Commit message: Add platform-independent .git "symlink"

This patch allows .git to be a regular textfile containing the path of
the real git directory (prefixed with "gitdir: "), which can be useful on
platforms lacking support for real symlinks.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
CVE: CVE-2010-2542
Vulnerability description: Stack-based buffer overflow in the is_git_directory function in setup.c in Git before 1.7.2.1 allows local users to gain privileges via a long gitdir: field in a .git file in a working copy.

Project: git
File: environment.c

char *get_object_directory(void)
{
	if (!git_object_dir)
		setup_git_env();
	return git_object_dir;
}

Project: git
File: setup.c

int check_repository_format(void)
{
	return check_repository_format_gently(NULL);
}

Project: git
File: setup.c

void verify_filename(const char *prefix, const char *arg)
{
	const char *name;
	struct stat st;

	if (*arg == '-')
		die("bad flag '%s' used after filename", arg);
	name = prefix ? prefix_filename(prefix, strlen(prefix), arg) : arg;
	if (!lstat(name, &st))
		return;
	if (errno == ENOENT)
		die("ambiguous argument '%s': unknown revision or path not in the working tree.\n"
		    "Use '--' to separate paths from revisions", arg);
	die("'%s': %s", arg, strerror(errno));
}

Project: git
File: environment.c

const char *get_git_work_tree(void)
{
	static int initialized = 0;
	if (!initialized) {
		work_tree = getenv(GIT_WORK_TREE_ENVIRONMENT);
		/* core.bare = true overrides implicit and config work tree */
		if (!work_tree && is_bare_repository_cfg < 1) {
			work_tree = git_work_tree_cfg;
			/* make_absolute_path also normalizes the path */
			if (work_tree && !is_absolute_path(work_tree))
				work_tree = xstrdup(make_absolute_path(git_path(work_tree)));
		} else if (work_tree)
			work_tree = xstrdup(make_absolute_path(work_tree));
		initialized = 1;
		if (work_tree)
			is_bare_repository_cfg = 0;
	}
	return work_tree;
}

Project: git
File: environment.c

char *get_refs_directory(void)
{
	if (!git_refs_dir)
		setup_git_env();
	return git_refs_dir;
}

Project: git
File: environment.c

int set_git_dir(const char *path)
{
	if (setenv(GIT_DIR_ENVIRONMENT, path, 1))
		return error("Could not set GIT_DIR to '%s'", path);
	setup_git_env();
	return 0;
}

Project: git
File: setup.c

const char *read_gitfile_gently(const char *path)
{
	char *buf;
	struct stat st;
	int fd;
	size_t len;

	if (stat(path, &st))
		return NULL;
	if (!S_ISREG(st.st_mode))
		return NULL;
	fd = open(path, O_RDONLY);
	if (fd < 0)
		die("Error opening %s: %s", path, strerror(errno));
	buf = xmalloc(st.st_size + 1);
	len = read_in_full(fd, buf, st.st_size);
	close(fd);
	if (len != st.st_size)
		die("Error reading %s", path);
	buf[len] = '\0';
	if (prefixcmp(buf, "gitdir: "))
		die("Invalid gitfile format: %s", path);
	while (buf[len - 1] == '\n' || buf[len - 1] == '\r')
		len--;
	if (len < 9)
		die("No path in gitfile: %s", path);
	buf[len] = '\0';
	if (!is_git_directory(buf + 8))
		die("Not a git repository: %s", buf + 8);
	path = make_absolute_path(buf + 8);
	free(buf);
	return path;
}

Project: git
File: environment.c

int is_bare_repository(void)
{
	/* if core.bare is not 'false', let's see if there is a work tree */
	return is_bare_repository_cfg && !get_git_work_tree();
}

