chunk: Add function to calculate Internet Checksums according to RFC 1071

src/libstrongswan/tests/suites/test_chunk.c

@@ -783,6 +783,51 @@ START_TEST(test_chunk_hash_static)
 }
 END_TEST
 
+/*******************************************************************************
+ * test for chunk_internet_checksum[_inc]()
+ */
+
+START_TEST(test_chunk_internet_checksum)
+{
+	chunk_t chunk;
+	u_int16_t sum;
+
+	chunk = chunk_from_chars(0x45,0x00,0x00,0x30,0x44,0x22,0x40,0x00,0x80,0x06,
+							 0x00,0x00,0x8c,0x7c,0x19,0xac,0xae,0x24,0x1e,0x2b);
+
+	sum = chunk_internet_checksum(chunk);
+	ck_assert_int_eq(0x442e, ntohs(sum));
+
+	sum = chunk_internet_checksum(chunk_create(chunk.ptr, 10));
+	sum = chunk_internet_checksum_inc(chunk_create(chunk.ptr+10, 10), sum);
+	ck_assert_int_eq(0x442e, ntohs(sum));
+
+	/* need to compensate for even/odd alignment */
+	sum = chunk_internet_checksum(chunk_create(chunk.ptr, 9));
+	sum = ntohs(sum);
+	sum = chunk_internet_checksum_inc(chunk_create(chunk.ptr+9, 11), sum);
+	sum = ntohs(sum);
+	ck_assert_int_eq(0x442e, ntohs(sum));
+
+	chunk = chunk_from_chars(0x45,0x00,0x00,0x30,0x44,0x22,0x40,0x00,0x80,0x06,
+							 0x00,0x00,0x8c,0x7c,0x19,0xac,0xae,0x24,0x1e);
+
+	sum = chunk_internet_checksum(chunk);
+	ck_assert_int_eq(0x4459, ntohs(sum));
+
+	sum = chunk_internet_checksum(chunk_create(chunk.ptr, 10));
+	sum = chunk_internet_checksum_inc(chunk_create(chunk.ptr+10, 9), sum);
+	ck_assert_int_eq(0x4459, ntohs(sum));
+
+	/* need to compensate for even/odd alignment */
+	sum = chunk_internet_checksum(chunk_create(chunk.ptr, 9));
+	sum = ntohs(sum);
+	sum = chunk_internet_checksum_inc(chunk_create(chunk.ptr+9, 10), sum);
+	sum = ntohs(sum);
+	ck_assert_int_eq(0x4459, ntohs(sum));
+}
+END_TEST
+
 /*******************************************************************************
  * test for chunk_map and friends
  */
@@ -1018,6 +1063,10 @@ Suite *chunk_suite_create()
 	tcase_add_test(tc, test_chunk_hash_static);
 	suite_add_tcase(s, tc);
 
+	tc = tcase_create("chunk_internet_checksum");
+	tcase_add_test(tc, test_chunk_internet_checksum);
+	suite_add_tcase(s, tc);
+
 	tc = tcase_create("chunk_map");
 	tcase_add_test(tc, test_chunk_map);
 	suite_add_tcase(s, tc);

src/libstrongswan/utils/chunk.c

@@ -987,6 +987,37 @@ u_int32_t chunk_hash_static(chunk_t chunk)
 	return chunk_mac(chunk, static_key);
 }
 
+/**
+ * Described in header.
+ */
+u_int16_t chunk_internet_checksum_inc(chunk_t data, u_int16_t checksum)
+{
+	u_int32_t sum = ntohs(~checksum);
+
+	while (data.len > 1)
+	{
+		sum += untoh16(data.ptr);
+		data = chunk_skip(data, 2);
+	}
+	if (data.len)
+	{
+		sum += (u_int16_t)*data.ptr << 8;
+	}
+	while (sum >> 16)
+	{
+		sum = (sum & 0xffff) + (sum >> 16);
+	}
+	return htons(~sum);
+}
+
+/**
+ * Described in header.
+ */
+u_int16_t chunk_internet_checksum(chunk_t data)
+{
+	return chunk_internet_checksum_inc(data, 0xffff);
+}
+
 /**
  * Described in header.
  */

src/libstrongswan/utils/chunk.h

@@ -411,6 +411,31 @@ u_int32_t chunk_hash_static_inc(chunk_t chunk, u_int32_t hash);
  */
 u_int64_t chunk_mac(chunk_t chunk, u_char *key);
 
+/**
+ * Calculate the Internet Checksum according to RFC 1071 for the given chunk.
+ *
+ * If the result is used with chunk_internet_checksum_inc() and the data length
+ * is not a multiple of 16 bit the checksum bytes have to be swapped to
+ * compensate the even/odd alignment.
+ *
+ * @param chunk			data to process
+ * @return				checksum (one's complement, network order)
+ */
+u_int16_t chunk_internet_checksum(chunk_t data);
+
+/**
+ * Extend the given Internet Checksum (one's complement, in network byte order)
+ * with the given data.
+ *
+ * If data is not a multiple of 16 bits the checksum may have to be swapped to
+ * compensate even/odd alignment (see chunk_internet_checksum()).
+ *
+ * @param chunk			data to process
+ * @param checksum		previous checksum (one's complement, network order)
+ * @return				checksum (one's complement, network order)
+ */
+u_int16_t chunk_internet_checksum_inc(chunk_t data, u_int16_t checksum);
+
 /**
  * printf hook function for chunk_t.
  *