Merge branch 'jk/sha1dc'

The "detect attempt to create collisions" variant of SHA-1
implementation by Marc Stevens (CWI) and Dan Shumow (Microsoft)
has been integrated and made the default.

* jk/sha1dc:
Makefile: make DC_SHA1 the default
t0013: add a basic sha1 collision detection test
Makefile: add DC_SHA1 knob
sha1dc: disable safe_hash feature
sha1dc: adjust header includes for git
sha1dc: add collision-detecting sha1 implementation

diff --combined Makefile
index a5a11e721aeb566edb64276e6c10e92b0cfbe574,fd4421eeb84801cee8303b5f19f6bd377fb26952..c80fec2920028f2ef971e7ebd6fe89d61de13d3c
--- 1/Makefile
--- 2/Makefile
+++ b/Makefile
@@@ -102,6 -102,8 +102,6 @@@ all:
  #
  # Define MKDIR_WO_TRAILING_SLASH if your mkdir() can't deal with trailing slash.
  #
 -# Define NO_MKSTEMPS if you don't have mkstemps in the C library.
 -#
  # Define NO_GECOS_IN_PWENT if you don't have pw_gecos in struct passwd
  # in the C library.
  #
@@@ -140,6 -142,13 +140,13 @@@
  # Define PPC_SHA1 environment variable when running make to make use of
  # a bundled SHA1 routine optimized for PowerPC.
  #
+ # Define DC_SHA1 to unconditionally enable the collision-detecting sha1
+ # algorithm. This is slower, but may detect attempted collision attacks.
+ # Takes priority over other *_SHA1 knobs.
+ #
+ # Define OPENSSL_SHA1 environment variable when running make to link
+ # with the SHA1 routine from openssl library.
+ #
  # Define SHA1_MAX_BLOCK_SIZE to limit the amount of data that will be hashed
  # in one call to the platform's SHA1_Update(). e.g. APPLE_COMMON_CRYPTO
  # wants 'SHA1_MAX_BLOCK_SIZE=1024L*1024L*1024L' defined.
@@@ -779,7 -788,6 +786,7 @@@ LIB_OBJS += notes-cache.
  LIB_OBJS += notes-merge.o
  LIB_OBJS += notes-utils.o
  LIB_OBJS += object.o
 +LIB_OBJS += oidset.o
  LIB_OBJS += pack-bitmap.o
  LIB_OBJS += pack-bitmap-write.o
  LIB_OBJS += pack-check.o
@@@ -931,7 -939,6 +938,7 @@@ BUILTIN_OBJS += builtin/prune.
  BUILTIN_OBJS += builtin/pull.o
  BUILTIN_OBJS += builtin/push.o
  BUILTIN_OBJS += builtin/read-tree.o
 +BUILTIN_OBJS += builtin/rebase--helper.o
  BUILTIN_OBJS += builtin/receive-pack.o
  BUILTIN_OBJS += builtin/reflog.o
  BUILTIN_OBJS += builtin/remote.o
@@@ -1280,6 -1287,9 +1287,6 @@@ ifdef MKDIR_WO_TRAILING_SLAS
        COMPAT_CFLAGS += -DMKDIR_WO_TRAILING_SLASH
        COMPAT_OBJS += compat/mkdir.o
  endif
 -ifdef NO_MKSTEMPS
 -      COMPAT_CFLAGS += -DNO_MKSTEMPS
 -endif
  ifdef NO_UNSETENV
        COMPAT_CFLAGS += -DNO_UNSETENV
        COMPAT_OBJS += compat/unsetenv.o
@@@ -1383,6 -1393,10 +1390,10 @@@ ifdef APPLE_COMMON_CRYPT
        SHA1_MAX_BLOCK_SIZE = 1024L*1024L*1024L
  endif
  
+ ifdef OPENSSL_SHA1
+       EXTLIBS += $(LIB_4_CRYPTO)
+       BASIC_CFLAGS += -DSHA1_OPENSSL
+ else
  ifdef BLK_SHA1
        LIB_OBJS += block-sha1/sha1.o
        BASIC_CFLAGS += -DSHA1_BLK
@@@ -1395,8 -1409,11 +1406,11 @@@ ifdef APPLE_COMMON_CRYPT
        COMPAT_CFLAGS += -DCOMMON_DIGEST_FOR_OPENSSL
        BASIC_CFLAGS += -DSHA1_APPLE
  else
-       EXTLIBS += $(LIB_4_CRYPTO)
-       BASIC_CFLAGS += -DSHA1_OPENSSL
+       DC_SHA1 := YesPlease
+       LIB_OBJS += sha1dc/sha1.o
+       LIB_OBJS += sha1dc/ubc_check.o
+       BASIC_CFLAGS += -DSHA1_DC
+ endif
  endif
  endif
  endif
@@@ -2223,6 -2240,7 +2237,7 @@@ GIT-BUILD-OPTIONS: FORC
        @echo NO_PYTHON=\''$(subst ','\'',$(subst ','\'',$(NO_PYTHON)))'\' >>$@+
        @echo NO_UNIX_SOCKETS=\''$(subst ','\'',$(subst ','\'',$(NO_UNIX_SOCKETS)))'\' >>$@+
        @echo PAGER_ENV=\''$(subst ','\'',$(subst ','\'',$(PAGER_ENV)))'\' >>$@+
+       @echo DC_SHA1=\''$(subst ','\'',$(subst ','\'',$(DC_SHA1)))'\' >>$@+
  ifdef TEST_OUTPUT_DIRECTORY
        @echo TEST_OUTPUT_DIRECTORY=\''$(subst ','\'',$(subst ','\'',$(TEST_OUTPUT_DIRECTORY)))'\' >>$@+
  endif
@@@ -2249,9 -2267,6 +2264,9 @@@ endi
  ifdef GIT_PERF_MAKE_OPTS
        @echo GIT_PERF_MAKE_OPTS=\''$(subst ','\'',$(subst ','\'',$(GIT_PERF_MAKE_OPTS)))'\' >>$@+
  endif
 +ifdef GIT_INTEROP_MAKE_OPTS
 +      @echo GIT_INTEROP_MAKE_OPTS=\''$(subst ','\'',$(subst ','\'',$(GIT_INTEROP_MAKE_OPTS)))'\' >>$@+
 +endif
  ifdef TEST_GIT_INDEX_VERSION
        @echo TEST_GIT_INDEX_VERSION=\''$(subst ','\'',$(subst ','\'',$(TEST_GIT_INDEX_VERSION)))'\' >>$@+
  endif