Make DSA_SIG and ECDSA_SIG getters const.

Reorder arguments to follow convention.

Also allow r/s to be NULL in DSA_SIG_get0, similarly to ECDSA_SIG_get0.

This complements GH1193 which adds non-const setters.
Reviewed-by: NRich Salz <rsalz@openssl.org>

crypto/dsa/dsa_ameth.c

@@ -437,9 +437,9 @@ static int dsa_sig_print(BIO *bp, const X509_ALGOR *sigalg,
     dsa_sig = d2i_DSA_SIG(NULL, &p, sig->length);
     if (dsa_sig) {
         int rv = 0;
-        BIGNUM *r, *s;
+        const BIGNUM *r, *s;
 
-        DSA_SIG_get0(&r, &s, dsa_sig);
+        DSA_SIG_get0(dsa_sig, &r, &s);
 
         if (BIO_write(bp, "\n", 1) != 1)
             goto err;

crypto/dsa/dsa_asn1.c

@@ -14,11 +14,6 @@
 #include <openssl/asn1t.h>
 #include <openssl/rand.h>
 
-struct DSA_SIG_st {
-    BIGNUM *r;
-    BIGNUM *s;
-};
-
 ASN1_SEQUENCE(DSA_SIG) = {
         ASN1_SIMPLE(DSA_SIG, r, CBIGNUM),
         ASN1_SIMPLE(DSA_SIG, s, CBIGNUM)
@@ -26,10 +21,12 @@ ASN1_SEQUENCE(DSA_SIG) = {
 
 IMPLEMENT_ASN1_FUNCTIONS_const(DSA_SIG)
 
-void DSA_SIG_get0(BIGNUM **pr, BIGNUM **ps, const DSA_SIG *sig)
+void DSA_SIG_get0(const DSA_SIG *sig, const BIGNUM **pr, const BIGNUM **ps)
 {
-    *pr = sig->r;
-    *ps = sig->s;
+    if (pr != NULL)
+        *pr = sig->r;
+    if (ps != NULL)
+        *ps = sig->s;
 }
 
 int DSA_SIG_set0(DSA_SIG *sig, BIGNUM *r, BIGNUM *s)

crypto/dsa/dsa_locl.h

@@ -32,6 +32,11 @@ struct dsa_st {
     CRYPTO_RWLOCK *lock;
 };
 
+struct DSA_SIG_st {
+    BIGNUM *r;
+    BIGNUM *s;
+};
+
 struct dsa_method {
     char *name;
     DSA_SIG *(*dsa_do_sign) (const unsigned char *dgst, int dlen, DSA *dsa);

crypto/dsa/dsa_ossl.c

@@ -51,7 +51,6 @@ static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
     BIGNUM *kinv = NULL;
     BIGNUM *m;
     BIGNUM *xr;
-    BIGNUM *r, *s;
     BN_CTX *ctx = NULL;
     int reason = ERR_R_BN_LIB;
     DSA_SIG *ret = NULL;
@@ -71,13 +70,11 @@ static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
     if (ret == NULL)
         goto err;
 
-    DSA_SIG_get0(&r, &s, ret);
-
     ctx = BN_CTX_new();
     if (ctx == NULL)
         goto err;
  redo:
-    if (!dsa_sign_setup(dsa, ctx, &kinv, &r, dgst, dlen))
+    if (!dsa_sign_setup(dsa, ctx, &kinv, &ret->r, dgst, dlen))
         goto err;
 
     if (dlen > BN_num_bytes(dsa->q))
@@ -91,21 +88,21 @@ static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
         goto err;
 
     /* Compute  s = inv(k) (m + xr) mod q */
-    if (!BN_mod_mul(xr, dsa->priv_key, r, dsa->q, ctx))
+    if (!BN_mod_mul(xr, dsa->priv_key, ret->r, dsa->q, ctx))
         goto err;               /* s = xr */
-    if (!BN_add(s, xr, m))
+    if (!BN_add(ret->s, xr, m))
         goto err;               /* s = m + xr */
-    if (BN_cmp(s, dsa->q) > 0)
-        if (!BN_sub(s, s, dsa->q))
+    if (BN_cmp(ret->s, dsa->q) > 0)
+        if (!BN_sub(ret->s, ret->s, dsa->q))
             goto err;
-    if (!BN_mod_mul(s, s, kinv, dsa->q, ctx))
+    if (!BN_mod_mul(ret->s, ret->s, kinv, dsa->q, ctx))
         goto err;
 
