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64cee65e DSH |
1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
0e521004 RL |
5 | EVP_PKEY_verify_recover_init, EVP_PKEY_verify_recover |
6 | - recover signature using a public key algorithm | |
64cee65e DSH |
7 | |
8 | =head1 SYNOPSIS | |
9 | ||
10 | #include <openssl/evp.h> | |
11 | ||
e54e1235 BL |
12 | int EVP_PKEY_verify_recover_init(EVP_PKEY_CTX *ctx); |
13 | int EVP_PKEY_verify_recover(EVP_PKEY_CTX *ctx, | |
e9b77246 BB |
14 | unsigned char *rout, size_t *routlen, |
15 | const unsigned char *sig, size_t siglen); | |
64cee65e DSH |
16 | |
17 | =head1 DESCRIPTION | |
18 | ||
0e521004 RL |
19 | EVP_PKEY_verify_recover_init() initializes a public key algorithm context |
20 | I<ctx> for 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. |
64cee65e | 24 | |
e54e1235 | 25 | The EVP_PKEY_verify_recover() function recovers signed data |
0e521004 RL |
26 | using I<ctx>. The signature is specified using the I<sig> and |
27 | I<siglen> parameters. If I<rout> is NULL then the maximum size of the output | |
28 | buffer is written to the I<routlen> parameter. If I<rout> is not NULL then | |
29 | before the call the I<routlen> parameter should contain the length of the | |
30 | I<rout> buffer, if the call is successful recovered data is written to | |
31 | I<rout> and the amount of data written to I<routlen>. | |
64cee65e DSH |
32 | |
33 | =head1 NOTES | |
34 | ||
35 | Normally an application is only interested in whether a signature verification | |
1bc74519 | 36 | operation is successful in those cases the EVP_verify() function should be |
64cee65e DSH |
37 | used. |
38 | ||
39 | Sometimes however it is useful to obtain the data originally signed using a | |
40 | signing operation. Only certain public key algorithms can recover a signature | |
41 | in this way (for example RSA in PKCS padding mode). | |
42 | ||
e54e1235 | 43 | After the call to EVP_PKEY_verify_recover_init() algorithm specific control |
64cee65e DSH |
44 | operations can be performed to set any appropriate parameters for the |
45 | operation. | |
46 | ||
e54e1235 | 47 | The function EVP_PKEY_verify_recover() can be called more than once on the same |
64cee65e DSH |
48 | context if several operations are performed using the same parameters. |
49 | ||
50 | =head1 RETURN VALUES | |
51 | ||
e54e1235 | 52 | EVP_PKEY_verify_recover_init() and EVP_PKEY_verify_recover() return 1 for success |
64cee65e DSH |
53 | and 0 or a negative value for failure. In particular a return value of -2 |
54 | indicates the operation is not supported by the public key algorithm. | |
55 | ||
cda77422 | 56 | =head1 EXAMPLES |
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57 | |
58 | Recover digest originally signed using PKCS#1 and SHA256 digest: | |
59 | ||
43636910 DSH |
60 | #include <openssl/evp.h> |
61 | #include <openssl/rsa.h> | |
62 | ||
63 | EVP_PKEY_CTX *ctx; | |
64 | unsigned char *rout, *sig; | |
1bc74519 | 65 | size_t routlen, siglen; |
43636910 | 66 | EVP_PKEY *verify_key; |
e9b77246 | 67 | |
2947af32 BB |
68 | /* |
69 | * NB: assumes verify_key, sig and siglen are already set up | |
43636910 DSH |
70 | * and that verify_key is an RSA public key |
71 | */ | |
9db6673e | 72 | ctx = EVP_PKEY_CTX_new(verify_key, NULL /* no engine */); |
43636910 | 73 | if (!ctx) |
2947af32 | 74 | /* Error occurred */ |
e54e1235 | 75 | if (EVP_PKEY_verify_recover_init(ctx) <= 0) |
2947af32 | 76 | /* Error */ |
43636910 | 77 | if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0) |
2947af32 | 78 | /* Error */ |
43636910 | 79 | if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0) |
2947af32 | 80 | /* Error */ |
43636910 DSH |
81 | |
82 | /* Determine buffer length */ | |
e54e1235 | 83 | if (EVP_PKEY_verify_recover(ctx, NULL, &routlen, sig, siglen) <= 0) |
2947af32 | 84 | /* Error */ |
43636910 DSH |
85 | |
86 | rout = OPENSSL_malloc(routlen); | |
87 | ||
88 | if (!rout) | |
2947af32 | 89 | /* malloc failure */ |
1bc74519 | 90 | |
e54e1235 | 91 | if (EVP_PKEY_verify_recover(ctx, rout, &routlen, sig, siglen) <= 0) |
2947af32 | 92 | /* Error */ |
43636910 DSH |
93 | |
94 | /* Recovered data is routlen bytes written to buffer rout */ | |
64cee65e DSH |
95 | |
96 | =head1 SEE ALSO | |
97 | ||
9b86974e RS |
98 | L<EVP_PKEY_CTX_new(3)>, |
99 | L<EVP_PKEY_encrypt(3)>, | |
100 | L<EVP_PKEY_decrypt(3)>, | |
101 | L<EVP_PKEY_sign(3)>, | |
102 | L<EVP_PKEY_verify(3)>, | |
1bc74519 | 103 | L<EVP_PKEY_derive(3)> |
64cee65e DSH |
104 | |
105 | =head1 HISTORY | |
106 | ||
fc5ecadd | 107 | These functions were added in OpenSSL 1.0.0. |
64cee65e | 108 | |
e2f92610 RS |
109 | =head1 COPYRIGHT |
110 | ||
48e5119a | 111 | Copyright 2013-2018 The OpenSSL Project Authors. All Rights Reserved. |
e2f92610 | 112 | |
4746f25a | 113 | Licensed under the Apache License 2.0 (the "License"). You may not use |
e2f92610 RS |
114 | this file except in compliance with the License. You can obtain a copy |
115 | in the file LICENSE in the source distribution or at | |
116 | L<https://www.openssl.org/source/license.html>. | |
117 | ||
118 | =cut |