sha1dc: update from upstream

Update sha1dc from the latest version by the upstream
maintainer[1].

See commit a0103914 ("sha1dc: update from upstream", 2017-05-20) for
the latest update. That update was done sans some whitespace changes
by upstream, which is why the diff here isn't the same as the upstream
cc46554..e139984.

It also brings in a change[2] upstream made which should hopefully
address the breakage in 2.13.1 on Cygwin, see [3]. Cygwin defines both
_BIG_ENDIAN and _LITTLE_ENDIAN.

Adam Dinwoodie reports on the mailing list that that upstream commit
fixes the issue on Cygwin[4].

1. https://github.com/cr-marcstevens/sha1collisiondetection/commit/e1399840b501a68ac6c8d7ed9a5cb1455480200e
2. https://github.com/cr-marcstevens/sha1collisiondetection/commit/a24eef58c0684078405f8c7a89f9b78271432005
3. <20170606100355.GC25777@dinwoodie.org> (https://public-inbox.org/git/20170606100355.GC25777@dinwoodie.org/)
4. <20170606124323.GD25777@dinwoodie.org> (https://public-inbox.org/git/20170606124323.GD25777@dinwoodie.org/)
Signed-off-by: NÆvar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

sha1dc/sha1.c

@@ -35,15 +35,33 @@
 #ifdef SHA1DC_BIGENDIAN
 #undef SHA1DC_BIGENDIAN
 #endif
-#if (!defined SHA1DC_FORCE_LITTLEENDIAN) && \
-    ((defined(__BYTE_ORDER) && (__BYTE_ORDER == __BIG_ENDIAN)) || \
-    (defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __BIG_ENDIAN__)) || \
-    defined(_BIG_ENDIAN) || defined(__BIG_ENDIAN__) || defined(__ARMEB__) || defined(__THUMBEB__) ||  defined(__AARCH64EB__) || \
-    defined(_MIPSEB) || defined(__MIPSEB) || defined(__MIPSEB__) || defined(SHA1DC_FORCE_BIGENDIAN))
 
+#if (defined(_BYTE_ORDER) || defined(__BYTE_ORDER) || defined(__BYTE_ORDER__))
+
+#if ((defined(_BYTE_ORDER) && (_BYTE_ORDER == _BIG_ENDIAN)) || \
+     (defined(__BYTE_ORDER) && (__BYTE_ORDER == __BIG_ENDIAN)) || \
+     (defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __BIG_ENDIAN__)) )
 #define SHA1DC_BIGENDIAN
+#endif
+
+#else
+
+#if (defined(_BIG_ENDIAN) || defined(__BIG_ENDIAN) || defined(__BIG_ENDIAN__) || \
+     defined(__ARMEB__) || defined(__THUMBEB__) || defined(__AARCH64EB__) || \
+     defined(__MIPSEB__) || defined(__MIPSEB) || defined(_MIPSEB) || \
+     defined(__sparc))
+#define SHA1DC_BIGENDIAN
+#endif
 
-#endif /*ENDIANNESS SELECTION*/
+#endif
+
+#if (defined(SHA1DC_FORCE_LITTLEENDIAN) && defined(SHA1DC_BIGENDIAN))
+#undef SHA1DC_BIGENDIAN
+#endif
+#if (defined(SHA1DC_FORCE_BIGENDIAN) && !defined(SHA1DC_BIGENDIAN))
+#define SHA1DC_BIGENDIAN
+#endif
+/*ENDIANNESS SELECTION*/
 
 #if (defined SHA1DC_FORCE_UNALIGNED_ACCESS || \
      defined(__amd64__) || defined(__amd64) || defined(__x86_64__) || defined(__x86_64) || \

sha1dc/sha1.h

@@ -61,9 +61,9 @@ void SHA1DCInit(SHA1_CTX*);
     Function to enable safe SHA-1 hashing:
     Collision attacks are thwarted by hashing a detected near-collision block 3 times.
     Think of it as extending SHA-1 from 80-steps to 240-steps for such blocks:
-	The best collision attacks against SHA-1 have complexity about 2^60,
-	thus for 240-steps an immediate lower-bound for the best cryptanalytic attacks would be 2^180.
-	An attacker would be better off using a generic birthday search of complexity 2^80.
+        The best collision attacks against SHA-1 have complexity about 2^60,
+        thus for 240-steps an immediate lower-bound for the best cryptanalytic attacks would be 2^180.
+        An attacker would be better off using a generic birthday search of complexity 2^80.
 
    Enabling safe SHA-1 hashing will result in the correct SHA-1 hash for messages where no collision attack was detected,
    but it will result in a different SHA-1 hash for messages where a collision attack was detected.