     /*
      * Redo if r or s is zero as required by FIPS 186-3: this is very
      * unlikely.
      */
-    if (BN_is_zero(r) || BN_is_zero(s))
+    if (BN_is_zero(ret->r) || BN_is_zero(ret->s))
         goto redo;
 
     rv = 1;
@@ -225,7 +222,7 @@ static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
     BN_CTX *ctx;
     BIGNUM *u1, *u2, *t1;
     BN_MONT_CTX *mont = NULL;
-    BIGNUM *r, *s;
+    const BIGNUM *r, *s;
     int ret = -1, i;
     if (!dsa->p || !dsa->q || !dsa->g) {
         DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MISSING_PARAMETERS);
@@ -250,7 +247,7 @@ static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
     if (u1 == NULL || u2 == NULL || t1 == NULL || ctx == NULL)
         goto err;
 
-    DSA_SIG_get0(&r, &s, sig);
+    DSA_SIG_get0(sig, &r, &s);
 
     if (BN_is_zero(r) || BN_is_negative(r) ||
         BN_ucmp(r, dsa->q) >= 0) {

crypto/ec/ec_asn1.c

@@ -1172,7 +1172,7 @@ DECLARE_ASN1_FUNCTIONS_const(ECDSA_SIG)
 DECLARE_ASN1_ENCODE_FUNCTIONS_const(ECDSA_SIG, ECDSA_SIG)
 IMPLEMENT_ASN1_FUNCTIONS_const(ECDSA_SIG)
 
-void ECDSA_SIG_get0(BIGNUM **pr, BIGNUM **ps, const ECDSA_SIG *sig)
+void ECDSA_SIG_get0(const ECDSA_SIG *sig, const BIGNUM **pr, const BIGNUM **ps)
 {
     if (pr != NULL)
         *pr = sig->r;

doc/crypto/DSA_SIG_new.pod

@@ -10,7 +10,7 @@ DSA_SIG_new, DSA_SIG_free - allocate and free DSA signature objects
 
  DSA_SIG *DSA_SIG_new(void);
  void DSA_SIG_free(DSA_SIG *a);
- void DSA_SIG_get0(BIGNUM **pr, BIGNUM **ps, const DSA_SIG *sig);
+ void DSA_SIG_get0(const DSA_SIG *sig, const BIGNUM **pr, const BIGNUM **ps);
  int DSA_SIG_set0(DSA_SIG *sig, BIGNUM *r, BIGNUM *s);
 
 =head1 DESCRIPTION
@@ -20,8 +20,8 @@ DSA_SIG_new() allocates and initializes a B<DSA_SIG> structure.
 DSA_SIG_free() frees the B<DSA_SIG> structure and its components. The
 values are erased before the memory is returned to the system.
 
-DSA_SIG_get0() returns internal pointers the B<r> and B<s> values contained
-in B<sig>. The values can then be examined or initialised.
+DSA_SIG_get0() returns internal pointers to the B<r> and B<s> values contained
+in B<sig>.
 
 The B<r> and B<s> values can be set by calling DSA_SIG_set0() and passing the
 new values for B<r> and B<s> as parameters to the function. Calling this

doc/crypto/ECDSA_SIG_new.pod

@@ -13,7 +13,7 @@ algorithm (ECDSA) functions
 
  ECDSA_SIG *ECDSA_SIG_new(void);
  void ECDSA_SIG_free(ECDSA_SIG *sig);
- void ECDSA_SIG_get0(BIGNUM **pr, BIGNUM **ps, const ECDSA_SIG *sig);
+ void ECDSA_SIG_get0(const ECDSA_SIG *sig, const BIGNUM **pr, const BIGNUM **ps);
  int ECDSA_SIG_set0(ECDSA_SIG *sig, BIGNUM *r, BIGNUM *s);
  int i2d_ECDSA_SIG(const ECDSA_SIG *sig, unsigned char **pp);
  ECDSA_SIG *d2i_ECDSA_SIG(ECDSA_SIG **sig, const unsigned char **pp, long len);
@@ -52,7 +52,7 @@ function also allocates the BIGNUMs) and initializes it.
 ECDSA_SIG_free() frees the B<ECDSA_SIG> structure B<sig>.
 
