thodg/libgit2/src/config_file.c

• Show log

  Commit

• Hash : 1e7799e8
  Author :
  Date : 2013-01-29T12:15:18
  

  Implement config key validation rules This is a new implementation of core git's config key checking rules that prevents non-alphanumeric characters (and '-') for the top-level section and key names inside of config files. This also validates the target section name when renaming sections.

Download

• src/config_file.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 "common.h"
  #include "config.h"
  #include "fileops.h"
  #include "filebuf.h"
  #include "buffer.h"
  #include "buf_text.h"
  #include "git2/config.h"
  #include "git2/types.h"
  #include "strmap.h"
  
  #include <ctype.h>
  #include <sys/types.h>
  #include <regex.h>
  
  GIT__USE_STRMAP;
  
  typedef struct cvar_t {
  	struct cvar_t *next;
  	git_config_entry *entry;
  } cvar_t;
  
  #define CVAR_LIST_HEAD(list) ((list)->head)
  
  #define CVAR_LIST_TAIL(list) ((list)->tail)
  
  #define CVAR_LIST_NEXT(var) ((var)->next)
  
  #define CVAR_LIST_EMPTY(list) ((list)->head == NULL)
  
  #define CVAR_LIST_APPEND(list, var) do {\
  	if (CVAR_LIST_EMPTY(list)) {\
  		CVAR_LIST_HEAD(list) = CVAR_LIST_TAIL(list) = var;\
  	} else {\
  		CVAR_LIST_NEXT(CVAR_LIST_TAIL(list)) = var;\
  		CVAR_LIST_TAIL(list) = var;\
  	}\
  } while(0)
  
  #define CVAR_LIST_REMOVE_HEAD(list) do {\
  	CVAR_LIST_HEAD(list) = CVAR_LIST_NEXT(CVAR_LIST_HEAD(list));\
  } while(0)
  
  #define CVAR_LIST_REMOVE_AFTER(var) do {\
  	CVAR_LIST_NEXT(var) = CVAR_LIST_NEXT(CVAR_LIST_NEXT(var));\
  } while(0)
  
  #define CVAR_LIST_FOREACH(list, iter)\
  	for ((iter) = CVAR_LIST_HEAD(list);\
  		 (iter) != NULL;\
  		 (iter) = CVAR_LIST_NEXT(iter))
  
  /*
   * Inspired by the FreeBSD functions
   */
  #define CVAR_LIST_FOREACH_SAFE(start, iter, tmp)\
  	for ((iter) = CVAR_LIST_HEAD(vars);\
  		 (iter) && (((tmp) = CVAR_LIST_NEXT(iter) || 1));\
  		 (iter) = (tmp))
  
  typedef struct {
  	git_config_backend parent;
  
  	git_strmap *values;
  
  	struct {
  		git_buf buffer;
  		char *read_ptr;
  		int line_number;
  		int eof;
  	} reader;
  
  	char  *file_path;
  	time_t file_mtime;
  	size_t file_size;
  
  	unsigned int level;
  } diskfile_backend;
  
  static int config_parse(diskfile_backend *cfg_file, unsigned int level);
  static int parse_variable(diskfile_backend *cfg, char **var_name, char **var_value);
  static int config_write(diskfile_backend *cfg, const char *key, const regex_t *preg, const char *value);
  static char *escape_value(const char *ptr);
  
  static void set_parse_error(diskfile_backend *backend, int col, const char *error_str)
  {
  	giterr_set(GITERR_CONFIG, "Failed to parse config file: %s (in %s:%d, column %d)",
  		error_str, backend->file_path, backend->reader.line_number, col);
  }
  
  static void cvar_free(cvar_t *var)
  {
  	if (var == NULL)
  		return;
  
  	git__free((char*)var->entry->name);
  	git__free((char *)var->entry->value);
  	git__free(var->entry);
  	git__free(var);
  }
  
  int git_config_file_normalize_section(char *start, char *end)
  {
  	char *scan;
  
  	if (start == end)
  		return GIT_EINVALIDSPEC;
  
