NAME

       ECDSA_SIG_new, ECDSA_SIG_free, ECDSA_SIG_get0, ECDSA_SIG_get0_r, ECDSA_SIG_get0_s,
       ECDSA_SIG_set0 - Functions for creating, destroying and manipulating ECDSA_SIG objects

SYNOPSIS

        #include <openssl/ecdsa.h>

        ECDSA_SIG *ECDSA_SIG_new(void);
        void ECDSA_SIG_free(ECDSA_SIG *sig);
        void ECDSA_SIG_get0(const ECDSA_SIG *sig, const BIGNUM **pr, const BIGNUM **ps);
        const BIGNUM *ECDSA_SIG_get0_r(const ECDSA_SIG *sig);
        const BIGNUM *ECDSA_SIG_get0_s(const ECDSA_SIG *sig);
        int ECDSA_SIG_set0(ECDSA_SIG *sig, BIGNUM *r, BIGNUM *s);

DESCRIPTION

       ECDSA_SIG is an opaque structure consisting of two BIGNUMs for the r and s value of an
       Elliptic Curve Digital Signature Algorithm (ECDSA) signature (see FIPS186-4 or X9.62).
       The ECDSA_SIG object was mainly used by the deprecated low level functions described in
       ECDSA_sign(3), it is still required in order to be able to set or get the values of r and
       s into or from a signature. This is mainly used for testing purposes as shown in the
       "EXAMPLES".

       ECDSA_SIG_new() allocates an empty ECDSA_SIG structure.  Note: before OpenSSL 1.1.0, the r
       and s components were initialised.

       ECDSA_SIG_free() frees the ECDSA_SIG structure sig.

       ECDSA_SIG_get0() returns internal pointers the r and s values contained in sig and stores
       them in *pr and *ps, respectively.  The pointer pr or ps can be NULL, in which case the
       corresponding value is not returned.

       The values r, s can also be retrieved separately by the corresponding function
       ECDSA_SIG_get0_r() and ECDSA_SIG_get0_s(), respectively.

       Non-NULL r and s values can be set on the sig by calling ECDSA_SIG_set0(). Calling this
       function transfers the memory management of the values to the ECDSA_SIG object, and
       therefore the values that have been passed in should not be freed by the caller.

       See i2d_ECDSA_SIG(3) and d2i_ECDSA_SIG(3) for information about encoding and decoding
       ECDSA signatures to/from DER.

RETURN VALUES

       ECDSA_SIG_new() returns NULL if the allocation fails.

       ECDSA_SIG_set0() returns 1 on success or 0 on failure.

       ECDSA_SIG_get0_r() and ECDSA_SIG_get0_s() return the corresponding value, or NULL if it is
       unset.

EXAMPLES

       Extract signature r and s values from a ECDSA signature of size signaturelen:

        ECDSA_SIG *obj;
        const BIGNUM *r, *s;

        /* Load a signature into the ECDSA_SIG object */
        obj = d2i_ECDSA_SIG(NULL, &signature, signaturelen);
        if (obj == NULL)
            /* error */

        r = ECDSA_SIG_get0_r(obj);
        s = ECDSA_SIG_get0_s(obj);
        if (r == NULL || s == NULL)
            /* error */

        /* Use BN_bn2binpad() here to convert to r and s into byte arrays */

        /*
         * Do not try to access I<r> or I<s> after calling ECDSA_SIG_free(),
         * as they are both freed by this call.
         */
        ECDSA_SIG_free(obj);

       Convert r and s byte arrays into an ECDSA_SIG signature of size signaturelen:

        ECDSA_SIG *obj = NULL;
        unsigned char *signature = NULL;
        size_t signaturelen;
        BIGNUM *rbn = NULL, *sbn = NULL;

        obj = ECDSA_SIG_new();
        if (obj == NULL)
            /* error */
        rbn = BN_bin2bn(r, rlen, NULL);
        sbn = BN_bin2bn(s, slen, NULL);
        if (rbn == NULL || sbn == NULL)
            /* error */

        if (!ECDSA_SIG_set0(obj, rbn, sbn))
            /* error */
        /* Set these to NULL since they are now owned by obj */
        rbn = sbn = NULL;

        signaturelen = i2d_ECDSA_SIG(obj, &signature);
        if (signaturelen <= 0)
            /* error */

        /*
         * This signature could now be passed to L<EVP_DigestVerify(3)>
         * or L<EVP_DigestVerifyFinal(3)>
         */

        BN_free(rbn);
        BN_free(sbn);
        OPENSSL_free(signature);
        ECDSA_SIG_free(obj);

CONFORMING TO

       ANSI X9.62, US Federal Information Processing Standard FIPS186-4 (Digital Signature
       Standard, DSS)

SEE ALSO

       EC_KEY_new(3), EVP_DigestSignInit(3), EVP_DigestVerifyInit(3), EVP_PKEY_sign(3)
       i2d_ECDSA_SIG(3), d2i_ECDSA_SIG(3), ECDSA_sign(3)

COPYRIGHT

       Copyright 2004-2022 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>.