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)