Merge ECDSA code that will stay into ecdsa.c

discussed with jsing

1 files changed, 821 insertions, 0 deletions

diff --git a/src/lib/libcrypto/ecdsa/ecdsa.c b/src/lib/libcrypto/ecdsa/ecdsa.c
new file mode 100644
index 0000000000..c831e9f716
--- /dev/null
+++ b/src/lib/libcrypto/ecdsa/ecdsa.c
@@ -0,0 +1,821 @@
+/* $OpenBSD: ecdsa.c,v 1.1 2023/07/05 12:18:21 tb Exp $ */
+/* ====================================================================
+ * Copyright (c) 2000-2002 The OpenSSL Project.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. All advertising materials mentioning features or use of this
+ *    software must display the following acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
+ *
+ * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
+ *    endorse or promote products derived from this software without
+ *    prior written permission. For written permission, please contact
+ *    licensing@OpenSSL.org.
+ *
+ * 5. Products derived from this software may not be called "OpenSSL"
+ *    nor may "OpenSSL" appear in their names without prior written
+ *    permission of the OpenSSL Project.
+ *
+ * 6. Redistributions of any form whatsoever must retain the following
+ *    acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
+ * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ * ====================================================================
+ *
+ * This product includes cryptographic software written by Eric Young
+ * (eay@cryptsoft.com).  This product includes software written by Tim
+ * Hudson (tjh@cryptsoft.com).
+ *
+ */
+
+#include <string.h>
+
+#include <openssl/opensslconf.h>
+
+#include <openssl/asn1t.h>
+#include <openssl/bn.h>
+#include <openssl/err.h>
+#include <openssl/evp.h>
+#include <openssl/objects.h>
+
+#include "bn_local.h"
+#include "ec_local.h"
+#include "ecdsa_local.h"
+
+static const ASN1_TEMPLATE ECDSA_SIG_seq_tt[] = {
+        {
+                .flags = 0,
+                .tag = 0,
+                .offset = offsetof(ECDSA_SIG, r),
+                .field_name = "r",
+                .item = &BIGNUM_it,
+        },
+        {
+                .flags = 0,
+                .tag = 0,
+                .offset = offsetof(ECDSA_SIG, s),
+                .field_name = "s",
+                .item = &BIGNUM_it,
+        },
+};
+
+const ASN1_ITEM ECDSA_SIG_it = {
+        .itype = ASN1_ITYPE_SEQUENCE,
+        .utype = V_ASN1_SEQUENCE,
+        .templates = ECDSA_SIG_seq_tt,
+        .tcount = sizeof(ECDSA_SIG_seq_tt) / sizeof(ASN1_TEMPLATE),
+        .funcs = NULL,
+        .size = sizeof(ECDSA_SIG),
+        .sname = "ECDSA_SIG",
+};
+
+ECDSA_SIG *ECDSA_SIG_new(void);
+void ECDSA_SIG_free(ECDSA_SIG *a);
+ECDSA_SIG *d2i_ECDSA_SIG(ECDSA_SIG **a, const unsigned char **in, long len);
+int i2d_ECDSA_SIG(const ECDSA_SIG *a, unsigned char **out);
+
+ECDSA_SIG *
+d2i_ECDSA_SIG(ECDSA_SIG **a, const unsigned char **in, long len)
+{
+        return (ECDSA_SIG *)ASN1_item_d2i((ASN1_VALUE **)a, in, len,
+            &ECDSA_SIG_it);
+}
+
+int
+i2d_ECDSA_SIG(const ECDSA_SIG *a, unsigned char **out)
+{
+        return ASN1_item_i2d((ASN1_VALUE *)a, out, &ECDSA_SIG_it);
+}
+
+ECDSA_SIG *
+ECDSA_SIG_new(void)
+{
+        return (ECDSA_SIG *)ASN1_item_new(&ECDSA_SIG_it);
+}
+
+void
+ECDSA_SIG_free(ECDSA_SIG *a)
+{
+        ASN1_item_free((ASN1_VALUE *)a, &ECDSA_SIG_it);
+}
+
+void
+ECDSA_SIG_get0(const ECDSA_SIG *sig, const BIGNUM **pr, const BIGNUM **ps)
+{
+        if (pr != NULL)
+                *pr = sig->r;
+        if (ps != NULL)
+                *ps = sig->s;
+}
+
+const BIGNUM *
+ECDSA_SIG_get0_r(const ECDSA_SIG *sig)
+{
+        return sig->r;
+}
+
+const BIGNUM *
+ECDSA_SIG_get0_s(const ECDSA_SIG *sig)
+{
+        return sig->s;
+}
+
+int
+ECDSA_SIG_set0(ECDSA_SIG *sig, BIGNUM *r, BIGNUM *s)
+{
+        if (r == NULL || s == NULL)
+                return 0;
+
+        BN_free(sig->r);
+        BN_free(sig->s);
+        sig->r = r;
+        sig->s = s;
+        return 1;
+}
+
+/*
+ * FIPS 186-5, section 6.4.1, step 2: convert hashed message into an integer.
