plucky (3) EVP_SignUpdate.3ssl.gz

Provided by: libssl-doc_3.4.1-1ubuntu1_all bug

NAME
       EVP_SignInit, EVP_SignInit_ex, EVP_SignUpdate, EVP_SignFinal_ex, EVP_SignFinal - EVP signing functions


SYNOPSIS
        #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);


DESCRIPTION
       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.


RETURN VALUES
       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).


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.

       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.cApplications
       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_SignFinal() will finalize the digest context and attempting to process additional
       data via EVP_SignUpdate() will result in an error.


BUGS
       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.


SEE ALSO
       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)


HISTORY
       The function EVP_SignFinal_ex() was added in OpenSSL 3.0.


       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>.