openssl: Allow build with OpenSSL 0.9.7

OpenSSL 0.9.7 does not include get_rfc3526_prime_1536() function, so
provide that functionality internally if needed. In addition, make
sha256_vector() building depend on whether SHA256 support is included
in the OpenSSL library. This with CONFIG_INTERNAL_SHA256=y in .config
allows OpenSSL without SHA256 support to be used.

src/crypto/crypto_openssl.c

@@ -33,6 +33,45 @@
 	des_ecb_encrypt((input), (output), *(ks), (enc))
 #endif /* openssl < 0.9.7 */
 
+static BIGNUM * get_group5_prime(void)
+{
+#if OPENSSL_VERSION_NUMBER < 0x00908000
+	static const unsigned char RFC3526_PRIME_1536[] = {
+		0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xC9,0x0F,0xDA,0xA2,
+		0x21,0x68,0xC2,0x34,0xC4,0xC6,0x62,0x8B,0x80,0xDC,0x1C,0xD1,
+		0x29,0x02,0x4E,0x08,0x8A,0x67,0xCC,0x74,0x02,0x0B,0xBE,0xA6,
+		0x3B,0x13,0x9B,0x22,0x51,0x4A,0x08,0x79,0x8E,0x34,0x04,0xDD,
+		0xEF,0x95,0x19,0xB3,0xCD,0x3A,0x43,0x1B,0x30,0x2B,0x0A,0x6D,
+		0xF2,0x5F,0x14,0x37,0x4F,0xE1,0x35,0x6D,0x6D,0x51,0xC2,0x45,
+		0xE4,0x85,0xB5,0x76,0x62,0x5E,0x7E,0xC6,0xF4,0x4C,0x42,0xE9,
+		0xA6,0x37,0xED,0x6B,0x0B,0xFF,0x5C,0xB6,0xF4,0x06,0xB7,0xED,
+		0xEE,0x38,0x6B,0xFB,0x5A,0x89,0x9F,0xA5,0xAE,0x9F,0x24,0x11,
+		0x7C,0x4B,0x1F,0xE6,0x49,0x28,0x66,0x51,0xEC,0xE4,0x5B,0x3D,
+		0xC2,0x00,0x7C,0xB8,0xA1,0x63,0xBF,0x05,0x98,0xDA,0x48,0x36,
+		0x1C,0x55,0xD3,0x9A,0x69,0x16,0x3F,0xA8,0xFD,0x24,0xCF,0x5F,
+		0x83,0x65,0x5D,0x23,0xDC,0xA3,0xAD,0x96,0x1C,0x62,0xF3,0x56,
+		0x20,0x85,0x52,0xBB,0x9E,0xD5,0x29,0x07,0x70,0x96,0x96,0x6D,
+		0x67,0x0C,0x35,0x4E,0x4A,0xBC,0x98,0x04,0xF1,0x74,0x6C,0x08,
+		0xCA,0x23,0x73,0x27,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+	};
+        return BN_bin2bn(RFC3526_PRIME_1536, sizeof(RFC3526_PRIME_1536), NULL);
+#else /* openssl < 0.9.8 */
+	return get_rfc3526_prime_1536(NULL);
+#endif /* openssl < 0.9.8 */
+}
+
+#if OPENSSL_VERSION_NUMBER < 0x00908000
+#ifndef OPENSSL_NO_SHA256
+#ifndef OPENSSL_FIPS
+#define NO_SHA256_WRAPPER
+#endif
+#endif
+
+#endif /* openssl < 0.9.8 */
+
+#ifdef OPENSSL_NO_SHA256
+#define NO_SHA256_WRAPPER
+#endif
 
 static int openssl_digest_vector(const EVP_MD *type, int non_fips,
 				 size_t num_elem, const u8 *addr[],
@@ -157,12 +196,14 @@ int sha1_vector(size_t num_elem, const u8 *addr[], const size_t *len, u8 *mac)
 }
 
 
+#ifndef NO_SHA256_WRAPPER
 int sha256_vector(size_t num_elem, const u8 *addr[], const size_t *len,
 		  u8 *mac)
 {
 	return openssl_digest_vector(EVP_sha256(), 0, num_elem, addr, len,
 				     mac);
 }
+#endif /* NO_SHA256_WRAPPER */
 
 
 void * aes_encrypt_init(const u8 *key, size_t len)
@@ -385,7 +426,7 @@ void * dh5_init(struct wpabuf **priv, struct wpabuf **publ)
 	if (dh->g == NULL || BN_set_word(dh->g, 2) != 1)
 		goto err;
 
-	dh->p = get_rfc3526_prime_1536(NULL);
+	dh->p = get_group5_prime();
 	if (dh->p == NULL)
 		goto err;