Squashed 'third_party/git/' content from commit cb71568594

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diff --git a/sha1dc/sha1.h b/sha1dc/sha1.h
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+/***
+* Copyright 2017 Marc Stevens <marc@marc-stevens.nl>, Dan Shumow <danshu@microsoft.com>
+* Distributed under the MIT Software License.
+* See accompanying file LICENSE.txt or copy at
+* https://opensource.org/licenses/MIT
+***/
+
+#ifndef SHA1DC_SHA1_H
+#define SHA1DC_SHA1_H
+
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
+#ifndef SHA1DC_NO_STANDARD_INCLUDES
+#include <stdint.h>
+#endif
+
+/* sha-1 compression function that takes an already expanded message, and additionally store intermediate states */
+/* only stores states ii (the state between step ii-1 and step ii) when DOSTORESTATEii is defined in ubc_check.h */
+void sha1_compression_states(uint32_t[5], const uint32_t[16], uint32_t[80], uint32_t[80][5]);
+
+/*
+// Function type for sha1_recompression_step_T (uint32_t ihvin[5], uint32_t ihvout[5], const uint32_t me2[80], const uint32_t state[5]).
+// Where 0 <= T < 80
+//       me2 is an expanded message (the expansion of an original message block XOR'ed with a disturbance vector's message block difference.)
+//       state is the internal state (a,b,c,d,e) before step T of the SHA-1 compression function while processing the original message block.
+// The function will return:
+//       ihvin: The reconstructed input chaining value.
+//       ihvout: The reconstructed output chaining value.
+*/
+typedef void(*sha1_recompression_type)(uint32_t*, uint32_t*, const uint32_t*, const uint32_t*);
+
+/* A callback function type that can be set to be called when a collision block has been found: */
+/* void collision_block_callback(uint64_t byteoffset, const uint32_t ihvin1[5], const uint32_t ihvin2[5], const uint32_t m1[80], const uint32_t m2[80]) */
+typedef void(*collision_block_callback)(uint64_t, const uint32_t*, const uint32_t*, const uint32_t*, const uint32_t*);
+
+/* The SHA-1 context. */
+typedef struct {
+	uint64_t total;
+	uint32_t ihv[5];
+	unsigned char buffer[64];
+	int found_collision;
+	int safe_hash;
+	int detect_coll;
+	int ubc_check;
+	int reduced_round_coll;
+	collision_block_callback callback;
+
+	uint32_t ihv1[5];
+	uint32_t ihv2[5];
+	uint32_t m1[80];
+	uint32_t m2[80];
+	uint32_t states[80][5];
+} SHA1_CTX;
+
+/* Initialize SHA-1 context. */
+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.
+
+   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.
+   This will automatically invalidate SHA-1 based digital signature forgeries.
+   Enabled by default.
+*/
+void SHA1DCSetSafeHash(SHA1_CTX*, int);
+
+/*
+    Function to disable or enable the use of Unavoidable Bitconditions (provides a significant speed up).
+    Enabled by default
+ */
+void SHA1DCSetUseUBC(SHA1_CTX*, int);
+
+/*
+    Function to disable or enable the use of Collision Detection.
+    Enabled by default.
+ */
+void SHA1DCSetUseDetectColl(SHA1_CTX*, int);
+
+/* function to disable or enable the detection of reduced-round SHA-1 collisions */
+/* disabled by default */
+void SHA1DCSetDetectReducedRoundCollision(SHA1_CTX*, int);
+
+/* function to set a callback function, pass NULL to disable */
+/* by default no callback set */
+void SHA1DCSetCallback(SHA1_CTX*, collision_block_callback);
+
+/* update SHA-1 context with buffer contents */
+void SHA1DCUpdate(SHA1_CTX*, const char*, size_t);
+
+/* obtain SHA-1 hash from SHA-1 context */
+/* returns: 0 = no collision detected, otherwise = collision found => warn user for active attack */
+int  SHA1DCFinal(unsigned char[20], SHA1_CTX*);
+
+#if defined(__cplusplus)
+}
+#endif
+
+#ifdef SHA1DC_CUSTOM_TRAILING_INCLUDE_SHA1_H
+#include SHA1DC_CUSTOM_TRAILING_INCLUDE_SHA1_H
+#endif
+
+#endif