  	/* Validate and downcase range */
  	for (scan = start; *scan; ++scan) {
  		if (end && scan >= end)
  			break;
  		if (isalnum(*scan))
  			*scan = tolower(*scan);
  		else if (*scan != '-' || scan == start)
  			return GIT_EINVALIDSPEC;
  	}
  
  	if (scan == start)
  		return GIT_EINVALIDSPEC;
  
  	return 0;
  }
  
  /* Take something the user gave us and make it nice for our hash function */
  static int normalize_name(const char *in, char **out)
  {
  	char *name, *fdot, *ldot;
  
  	assert(in && out);
  
  	name = git__strdup(in);
  	GITERR_CHECK_ALLOC(name);
  
  	fdot = strchr(name, '.');
  	ldot = strrchr(name, '.');
  
  	if (fdot == NULL || fdot == name || ldot == NULL || !ldot[1])
  		goto invalid;
  
  	/* Validate and downcase up to first dot and after last dot */
  	if (git_config_file_normalize_section(name, fdot) < 0 ||
  		git_config_file_normalize_section(ldot + 1, NULL) < 0)
  		goto invalid;
  
  	/* If there is a middle range, make sure it doesn't have newlines */
  	while (fdot < ldot)
  		if (*fdot++ == '\n')
  			goto invalid;
  
  	*out = name;
  	return 0;
  
  invalid:
  	git__free(name);
  	giterr_set(GITERR_CONFIG, "Invalid config item name '%s'", in);
  	return GIT_EINVALIDSPEC;
  }
  
  static void free_vars(git_strmap *values)
  {
  	cvar_t *var = NULL;
  
  	if (values == NULL)
  		return;
  
  	git_strmap_foreach_value(values, var,
  		while (var != NULL) {
  			cvar_t *next = CVAR_LIST_NEXT(var);
  			cvar_free(var);
  			var = next;
  		});
  
  	git_strmap_free(values);
  }
  
  static int config_open(git_config_backend *cfg, unsigned int level)
  {
  	int res;
  	diskfile_backend *b = (diskfile_backend *)cfg;
  
  	b->level = level;
  
  	b->values = git_strmap_alloc();
  	GITERR_CHECK_ALLOC(b->values);
  
  	git_buf_init(&b->reader.buffer, 0);
  	res = git_futils_readbuffer_updated(
  		&b->reader.buffer, b->file_path, &b->file_mtime, &b->file_size, NULL);
  
  	/* It's fine if the file doesn't exist */
  	if (res == GIT_ENOTFOUND)
  		return 0;
  
  	if (res < 0 || (res = config_parse(b, level)) < 0) {
  		free_vars(b->values);
  		b->values = NULL;
  	}
  
  	git_buf_free(&b->reader.buffer);
  	return res;
  }
  
  static int config_refresh(git_config_backend *cfg)
  {
  	int res, updated = 0;
  	diskfile_backend *b = (diskfile_backend *)cfg;
  	git_strmap *old_values;
  
  	res = git_futils_readbuffer_updated(
  		&b->reader.buffer, b->file_path, &b->file_mtime, &b->file_size, &updated);
  	if (res < 0 || !updated)
  		return (res == GIT_ENOTFOUND) ? 0 : res;
  
  	/* need to reload - store old values and prep for reload */
  	old_values = b->values;
  	b->values = git_strmap_alloc();
  	GITERR_CHECK_ALLOC(b->values);
  
  	if ((res = config_parse(b, b->level)) < 0) {
  		free_vars(b->values);
  		b->values = old_values;
  	} else {
  		free_vars(old_values);
  	}
  
  	git_buf_free(&b->reader.buffer);
  	return res;
  }
  
  static void backend_free(git_config_backend *_backend)
  {
  	diskfile_backend *backend = (diskfile_backend *)_backend;
  
  	if (backend == NULL)
  		return;
  
  	git__free(backend->file_path);
  	free_vars(backend->values);
  	git__free(backend);
  }
  
  static int file_foreach(
  	git_config_backend *backend,
  	const char *regexp,
  	int (*fn)(const git_config_entry *, void *),
  	void *data)
  {
  	diskfile_backend *b = (diskfile_backend *)backend;
  	cvar_t *var, *next_var;
  	const char *key;
  	regex_t regex;
  	int result = 0;
  
  	if (!b->values)
  		return 0;
  
  	if (regexp != NULL) {
  		if ((result = regcomp(&regex, regexp, REG_EXTENDED)) < 0) {
  			giterr_set_regex(&regex, result);
  			regfree(&regex);
  			return -1;
  		}
  	}
  
  	git_strmap_foreach(b->values, key, var,
  		for (; var != NULL; var = next_var) {
  			next_var = CVAR_LIST_NEXT(var);
  
  			/* skip non-matching keys if regexp was provided */
  			if (regexp && regexec(&regex, key, 0, NULL, 0) != 0)
  				continue;
  
