thodg/libgit2/src/parse.c
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Hash : d1bfe614
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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
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/* * 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; }