83 lines
3.2 KiB
Text
83 lines
3.2 KiB
Text
|
=pod
|
||
|
|
|
||
|
|
=head1 NAME
|
||
|
|
|
||
|
|
EVP_DigestVerifyInit, EVP_DigestVerifyUpdate, EVP_DigestVerifyFinal - EVP signature verification functions
|
||
|
|
|
||
|
|
=head1 SYNOPSIS
|
||
|
|
|
||
|
|
#include <openssl/evp.h>
|
||
|
|
|
||
|
|
int EVP_DigestVerifyInit(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx,
|
||
|
|
const EVP_MD *type, ENGINE *e, EVP_PKEY *pkey);
|
||
|
|
int EVP_DigestVerifyUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
|
||
|
|
int EVP_DigestVerifyFinal(EVP_MD_CTX *ctx, unsigned char *sig, size_t siglen);
|
||
|
|
|
||
|
|
=head1 DESCRIPTION
|
||
|
|
|
||
|
|
The EVP signature routines are a high level interface to digital signatures.
|
||
|
|
|
||
|
|
EVP_DigestVerifyInit() sets up verification context B<ctx> to use digest
|
||
|
|
B<type> from ENGINE B<impl> and public key B<pkey>. B<ctx> must be initialized
|
||
|
|
with EVP_MD_CTX_init() before calling this function. If B<pctx> is not NULL the
|
||
|
|
EVP_PKEY_CTX of the verification operation will be written to B<*pctx>: this
|
||
|
|
can be used to set alternative verification options.
|
||
|
|
|
||
|
|
EVP_DigestVerifyUpdate() hashes B<cnt> bytes of data at B<d> into the
|
||
|
|
verification context B<ctx>. This function can be called several times on the
|
||
|
|
same B<ctx> to include additional data. This function is currently implemented
|
||
|
|
using a macro.
|
||
|
|
|
||
|
|
EVP_DigestVerifyFinal() verifies the data in B<ctx> against the signature in
|
||
|
|
B<sig> of length B<siglen>.
|
||
|
|
|
||
|
|
=head1 RETURN VALUES
|
||
|
|
|
||
|
|
EVP_DigestVerifyInit() and EVP_DigestVerifyUpdate() return 1 for success and 0
|
||
|
|
or a negative value for failure. In particular a return value of -2 indicates
|
||
|
|
the operation is not supported by the public key algorithm.
|
||
|
|
|
||
|
|
Unlike other functions the return value 0 from EVP_DigestVerifyFinal() only
|
||
|
|
indicates that the signature did not not verify successfully (that is tbs did
|
||
|
|
not match the original data or the signature was of invalid form) it is not an
|
||
|
|
indication of a more serious error.
|
||
|
|
|
||
|
|
The error codes can be obtained from L<ERR_get_error(3)|ERR_get_error(3)>.
|
||
|
|
|
||
|
|
=head1 NOTES
|
||
|
|
|
||
|
|
The B<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.
|
||
|
|
|
||
|
|
In previous versions of OpenSSL there was a link between message digest types
|
||
|
|
and public key algorithms. This meant that "clone" digests such as EVP_dss1()
|
||
|
|
needed to be used to sign using SHA1 and DSA. This is no longer necessary and
|
||
|
|
the use of clone digest is now discouraged.
|
||
|
|
|
||
|
|
For some key types and parameters the random number generator must be seeded
|
||
|
|
or the operation will fail.
|
||
|
|
|
||
|
|
The call to EVP_DigestVerifyFinal() internally finalizes a copy of the digest
|
||
|
|
context. This means that calls to EVP_VerifyUpdate() and EVP_VerifyFinal() can
|
||
|
|
be called later to digest and verify additional data.
|
||
|
|
|
||
|
|
Since only a copy of the digest context is ever finalized the context must
|
||
|
|
be cleaned up after use by calling EVP_MD_CTX_cleanup() or a memory leak
|
||
|
|
will occur.
|
||
|
|
|
||
|
|
=head1 SEE ALSO
|
||
|
|
|
||
|
|
L<EVP_DigestSignInit(3)|EVP_DigestSignInit(3)>,
|
||
|
|
L<EVP_DigestInit(3)|EVP_DigestInit(3)>, L<err(3)|err(3)>,
|
||
|
|
L<evp(3)|evp(3)>, L<hmac(3)|hmac(3)>, L<md2(3)|md2(3)>,
|
||
|
|
L<md5(3)|md5(3)>, L<mdc2(3)|mdc2(3)>, L<ripemd(3)|ripemd(3)>,
|
||
|
|
L<sha(3)|sha(3)>, L<dgst(1)|dgst(1)>
|
||
|
|
|
||
|
|
=head1 HISTORY
|
||
|
|
|
||
|
|
EVP_DigestVerifyInit(), EVP_DigestVerifyUpdate() and EVP_DigestVerifyFinal()
|
||
|
|
were first added to OpenSSL 0.9.9.
|
||
|
|
|
||
|
|
=cut
|