  			/* abort iterator on non-zero return value */
  			if (fn(var->entry, data)) {
  				giterr_clear();
  				result = GIT_EUSER;
  				goto cleanup;
  			}
  		}
  	);
  
  cleanup:
  	if (regexp != NULL)
  		regfree(&regex);
  
  	return result;
  }
  
  static int config_set(git_config_backend *cfg, const char *name, const char *value)
  {
  	cvar_t *var = NULL, *old_var;
  	diskfile_backend *b = (diskfile_backend *)cfg;
  	char *key, *esc_value = NULL;
  	khiter_t pos;
  	int rval, ret;
  
  	if ((rval = normalize_name(name, &key)) < 0)
  		return rval;
  
  	/*
  	 * Try to find it in the existing values and update it if it
  	 * only has one value.
  	 */
  	pos = git_strmap_lookup_index(b->values, key);
  	if (git_strmap_valid_index(b->values, pos)) {
  		cvar_t *existing = git_strmap_value_at(b->values, pos);
  		char *tmp = NULL;
  
  		git__free(key);
  
  		if (existing->next != NULL) {
  			giterr_set(GITERR_CONFIG, "Multivar incompatible with simple set");
  			return -1;
  		}
  
  		/* don't update if old and new values already match */
  		if ((!existing->entry->value && !value) ||
  			(existing->entry->value && value && !strcmp(existing->entry->value, value)))
  			return 0;
  
  		if (value) {
  			tmp = git__strdup(value);
  			GITERR_CHECK_ALLOC(tmp);
  			esc_value = escape_value(value);
  			GITERR_CHECK_ALLOC(esc_value);
  		}
  
  		git__free((void *)existing->entry->value);
  		existing->entry->value = tmp;
  
  		ret = config_write(b, existing->entry->name, NULL, esc_value);
  
  		git__free(esc_value);
  		return ret;
  	}
  
  	var = git__malloc(sizeof(cvar_t));
  	GITERR_CHECK_ALLOC(var);
  	memset(var, 0x0, sizeof(cvar_t));
  	var->entry = git__malloc(sizeof(git_config_entry));
  	GITERR_CHECK_ALLOC(var->entry);
  	memset(var->entry, 0x0, sizeof(git_config_entry));
  
  	var->entry->name = key;
  	var->entry->value = NULL;
  
  	if (value) {
  		var->entry->value = git__strdup(value);
  		GITERR_CHECK_ALLOC(var->entry->value);
  		esc_value = escape_value(value);
  		GITERR_CHECK_ALLOC(esc_value);
  	}
  
  	if (config_write(b, key, NULL, esc_value) < 0) {
  		git__free(esc_value);
  		cvar_free(var);
  		return -1;
  	}
  
  	git__free(esc_value);
  	git_strmap_insert2(b->values, key, var, old_var, rval);
  	if (rval < 0)
  		return -1;
  	if (old_var != NULL)
  		cvar_free(old_var);
  
  	return 0;
  }
  
  /*
   * Internal function that actually gets the value in string form
   */
  static int config_get(const git_config_backend *cfg, const char *name, const git_config_entry **out)
  {
  	diskfile_backend *b = (diskfile_backend *)cfg;
  	char *key;
  	khiter_t pos;
  	int error;
  
  	if ((error = normalize_name(name, &key)) < 0)
  		return error;
  
  	pos = git_strmap_lookup_index(b->values, key);
  	git__free(key);
  
  	/* no error message; the config system will write one */
  	if (!git_strmap_valid_index(b->values, pos))
  		return GIT_ENOTFOUND;
  
  	*out = ((cvar_t *)git_strmap_value_at(b->values, pos))->entry;
  
  	return 0;
  }
  
  static int config_get_multivar(
  	git_config_backend *cfg,
  	const char *name,
  	const char *regex_str,
  	int (*fn)(const git_config_entry *, void *),
  	void *data)
  {
  	cvar_t *var;
  	diskfile_backend *b = (diskfile_backend *)cfg;
  	char *key;
  	khiter_t pos;
  	int error;
  
  	if ((error = normalize_name(name, &key)) < 0)
  		return error;
  
  	pos = git_strmap_lookup_index(b->values, key);
  	git__free(key);
  
  	if (!git_strmap_valid_index(b->values, pos))
  		return GIT_ENOTFOUND;
  
  	var = git_strmap_value_at(b->values, pos);
  
  	if (regex_str != NULL) {
  		regex_t regex;
  		int result;
  
