1.\" $OpenBSD: EVP_PKEY_verify.3,v 1.8 2024/12/06 14:27:49 schwarze Exp $ 2.\" full merge up to: OpenSSL 48e5119a Jan 19 10:49:22 2018 +0100 3.\" 4.\" This file was written by Dr. Stephen Henson <steve@openssl.org>. 5.\" Copyright (c) 2006, 2009, 2010, 2013, 2018 The OpenSSL Project. 6.\" All rights reserved. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in 17.\" the documentation and/or other materials provided with the 18.\" distribution. 19.\" 20.\" 3. All advertising materials mentioning features or use of this 21.\" software must display the following acknowledgment: 22.\" "This product includes software developed by the OpenSSL Project 23.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" 24.\" 25.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to 26.\" endorse or promote products derived from this software without 27.\" prior written permission. For written permission, please contact 28.\" openssl-core@openssl.org. 29.\" 30.\" 5. Products derived from this software may not be called "OpenSSL" 31.\" nor may "OpenSSL" appear in their names without prior written 32.\" permission of the OpenSSL Project. 33.\" 34.\" 6. Redistributions of any form whatsoever must retain the following 35.\" acknowledgment: 36.\" "This product includes software developed by the OpenSSL Project 37.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" 38.\" 39.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY 40.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 41.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 42.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR 43.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 44.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 45.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 46.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 47.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 48.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 49.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 50.\" OF THE POSSIBILITY OF SUCH DAMAGE. 51.\" 52.Dd $Mdocdate: December 6 2024 $ 53.Dt EVP_PKEY_VERIFY 3 54.Os 55.Sh NAME 56.Nm EVP_PKEY_verify_init , 57.Nm EVP_PKEY_verify 58.Nd signature verification using a public key algorithm 59.Sh SYNOPSIS 60.In openssl/evp.h 61.Ft int 62.Fo EVP_PKEY_verify_init 63.Fa "EVP_PKEY_CTX *ctx" 64.Fc 65.Ft int 66.Fo EVP_PKEY_verify 67.Fa "EVP_PKEY_CTX *ctx" 68.Fa "const unsigned char *sig" 69.Fa "size_t siglen" 70.Fa "const unsigned char *tbs" 71.Fa "size_t tbslen" 72.Fc 73.Sh DESCRIPTION 74The 75.Fn EVP_PKEY_verify_init 76function initializes a public key algorithm context using key 77.Fa ctx->pkey 78for a signature verification operation. 79.Pp 80The 81.Fn EVP_PKEY_verify 82function performs a public key verification operation using 83.Fa ctx . 84The signature is specified using the 85.Fa sig 86and 87.Fa siglen 88parameters. 89The verified data (i.e. the data believed originally signed) is 90specified using the 91.Fa tbs 92and 93.Fa tbslen 94parameters. 95.Pp 96After the call to 97.Fn EVP_PKEY_verify_init , 98algorithm specific control operations can be performed to set any 99appropriate parameters for the operation. 100.Pp 101The function 102.Fn EVP_PKEY_verify 103can be called more than once on the same context if several operations 104are performed using the same parameters. 105.Sh RETURN VALUES 106.Fn EVP_PKEY_verify_init 107and 108.Fn EVP_PKEY_verify 109return 1 if the verification was successful and 0 if it failed. 110Unlike other functions the return value 0 from 111.Fn EVP_PKEY_verify 112only indicates that the signature did not verify successfully. 113That is, 114.Fa tbs 115did not match the original data or the signature was of invalid form. 116It is not an indication of a more serious error. 117.Pp 118A negative value indicates an error other that signature verification 119failure. 120In particular, a return value of -2 indicates the operation is not 121supported by the public key algorithm. 122.Sh EXAMPLES 123Verify signature using PKCS#1 and SHA256 digest: 124.Bd -literal -offset 3n 125#include <openssl/evp.h> 126#include <openssl/rsa.h> 127 128EVP_PKEY_CTX *ctx; 129unsigned char *md, *sig; 130size_t mdlen, siglen; 131EVP_PKEY *verify_key; 132 133/* 134 * Assumes that verify_key, sig, siglen, md, and mdlen are already set up 135 * and that verify_key is an RSA public key. 136 */ 137ctx = EVP_PKEY_CTX_new(verify_key, NULL); 138if (!ctx) 139 /* Error occurred */ 140if (EVP_PKEY_verify_init(ctx) <= 0) 141 /* Error */ 142if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0) 143 /* Error */ 144if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0) 145 /* Error */ 146 147/* Perform operation */ 148ret = EVP_PKEY_verify(ctx, sig, siglen, md, mdlen); 149 150/* 151 * ret == 1 indicates success, 0 verify failure, 152 * and < 0 some other error. 153 */ 154.Ed 155.Sh SEE ALSO 156.Xr EVP_PKEY_CTX_new 3 , 157.Xr EVP_PKEY_decrypt 3 , 158.Xr EVP_PKEY_derive 3 , 159.Xr EVP_PKEY_encrypt 3 , 160.Xr EVP_PKEY_sign 3 , 161.Xr EVP_PKEY_verify_recover 3 162.Sh HISTORY 163.Fn EVP_PKEY_verify_init 164and 165.Fn EVP_PKEY_verify 166first appeared in OpenSSL 1.0.0 and have been available since 167.Ox 4.9 . 168