thodg/libgit2/src/parse.c

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• Hash : d1bfe614
  Author :
  Date : 2018-08-04T19:30:40
  

  parse: Do not initialize the content in context to NULL String operations in libgit2 are supposed to never receive `NULL`, e.g. they are not `NULL`-save. In the case of `git__linenlen()`, invocation with `NULL` leads to undefined behavior. In a `git_parse_ctx` however, the `content` field used in these operations was initialized to `NULL` if the `git_parse_ctx_init()` was called with `NULL` for `content` or `0` for `content_len`. For the latter case, the initialization function even contained some logic for initializing `content` with `NULL`. This commit mitigates triggering undefined behavior by rewriting the logic. Now `content` is always initialized to a non-null buffer. Instead of a null buffer, an empty string is used for denoting an empty buffer.

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• src/parse.c

• /*
   * 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.
   */
  #include "parse.h"
  
  int git_parse_ctx_init(git_parse_ctx *ctx, const char *content, size_t content_len)
  {
  	if (content && content_len) {
  		ctx->content = content;
  		ctx->content_len = content_len;
  	} else {
  		ctx->content = "";
  		ctx->content_len = 0;
  	}
  
  	ctx->remain = ctx->content;
  	ctx->remain_len = ctx->content_len;
  	ctx->line = ctx->remain;
  	ctx->line_len = git__linenlen(ctx->line, ctx->remain_len);
  	ctx->line_num = 1;
  
  	return 0;
  }
  
  void git_parse_ctx_clear(git_parse_ctx *ctx)
  {
  	memset(ctx, 0, sizeof(*ctx));
  	ctx->content = "";
  }
  
  void git_parse_advance_line(git_parse_ctx *ctx)
  {
  	ctx->line += ctx->line_len;
  	ctx->remain_len -= ctx->line_len;
  	ctx->line_len = git__linenlen(ctx->line, ctx->remain_len);
  	ctx->line_num++;
  }
  
  void git_parse_advance_chars(git_parse_ctx *ctx, size_t char_cnt)
  {
  	ctx->line += char_cnt;
  	ctx->remain_len -= char_cnt;
  	ctx->line_len -= char_cnt;
  }
  
  int git_parse_advance_expected(
  	git_parse_ctx *ctx,
  	const char *expected,
  	size_t expected_len)
  {
  	if (ctx->line_len < expected_len)
  		return -1;
  
  	if (memcmp(ctx->line, expected, expected_len) != 0)
  		return -1;
  
  	git_parse_advance_chars(ctx, expected_len);
  	return 0;
  }
  
  int git_parse_advance_ws(git_parse_ctx *ctx)
  {
  	int ret = -1;
  
  	while (ctx->line_len > 0 &&
  		ctx->line[0] != '\n' &&
  		git__isspace(ctx->line[0])) {
  		ctx->line++;
  		ctx->line_len--;
  		ctx->remain_len--;
  		ret = 0;
  	}
  
  	return ret;
  }
  
  int git_parse_advance_nl(git_parse_ctx *ctx)
  {
  	if (ctx->line_len != 1 || ctx->line[0] != '\n')
  		return -1;
  
  	git_parse_advance_line(ctx);
  	return 0;
  }
  
  int git_parse_advance_digit(int64_t *out, git_parse_ctx *ctx, int base)
  {
  	const char *end;
  	int ret;
  
  	if (ctx->line_len < 1 || !git__isdigit(ctx->line[0]))
  		return -1;
  
  	if ((ret = git__strntol64(out, ctx->line, ctx->line_len, &end, base)) < 0)
  		return -1;
  
  	git_parse_advance_chars(ctx, (end - ctx->line));
  	return 0;
  }
  
  int git_parse_peek(char *out, git_parse_ctx *ctx, int flags)
  {
  	size_t remain = ctx->line_len;
  	const char *ptr = ctx->line;
  
  	while (remain) {
  		char c = *ptr;
  
  		if ((flags & GIT_PARSE_PEEK_SKIP_WHITESPACE) &&
  		    git__isspace(c)) {
  			remain--;
  			ptr++;
  			continue;
  		}
  
  		*out = c;
  		return 0;
  	}
  
  	return -1;
  }
  

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