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

diff --git a/src/libstrongswan/tests/suites/test_chunk.c b/src/libstrongswan/tests/suites/test_chunk.c
index b33d70e..d71e010 100644 (file)
--- a/src/libstrongswan/tests/suites/test_chunk.c
+++ b/src/libstrongswan/tests/suites/test_chunk.c
@@ -784,6 +784,51 @@ 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);

diff --git a/src/libstrongswan/utils/chunk.c b/src/libstrongswan/utils/chunk.c
index 1a9674f..4b24b37 100644 (file)
--- a/src/libstrongswan/utils/chunk.c
+++ b/src/libstrongswan/utils/chunk.c
@@ -990,6 +990,37 @@ u_int32_t chunk_hash_static(chunk_t chunk)
 /**
  * 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.
+ */
 int chunk_printf_hook(printf_hook_data_t *data, printf_hook_spec_t *spec,
                                          const void *const *args)
 {

diff --git a/src/libstrongswan/utils/chunk.h b/src/libstrongswan/utils/chunk.h
index 9951ff3..0daa2e1 100644 (file)
--- a/src/libstrongswan/utils/chunk.h
+++ b/src/libstrongswan/utils/chunk.h
@@ -412,6 +412,31 @@ 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.
  *
  * Arguments are: