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1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
e54e1235 | 5 | EVP_PKEY_verify_recover_init, EVP_PKEY_verify_recover - recover signature using a public key algorithm |
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6 | |
7 | =head1 SYNOPSIS | |
8 | ||
9 | #include <openssl/evp.h> | |
10 | ||
e54e1235 BL |
11 | int EVP_PKEY_verify_recover_init(EVP_PKEY_CTX *ctx); |
12 | int EVP_PKEY_verify_recover(EVP_PKEY_CTX *ctx, | |
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13 | unsigned char *rout, size_t *routlen, |
14 | const unsigned char *sig, size_t siglen); | |
15 | ||
16 | =head1 DESCRIPTION | |
17 | ||
e54e1235 | 18 | The EVP_PKEY_verify_recover_init() function initializes a public key algorithm |
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19 | context using key B<pkey> for a verify recover operation. |
20 | ||
e54e1235 | 21 | The EVP_PKEY_verify_recover() function recovers signed data |
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22 | using B<ctx>. The signature is specified using the B<sig> and |
23 | B<siglen> parameters. If B<rout> is B<NULL> then the maximum size of the output | |
24 | buffer is written to the B<routlen> parameter. If B<rout> is not B<NULL> then | |
25 | before the call the B<routlen> parameter should contain the length of the | |
26 | B<rout> buffer, if the call is successful recovered data is written to | |
27 | B<rout> and the amount of data written to B<routlen>. | |
28 | ||
29 | =head1 NOTES | |
30 | ||
31 | Normally an application is only interested in whether a signature verification | |
32 | operation is successful in those cases the EVP_verify() function should be | |
33 | used. | |
34 | ||
35 | Sometimes however it is useful to obtain the data originally signed using a | |
36 | signing operation. Only certain public key algorithms can recover a signature | |
37 | in this way (for example RSA in PKCS padding mode). | |
38 | ||
e54e1235 | 39 | After the call to EVP_PKEY_verify_recover_init() algorithm specific control |
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40 | operations can be performed to set any appropriate parameters for the |
41 | operation. | |
42 | ||
e54e1235 | 43 | The function EVP_PKEY_verify_recover() can be called more than once on the same |
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44 | context if several operations are performed using the same parameters. |
45 | ||
46 | =head1 RETURN VALUES | |
47 | ||
e54e1235 | 48 | EVP_PKEY_verify_recover_init() and EVP_PKEY_verify_recover() return 1 for success |
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49 | and 0 or a negative value for failure. In particular a return value of -2 |
50 | indicates the operation is not supported by the public key algorithm. | |
51 | ||
52 | =head1 EXAMPLE | |
53 | ||
54 | Recover digest originally signed using PKCS#1 and SHA256 digest: | |
55 | ||
43636910 DSH |
56 | #include <openssl/evp.h> |
57 | #include <openssl/rsa.h> | |
58 | ||
59 | EVP_PKEY_CTX *ctx; | |
60 | unsigned char *rout, *sig; | |
61 | size_t routlen, siglen; | |
62 | EVP_PKEY *verify_key; | |
63 | /* NB: assumes verify_key, sig and siglen are already set up | |
64 | * and that verify_key is an RSA public key | |
65 | */ | |
66 | ctx = EVP_PKEY_CTX_new(verify_key); | |
67 | if (!ctx) | |
68 | /* Error occurred */ | |
e54e1235 | 69 | if (EVP_PKEY_verify_recover_init(ctx) <= 0) |
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70 | /* Error */ |
71 | if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0) | |
72 | /* Error */ | |
73 | if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0) | |
74 | /* Error */ | |
75 | ||
76 | /* Determine buffer length */ | |
e54e1235 | 77 | if (EVP_PKEY_verify_recover(ctx, NULL, &routlen, sig, siglen) <= 0) |
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78 | /* Error */ |
79 | ||
80 | rout = OPENSSL_malloc(routlen); | |
81 | ||
82 | if (!rout) | |
83 | /* malloc failure */ | |
84 | ||
e54e1235 | 85 | if (EVP_PKEY_verify_recover(ctx, rout, &routlen, sig, siglen) <= 0) |
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86 | /* Error */ |
87 | ||
88 | /* Recovered data is routlen bytes written to buffer rout */ | |
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89 | |
90 | =head1 SEE ALSO | |
91 | ||
9b86974e RS |
92 | L<EVP_PKEY_CTX_new(3)>, |
93 | L<EVP_PKEY_encrypt(3)>, | |
94 | L<EVP_PKEY_decrypt(3)>, | |
95 | L<EVP_PKEY_sign(3)>, | |
96 | L<EVP_PKEY_verify(3)>, | |
97 | L<EVP_PKEY_derive(3)> | |
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98 | |
99 | =head1 HISTORY | |
100 | ||
fb552ac6 | 101 | These functions were first added to OpenSSL 1.0.0. |
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102 | |
103 | =cut |