 ECDSA_SIG_get0() returns internal pointers the B<r> and B<s> values contained
-in B<sig>. The values can then be examined or initialised.
+in B<sig>.
 
 The B<r> and B<s> values can be set by calling ECDSA_SIG_set0() and passing the
 new values for B<r> and B<s> as parameters to the function. Calling this

include/openssl/dsa.h

@@ -81,7 +81,7 @@ DSA_SIG *DSA_SIG_new(void);
 void DSA_SIG_free(DSA_SIG *a);
 int i2d_DSA_SIG(const DSA_SIG *a, unsigned char **pp);
 DSA_SIG *d2i_DSA_SIG(DSA_SIG **v, const unsigned char **pp, long length);
-void DSA_SIG_get0(BIGNUM **pr, BIGNUM **ps, const DSA_SIG *sig);
+void DSA_SIG_get0(const DSA_SIG *sig, const BIGNUM **pr, const BIGNUM **ps);
 int DSA_SIG_set0(DSA_SIG *sig, BIGNUM *r, BIGNUM *s);
 
 DSA_SIG *DSA_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);

include/openssl/ec.h

@@ -1076,7 +1076,7 @@ ECDSA_SIG *d2i_ECDSA_SIG(ECDSA_SIG **sig, const unsigned char **pp, long len);
  *  \param  pr   pointer to BIGNUM pointer for r (may be NULL)
  *  \param  ps   pointer to BIGNUM pointer for s (may be NULL)
  */
-void ECDSA_SIG_get0(BIGNUM **pr, BIGNUM **ps, const ECDSA_SIG *sig);
+void ECDSA_SIG_get0(const ECDSA_SIG *sig, const BIGNUM **pr, const BIGNUM **ps);
 
 /** Setter for r and s fields of ECDSA_SIG
  *  \param  sig  pointer to ECDSA_SIG pointer

test/ecdsatest.c

@@ -145,7 +145,7 @@ int x9_62_test_internal(BIO *out, int nid, const char *r_in, const char *s_in)
     ECDSA_SIG *signature = NULL;
     BIGNUM *r = NULL, *s = NULL;
     BIGNUM *kinv = NULL, *rp = NULL;
-    BIGNUM *sig_r, *sig_s;
+    const BIGNUM *sig_r, *sig_s;
 
     if (md_ctx == NULL)
         goto x962_int_err;
@@ -180,7 +180,7 @@ int x9_62_test_internal(BIO *out, int nid, const char *r_in, const char *s_in)
         goto x962_int_err;
     if (!BN_dec2bn(&r, r_in) || !BN_dec2bn(&s, s_in))
         goto x962_int_err;
-    ECDSA_SIG_get0(&sig_r, &sig_s, signature);
+    ECDSA_SIG_get0(signature, &sig_r, &sig_s);
     if (BN_cmp(sig_r, r) || BN_cmp(sig_s, s))
         goto x962_int_err;
     BIO_printf(out, ".");
@@ -251,13 +251,15 @@ int test_builtin(BIO *out)
     size_t crv_len = 0, n = 0;
     EC_KEY *eckey = NULL, *wrong_eckey = NULL;
     EC_GROUP *group;
-    ECDSA_SIG *ecdsa_sig = NULL;
+    ECDSA_SIG *ecdsa_sig = NULL, *modified_sig = NULL;
     unsigned char digest[20], wrong_digest[20];
     unsigned char *signature = NULL;
     const unsigned char *sig_ptr;
     unsigned char *sig_ptr2;
     unsigned char *raw_buf = NULL;
-    BIGNUM *sig_r, *sig_s;
+    const BIGNUM *sig_r, *sig_s;
+    BIGNUM *modified_r = NULL, *modified_s = NULL;
+    BIGNUM *unmodified_r = NULL, *unmodified_s = NULL;
     unsigned int sig_len, degree, r_len, s_len, bn_len, buf_len;
     int nid, ret = 0;
 
