a528d4f0a9
If something was "present in all versions" of SSLeay, or if it was added to a version of SSLeay (and therefore predates OpenSSL), remove mention of it. Documentation history now starts with OpenSSL. Remove mention of all history before OpenSSL 0.9.8, inclusive. Remove all AUTHOR sections. Reviewed-by: Tim Hudson <tjh@openssl.org>
89 lines
2.9 KiB
Plaintext
89 lines
2.9 KiB
Plaintext
=pod
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=head1 NAME
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EVP_VerifyInit, EVP_VerifyUpdate, EVP_VerifyFinal - EVP signature verification functions
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=head1 SYNOPSIS
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#include <openssl/evp.h>
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int EVP_VerifyInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
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int EVP_VerifyUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
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int EVP_VerifyFinal(EVP_MD_CTX *ctx,unsigned char *sigbuf, unsigned int siglen,EVP_PKEY *pkey);
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int EVP_VerifyInit(EVP_MD_CTX *ctx, const EVP_MD *type);
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=head1 DESCRIPTION
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The EVP signature verification routines are a high level interface to digital
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signatures.
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EVP_VerifyInit_ex() sets up verification context B<ctx> to use digest
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B<type> from ENGINE B<impl>. B<ctx> must be initialized by calling
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EVP_MD_CTX_init() before calling this function.
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EVP_VerifyUpdate() hashes B<cnt> bytes of data at B<d> into the
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verification context B<ctx>. This function can be called several times on the
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same B<ctx> to include additional data.
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EVP_VerifyFinal() verifies the data in B<ctx> using the public key B<pkey>
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and against the B<siglen> bytes at B<sigbuf>.
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EVP_VerifyInit() initializes verification context B<ctx> to use the default
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implementation of digest B<type>.
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=head1 RETURN VALUES
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EVP_VerifyInit_ex() and EVP_VerifyUpdate() return 1 for success and 0 for
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failure.
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EVP_VerifyFinal() returns 1 for a correct signature, 0 for failure and -1 if some
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other error occurred.
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The error codes can be obtained by L<ERR_get_error(3)>.
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=head1 NOTES
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The B<EVP> interface to digital signatures should almost always be used in
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preference to the low level interfaces. This is because the code then becomes
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transparent to the algorithm used and much more flexible.
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Due to the link between message digests and public key algorithms the correct
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digest algorithm must be used with the correct public key type. A list of
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algorithms and associated public key algorithms appears in
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L<EVP_DigestInit(3)>.
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The call to EVP_VerifyFinal() internally finalizes a copy of the digest context.
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This means that calls to EVP_VerifyUpdate() and EVP_VerifyFinal() can be called
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later to digest and verify additional data.
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Since only a copy of the digest context is ever finalized the context must
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be cleaned up after use by calling EVP_MD_CTX_cleanup() or a memory leak
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will occur.
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=head1 BUGS
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Older versions of this documentation wrongly stated that calls to
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EVP_VerifyUpdate() could not be made after calling EVP_VerifyFinal().
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Since the public key is passed in the call to EVP_SignFinal() any error
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relating to the private key (for example an unsuitable key and digest
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combination) will not be indicated until after potentially large amounts of
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data have been passed through EVP_SignUpdate().
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It is not possible to change the signing parameters using these function.
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The previous two bugs are fixed in the newer EVP_VerifyDigest*() function.
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=head1 SEE ALSO
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L<evp(3)>,
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L<EVP_SignInit(3)>,
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L<EVP_DigestInit(3)>, L<err(3)>,
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L<evp(3)>, L<hmac(3)>, L<md2(3)>,
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L<md5(3)>, L<mdc2(3)>, L<ripemd(3)>,
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L<sha(3)>, L<dgst(1)>
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=cut
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