+ * Use the order_bits leftmost bits if it exceeds the group order.
+ */
+static int
+ecdsa_prepare_digest(const unsigned char *digest, int digest_len,
+    const EC_KEY *key, BIGNUM *e)
+{
+        const EC_GROUP *group;
+        int digest_bits, order_bits;
+
+        if (!BN_bin2bn(digest, digest_len, e)) {
+                ECDSAerror(ERR_R_BN_LIB);
+                return 0;
+        }
+
+        if ((group = EC_KEY_get0_group(key)) == NULL)
+                return 0;
+        order_bits = EC_GROUP_order_bits(group);
+
+        digest_bits = 8 * digest_len;
+        if (digest_bits <= order_bits)
+                return 1;
+
+        return BN_rshift(e, e, digest_bits - order_bits);
+}
+
+int
+ecdsa_sign(int type, const unsigned char *digest, int digest_len,
+    unsigned char *signature, unsigned int *signature_len, const BIGNUM *kinv,
+    const BIGNUM *r, EC_KEY *key)
+{
+        ECDSA_SIG *sig;
+        int out_len = 0;
+        int ret = 0;
+
+        if ((sig = ECDSA_do_sign_ex(digest, digest_len, kinv, r, key)) == NULL)
+                goto err;
+
+        if ((out_len = i2d_ECDSA_SIG(sig, &signature)) < 0) {
+                out_len = 0;
+                goto err;
+        }
+
+        ret = 1;
+
+ err:
+        *signature_len = out_len;
+        ECDSA_SIG_free(sig);
+
+        return ret;
+}
+
+/*
+ * FIPS 186-5, section 6.4.1, steps 3-8 and 11: Generate k, calculate r and
+ * kinv, and clear it. If r == 0, try again with a new random k.