Project: git
File: environment.c

static void setup_git_env(void)
{
	git_dir = getenv(GIT_DIR_ENVIRONMENT);
	if (!git_dir)
		git_dir = read_gitfile_gently(DEFAULT_GIT_DIR_ENVIRONMENT);
	if (!git_dir)
		git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
	git_object_dir = getenv(DB_ENVIRONMENT);
	if (!git_object_dir) {
		git_object_dir = xmalloc(strlen(git_dir) + 9);
		sprintf(git_object_dir, "%s/objects", git_dir);
	}
	git_refs_dir = xmalloc(strlen(git_dir) + 6);
	sprintf(git_refs_dir, "%s/refs", git_dir);
	git_index_file = getenv(INDEX_ENVIRONMENT);
	if (!git_index_file) {
		git_index_file = xmalloc(strlen(git_dir) + 7);
		sprintf(git_index_file, "%s/index", git_dir);
	}
	git_graft_file = getenv(GRAFT_ENVIRONMENT);
	if (!git_graft_file)
		git_graft_file = xstrdup(git_path("info/grafts"));
}

Project: git
File: environment.c

char *get_index_file(void)
{
	if (!git_index_file)
		setup_git_env();
	return git_index_file;
}

Project: git
File: setup.c

int git_config_perm(const char *var, const char *value)
{
	if (value) {
		int i;
		if (!strcmp(value, "umask"))
			return PERM_UMASK;
		if (!strcmp(value, "group"))
			return PERM_GROUP;
		if (!strcmp(value, "all") ||
		    !strcmp(value, "world") ||
		    !strcmp(value, "everybody"))
			return PERM_EVERYBODY;
		i = atoi(value);
		if (i > 1)
			return i;
	}
	return git_config_bool(var, value);
}

Project: git
File: setup.c

const char *setup_git_directory_gently(int *nongit_ok)
{
	const char *work_tree_env = getenv(GIT_WORK_TREE_ENVIRONMENT);
	static char cwd[PATH_MAX+1];
	const char *gitdirenv;
	const char *gitfile_dir;
	int len, offset;

	/*
	 * Let's assume that we are in a git repository.
	 * If it turns out later that we are somewhere else, the value will be
	 * updated accordingly.
	 */
	if (nongit_ok)
		*nongit_ok = 0;

	/*
	 * If GIT_DIR is set explicitly, we're not going
	 * to do any discovery, but we still do repository
	 * validation.
	 */
	gitdirenv = getenv(GIT_DIR_ENVIRONMENT);
	if (gitdirenv) {
		if (PATH_MAX - 40 < strlen(gitdirenv))
			die("'$%s' too big", GIT_DIR_ENVIRONMENT);
		if (is_git_directory(gitdirenv)) {
			static char buffer[1024 + 1];
			const char *retval;

			if (!work_tree_env) {
				retval = set_work_tree(gitdirenv);
				/* config may override worktree */
				if (check_repository_format_gently(nongit_ok))
					return NULL;
				return retval;
			}
			if (check_repository_format_gently(nongit_ok))
				return NULL;
			retval = get_relative_cwd(buffer, sizeof(buffer) - 1,
					get_git_work_tree());
			if (!retval || !*retval)
				return NULL;
			set_git_dir(make_absolute_path(gitdirenv));
			if (chdir(work_tree_env) < 0)
				die ("Could not chdir to %s", work_tree_env);
			strcat(buffer, "/");
			return retval;
		}
		if (nongit_ok) {
			*nongit_ok = 1;
			return NULL;
		}
		die("Not a git repository: '%s'", gitdirenv);
	}

	if (!getcwd(cwd, sizeof(cwd)-1))
		die("Unable to read current working directory");

	/*
	 * Test in the following order (relative to the cwd):
	 * - .git (file containing "gitdir: <path>")
	 * - .git/
	 * - ./ (bare)
	 * - ../.git
	 * - ../.git/
	 * - ../ (bare)
	 * - ../../.git/
	 *   etc.
	 */
	offset = len = strlen(cwd);
	for (;;) {
		gitfile_dir = read_gitfile_gently(DEFAULT_GIT_DIR_ENVIRONMENT);
		if (gitfile_dir) {
			if (set_git_dir(gitfile_dir))
				die("Repository setup failed");
			break;
		}
		if (is_git_directory(DEFAULT_GIT_DIR_ENVIRONMENT))
			break;
		if (is_git_directory(".")) {
			inside_git_dir = 1;
			if (!work_tree_env)
				inside_work_tree = 0;
			setenv(GIT_DIR_ENVIRONMENT, ".", 1);
			check_repository_format_gently(nongit_ok);
			return NULL;
		}
		chdir("..");
		do {
			if (!offset) {
				if (nongit_ok) {
					if (chdir(cwd))
						die("Cannot come back to cwd");
					*nongit_ok = 1;
					return NULL;
				}
				die("Not a git repository");
			}
		} while (cwd[--offset] != '/');
	}

