OpenSSL: Fix crypto_bignum_to_bin() with padlen == 0

The earlier change to add support for BN_bn2binpad() and
BN_bn2bin_padded() broke this function for cases where no padding is
used (padlen == 0). Those would have always failed after the changes and
the function would return -1. There are no such cases in the current
hostap.git, so this did not have any real issues, but anyway, better fix
this function to match its documentation.

Fixes: 1e237903f5b5 ("OpenSSL: Use BN_bn2binpad() or BN_bn2bin_padded() if available")
Signed-off-by: Jouni Malinen <j@w1.fi>

diff --git a/src/crypto/crypto_openssl.c b/src/crypto/crypto_openssl.c
index fb278c2d2939c394ffd621ec8fb8d6153c311078..aa5b9b4c74f1e72737f28259c39c006862b35c60 100644 (file)
--- a/src/crypto/crypto_openssl.c
+++ b/src/crypto/crypto_openssl.c
@@ -1295,13 +1295,7 @@ void crypto_bignum_deinit(struct crypto_bignum *n, int clear)
 int crypto_bignum_to_bin(const struct crypto_bignum *a,
                         u8 *buf, size_t buflen, size_t padlen)
 {
-#ifdef OPENSSL_IS_BORINGSSL
-#else /* OPENSSL_IS_BORINGSSL */
-#if OPENSSL_VERSION_NUMBER >= 0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
-#else
        int num_bytes, offset;
-#endif
-#endif /* OPENSSL_IS_BORINGSSL */
 
        if (TEST_FAIL())
                return -1;
@@ -1309,14 +1303,18 @@ int crypto_bignum_to_bin(const struct crypto_bignum *a,
        if (padlen > buflen)
                return -1;
 
+       if (padlen) {
 #ifdef OPENSSL_IS_BORINGSSL
-       if (BN_bn2bin_padded(buf, padlen, (const BIGNUM *) a) == 0)
-               return -1;
-       return padlen;
+               if (BN_bn2bin_padded(buf, padlen, (const BIGNUM *) a) == 0)
+                       return -1;
+               return padlen;
 #else /* OPENSSL_IS_BORINGSSL */
 #if OPENSSL_VERSION_NUMBER >= 0x10100000L && !defined(LIBRESSL_VERSION_NUMBER)
-       return BN_bn2binpad((const BIGNUM *) a, buf, padlen);
-#else
+               return BN_bn2binpad((const BIGNUM *) a, buf, padlen);
+#endif
+#endif
+       }
+
        num_bytes = BN_num_bytes((const BIGNUM *) a);
        if ((size_t) num_bytes > buflen)
                return -1;
@@ -1329,8 +1327,6 @@ int crypto_bignum_to_bin(const struct crypto_bignum *a,
        BN_bn2bin((const BIGNUM *) a, buf + offset);
 
        return num_bytes + offset;
-#endif
-#endif /* OPENSSL_IS_BORINGSSL */
 }