+ */
+
+int
+ecdsa_sign_setup(EC_KEY *key, BN_CTX *in_ctx, BIGNUM **out_kinv, BIGNUM **out_r)
+{
+        const EC_GROUP *group;
+        EC_POINT *point = NULL;
+        BN_CTX *ctx = NULL;
+        BIGNUM *k = NULL, *r = NULL;
+        const BIGNUM *order;
+        BIGNUM *x;
+        int order_bits;
+        int ret = 0;
+
+        BN_free(*out_kinv);
+        *out_kinv = NULL;
+
+        BN_free(*out_r);
+        *out_r = NULL;
+
+        if (key == NULL) {
+                ECDSAerror(ERR_R_PASSED_NULL_PARAMETER);
+                goto err;
+        }
+        if ((group = EC_KEY_get0_group(key)) == NULL) {
+                ECDSAerror(ERR_R_PASSED_NULL_PARAMETER);
+                goto err;
+        }
+
+        if ((k = BN_new()) == NULL)
+                goto err;
+        if ((r = BN_new()) == NULL)
+                goto err;
+
+        if ((ctx = in_ctx) == NULL)
+                ctx = BN_CTX_new();
+        if (ctx == NULL) {
+                ECDSAerror(ERR_R_MALLOC_FAILURE);
+                goto err;
+        }
+
+        BN_CTX_start(ctx);
+
+        if ((x = BN_CTX_get(ctx)) == NULL)
+                goto err;
+
+        if ((point = EC_POINT_new(group)) == NULL) {
+                ECDSAerror(ERR_R_EC_LIB);
+                goto err;
+        }
+        if ((order = EC_GROUP_get0_order(group)) == NULL) {
+                ECDSAerror(ERR_R_EC_LIB);
+                goto err;
+        }
+
+        if (BN_cmp(order, BN_value_one()) <= 0) {
+                ECDSAerror(EC_R_INVALID_GROUP_ORDER);
+                goto err;
+        }
+
+        /* Reject curves with an order that is smaller than 80 bits. */
+        if ((order_bits = BN_num_bits(order)) < 80) {
+                ECDSAerror(EC_R_INVALID_GROUP_ORDER);
+                goto err;
+        }
+
+        /* Preallocate space. */
+        if (!BN_set_bit(k, order_bits) ||
+            !BN_set_bit(r, order_bits) ||
+            !BN_set_bit(x, order_bits))
+                goto err;
+
+        /* Step 11: repeat until r != 0. */
+        do {
+                /* Step 3: generate random k. */
+                if (!bn_rand_interval(k, BN_value_one(), order)) {
+                        ECDSAerror(ECDSA_R_RANDOM_NUMBER_GENERATION_FAILED);
+                        goto err;
+                }
+
+                /*
+                 * We do not want timing information to leak the length of k,
+                 * so we compute G * k using an equivalent scalar of fixed
+                 * bit-length.
+                 *
+                 * We unconditionally perform both of these additions to prevent
+                 * a small timing information leakage.  We then choose the sum
+                 * that is one bit longer than the order.  This guarantees the
+                 * code path used in the constant time implementations
+                 * elsewhere.
+                 *
+                 * TODO: revisit the bn_copy aiming for a memory access agnostic
+                 * conditional copy.
+                 */
+                if (!BN_add(r, k, order) ||
+                    !BN_add(x, r, order) ||
+                    !bn_copy(k, BN_num_bits(r) > order_bits ? r : x))
+                        goto err;
+
+                BN_set_flags(k, BN_FLG_CONSTTIME);
+
+                /* Step 5: P = k * G. */
+                if (!EC_POINT_mul(group, point, k, NULL, NULL, ctx)) {
+                        ECDSAerror(ERR_R_EC_LIB);
+                        goto err;
+                }
+                /* Steps 6 (and 7): from P = (x, y) retain the x-coordinate. */
+                if (!EC_POINT_get_affine_coordinates(group, point, x, NULL,
+                    ctx)) {
+                        ECDSAerror(ERR_R_EC_LIB);
+                        goto err;
+                }
+                /* Step 8: r = x (mod order). */
+                if (!BN_nnmod(r, x, order, ctx)) {
+                        ECDSAerror(ERR_R_BN_LIB);
+                        goto err;
+                }
+        } while (BN_is_zero(r));
+
+        /* Step 4: calculate kinv. */
+        if (BN_mod_inverse_ct(k, k, order, ctx) == NULL) {
+                ECDSAerror(ERR_R_BN_LIB);
+                goto err;
+        }
+
+        *out_kinv = k;
+        k = NULL;
+
+        *out_r = r;
+        r = NULL;
+
+        ret = 1;
+
+ err:
+        BN_CTX_end(ctx);
+        if (ctx != in_ctx)
+                BN_CTX_free(ctx);
+        BN_free(k);
+        BN_free(r);
+        EC_POINT_free(point);
+
+        return ret;
+}
+
+/*
+ * FIPS 186-5, section 6.4.1, step 9: compute s = inv(k)(e + xr) mod order.
+ * In order to reduce the possibility of a side-channel attack, the following
+ * is calculated using a random blinding value b in [1, order):
+ * s = inv(b)(be + bxr)inv(k) mod order.
