NAME
EVP_DigestVerifyInit,
EVP_DigestVerifyUpdate,
EVP_DigestVerifyFinal,
EVP_DigestVerify —
EVP signature verification
functions
SYNOPSIS
#include
<openssl/evp.h>
int
EVP_DigestVerifyInit(EVP_MD_CTX
*ctx, EVP_PKEY_CTX **pctx, const
EVP_MD *type, ENGINE *engine,
EVP_PKEY *pkey);
int
EVP_DigestVerifyUpdate(EVP_MD_CTX
*ctx, const void *d, size_t
cnt);
int
EVP_DigestVerifyFinal(EVP_MD_CTX
*ctx, const unsigned char *sig,
size_t siglen);
int
EVP_DigestVerify(EVP_MD_CTX
*ctx, const unsigned char *sig,
size_t siglen, const unsigned char
*tbs, size_t *tbslen);
DESCRIPTION
The EVP signature routines are a high-level interface to digital signatures.
EVP_DigestVerifyInit()
sets up verification context ctx to use digest
type and public key pkey.
ctx must be initialized with
EVP_MD_CTX_init(3) before calling this function. If
pctx is not NULL, the
EVP_PKEY_CTX of the verification operation will be
written to *pctx: this can be used to set alternative
verification options. Any existing value in *.Fa pctx is overwritten. The
EVP_PKEY_CTX value returned must not be freed directly
by the application. It will be freed automatically when the
EVP_MD_CTX is freed. The ENGINE
*engine argument is always ignored and passing
NULL is recommended.
EVP_DigestVerifyUpdate()
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. This function is currently implemented using a macro.
EVP_DigestVerifyFinal()
verifies the data in ctx against the signature in
sig of length siglen.
EVP_DigestVerify()
verifies tbslen bytes at tbs
against the signature in sig of length
siglen. EVP_DigestVerify() is
a one shot operation which verifies a single block of data in one function
call. For algorithms that support streaming it is equivalent to calling
EVP_DigestVerifyUpdate() and
EVP_DigestVerifyFinal().
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.
The call to
EVP_DigestVerifyFinal()
internally finalizes a copy of the digest context. This means that
EVP_VerifyUpdate(3) and
EVP_VerifyFinal(3) 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_free(3) or a memory leak will occur.
RETURN VALUES
EVP_DigestVerifyInit() and
EVP_DigestVerifyUpdate() return 1 for success and 0
for failure.
EVP_DigestVerifyFinal() and
EVP_DigestVerify() return 1 for success; any other
value indicates failure. A return value of 0 indicates that the signature
did not verify successfully (that is, the signature did not match the
original data or the signature had an invalid form), while other values
indicate a more serious error (and sometimes also indicate an invalid
signature form).
The error codes can be obtained from ERR_get_error(3).
SEE ALSO
evp(3), EVP_DigestInit(3), EVP_DigestSignInit(3), EVP_PKEY_meth_set_verifyctx(3)
HISTORY
EVP_DigestVerifyInit(),
EVP_DigestVerifyUpdate(), and
EVP_DigestVerifyFinal() first appeared in OpenSSL
1.0.0 and have been available since OpenBSD 4.9.
EVP_DigestVerify() first appeared in
OpenSSL 1.1.1 and has been available since OpenBSD
7.0.