Add ECDSA_SIG_get0_r and ECDSA_SIG_get0_s.

OpenSSL 1.1.1 added some more convenient versions of ECDSA_SIG_get0.
Node.js uses them.

Change-Id: I425e8a0c2e43c34130f30d902090b839f1a67186
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/40044
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: David Benjamin <davidben@google.com>

crypto/fipsmodule/ecdsa/ecdsa.c

diff --git a/crypto/fipsmodule/ecdsa/ecdsa.c b/crypto/fipsmodule/ecdsa/ecdsa.c
index 38771d5..56d9f16 100644
--- a/crypto/fipsmodule/ecdsa/ecdsa.c
+++ b/crypto/fipsmodule/ecdsa/ecdsa.c
@@ -122,6 +122,14 @@
   OPENSSL_free(sig);
 }
 
+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;
+}
+
 void ECDSA_SIG_get0(const ECDSA_SIG *sig, const BIGNUM **out_r,
                     const BIGNUM **out_s) {
   if (out_r != NULL) {

include/openssl/ecdsa.h

diff --git a/include/openssl/ecdsa.h b/include/openssl/ecdsa.h
index d4d353e..9cd19a5 100644
--- a/include/openssl/ecdsa.h
+++ b/include/openssl/ecdsa.h
@@ -106,6 +106,12 @@
 // ECDSA_SIG_free frees |sig| its member |BIGNUM|s.
 OPENSSL_EXPORT void ECDSA_SIG_free(ECDSA_SIG *sig);
 
+// ECDSA_SIG_get0_r returns the r component of |sig|.
+OPENSSL_EXPORT const BIGNUM *ECDSA_SIG_get0_r(const ECDSA_SIG *sig);
+
+// ECDSA_SIG_get0_s returns the s component of |sig|.
+OPENSSL_EXPORT const BIGNUM *ECDSA_SIG_get0_s(const ECDSA_SIG *sig);
+
 // ECDSA_SIG_get0 sets |*out_r| and |*out_s|, if non-NULL, to the two
 // components of |sig|.
 OPENSSL_EXPORT void ECDSA_SIG_get0(const ECDSA_SIG *sig, const BIGNUM **out_r,