	inside_git_dir = 0;
	if (!work_tree_env)
		inside_work_tree = 1;
	git_work_tree_cfg = xstrndup(cwd, offset);
	if (check_repository_format_gently(nongit_ok))
		return NULL;
	if (offset == len)
		return NULL;

	/* Make "offset" point to past the '/', and add a '/' at the end */
	offset++;
	cwd[len++] = '/';
	cwd[len] = 0;
	return cwd + offset;
}

Project: git
File: setup.c

const char *setup_git_directory(void)
{
	const char *retval = setup_git_directory_gently(NULL);

	/* If the work tree is not the default one, recompute prefix */
	if (inside_work_tree < 0) {
		static char buffer[PATH_MAX + 1];
		char *rel;
		if (retval && chdir(retval))
			die ("Could not jump back into original cwd");
		rel = get_relative_cwd(buffer, PATH_MAX, get_git_work_tree());
		return rel && *rel ? strcat(rel, "/") : NULL;
	}

	return retval;
}

Project: git
File: environment.c

char *get_graft_file(void)
{
	if (!git_graft_file)
		setup_git_env();
	return git_graft_file;
}

Project: git
File: setup.c

const char *prefix_filename(const char *pfx, int pfx_len, const char *arg)
{
	static char path[PATH_MAX];
	if (!pfx || !*pfx || is_absolute_path(arg))
		return arg;
	memcpy(path, pfx, pfx_len);
	strcpy(path + pfx_len, arg);
	return path;
}

Project: git
File: setup.c

void verify_non_filename(const char *prefix, const char *arg)
{
	const char *name;
	struct stat st;

	if (!is_inside_work_tree() || is_inside_git_dir())
		return;
	if (*arg == '-')
		return; /* flag */
	name = prefix ? prefix_filename(prefix, strlen(prefix), arg) : arg;
	if (!lstat(name, &st))
		die("ambiguous argument '%s': both revision and filename\n"
		    "Use '--' to separate filenames from revisions", arg);
	if (errno != ENOENT && errno != ENOTDIR)
		die("'%s': %s", arg, strerror(errno));
}

Project: git
File: setup.c

void setup_work_tree(void)
{
	const char *work_tree, *git_dir;
	static int initialized = 0;

	if (initialized)
		return;
	work_tree = get_git_work_tree();
	git_dir = get_git_dir();
	if (!is_absolute_path(git_dir))
		set_git_dir(make_absolute_path(git_dir));
	if (!work_tree || chdir(work_tree))
		die("This operation must be run in a work tree");
	initialized = 1;
}

Project: git
File: setup.c

static const char *set_work_tree(const char *dir)
{
	char buffer[PATH_MAX + 1];

	if (!getcwd(buffer, sizeof(buffer)))
		die ("Could not get the current working directory");
	git_work_tree_cfg = xstrdup(buffer);
	inside_work_tree = 1;

	return NULL;
}

Project: git
File: setup.c

const char **get_pathspec(const char *prefix, const char **pathspec)
{
	const char *entry = *pathspec;
	const char **src, **dst;
	int prefixlen;

	if (!prefix && !entry)
		return NULL;

	if (!entry) {
		static const char *spec[2];
		spec[0] = prefix;
		spec[1] = NULL;
		return spec;
	}

	/* Otherwise we have to re-write the entries.. */
	src = pathspec;
	dst = pathspec;
	prefixlen = prefix ? strlen(prefix) : 0;
	while (*src) {
		const char *p = prefix_path(prefix, prefixlen, *src);
		if (p)
			*(dst++) = p;
		else
			exit(128); /* error message already given */
		src++;
	}
	*dst = NULL;
	if (!*pathspec)
		return NULL;
	return pathspec;
}

