EVP_DigestSignInit - EVP signing functions
#include <openssl/evp.h> int EVP_DigestSignInit(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx, const EVP_MD *type, ENGINE *e, EVP_PKEY *pkey); int EVP_DigestSignUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt); int EVP_DigestSignFinal(EVP_MD_CTX *ctx, unsigned char *sig, size_t *siglen);
OpenSSL EVP_DigestSignInit(3openssl)
NAME
EVP_DigestSignInit, EVP_DigestSignUpdate, EVP_DigestSignFinal - EVP
signing functions
SYNOPSIS
#include <openssl/evp.h>
int EVP_DigestSignInit(EVP_MD_CTX *ctx, EVP_PKEY_CTX **pctx,
const EVP_MD *type, ENGINE *e, EVP_PKEY *pkey);
int EVP_DigestSignUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt);
int EVP_DigestSignFinal(EVP_MD_CTX *ctx, unsigned char *sig, size_t *siglen);
DESCRIPTION
The EVP signature routines are a high level interface to digital
signatures.
EVP_DigestSignInit() sets up signing context ctx to use digest type
from ENGINE impl and private 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 signing operation will be written to *pctx:
this can be used to set alternative signing 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). The digest type may be
NULL if the signing algorithm supports it.
EVP_DigestSignUpdate() 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. This function is currently implemented usig
a macro.
EVP_DigestSignFinal() signs the data in ctx places the signature in
sig. If sig is NULL then the maximum size of the output buffer is
written to the siglen parameter. If sig is not NULL then before the
call the siglen parameter should contain the length of the sig buffer,
if the call is successful the signature is written to sig and the
amount of data written to siglen.
RETURN VALUES
EVP_DigestSignInit() EVP_DigestSignUpdate() and EVP_DigestSignaFinal()
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.
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_DigestSignFinal() internally finalizes a copy of the
digest context. This means that calls to EVP_DigestSignUpdate() and
EVP_DigestSignFinal() 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_cleanup() or a
memory leak will occur.
The use of EVP_PKEY_size() with these functions is discouraged because
some signature operations may have a signature length which depends on
the parameters set. As a result EVP_PKEY_size() would have to return a
value which indicates the maximum possible signature for any set of
parameters.
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_DigestVerifyInit(3), EVP_DigestInit(3), err(3), evp(3), hmac(3),
md2(3), md5(3), mdc2(3), ripemd(3), sha(3), dgst(1)
HISTORY
EVP_DigestSignInit(), EVP_DigestSignUpdate() and EVP_DigestSignFinal()
were first added to OpenSSL 1.0.0.
1.0.2ze 2022-05-03
EVP_DigestSignInit(3openssl)