+ */
+
+static int
+ecdsa_compute_s(BIGNUM **out_s, const BIGNUM *e, const BIGNUM *kinv,
+    const BIGNUM *r, const EC_KEY *key, BN_CTX *ctx)
+{
+        const EC_GROUP *group;
+        const BIGNUM *order, *priv_key;
+        BIGNUM *b, *binv, *be, *bxr;
+        BIGNUM *s = NULL;
+        int ret = 0;
+
+        *out_s = NULL;
+
+        BN_CTX_start(ctx);
+
+        if ((group = EC_KEY_get0_group(key)) == NULL) {
+                ECDSAerror(ERR_R_PASSED_NULL_PARAMETER);
+                goto err;
+        }
+        if ((order = EC_GROUP_get0_order(group)) == NULL) {
+                ECDSAerror(ERR_R_EC_LIB);
+                goto err;
+        }
+        if ((priv_key = EC_KEY_get0_private_key(key)) == NULL) {
+                ECDSAerror(ERR_R_PASSED_NULL_PARAMETER);
+                goto err;
+        }
+
+        if ((b = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((binv = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((be = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((bxr = BN_CTX_get(ctx)) == NULL)
+                goto err;
+
+        if ((s = BN_new()) == NULL)
+                goto err;
+
+        /*
+         * In a valid ECDSA signature, r must be in [1, order). Since r can be
+         * caller provided - either directly or by replacing sign_setup() - we
+         * can't rely on this being the case.
+         */
+        if (BN_cmp(r, BN_value_one()) < 0 || BN_cmp(r, order) >= 0) {
+                ECDSAerror(ECDSA_R_BAD_SIGNATURE);
+                goto err;
+        }
+
+        if (!bn_rand_interval(b, BN_value_one(), order)) {
+                ECDSAerror(ERR_R_BN_LIB);
+                goto err;
+        }
+
+        if (BN_mod_inverse_ct(binv, b, order, ctx) == NULL) {
+                ECDSAerror(ERR_R_BN_LIB);
+                goto err;
+        }
+
+        if (!BN_mod_mul(bxr, b, priv_key, order, ctx)) {
+                ECDSAerror(ERR_R_BN_LIB);
+                goto err;
+        }
+        if (!BN_mod_mul(bxr, bxr, r, order, ctx)) {
+                ECDSAerror(ERR_R_BN_LIB);
+                goto err;
+        }
+        if (!BN_mod_mul(be, b, e, order, ctx)) {
+                ECDSAerror(ERR_R_BN_LIB);
+                goto err;
+        }
+        if (!BN_mod_add(s, be, bxr, order, ctx)) {
+                ECDSAerror(ERR_R_BN_LIB);
+                goto err;
+        }
+        /* s = b(e + xr)k^-1 */
+        if (!BN_mod_mul(s, s, kinv, order, ctx)) {
+                ECDSAerror(ERR_R_BN_LIB);
+                goto err;
+        }
+        /* s = (e + xr)k^-1 */
+        if (!BN_mod_mul(s, s, binv, order, ctx)) {
+                ECDSAerror(ERR_R_BN_LIB);
+                goto err;
+        }
+
+        /* Step 11: if s == 0 start over. */
+        if (!BN_is_zero(s)) {
+                *out_s = s;
+                s = NULL;
+        }
+
+        ret = 1;
+
+ err:
+        BN_CTX_end(ctx);
+        BN_free(s);
+
+        return ret;
+}
+
+/*
+ * It is too expensive to check curve parameters on every sign operation.
+ * Instead, cap the number of retries. A single retry is very unlikely, so
+ * allowing 32 retries is amply enough.
+ */
+#define ECDSA_MAX_SIGN_ITERATIONS               32
+
+/*
+ * FIPS 186-5: Section 6.4.1: ECDSA signature generation, steps 2-12.
+ * The caller provides the hash of the message, thus performs step 1.
+ * Step 10, zeroing k and kinv, is done by BN_free().
