thodg/libgit2/src/integer.h

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• Hash : 37141ff7
  Author :
  Date : 2019-10-21T18:56:59
  

  patch_parse: detect overflow when calculating old/new line position When the patch contains lines close to INT_MAX, then it may happen that we end up with an integer overflow when calculating the line of the current diff hunk. Reject such patches as unreasonable to avoid the integer overflow. As the calculation is performed on integers, we introduce two new helpers `git__add_int_overflow` and `git__sub_int_overflow` that perform the integer overflow check in a generic way.

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• src/integer.h

• /*
   * Copyright (C) the libgit2 contributors. All rights reserved.
   *
   * This file is part of libgit2, distributed under the GNU GPL v2 with
   * a Linking Exception. For full terms see the included COPYING file.
   */
  #ifndef INCLUDE_integer_h__
  #define INCLUDE_integer_h__
  
  /** @return true if p fits into the range of a size_t */
  GIT_INLINE(int) git__is_sizet(git_off_t p)
  {
  	size_t r = (size_t)p;
  	return p == (git_off_t)r;
  }
  
  /** @return true if p fits into the range of an ssize_t */
  GIT_INLINE(int) git__is_ssizet(size_t p)
  {
  	ssize_t r = (ssize_t)p;
  	return p == (size_t)r;
  }
  
  /** @return true if p fits into the range of a uint16_t */
  GIT_INLINE(int) git__is_uint16(size_t p)
  {
  	uint16_t r = (uint16_t)p;
  	return p == (size_t)r;
  }
  
  /** @return true if p fits into the range of a uint32_t */
  GIT_INLINE(int) git__is_uint32(size_t p)
  {
  	uint32_t r = (uint32_t)p;
  	return p == (size_t)r;
  }
  
  /** @return true if p fits into the range of an unsigned long */
  GIT_INLINE(int) git__is_ulong(git_off_t p)
  {
  	unsigned long r = (unsigned long)p;
  	return p == (git_off_t)r;
  }
  
  /** @return true if p fits into the range of an int */
  GIT_INLINE(int) git__is_int(long long p)
  {
  	int r = (int)p;
  	return p == (long long)r;
  }
  
  /* Use clang/gcc compiler intrinsics whenever possible */
  #if (__has_builtin(__builtin_add_overflow) || \
       (defined(__GNUC__) && (__GNUC__ >= 5)))
  
  # if (SIZE_MAX == UINT_MAX)
  #  define git__add_sizet_overflow(out, one, two) \
       __builtin_uadd_overflow(one, two, out)
  #  define git__multiply_sizet_overflow(out, one, two) \
       __builtin_umul_overflow(one, two, out)
  # elif (SIZE_MAX == ULONG_MAX)
  #  define git__add_sizet_overflow(out, one, two) \
       __builtin_uaddl_overflow(one, two, out)
  #  define git__multiply_sizet_overflow(out, one, two) \
       __builtin_umull_overflow(one, two, out)
  # elif (SIZE_MAX == ULLONG_MAX)
  #  define git__add_sizet_overflow(out, one, two) \
       __builtin_uaddll_overflow(one, two, out)
  #  define git__multiply_sizet_overflow(out, one, two) \
       __builtin_umulll_overflow(one, two, out)
  # else
  #  error compiler has add with overflow intrinsics but SIZE_MAX is unknown
  # endif
  
  # define git__add_int_overflow(out, one, two) \
      __builtin_sadd_overflow(one, two, out)
  # define git__sub_int_overflow(out, one, two) \
      __builtin_ssub_overflow(one, two, out)
  
  /* Use Microsoft's safe integer handling functions where available */
  #elif defined(_MSC_VER)
  
  # define ENABLE_INTSAFE_SIGNED_FUNCTIONS
  # include <intsafe.h>
  
  # define git__add_sizet_overflow(out, one, two) \
      (SizeTAdd(one, two, out) != S_OK)
  # define git__multiply_sizet_overflow(out, one, two) \
      (SizeTMult(one, two, out) != S_OK)
  #define git__add_int_overflow(out, one, two) \
      (IntAdd(one, two, out) != S_OK)
  #define git__sub_int_overflow(out, one, two) \
      (IntSub(one, two, out) != S_OK)
  
  #else
  
  /**
   * Sets `one + two` into `out`, unless the arithmetic would overflow.
   * @return false if the result fits in a `size_t`, true on overflow.
   */
  GIT_INLINE(bool) git__add_sizet_overflow(size_t *out, size_t one, size_t two)
  {
  	if (SIZE_MAX - one < two)
  		return true;
  	*out = one + two;
  	return false;
  }
  
  /**
   * Sets `one * two` into `out`, unless the arithmetic would overflow.
   * @return false if the result fits in a `size_t`, true on overflow.
   */
  GIT_INLINE(bool) git__multiply_sizet_overflow(size_t *out, size_t one, size_t two)
  {
  	if (one && SIZE_MAX / one < two)
  		return true;
  	*out = one * two;
  	return false;
  }
  
  GIT_INLINE(bool) git__add_int_overflow(int *out, int one, int two)
  {
  	if ((two > 0 && one > (INT_MAX - two)) ||
  	    (two < 0 && one < (INT_MIN - two)))
  		return true;
  	*out = one + two;
  	return false;
  }
  
  GIT_INLINE(bool) git__sub_int_overflow(int *out, int one, int two)
  {
  	if ((two > 0 && one < (INT_MIN + two)) ||
  	    (two < 0 && one > (INT_MAX + two)))
  		return true;
  	*out = one - two;
  	return false;
  }
  
  #endif
  
  #endif
  

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