liblzma: Try to use SHA-256 from the operating system.

If the operating system libc or other base libraries
provide SHA-256, use that instead of our own copy.
Note that this doesn't use OpenSSL or libgcrypt or
such libraries to avoid creating dependencies to
other packages.

This supports at least FreeBSD, NetBSD, OpenBSD, Solaris,
MINIX, and Darwin. They all provide similar but not
identical SHA-256 APIs; everyone is a little different.

Thanks to Wim Lewis for the original patch, improvements,
and testing.

configure.ac

@@ -535,6 +535,60 @@ TUKLIB_PHYSMEM
 TUKLIB_CPUCORES
 TUKLIB_MBSTR
 
+# Check for system-provided SHA-256. At least the following is supported:
+#
+# OS       Headers                     Library  Type           Function
+# FreeBSD  sys/types.h + sha256.h      libmd    SHA256_CTX     SHA256_Init
+# NetBSD   sys/types.h + sha2.h                 SHA256_CTX     SHA256_Init
+# OpenBSD  sys/types.h + sha2.h                 SHA2_CTX       SHA256Init
+# Solaris  sys/types.h + sha2.h        libmd    SHA256_CTX     SHA256Init
+# MINIX 3  sys/types.h + minix/sha2.h  libutil  SHA256_CTX     SHA256_Init
+# Darwin   CommonCrypto/CommonDigest.h          CC_SHA256_CTX  CC_SHA256_Init
+#
+# Note that Darwin's CC_SHA256_Update takes buffer size as uint32_t instead
+# of size_t.
+#
+# We don't check for e.g. OpenSSL or libgcrypt because we don't want
+# to introduce dependencies to other packages by default. Maybe such
+# libraries could be supported via additional configure options though.
+#
+if test "x$enable_check_sha256" = "xyes"; then
+	# Test for Common Crypto before others, because Darwin has sha256.h
+	# too and we don't want to use that, because on older versions it
+	# uses OpenSSL functions, whose SHA256_Init is not guaranteed to
+	# succeed.
+	sha256_header_found=no
+	AC_CHECK_HEADERS(
+		[CommonCrypto/CommonDigest.h sha256.h sha2.h minix/sha2.h],
+		[sha256_header_found=yes ; break])
+	if test "x$sha256_header_found" = xyes; then
+		AC_CHECK_TYPES([CC_SHA256_CTX, SHA256_CTX, SHA2_CTX], [], [],
+			[[#ifdef HAVE_SYS_TYPES
+			  # include <sys/types.h>
+			  #endif
+			  #ifdef HAVE_COMMONCRYPTO_COMMONDIGEST_H
+			  # include <CommonCrypto/CommonDigest.h>
+			  #endif
+			  #ifdef HAVE_SHA256_H
+			  # include <sha256.h>
+			  #endif
+			  #ifdef HAVE_SHA2_H
+			  # include <sha2.h>
+			  #endif
+			  #ifdef HAVE_MINIX_SHA2_H
+			  # include <minix/sha2.h>
+			  #endif]])
+		AC_SEARCH_LIBS([SHA256_Init], [md util])
+		AC_SEARCH_LIBS([SHA256Init], [md])
+		AC_CHECK_FUNCS([CC_SHA256_Init SHA256_Init SHA256Init],
+			[break])
+	fi
+fi
+AM_CONDITIONAL([COND_INTERNAL_SHA256],
+	[test "x$ac_cv_func_SHA256_Init" != xyes \
+		&& test "x$ac_cv_func_SHA256Init" != xyes \
+		&& test "x$ac_cv_func_CC_SHA256_Init" != xyes])
+
 
 ###############################################################################
 # If using GCC, set some additional AM_CFLAGS:

src/liblzma/check/Makefile.inc

@@ -47,5 +47,7 @@ endif
 endif
 
 if COND_CHECK_SHA256
+if COND_INTERNAL_SHA256
 liblzma_la_SOURCES += check/sha256.c
 endif
+endif

src/liblzma/check/check.h

@@ -15,6 +15,43 @@
 
 #include "common.h"
 