+ */
+
+ECDSA_SIG *
+ecdsa_sign_sig(const unsigned char *digest, int digest_len,
+    const BIGNUM *in_kinv, const BIGNUM *in_r, EC_KEY *key)
+{
+        BN_CTX *ctx = NULL;
+        BIGNUM *kinv = NULL, *r = NULL, *s = NULL;
+        BIGNUM *e;
+        int caller_supplied_values = 0;
+        int attempts = 0;
+        ECDSA_SIG *sig = NULL;
+
+        if ((ctx = BN_CTX_new()) == NULL) {
+                ECDSAerror(ERR_R_MALLOC_FAILURE);
+                goto err;
+        }
+
+        BN_CTX_start(ctx);
+
+        if ((e = BN_CTX_get(ctx)) == NULL)
+                goto err;
+
+        /* Step 2: convert hash into an integer. */
+        if (!ecdsa_prepare_digest(digest, digest_len, key, e))
+                goto err;
+
+        if (in_kinv != NULL && in_r != NULL) {
+                /*
+                 * Use the caller's kinv and r. Don't call ECDSA_sign_setup().
+                 * If we're unable to compute a valid signature, the caller
+                 * must provide new values.
+                 */
+                caller_supplied_values = 1;
+
+                if ((kinv = BN_dup(in_kinv)) == NULL) {
+                        ECDSAerror(ERR_R_MALLOC_FAILURE);
+                        goto err;
+                }
+                if ((r = BN_dup(in_r)) == NULL) {
+                        ECDSAerror(ERR_R_MALLOC_FAILURE);
+                        goto err;
+                }
+        }
+
+        do {
+                /* Steps 3-8: calculate kinv and r. */
+                if (!caller_supplied_values) {
+                        if (!ECDSA_sign_setup(key, ctx, &kinv, &r)) {
+                                ECDSAerror(ERR_R_ECDSA_LIB);
+                                goto err;
+                        }
+                }
+
+                /*
+                 * Steps 9 and 11: if s is non-NULL, we have a valid signature.
+                 */
+                if (!ecdsa_compute_s(&s, e, kinv, r, key, ctx))
+                        goto err;
+                if (s != NULL)
+                        break;
+
+                if (caller_supplied_values) {
+                        ECDSAerror(ECDSA_R_NEED_NEW_SETUP_VALUES);
+                        goto err;
+                }
+
+                if (++attempts > ECDSA_MAX_SIGN_ITERATIONS) {
+                        ECDSAerror(EC_R_WRONG_CURVE_PARAMETERS);
+                        goto err;
+                }
+        } while (1);
+
+        /* Step 12: output (r, s). */
+        if ((sig = ECDSA_SIG_new()) == NULL) {
+                ECDSAerror(ERR_R_MALLOC_FAILURE);
+                goto err;
+        }
+        if (!ECDSA_SIG_set0(sig, r, s)) {
+                ECDSA_SIG_free(sig);
+                goto err;
+        }
+        r = NULL;
+        s = NULL;
+
+ err:
+        BN_CTX_end(ctx);
+        BN_CTX_free(ctx);
+        BN_free(kinv);
+        BN_free(r);
+        BN_free(s);
+
+        return sig;
+}
+
+int
+ecdsa_verify(int type, const unsigned char *digest, int digest_len,
+    const unsigned char *sigbuf, int sig_len, EC_KEY *key)
+{
+        ECDSA_SIG *s;
+        unsigned char *der = NULL;
+        const unsigned char *p;
+        int der_len = 0;
+        int ret = -1;
+
+        if ((s = ECDSA_SIG_new()) == NULL)
+                goto err;
+
+        p = sigbuf;
+        if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL)
+                goto err;
+
+        /* Ensure signature uses DER and doesn't have trailing garbage */
+        if ((der_len = i2d_ECDSA_SIG(s, &der)) != sig_len)
+                goto err;
+        if (timingsafe_memcmp(sigbuf, der, der_len))
+                goto err;
+
+        ret = ECDSA_do_verify(digest, digest_len, s, key);
+
+ err:
+        freezero(der, der_len);
+        ECDSA_SIG_free(s);
+
+        return ret;
+}
+
+/*
+ * FIPS 186-5, section 6.4.2: ECDSA signature verification.
