EVP_SignInit, EVP_SignInit_ex, EVP_SignUpdate, EVP_SignFinal_ex, EVP_SignFinal -
EVP signing functions
#include <openssl/evp.h>
int EVP_SignInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
int EVP_SignUpdate(EVP_MD_CTX *ctx, const void *d, unsigned int cnt);
int EVP_SignFinal_ex(EVP_MD_CTX *ctx, unsigned char *md, unsigned int *s,
EVP_PKEY *pkey, OSSL_LIB_CTX *libctx, const char *propq);
int EVP_SignFinal(EVP_MD_CTX *ctx, unsigned char *sig, unsigned int *s,
EVP_PKEY *pkey);
void EVP_SignInit(EVP_MD_CTX *ctx, const EVP_MD *type);
The EVP signature routines are a high-level interface to digital signatures.
EVP_SignInit_ex() sets up signing context
ctx to use digest
type from
ENGINE impl.
ctx must be created with
EVP_MD_CTX_new() before calling this function.
EVP_SignUpdate() hashes
cnt bytes of data at
d into the
signature context
ctx. This function can be called several times on the
same
ctx to include additional data.
EVP_SignFinal_ex() signs the data in
ctx using the private key
pkey and places the signature in
sig. The library context
libctx and property query
propq are used when creating a context
to use with the key
pkey.
sig must be at least
"EVP_PKEY_get_size(pkey)" bytes in size.
s is an OUT
parameter, and not used as an IN parameter. The number of bytes of data
written (i.e. the length of the signature) will be written to the integer at
s, at most "EVP_PKEY_get_size(pkey)" bytes will be written.
EVP_SignFinal() is similar to
EVP_SignFinal_ex() but uses default
values of NULL for the library context
libctx and the property query
propq.
EVP_SignInit() initializes a signing context
ctx to use the
default implementation of digest
type.
EVP_SignInit_ex(),
EVP_SignUpdate(),
EVP_SignFinal_ex() and
EVP_SignFinal() return 1 for success and 0 for failure.
The error codes can be obtained by
ERR_get_error(3).
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.
When signing with some private key types the random number generator must be
seeded. If the automatic seeding or reseeding of the OpenSSL CSPRNG fails due
to external circumstances (see
RAND(7)), the operation will fail.
The call to
EVP_SignFinal() internally finalizes a copy of the digest
context. This means that calls to
EVP_SignUpdate() and
EVP_SignFinal() can be called later to digest and sign 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() or a memory leak will
occur.
Older versions of this documentation wrongly stated that calls to
EVP_SignUpdate() could not be made after calling
EVP_SignFinal().
Since the private 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_DigestSign*() functions.
EVP_PKEY_get_size(3),
EVP_PKEY_get_bits(3),
EVP_PKEY_get_security_bits(3),
EVP_VerifyInit(3),
EVP_DigestInit(3),
evp(7),
HMAC(3),
MD2(3),
MD5(3),
MDC2(3),
RIPEMD160(3),
SHA1(3),
openssl-dgst(1)
The function
EVP_SignFinal_ex() was added in OpenSSL 3.0.
Copyright 2000-2021 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>.