  		/* regex matching; build the regex */
  		result = regcomp(&regex, regex_str, REG_EXTENDED);
  		if (result < 0) {
  			giterr_set_regex(&regex, result);
  			regfree(&regex);
  			return -1;
  		}
  
  		/* and throw the callback only on the variables that
  		 * match the regex */
  		do {
  			if (regexec(&regex, var->entry->value, 0, NULL, 0) == 0) {
  				/* early termination by the user is not an error;
  				 * just break and return successfully */
  				if (fn(var->entry, data) < 0)
  					break;
  			}
  
  			var = var->next;
  		} while (var != NULL);
  		regfree(&regex);
  	} else {
  		/* no regex; go through all the variables */
  		do {
  			/* early termination by the user is not an error;
  			 * just break and return successfully */
  			if (fn(var->entry, data) < 0)
  				break;
  
  			var = var->next;
  		} while (var != NULL);
  	}
  
  	return 0;
  }
  
  static int config_set_multivar(
  	git_config_backend *cfg, const char *name, const char *regexp, const char *value)
  {
  	int replaced = 0;
  	cvar_t *var, *newvar;
  	diskfile_backend *b = (diskfile_backend *)cfg;
  	char *key;
  	regex_t preg;
  	int result;
  	khiter_t pos;
  
  	assert(regexp);
  
  	if ((result = normalize_name(name, &key)) < 0)
  		return result;
  
  	pos = git_strmap_lookup_index(b->values, key);
  	if (!git_strmap_valid_index(b->values, pos)) {
  		git__free(key);
  		return GIT_ENOTFOUND;
  	}
  
  	var = git_strmap_value_at(b->values, pos);
  
  	result = regcomp(&preg, regexp, REG_EXTENDED);
  	if (result < 0) {
  		git__free(key);
  		giterr_set_regex(&preg, result);
  		regfree(&preg);
  		return -1;
  	}
  
  	for (;;) {
  		if (regexec(&preg, var->entry->value, 0, NULL, 0) == 0) {
  			char *tmp = git__strdup(value);
  			GITERR_CHECK_ALLOC(tmp);
  
  			git__free((void *)var->entry->value);
  			var->entry->value = tmp;
  			replaced = 1;
  		}
  
  		if (var->next == NULL)
  			break;
  
  		var = var->next;
  	}
  
  	/* If we've reached the end of the variables and we haven't found it yet, we need to append it */
  	if (!replaced) {
  		newvar = git__malloc(sizeof(cvar_t));
  		GITERR_CHECK_ALLOC(newvar);
  		memset(newvar, 0x0, sizeof(cvar_t));
  		newvar->entry = git__malloc(sizeof(git_config_entry));
  		GITERR_CHECK_ALLOC(newvar->entry);
  		memset(newvar->entry, 0x0, sizeof(git_config_entry));
  
  		newvar->entry->name = git__strdup(var->entry->name);
  		GITERR_CHECK_ALLOC(newvar->entry->name);
  
  		newvar->entry->value = git__strdup(value);
  		GITERR_CHECK_ALLOC(newvar->entry->value);
  
  		newvar->entry->level = var->entry->level;
  
  		var->next = newvar;
  	}
  
  	result = config_write(b, key, &preg, value);
  
  	git__free(key);
  	regfree(&preg);
  
  	return result;
  }
  
  static int config_delete(git_config_backend *cfg, const char *name)
  {
  	cvar_t *var;
  	diskfile_backend *b = (diskfile_backend *)cfg;
  	char *key;
  	int result;
  	khiter_t pos;
  
  	if ((result = normalize_name(name, &key)) < 0)
  		return result;
  
  	pos = git_strmap_lookup_index(b->values, key);
  	git__free(key);
  
  	if (!git_strmap_valid_index(b->values, pos)) {
  		giterr_set(GITERR_CONFIG, "Could not find key '%s' to delete", name);
  		return GIT_ENOTFOUND;
  	}
  
  	var = git_strmap_value_at(b->values, pos);
  
  	if (var->next != NULL) {
  		giterr_set(GITERR_CONFIG, "Cannot delete multivar with a single delete");
  		return -1;
  	}
  
  	git_strmap_delete_at(b->values, pos);
  
  	result = config_write(b, var->entry->name, NULL, NULL);
  
  	cvar_free(var);
  	return result;
  }
  
  int git_config_file__ondisk(git_config_backend **out, const char *path)
  {
  	diskfile_backend *backend;
  