+ * The caller provides us with the hash of the message, so has performed step 2.
+ */
+
+int
+ecdsa_verify_sig(const unsigned char *digest, int digest_len,
+    const ECDSA_SIG *sig, EC_KEY *key)
+{
+        const EC_GROUP *group;
+        const EC_POINT *pub_key;
+        EC_POINT *point = NULL;
+        const BIGNUM *order;
+        BN_CTX *ctx = NULL;
+        BIGNUM *e, *sinv, *u, *v, *x;
+        int ret = -1;
+
+        if (key == NULL || sig == NULL) {
+                ECDSAerror(ECDSA_R_MISSING_PARAMETERS);
+                goto err;
+        }
+        if ((group = EC_KEY_get0_group(key)) == NULL) {
+                ECDSAerror(ECDSA_R_MISSING_PARAMETERS);
+                goto err;
+        }
+        if ((pub_key = EC_KEY_get0_public_key(key)) == NULL) {
+                ECDSAerror(ECDSA_R_MISSING_PARAMETERS);
+                goto err;
+        }
+
+        if ((ctx = BN_CTX_new()) == NULL) {
+                ECDSAerror(ERR_R_MALLOC_FAILURE);
+                goto err;
+        }
+
+        BN_CTX_start(ctx);
+
+        if ((e = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((sinv = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((u = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((v = BN_CTX_get(ctx)) == NULL)
+                goto err;
+        if ((x = BN_CTX_get(ctx)) == NULL)
+                goto err;
+
+        if ((order = EC_GROUP_get0_order(group)) == NULL) {
+                ECDSAerror(ERR_R_EC_LIB);
+                goto err;
+        }
+
+        /* Step 1: verify that r and s are in the range [1, order). */
+        if (BN_cmp(sig->r, BN_value_one()) < 0 || BN_cmp(sig->r, order) >= 0) {
+                ECDSAerror(ECDSA_R_BAD_SIGNATURE);
+                ret = 0;
+                goto err;
+        }
+        if (BN_cmp(sig->s, BN_value_one()) < 0 || BN_cmp(sig->s, order) >= 0) {
+                ECDSAerror(ECDSA_R_BAD_SIGNATURE);
+                ret = 0;
+                goto err;
+        }
+
+        /* Step 3: convert the hash into an integer. */
+        if (!ecdsa_prepare_digest(digest, digest_len, key, e))
+                goto err;
+
+        /* Step 4: compute the inverse of s modulo order. */
+        if (BN_mod_inverse_ct(sinv, sig->s, order, ctx) == NULL) {
+                ECDSAerror(ERR_R_BN_LIB);
+                goto err;
+        }
+        /* Step 5: compute u = s^-1 * e and v = s^-1 * r (modulo order). */
+        if (!BN_mod_mul(u, e, sinv, order, ctx)) {
+                ECDSAerror(ERR_R_BN_LIB);
+                goto err;
+        }
+        if (!BN_mod_mul(v, sig->r, sinv, order, ctx)) {
+                ECDSAerror(ERR_R_BN_LIB);
+                goto err;
+        }
+
+        /*
+         * Steps 6 and 7: compute R = G * u + pub_key * v = (x, y). Reject if
+         * it's the point at infinity - getting affine coordinates fails. Keep
+         * the x coordinate.
