EVP_VERIFYINIT(3ossl) OpenSSL EVP_VERIFYINIT(3ossl)
NAME
EVP_VerifyInit_ex, EVP_VerifyInit, EVP_VerifyUpdate,
EVP_VerifyFinal_ex, 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_ex(EVP_MD_CTX *ctx, const unsigned char *sigbuf,
unsigned int siglen, EVP_PKEY *pkey,
OSSL_LIB_CTX *libctx, const char *propq);
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 created by calling EVP_MD_CTX_new()
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_ex() verifies the data in ctx using the public key pkey
and siglen bytes in sigbuf. The library context libctx and property
query propq are used when creating a context to use with the key pkey.
EVP_VerifyFinal() is similar to EVP_VerifyFinal_ex() but uses default
values of NULL for the library context libctx and the property query
propq.
EVP_VerifyInit(3) 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_ex() and EVP_VerifyFinal() return 1 for a correct
signature, 0 for failure and a negative value 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.
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. Applications may disable this behavior by setting the
EVP_MD_CTX_FLAG_FINALISE context flag via EVP_MD_CTX_set_flags(3).
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() or a memory
leak will occur.
Note that not all providers support continuation, in case the selected
provider does not allow to duplicate contexts EVP_VerifyFinal() will
finalize the digest context and attempting to process additional data
via EVP_VerifyUpdate() will result in an error.
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_DigestVerify*()
function.
SEE ALSO
evp(7), EVP_SignInit(3), EVP_DigestInit(3), evp(7), HMAC(3), MD2(3),
MD5(3), MDC2(3), RIPEMD160(3), SHA1(3), openssl-dgst(1)
HISTORY
The function EVP_VerifyFinal_ex() was added in OpenSSL 3.0.
COPYRIGHT
Copyright 2000-2023 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file LICENSE in the source distribution or at
<https://www.openssl.org/source/license.html>.
3.3.2 2024-09-04 EVP_VERIFYINIT(3ossl)
openssl 3.3.2 - Generated Sat Sep 14 09:18:35 CDT 2024