EVP signature verification
*ctx, const EVP_MD *type, ENGINE
*ctx, const void *d, unsigned
unsigned char *sigbuf, unsigned int
siglen, EVP_PKEY *pkey);
const EVP_MD *type);
The EVP signature verification routines are a high level interface to digital signatures.
sets up a verification context ctx to use the digest
type from ENGINE
impl. ctx must be initialized by
EVP_MD_CTX_init(3) before calling this function.
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
verifies the data in ctx using the public key
pkey and against the siglen
bytes at sigbuf.
initializes a verification context ctx to use the
default implementation of digest type.
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
internally finalizes a copy of the digest context. This means that calls to
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(3), or a memory leak will occur.
EVP_VerifyUpdate() return 1 for success and 0 for
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).
ERR(3), evp(3), EVP_DigestInit(3), EVP_SignInit(3)
EVP_VerifyFinal() are available in all versions of
SSLeay and OpenSSL.
EVP_VerifyInit_ex() was added in OpenSSL
Older versions of this documentation wrongly stated that calls to
EVP_VerifyUpdate() could not be made after calling
Since the public key is passed in the call to EVP_SignFinal(3), 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(3).
It is not possible to change the signing parameters using these functions.
The previous two bugs are fixed in the newer functions of the EVP_DigestVerifyInit(3) family.