+#if defined(HAVE_COMMONCRYPTO_COMMONDIGEST_H)
+#	include <CommonCrypto/CommonDigest.h>
+#elif defined(HAVE_SHA256_H)
+#	include <sys/types.h>
+#	include <sha256.h>
+#elif defined(HAVE_SHA2_H)
+#	include <sys/types.h>
+#	include <sha2.h>
+#elif defined(HAVE_MINIX_SHA2_H)
+#	include <sys/types.h>
+#	include <minix/sha2.h>
+#endif
+
+#if defined(HAVE_CC_SHA256_CTX)
+typedef CC_SHA256_CTX lzma_sha256_state;
+#elif defined(HAVE_SHA256_CTX)
+typedef SHA256_CTX lzma_sha256_state;
+#elif defined(HAVE_SHA2_CTX)
+typedef SHA2_CTX lzma_sha256_state;
+#else
+/// State for the internal SHA-256 implementation
+typedef struct {
+	/// Internal state
+	uint32_t state[8];
+
+	/// Size of the message excluding padding
+	uint64_t size;
+} lzma_sha256_state;
+#endif
+
+#if defined(HAVE_CC_SHA256_INIT)
+#	define LZMA_SHA256FUNC(x) CC_SHA256_ ## x
+#elif defined(HAVE_SHA256_INIT)
+#	define LZMA_SHA256FUNC(x) SHA256_ ## x
+#elif defined(HAVE_SHA256INIT)
+#	define LZMA_SHA256FUNC(x) SHA256 ## x
+#endif
 
 // Index hashing needs the best possible hash function (preferably
 // a cryptographic hash) for maximum reliability.
@@ -43,14 +80,7 @@ typedef struct {
 	union {
 		uint32_t crc32;
 		uint64_t crc64;
-
+		lzma_sha256_state sha256;
-		struct {
-			/// Internal state
-			uint32_t state[8];
-
-			/// Size of the message excluding padding
-			uint64_t size;
-		} sha256;
 	} state;
 
 } lzma_check_state;
@@ -82,6 +112,8 @@ extern void lzma_check_update(lzma_check_state *check, lzma_check type,
 extern void lzma_check_finish(lzma_check_state *check, lzma_check type);
 
 
+#ifndef LZMA_SHA256FUNC
+
 /// Prepare SHA-256 state for new input.
 extern void lzma_sha256_init(lzma_check_state *check);
 
@@ -92,4 +124,39 @@ extern void lzma_sha256_update(
 /// Finish the SHA-256 calculation and store the result to check->buffer.u8.
 extern void lzma_sha256_finish(lzma_check_state *check);
 
+
+#else
+
+static inline void
+lzma_sha256_init(lzma_check_state *check)
+{
+	LZMA_SHA256FUNC(Init)(&check->state.sha256);
+}
+
+
+static inline void
+lzma_sha256_update(const uint8_t *buf, size_t size, lzma_check_state *check)
+{
+#if defined(HAVE_CC_SHA256_INIT) && SIZE_MAX > UINT32_MAX
+	// Darwin's CC_SHA256_Update takes uint32_t as the buffer size,
+	// so use a loop to support size_t.
+	while (size > UINT32_MAX) {
+		LZMA_SHA256FUNC(Update)(&check->state.sha256, buf, UINT32_MAX);
+		buf += UINT32_MAX;
+		size -= UINT32_MAX;
+	}
+#endif
+
+	LZMA_SHA256FUNC(Update)(&check->state.sha256, buf, size);
+}
+
+
+static inline void
+lzma_sha256_finish(lzma_check_state *check)
+{
+	LZMA_SHA256FUNC(Final)(check->buffer.u8, &check->state.sha256);
+}
+
+#endif
+
 #endif