1=pod 2 3=head1 NAME 4 5EVP_VerifyInit_ex, 6EVP_VerifyInit, EVP_VerifyUpdate, EVP_VerifyFinal 7- EVP signature verification functions 8 9=head1 SYNOPSIS 10 11 #include <openssl/evp.h> 12 13 int EVP_VerifyInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl); 14 int EVP_VerifyUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt); 15 int EVP_VerifyFinal(EVP_MD_CTX *ctx, unsigned char *sigbuf, unsigned int siglen, 16 EVP_PKEY *pkey); 17 18 int EVP_VerifyInit(EVP_MD_CTX *ctx, const EVP_MD *type); 19 20=head1 DESCRIPTION 21 22The EVP signature verification routines are a high level interface to digital 23signatures. 24 25EVP_VerifyInit_ex() sets up verification context B<ctx> to use digest 26B<type> from ENGINE B<impl>. B<ctx> must be created by calling 27EVP_MD_CTX_new() before calling this function. 28 29EVP_VerifyUpdate() hashes B<cnt> bytes of data at B<d> into the 30verification context B<ctx>. This function can be called several times on the 31same B<ctx> to include additional data. 32 33EVP_VerifyFinal() verifies the data in B<ctx> using the public key B<pkey> 34and against the B<siglen> bytes at B<sigbuf>. 35 36EVP_VerifyInit() initializes verification context B<ctx> to use the default 37implementation of digest B<type>. 38 39=head1 RETURN VALUES 40 41EVP_VerifyInit_ex() and EVP_VerifyUpdate() return 1 for success and 0 for 42failure. 43 44EVP_VerifyFinal() returns 1 for a correct signature, 0 for failure and -1 if some 45other error occurred. 46 47The error codes can be obtained by L<ERR_get_error(3)>. 48 49=head1 NOTES 50 51The B<EVP> interface to digital signatures should almost always be used in 52preference to the low level interfaces. This is because the code then becomes 53transparent to the algorithm used and much more flexible. 54 55The call to EVP_VerifyFinal() internally finalizes a copy of the digest context. 56This means that calls to EVP_VerifyUpdate() and EVP_VerifyFinal() can be called 57later to digest and verify additional data. 58 59Since only a copy of the digest context is ever finalized the context must 60be cleaned up after use by calling EVP_MD_CTX_free() or a memory leak 61will occur. 62 63=head1 BUGS 64 65Older versions of this documentation wrongly stated that calls to 66EVP_VerifyUpdate() could not be made after calling EVP_VerifyFinal(). 67 68Since the public key is passed in the call to EVP_SignFinal() any error 69relating to the private key (for example an unsuitable key and digest 70combination) will not be indicated until after potentially large amounts of 71data have been passed through EVP_SignUpdate(). 72 73It is not possible to change the signing parameters using these function. 74 75The previous two bugs are fixed in the newer EVP_DigestVerify*() function. 76 77=head1 SEE ALSO 78 79L<evp(7)>, 80L<EVP_SignInit(3)>, 81L<EVP_DigestInit(3)>, 82L<evp(7)>, L<HMAC(3)>, L<MD2(3)>, 83L<MD5(3)>, L<MDC2(3)>, L<RIPEMD160(3)>, 84L<SHA1(3)>, L<dgst(1)> 85 86=head1 COPYRIGHT 87 88Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved. 89 90Licensed under the OpenSSL license (the "License"). You may not use 91this file except in compliance with the License. You can obtain a copy 92in the file LICENSE in the source distribution or at 93L<https://www.openssl.org/source/license.html>. 94 95=cut 96