1=pod 2 3=head1 NAME 4 5EVP_PKEY_verify_init, EVP_PKEY_verify_init_ex, EVP_PKEY_verify 6- signature verification using a public key algorithm 7 8=head1 SYNOPSIS 9 10 #include <openssl/evp.h> 11 12 int EVP_PKEY_verify_init(EVP_PKEY_CTX *ctx); 13 int EVP_PKEY_verify_init_ex(EVP_PKEY_CTX *ctx, const OSSL_PARAM params[]); 14 int EVP_PKEY_verify(EVP_PKEY_CTX *ctx, 15 const unsigned char *sig, size_t siglen, 16 const unsigned char *tbs, size_t tbslen); 17 18=head1 DESCRIPTION 19 20EVP_PKEY_verify_init() initializes a public key algorithm context I<ctx> for 21signing using the algorithm given when the context was created 22using L<EVP_PKEY_CTX_new(3)> or variants thereof. The algorithm is used to 23fetch a B<EVP_SIGNATURE> method implicitly, see L<provider(7)/Implicit fetch> 24for more information about implicit fetches. 25 26EVP_PKEY_verify_init_ex() is the same as EVP_PKEY_verify_init() but additionally 27sets the passed parameters I<params> on the context before returning. 28 29The EVP_PKEY_verify() function performs a public key verification operation 30using I<ctx>. The signature is specified using the I<sig> and 31I<siglen> parameters. The verified data (i.e. the data believed originally 32signed) is specified using the I<tbs> and I<tbslen> parameters. 33 34=head1 NOTES 35 36After the call to EVP_PKEY_verify_init() algorithm specific control 37operations can be performed to set any appropriate parameters for the 38operation. 39 40The function EVP_PKEY_verify() can be called more than once on the same 41context if several operations are performed using the same parameters. 42 43=head1 RETURN VALUES 44 45EVP_PKEY_verify_init() and EVP_PKEY_verify() return 1 if the verification was 46successful and 0 if it failed. Unlike other functions the return value 0 from 47EVP_PKEY_verify() only indicates that the signature did not verify 48successfully (that is tbs did not match the original data or the signature was 49of invalid form) it is not an indication of a more serious error. 50 51A negative value indicates an error other that signature verification failure. 52In particular a return value of -2 indicates the operation is not supported by 53the public key algorithm. 54 55=head1 EXAMPLES 56 57Verify signature using PKCS#1 and SHA256 digest: 58 59 #include <openssl/evp.h> 60 #include <openssl/rsa.h> 61 62 EVP_PKEY_CTX *ctx; 63 unsigned char *md, *sig; 64 size_t mdlen, siglen; 65 EVP_PKEY *verify_key; 66 67 /* 68 * NB: assumes verify_key, sig, siglen md and mdlen are already set up 69 * and that verify_key is an RSA public key 70 */ 71 ctx = EVP_PKEY_CTX_new(verify_key, NULL /* no engine */); 72 if (!ctx) 73 /* Error occurred */ 74 if (EVP_PKEY_verify_init(ctx) <= 0) 75 /* Error */ 76 if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0) 77 /* Error */ 78 if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0) 79 /* Error */ 80 81 /* Perform operation */ 82 ret = EVP_PKEY_verify(ctx, sig, siglen, md, mdlen); 83 84 /* 85 * ret == 1 indicates success, 0 verify failure and < 0 for some 86 * other error. 87 */ 88 89=head1 SEE ALSO 90 91L<EVP_PKEY_CTX_new(3)>, 92L<EVP_PKEY_encrypt(3)>, 93L<EVP_PKEY_decrypt(3)>, 94L<EVP_PKEY_sign(3)>, 95L<EVP_PKEY_verify_recover(3)>, 96L<EVP_PKEY_derive(3)> 97 98=head1 HISTORY 99 100The EVP_PKEY_verify_init() and EVP_PKEY_verify() functions were added in 101OpenSSL 1.0.0. 102 103The EVP_PKEY_verify_init_ex() function was added in OpenSSL 3.0. 104 105=head1 COPYRIGHT 106 107Copyright 2006-2021 The OpenSSL Project Authors. All Rights Reserved. 108 109Licensed under the Apache License 2.0 (the "License"). You may not use 110this file except in compliance with the License. You can obtain a copy 111in the file LICENSE in the source distribution or at 112L<https://www.openssl.org/source/license.html>. 113 114=cut 115