159191Skris=pod 259191Skris 359191Skris=head1 NAME 459191Skris 559191SkrisEVP_VerifyInit, EVP_VerifyUpdate, EVP_VerifyFinal - EVP signature verification functions 659191Skris 759191Skris=head1 SYNOPSIS 859191Skris 959191Skris #include <openssl/evp.h> 1059191Skris 11109998Smarkm int EVP_VerifyInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl); 12109998Smarkm int EVP_VerifyUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt); 1359191Skris int EVP_VerifyFinal(EVP_MD_CTX *ctx,unsigned char *sigbuf, unsigned int siglen,EVP_PKEY *pkey); 1459191Skris 15109998Smarkm int EVP_VerifyInit(EVP_MD_CTX *ctx, const EVP_MD *type); 16109998Smarkm 1759191Skris=head1 DESCRIPTION 1859191Skris 1959191SkrisThe EVP signature verification routines are a high level interface to digital 2059191Skrissignatures. 2159191Skris 22109998SmarkmEVP_VerifyInit_ex() sets up verification context B<ctx> to use digest 23109998SmarkmB<type> from ENGINE B<impl>. B<ctx> must be initialized by calling 24109998SmarkmEVP_MD_CTX_init() before calling this function. 2559191Skris 2659191SkrisEVP_VerifyUpdate() hashes B<cnt> bytes of data at B<d> into the 2768651Skrisverification context B<ctx>. This function can be called several times on the 2859191Skrissame B<ctx> to include additional data. 2959191Skris 3059191SkrisEVP_VerifyFinal() verifies the data in B<ctx> using the public key B<pkey> 31109998Smarkmand against the B<siglen> bytes at B<sigbuf>. 3259191Skris 33109998SmarkmEVP_VerifyInit() initializes verification context B<ctx> to use the default 34109998Smarkmimplementation of digest B<type>. 35109998Smarkm 3659191Skris=head1 RETURN VALUES 3759191Skris 38109998SmarkmEVP_VerifyInit_ex() and EVP_VerifyUpdate() return 1 for success and 0 for 39109998Smarkmfailure. 4059191Skris 4159191SkrisEVP_VerifyFinal() returns 1 for a correct signature, 0 for failure and -1 if some 4259191Skrisother error occurred. 4359191Skris 4459191SkrisThe error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>. 4559191Skris 4659191Skris=head1 NOTES 4759191Skris 4859191SkrisThe B<EVP> interface to digital signatures should almost always be used in 4959191Skrispreference to the low level interfaces. This is because the code then becomes 5059191Skristransparent to the algorithm used and much more flexible. 5159191Skris 5259191SkrisDue to the link between message digests and public key algorithms the correct 5359191Skrisdigest algorithm must be used with the correct public key type. A list of 5459191Skrisalgorithms and associated public key algorithms appears in 5559191SkrisL<EVP_DigestInit(3)|EVP_DigestInit(3)>. 5659191Skris 57109998SmarkmThe call to EVP_VerifyFinal() internally finalizes a copy of the digest context. 58109998SmarkmThis means that calls to EVP_VerifyUpdate() and EVP_VerifyFinal() can be called 59109998Smarkmlater to digest and verify additional data. 60109998Smarkm 61109998SmarkmSince only a copy of the digest context is ever finalized the context must 62109998Smarkmbe cleaned up after use by calling EVP_MD_CTX_cleanup() or a memory leak 63109998Smarkmwill occur. 64109998Smarkm 6559191Skris=head1 BUGS 6659191Skris 67109998SmarkmOlder versions of this documentation wrongly stated that calls to 68109998SmarkmEVP_VerifyUpdate() could not be made after calling EVP_VerifyFinal(). 6959191Skris 70238405SjkimSince the public key is passed in the call to EVP_SignFinal() any error 71238405Sjkimrelating to the private key (for example an unsuitable key and digest 72238405Sjkimcombination) will not be indicated until after potentially large amounts of 73238405Sjkimdata have been passed through EVP_SignUpdate(). 74238405Sjkim 75238405SjkimIt is not possible to change the signing parameters using these function. 76238405Sjkim 77238405SjkimThe previous two bugs are fixed in the newer EVP_VerifyDigest*() function. 78238405Sjkim 7959191Skris=head1 SEE ALSO 8059191Skris 8168651SkrisL<evp(3)|evp(3)>, 8259191SkrisL<EVP_SignInit(3)|EVP_SignInit(3)>, 8359191SkrisL<EVP_DigestInit(3)|EVP_DigestInit(3)>, L<err(3)|err(3)>, 8459191SkrisL<evp(3)|evp(3)>, L<hmac(3)|hmac(3)>, L<md2(3)|md2(3)>, 8559191SkrisL<md5(3)|md5(3)>, L<mdc2(3)|mdc2(3)>, L<ripemd(3)|ripemd(3)>, 86100936SnectarL<sha(3)|sha(3)>, L<dgst(1)|dgst(1)> 8759191Skris 8859191Skris=head1 HISTORY 8959191Skris 9059191SkrisEVP_VerifyInit(), EVP_VerifyUpdate() and EVP_VerifyFinal() are 9159191Skrisavailable in all versions of SSLeay and OpenSSL. 9259191Skris 93109998SmarkmEVP_VerifyInit_ex() was added in OpenSSL 0.9.7 94109998Smarkm 9559191Skris=cut 96