Project: git
File: setup.c

const char *prefix_path(const char *prefix, int len, const char *path)
{
	const char *orig = path;
	char *sanitized = xmalloc(len + strlen(path) + 1);
	if (is_absolute_path(orig))
		strcpy(sanitized, path);
	else {
		if (len)
			memcpy(sanitized, prefix, len);
		strcpy(sanitized + len, path);
	}
	if (sanitary_path_copy(sanitized, sanitized))
		goto error_out;
	if (is_absolute_path(orig)) {
		const char *work_tree = get_git_work_tree();
		size_t len = strlen(work_tree);
		size_t total = strlen(sanitized) + 1;
		if (strncmp(sanitized, work_tree, len) ||
		    (sanitized[len] != '\0' && sanitized[len] != '/')) {
		error_out:
			error("'%s' is outside repository", orig);
			free(sanitized);
			return NULL;
		}
		if (sanitized[len] == '/')
			len++;
		memmove(sanitized, sanitized + len, total - len);
	}
	return sanitized;
}

Project: git
File: setup.c

static int sanitary_path_copy(char *dst, const char *src)
{
	char *dst0 = dst;

	if (*src == '/') {
		*dst++ = '/';
		while (*src == '/')
			src++;
	}

	for (;;) {
		char c = *src;

		/*
		 * A path component that begins with . could be
		 * special:
		 * (1) "." and ends   -- ignore and terminate.
		 * (2) "./"           -- ignore them, eat slash and continue.
		 * (3) ".." and ends  -- strip one and terminate.
		 * (4) "../"          -- strip one, eat slash and continue.
		 */
		if (c == '.') {
			switch (src[1]) {
			case '\0':
				/* (1) */
				src++;
				break;
			case '/':
				/* (2) */
				src += 2;
				while (*src == '/')
					src++;
				continue;
			case '.':
				switch (src[2]) {
				case '\0':
					/* (3) */
					src += 2;
					goto up_one;
				case '/':
					/* (4) */
					src += 3;
					while (*src == '/')
						src++;
					goto up_one;
				}
			}
		}

		/* copy up to the next '/', and eat all '/' */
		while ((c = *src++) != '\0' && c != '/')
			*dst++ = c;
		if (c == '/') {
			*dst++ = c;
			while (c == '/')
				c = *src++;
			src--;
		} else if (!c)
			break;
		continue;

	up_one:
		/*
		 * dst0..dst is prefix portion, and dst[-1] is '/';
		 * go up one level.
		 */
		dst -= 2; /* go past trailing '/' if any */
		if (dst < dst0)
			return -1;
		while (1) {
			if (dst <= dst0)
				break;
			c = *dst--;
			if (c == '/') {
				dst += 2;
				break;
			}
		}
	}
	*dst = '\0';
	return 0;
}

Project: git
File: setup.c

static int check_repository_format_gently(int *nongit_ok)
{
	git_config(check_repository_format_version);
	if (GIT_REPO_VERSION < repository_format_version) {
		if (!nongit_ok)
			die ("Expected git repo version <= %d, found %d",
			     GIT_REPO_VERSION, repository_format_version);
		warning("Expected git repo version <= %d, found %d",
			GIT_REPO_VERSION, repository_format_version);
		warning("Please upgrade Git");
		*nongit_ok = -1;
		return -1;
	}
	return 0;
}

Project: git
File: environment.c

const char *get_git_dir(void)
{
	if (!git_dir)
		setup_git_env();
	return git_dir;
}

Project: git
File: setup.c

int check_repository_format_version(const char *var, const char *value)
{
	if (strcmp(var, "core.repositoryformatversion") == 0)
		repository_format_version = git_config_int(var, value);
	else if (strcmp(var, "core.sharedrepository") == 0)
		shared_repository = git_config_perm(var, value);
	else if (strcmp(var, "core.bare") == 0) {
		is_bare_repository_cfg = git_config_bool(var, value);
		if (is_bare_repository_cfg == 1)
			inside_work_tree = -1;
	} else if (strcmp(var, "core.worktree") == 0) {
		if (!value)
			return config_error_nonbool(var);
		free(git_work_tree_cfg);
		git_work_tree_cfg = xstrdup(value);
		inside_work_tree = -1;
	}
	return 0;
}