EVP_DigestVerifyInit - EVP signature verification functions
#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, size_t cnt); int EVP_DigestVerifyFinal(EVP_MD_CTX *ctx, const unsigned char *sig, size_t siglen);
OpenSSL EVP_DigestVerifyInit(3openssl)
NAME
EVP_DigestVerifyInit, EVP_DigestVerifyUpdate, EVP_DigestVerifyFinal -
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 *e, 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);
DESCRIPTION
The EVP signature routines are a high level interface to digital
signatures.
EVP_DigestVerifyInit() sets up verification context ctx to use digest
type from ENGINE impl and public key pkey. ctx must be initialized with
EVP_MD_CTX_init() 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. Note
that any existing value in *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).
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.
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.
EVP_DigestVerifyFinal() returns 1 for success; any other value
indicates failure. A return value of zero indicates that the signature
did not verify successfully (that is, tbs 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).
ATTRIBUTES
See attributes(7) for descriptions of the following attributes:
+---------------+--------------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+--------------------------+
|Availability | library/security/openssl |
+---------------+--------------------------+
|Stability | Pass-through uncommitted |
+---------------+--------------------------+
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.
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 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.
Source code for open source software components in Oracle Solaris can
be found at https://www.oracle.com/downloads/opensource/solaris-source-
code-downloads.html.
This software was built from source available at
https://github.com/oracle/solaris-userland. The original community
source was downloaded from
https://www.openssl.org/source/openssl-1.0.2ze.tar.gz.
Further information about this software can be found on the open source
community website at https://www.openssl.org/.
SEE ALSO
EVP_DigestSignInit(3), EVP_DigestInit(3), err(3), evp(3), hmac(3),
md2(3), md5(3), mdc2(3), ripemd(3), sha(3), dgst(1)
HISTORY
EVP_DigestVerifyInit(), EVP_DigestVerifyUpdate() and
EVP_DigestVerifyFinal() were first added to OpenSSL 1.0.0.
1.0.2ze 2022-05-03
EVP_DigestVerifyInit(3openssl)