af32 | 83 | /* Error */ |
43636910 DSH |
84 | |
85 | /* Determine buffer length */ | |
86 | if (EVP_PKEY_sign(ctx, NULL, &siglen, md, mdlen) <= 0) | |
2947af32 | 87 | /* Error */ |
43636910 DSH |
88 | |
89 | sig = OPENSSL_malloc(siglen); | |
90 | ||
91 | if (!sig) | |
2947af32 | 92 | /* malloc failure */ |
1bc74519 | 93 | |
43636910 | 94 | if (EVP_PKEY_sign(ctx, sig, &siglen, md, mdlen) <= 0) |
2947af32 | 95 | /* Error */ |
43636910 DSH |
96 | |
97 | /* Signature is siglen bytes written to buffer sig */ | |
ba544377 | 98 | |
ba544377 DSH |
99 | |
100 | =head1 SEE ALSO | |
101 | ||
9b86974e RS |
102 | L<EVP_PKEY_CTX_new(3)>, |
103 | L<EVP_PKEY_CTX_ctrl(3)>, | |
104 | L<EVP_PKEY_encrypt(3)>, | |
105 | L<EVP_PKEY_decrypt(3)>, | |
106 | L<EVP_PKEY_verify(3)>, | |
107 | L<EVP_PKEY_verify_recover(3)>, | |
1bc74519 | 108 | L<EVP_PKEY_derive(3)> |
ba544377 DSH |
109 | |
110 | =head1 HISTORY | |
111 | ||
ee22fca5 P |
112 | The EVP_PKEY_sign_init() and EVP_PKEY_sign() functions were added in |
113 | OpenSSL 1.0.0. | |
114 | ||
115 | The EVP_PKEY_sign_init_ex() function was added in OpenSSL 3.0. | |
ba544377 | 116 | |
e2f92610 RS |
117 | =head1 COPYRIGHT |
118 | ||
3c2bdd7d | 119 | Copyright 2006-2021 The OpenSSL Project Authors. All Rights Reserved. |
e2f92610 | 120 | |
4746f25a | 121 | Licensed under the Apache License 2.0 (the "License"). You may not use |
e2f92610 RS |
122 | this file except in compliance with the License. You can obtain a copy |
123 | in the file LICENSE in the source distribution or at | |
124 | L<https://www.openssl.org/source/license.html>. | |
125 | ||
126 | =cut |