NAME¶
EVP_VerifyInit, EVP_VerifyUpdate, EVP_VerifyFinal - EVP signature verification
functions
SYNOPSIS¶
#include <openssl/evp.h>
int EVP_VerifyInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
int EVP_VerifyUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
int EVP_VerifyFinal(EVP_MD_CTX *ctx,unsigned char *sigbuf, unsigned int siglen,EVP_PKEY *pkey);
int EVP_VerifyInit(EVP_MD_CTX *ctx, const EVP_MD *type);
DESCRIPTION¶
The EVP signature verification routines are a high level interface to digital
signatures.
EVP_VerifyInit_ex() sets up verification context
ctx to use digest
type from ENGINE
impl.
ctx must be initialized by calling
EVP_MD_CTX_init() before calling this function.
EVP_VerifyUpdate() hashes
cnt bytes of data at
d into the
verification context
ctx. This function can be called several times on
the same
ctx to include additional data.
EVP_VerifyFinal() verifies the data in
ctx using the public key
pkey and against the
siglen bytes at
sigbuf.
EVP_VerifyInit() initializes verification context
ctx to use the
default implementation of digest
type.
RETURN VALUES¶
EVP_VerifyInit_ex() and
EVP_VerifyUpdate() return 1 for success
and 0 for failure.
EVP_VerifyFinal() returns 1 for a correct signature, 0 for failure and -1
if some other error occurred.
The error codes can be obtained by
ERR_get_error(3).
NOTES¶
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.
Due to the link between message digests and public key algorithms the correct
digest algorithm must be used with the correct public key type. A list of
algorithms and associated public key algorithms appears in
EVP_DigestInit(3).
The call to
EVP_VerifyFinal() 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.
BUGS¶
Older versions of this documentation wrongly stated that calls to
EVP_VerifyUpdate() could not be made after calling
EVP_VerifyFinal().
Since the public key is passed in the call to
EVP_SignFinal() any error
relating to the private key (for example an unsuitable key and digest
combination) will not be indicated until after potentially large amounts of
data have been passed through
EVP_SignUpdate().
It is not possible to change the signing parameters using these function.
The previous two bugs are fixed in the newer EVP_VerifyDigest*() function.
SEE ALSO¶
evp(3),
EVP_SignInit(3),
EVP_DigestInit(3),
err(3),
evp(3),
hmac(3),
md2(3),
md5(3),
mdc2(3),
ripemd(3),
sha(3),
dgst(1)
HISTORY¶
EVP_VerifyInit(),
EVP_VerifyUpdate() and
EVP_VerifyFinal()
are available in all versions of SSLeay and OpenSSL.
EVP_VerifyInit_ex() was added in OpenSSL 0.9.7