Avoid some buffer overflows in ecdsatest

The ASN.1 encoding of the modified ECDSA signature can grow in size due to
padding of the ASN.1 integers. Instead of reusing the same signature buffer
freshly allocate it. Avoids some buffer overflows caught by ASAN.

1 files changed, 14 insertions, 4 deletions

diff --git a/src/regress/lib/libcrypto/ecdsa/ecdsatest.c b/src/regress/lib/libcrypto/ecdsa/ecdsatest.c
index 683260aeee..5e2419a91f 100644
--- a/src/regress/lib/libcrypto/ecdsa/ecdsatest.c
+++ b/src/regress/lib/libcrypto/ecdsa/ecdsatest.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: ecdsatest.c,v 1.9 2022/03/31 09:36:09 tb Exp $        */
+/*      $OpenBSD: ecdsatest.c,v 1.10 2022/08/31 09:33:39 tb Exp $       */
 /*
  * Written by Nils Larsch for the OpenSSL project.
  */
@@ -251,7 +251,8 @@ test_builtin(BIO *out)
                 BIO_printf(out, ".");
                 (void)BIO_flush(out);
                 /* create signature */
-                sig_len = ECDSA_size(eckey);
+                if ((sig_len = ECDSA_size(eckey)) == 0)
+                        goto builtin_err;
                 if ((signature = malloc(sig_len)) == NULL)
                         goto builtin_err;
                 if (!ECDSA_sign(0, digest, 20, signature, &sig_len, eckey)) {
@@ -332,8 +333,13 @@ test_builtin(BIO *out)
                 r = NULL;
                 s = NULL;
 
+                free(signature);
+                signature = NULL;
+
                 sig_ptr2 = signature;
-                sig_len = i2d_ECDSA_SIG(ecdsa_sig, &sig_ptr2);
+                if ((sig_len = i2d_ECDSA_SIG(ecdsa_sig, &sig_ptr2)) <= 0)
+                        goto builtin_err;
+
                 if (ECDSA_verify(0, digest, 20, signature, sig_len,
                     eckey) == 1) {
                         BIO_printf(out, " failed\n");
@@ -349,8 +355,12 @@ test_builtin(BIO *out)
                 r = NULL;
                 s = NULL;
 
+                free(signature);
+                signature = NULL;
+
                 sig_ptr2 = signature;
-                sig_len = i2d_ECDSA_SIG(ecdsa_sig, &sig_ptr2);
+                if ((sig_len = i2d_ECDSA_SIG(ecdsa_sig, &sig_ptr2)) <= 0)
+                        goto builtin_err;
                 if (ECDSA_verify(0, digest, 20, signature, sig_len,
                     eckey) != 1) {
                         BIO_printf(out, " failed\n");