@@ -388,7 +390,7 @@ int test_builtin(BIO *out)
             goto builtin_err;
         }
 
-        ECDSA_SIG_get0(&sig_r, &sig_s, ecdsa_sig);
+        ECDSA_SIG_get0(ecdsa_sig, &sig_r, &sig_s);
 
         /* Store the two BIGNUMs in raw_buf. */
         r_len = BN_num_bytes(sig_r);
@@ -409,12 +411,18 @@ int test_builtin(BIO *out)
         dirt = raw_buf[11] ? raw_buf[11] : 1;
         raw_buf[offset] ^= dirt;
         /* Now read the BIGNUMs back in from raw_buf. */
-        if ((BN_bin2bn(raw_buf, bn_len, sig_r) == NULL) ||
-            (BN_bin2bn(raw_buf + bn_len, bn_len, sig_s) == NULL))
+        modified_sig = ECDSA_SIG_new();
+        if (modified_sig == NULL)
             goto builtin_err;
-
+        if (((modified_r = BN_bin2bn(raw_buf, bn_len, NULL)) == NULL)
+            || ((modified_s = BN_bin2bn(raw_buf + bn_len, bn_len, NULL)) == NULL)
+            || !ECDSA_SIG_set0(modified_sig, modified_r, modified_s)) {
+            BN_free(modified_r);
+            BN_free(modified_s);
+            goto builtin_err;
+        }
         sig_ptr2 = signature;
-        sig_len = i2d_ECDSA_SIG(ecdsa_sig, &sig_ptr2);
+        sig_len = i2d_ECDSA_SIG(modified_sig, &sig_ptr2);
         if (ECDSA_verify(0, digest, 20, signature, sig_len, eckey) == 1) {
             BIO_printf(out, " failed\n");
             goto builtin_err;
@@ -423,12 +431,16 @@ int test_builtin(BIO *out)
          * Sanity check: undo the modification and verify signature.
          */
         raw_buf[offset] ^= dirt;
-        if ((BN_bin2bn(raw_buf, bn_len, sig_r) == NULL) ||
-            (BN_bin2bn(raw_buf + bn_len, bn_len, sig_s) == NULL))
+        if (((unmodified_r = BN_bin2bn(raw_buf, bn_len, NULL)) == NULL)
+            || ((unmodified_s = BN_bin2bn(raw_buf + bn_len, bn_len, NULL)) == NULL)
+            || !ECDSA_SIG_set0(modified_sig, unmodified_r, unmodified_s)) {
+            BN_free(unmodified_r);
+            BN_free(unmodified_s);
             goto builtin_err;
+        }
 
         sig_ptr2 = signature;
-        sig_len = i2d_ECDSA_SIG(ecdsa_sig, &sig_ptr2);
+        sig_len = i2d_ECDSA_SIG(modified_sig, &sig_ptr2);
         if (ECDSA_verify(0, digest, 20, signature, sig_len, eckey) != 1) {
             BIO_printf(out, " failed\n");
             goto builtin_err;
@@ -448,6 +460,8 @@ int test_builtin(BIO *out)
         wrong_eckey = NULL;
         ECDSA_SIG_free(ecdsa_sig);
         ecdsa_sig = NULL;
+        ECDSA_SIG_free(modified_sig);
+        modified_sig = NULL;
         OPENSSL_free(raw_buf);
         raw_buf = NULL;
     }
@@ -457,6 +471,7 @@ int test_builtin(BIO *out)
     EC_KEY_free(eckey);
     EC_KEY_free(wrong_eckey);
     ECDSA_SIG_free(ecdsa_sig);
+    ECDSA_SIG_free(modified_sig);
     OPENSSL_free(signature);
     OPENSSL_free(raw_buf);
     OPENSSL_free(curves);