+         */
+        if ((point = EC_POINT_new(group)) == NULL) {
+                ECDSAerror(ERR_R_MALLOC_FAILURE);
+                goto err;
+        }
+        if (!EC_POINT_mul(group, point, u, pub_key, v, ctx)) {
+                ECDSAerror(ERR_R_EC_LIB);
+                goto err;
+        }
+        if (!EC_POINT_get_affine_coordinates(group, point, x, NULL, ctx)) {
+                ECDSAerror(ERR_R_EC_LIB);
+                goto err;
+        }
+        /* Step 8: convert x to a number in [0, order). */
+        if (!BN_nnmod(x, x, order, ctx)) {
+                ECDSAerror(ERR_R_BN_LIB);
+                goto err;
+        }
+
+        /* Step 9: the signature is valid iff the x-coordinate is equal to r. */
+        ret = (BN_cmp(x, sig->r) == 0);
+
+ err:
+        BN_CTX_end(ctx);
+        BN_CTX_free(ctx);
+        EC_POINT_free(point);
+
+        return ret;
+}
+
+ECDSA_SIG *
+ECDSA_do_sign(const unsigned char *digest, int digest_len, EC_KEY *key)
+{
+        return ECDSA_do_sign_ex(digest, digest_len, NULL, NULL, key);
+}
+
+ECDSA_SIG *
+ECDSA_do_sign_ex(const unsigned char *digest, int digest_len,
+    const BIGNUM *kinv, const BIGNUM *out_r, EC_KEY *key)
+{
+        if (key->meth->sign_sig == NULL) {
+                ECDSAerror(EVP_R_METHOD_NOT_SUPPORTED);
+                return 0;
+        }
+        return key->meth->sign_sig(digest, digest_len, kinv, out_r, key);
+}
+
+int
+ECDSA_sign(int type, const unsigned char *digest, int digest_len,
+    unsigned char *signature, unsigned int *signature_len, EC_KEY *key)
+{
+        return ECDSA_sign_ex(type, digest, digest_len, signature, signature_len,
+            NULL, NULL, key);
+}
+
+int
+ECDSA_sign_ex(int type, const unsigned char *digest, int digest_len,
+    unsigned char *signature, unsigned int *signature_len, const BIGNUM *kinv,
+    const BIGNUM *r, EC_KEY *key)
+{
+        if (key->meth->sign == NULL) {
+                ECDSAerror(EVP_R_METHOD_NOT_SUPPORTED);
+                return 0;
+        }
+        return key->meth->sign(type, digest, digest_len, signature,
+            signature_len, kinv, r, key);
+}
+
+int
+ECDSA_sign_setup(EC_KEY *key, BN_CTX *in_ctx, BIGNUM **out_kinv,
+    BIGNUM **out_r)
+{
+        if (key->meth->sign_setup == NULL) {
+                ECDSAerror(EVP_R_METHOD_NOT_SUPPORTED);
+                return 0;
+        }
+        return key->meth->sign_setup(key, in_ctx, out_kinv, out_r);
+}
+
+int
+ECDSA_do_verify(const unsigned char *digest, int digest_len,
+    const ECDSA_SIG *sig, EC_KEY *key)
+{
+        if (key->meth->verify_sig == NULL) {
+                ECDSAerror(EVP_R_METHOD_NOT_SUPPORTED);
+                return 0;
+        }
+        return key->meth->verify_sig(digest, digest_len, sig, key);
+}
+
+int
+ECDSA_verify(int type, const unsigned char *digest, int digest_len,
+    const unsigned char *sigbuf, int sig_len, EC_KEY *key)
+{
+        if (key->meth->verify == NULL) {
+                ECDSAerror(EVP_R_METHOD_NOT_SUPPORTED);
+                return 0;
+        }
+        return key->meth->verify(type, digest, digest_len, sigbuf, sig_len, key);
+}
+
+int
+ECDSA_size(const EC_KEY *r)
+{
+        const EC_GROUP *group;
+        const BIGNUM *order = NULL;
+        ECDSA_SIG sig;
+        int ret = 0;
+
+        if (r == NULL)
+                goto err;
+
+        if ((group = EC_KEY_get0_group(r)) == NULL)
+                goto err;
+
+        if ((order = EC_GROUP_get0_order(group)) == NULL)
+                goto err;
+
+        sig.r = (BIGNUM *)order;
+        sig.s = (BIGNUM *)order;
+
+        if ((ret = i2d_ECDSA_SIG(&sig, NULL)) < 0)
+                ret = 0;
+
+ err:
+        return ret;
+}