.\" $OpenBSD: EVP_DigestVerifyInit.3,v 1.16 2024/11/08 22:23:35 schwarze Exp $ .\" full merge up to OpenSSL f097e875 Aug 23 11:37:22 2018 +0100 .\" selective merge up to 24a535ea Sep 22 13:14:20 2020 +0100 .\" .\" This file was written by Dr. Stephen Henson . .\" Copyright (c) 2006, 2009, 2014, 2015, 2016, 2017 The OpenSSL Project. .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in .\" the documentation and/or other materials provided with the .\" distribution. .\" .\" 3. 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Redistributions of any form whatsoever must retain the following .\" acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" .\" .\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY .\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: November 8 2024 $ .Dt EVP_DIGESTVERIFYINIT 3 .Os .Sh NAME .Nm EVP_DigestVerifyInit , .Nm EVP_DigestVerifyUpdate , .Nm EVP_DigestVerifyFinal , .Nm EVP_DigestVerify .Nd EVP signature verification functions .Sh SYNOPSIS .In openssl/evp.h .Ft int .Fo EVP_DigestVerifyInit .Fa "EVP_MD_CTX *ctx" .Fa "EVP_PKEY_CTX **pctx" .Fa "const EVP_MD *type" .Fa "ENGINE *engine" .Fa "EVP_PKEY *pkey" .Fc .Ft int .Fo EVP_DigestVerifyUpdate .Fa "EVP_MD_CTX *ctx" .Fa "const void *d" .Fa "size_t cnt" .Fc .Ft int .Fo EVP_DigestVerifyFinal .Fa "EVP_MD_CTX *ctx" .Fa "const unsigned char *sig" .Fa "size_t siglen" .Fc .Ft int .Fo EVP_DigestVerify .Fa "EVP_MD_CTX *ctx" .Fa "const unsigned char *sig" .Fa "size_t siglen" .Fa "const unsigned char *tbs" .Fa "size_t *tbslen" .Fc .Sh DESCRIPTION The EVP signature routines are a high-level interface to digital signatures. .Pp .Fn EVP_DigestVerifyInit sets up the verification context .Fa ctx to use the digest .Fa type and the public key .Fa pkey . Before calling this function, obtain .Fa ctx from .Xr EVP_MD_CTX_new 3 or call .Xr EVP_MD_CTX_reset 3 on it. The .Fa engine argument is always ignored and passing .Dv NULL is recommended. .Pp If .Fa pctx is not .Dv NULL , any pointer passed in as .Pf * Fa pctx is ignored and overwritten by an internal pointer to the .Vt EVP_PKEY_CTX used by the verification operation: this can be used to set alternative signing options. The returned .Vt EVP_PKEY_CTX must not be freed by the application. It is freed automatically when the .Vt EVP_MD_CTX is freed. .Pp .Fn EVP_DigestVerifyUpdate hashes .Fa cnt bytes of data at .Fa d into the verification context .Fa ctx . This function can be called several times on the same .Fa ctx to include additional data. This function is currently implemented using a macro. .Pp .Fn EVP_DigestVerifyFinal verifies the data in .Fa ctx against the signature in .Fa sig of length .Fa siglen . .Pp .Fn EVP_DigestVerify verifies .Fa tbslen bytes at .Fa tbs against the signature in .Fa sig of length .Fa siglen . .Fn EVP_DigestVerify is a one shot operation which verifies a single block of data in one function call. For algorithms that support streaming it is equivalent to calling .Fn EVP_DigestVerifyUpdate and .Fn EVP_DigestVerifyFinal . .\" For algorithms which do not support streaming .\" (e.g. PureEdDSA) .\" it is the only way to verify data. .Pp The EVP interface to digital signatures should almost always be used in preference to the low-level interfaces. This is because the code then becomes transparent to the algorithm used and much more flexible. .Pp The call to .Fn EVP_DigestVerifyFinal internally finalizes a copy of the digest context. This means that .Xr EVP_VerifyUpdate 3 and .Xr EVP_VerifyFinal 3 can be called later to digest and verify additional data. .Pp Since only a copy of the digest context is ever finalized, the context must be cleaned up after use by calling .Xr EVP_MD_CTX_free 3 or a memory leak will occur. .Sh RETURN VALUES .Fn EVP_DigestVerifyInit and .Fn EVP_DigestVerifyUpdate return 1 for success and 0 for failure. .Pp .Fn EVP_DigestVerifyFinal and .Fn EVP_DigestVerify return 1 for success; any other value indicates failure. A return value of 0 indicates that the signature did not verify successfully (that is, the signature did not match the original data or the signature had an invalid form), while other values indicate a more serious error (and sometimes also indicate an invalid signature form). .Pp The error codes can be obtained from .Xr ERR_get_error 3 . .Sh SEE ALSO .Xr evp 3 , .Xr EVP_DigestInit 3 , .Xr EVP_DigestSignInit 3 , .Xr EVP_PKEY_meth_set_verifyctx 3 .Sh HISTORY .Fn EVP_DigestVerifyInit , .Fn EVP_DigestVerifyUpdate , and .Fn EVP_DigestVerifyFinal first appeared in OpenSSL 1.0.0 and have been available since .Ox 4.9 . .Pp .Fn EVP_DigestVerify first appeared in OpenSSL 1.1.1 and has been available since .Ox 7.0 .