  	backend = git__calloc(1, sizeof(diskfile_backend));
  	GITERR_CHECK_ALLOC(backend);
  
  	backend->parent.version = GIT_CONFIG_BACKEND_VERSION;
  
  	backend->file_path = git__strdup(path);
  	GITERR_CHECK_ALLOC(backend->file_path);
  
  	backend->parent.open = config_open;
  	backend->parent.get = config_get;
  	backend->parent.get_multivar = config_get_multivar;
  	backend->parent.set = config_set;
  	backend->parent.set_multivar = config_set_multivar;
  	backend->parent.del = config_delete;
  	backend->parent.foreach = file_foreach;
  	backend->parent.refresh = config_refresh;
  	backend->parent.free = backend_free;
  
  	*out = (git_config_backend *)backend;
  
  	return 0;
  }
  
  static int cfg_getchar_raw(diskfile_backend *cfg)
  {
  	int c;
  
  	c = *cfg->reader.read_ptr++;
  
  	/*
  	Win 32 line breaks: if we find a \r\n sequence,
  	return only the \n as a newline
  	*/
  	if (c == '\r' && *cfg->reader.read_ptr == '\n') {
  		cfg->reader.read_ptr++;
  		c = '\n';
  	}
  
  	if (c == '\n')
  		cfg->reader.line_number++;
  
  	if (c == 0) {
  		cfg->reader.eof = 1;
  		c = '\n';
  	}
  
  	return c;
  }
  
  #define SKIP_WHITESPACE (1 << 1)
  #define SKIP_COMMENTS (1 << 2)
  
  static int cfg_getchar(diskfile_backend *cfg_file, int flags)
  {
  	const int skip_whitespace = (flags & SKIP_WHITESPACE);
  	const int skip_comments = (flags & SKIP_COMMENTS);
  	int c;
  
  	assert(cfg_file->reader.read_ptr);
  
  	do c = cfg_getchar_raw(cfg_file);
  	while (skip_whitespace && git__isspace(c) &&
  	       !cfg_file->reader.eof);
  
  	if (skip_comments && (c == '#' || c == ';')) {
  		do c = cfg_getchar_raw(cfg_file);
  		while (c != '\n');
  	}
  
  	return c;
  }
  
  /*
   * Read the next char, but don't move the reading pointer.
   */
  static int cfg_peek(diskfile_backend *cfg, int flags)
  {
  	void *old_read_ptr;
  	int old_lineno, old_eof;
  	int ret;
  
  	assert(cfg->reader.read_ptr);
  
  	old_read_ptr = cfg->reader.read_ptr;
  	old_lineno = cfg->reader.line_number;
  	old_eof = cfg->reader.eof;
  
  	ret = cfg_getchar(cfg, flags);
  
  	cfg->reader.read_ptr = old_read_ptr;
  	cfg->reader.line_number = old_lineno;
  	cfg->reader.eof = old_eof;
  
  	return ret;
  }
  
  /*
   * Read and consume a line, returning it in newly-allocated memory.
   */
  static char *cfg_readline(diskfile_backend *cfg, bool skip_whitespace)
  {
  	char *line = NULL;
  	char *line_src, *line_end;
  	size_t line_len;
  
  	line_src = cfg->reader.read_ptr;
  
  	if (skip_whitespace) {
  		/* Skip empty empty lines */
  		while (git__isspace(*line_src))
  			++line_src;
  	}
  
  	line_end = strchr(line_src, '\n');
  
  	/* no newline at EOF */
  	if (line_end == NULL)
  		line_end = strchr(line_src, 0);
  
  	line_len = line_end - line_src;
  
  	line = git__malloc(line_len + 1);
  	if (line == NULL)
  		return NULL;
  
  	memcpy(line, line_src, line_len);
  
  	do line[line_len] = '\0';
  	while (line_len-- > 0 && git__isspace(line[line_len]));
  
  	if (*line_end == '\n')
  		line_end++;
  
  	if (*line_end == '\0')
  		cfg->reader.eof = 1;
  
  	cfg->reader.line_number++;
  	cfg->reader.read_ptr = line_end;
  
  	return line;
  }
  
  /*
   * Consume a line, without storing it anywhere
   */
  static void cfg_consume_line(diskfile_backend *cfg)
  {
  	char *line_start, *line_end;
  
  	line_start = cfg->reader.read_ptr;
  	line_end = strchr(line_start, '\n');
  	/* No newline at EOF */
  	if(line_end == NULL){
  		line_end = strchr(line_start, '\0');
  	}
  
  	if (*line_end == '\n')
  		line_end++;
  
  	if (*line_end == '\0')
  		cfg->reader.eof = 1;
  
  	cfg->reader.line_number++;
  	cfg->reader.read_ptr = line_end;
  }
  
  GIT_INLINE(int) config_keychar(int c)
  {
  	return isalnum(c) || c == '-';
  }
  
  static int parse_section_header_ext(diskfile_backend *cfg, const char *line, const char *base_name, char **section_name)
  {
  	int c, rpos;
  	char *first_quote, *last_quote;
  	git_buf buf = GIT_BUF_INIT;
  	int quote_marks;
  	/*
  	 * base_name is what came before the space. We should be at the
  	 * first quotation mark, except for now, line isn't being kept in
  	 * sync so we only really use it to calculate the length.
  	 */
  
  	first_quote = strchr(line, '"');
  	last_quote = strrchr(line, '"');
  
  	if (last_quote - first_quote == 0) {
  		set_parse_error(cfg, 0, "Missing closing quotation mark in section header");
  		return -1;
  	}
  
  	git_buf_grow(&buf, strlen(base_name) + last_quote - first_quote + 2);
  	git_buf_printf(&buf, "%s.", base_name);
  
  	rpos = 0;
  	quote_marks = 0;
  
  	line = first_quote;
  	c = line[rpos++];
  
  	/*
  	 * At the end of each iteration, whatever is stored in c will be
  	 * added to the string. In case of error, jump to out
  	 */
  	do {
  		if (quote_marks == 2) {
  			set_parse_error(cfg, rpos, "Unexpected text after closing quotes");
  			git_buf_free(&buf);
  			return -1;
  		}
  
  		switch (c) {
  		case '"':
  			++quote_marks;
  			continue;
  
  		case '\\':
  			c = line[rpos++];
  
  			switch (c) {
  			case '"':
  			case '\\':
  				break;
  
  			default:
  				set_parse_error(cfg, rpos, "Unsupported escape sequence");
  				git_buf_free(&buf);
  				return -1;
  			}
  
  		default:
  			break;
  		}
  
  		git_buf_putc(&buf, c);
  	} while ((c = line[rpos++]) != ']');
  
  	*section_name = git_buf_detach(&buf);
  	return 0;
  }
  
  static int parse_section_header(diskfile_backend *cfg, char **section_out)
  {
  	char *name, *name_end;
  	int name_length, c, pos;
  	int result;
  	char *line;
  
  	line = cfg_readline(cfg, true);
  	if (line == NULL)
  		return -1;
  
  	/* find the end of the variable's name */
  	name_end = strchr(line, ']');
  	if (name_end == NULL) {
  		git__free(line);
  		set_parse_error(cfg, 0, "Missing ']' in section header");
  		return -1;
  	}
  
  	name = (char *)git__malloc((size_t)(name_end - line) + 1);
  	GITERR_CHECK_ALLOC(name);
  
  	name_length = 0;
  	pos = 0;
  
  	/* Make sure we were given a section header */
  	c = line[pos++];
  	assert(c == '[');
  
  	c = line[pos++];
  
  	do {
  		if (git__isspace(c)){
  			name[name_length] = '\0';
  			result = parse_section_header_ext(cfg, line, name, section_out);
  			git__free(line);
  			git__free(name);
  			return result;
  		}
  
  		if (!config_keychar(c) && c != '.') {
  			set_parse_error(cfg, pos, "Unexpected character in header");
  			goto fail_parse;
  		}
  
  		name[name_length++] = (char) tolower(c);
  
  	} while ((c = line[pos++]) != ']');
  
  	if (line[pos - 1] != ']') {
  		set_parse_error(cfg, pos, "Unexpected end of file");
  		goto fail_parse;
  	}
  
  	git__free(line);
  
  	name[name_length] = 0;
  	*section_out = name;
  
  	return 0;
  
  fail_parse:
  	git__free(line);
  	git__free(name);
  	return -1;
  }
  
  static int skip_bom(diskfile_backend *cfg)
  {
  	git_bom_t bom;
  	int bom_offset = git_buf_text_detect_bom(&bom,
  		&cfg->reader.buffer, cfg->reader.read_ptr - cfg->reader.buffer.ptr);
  
  	if (bom == GIT_BOM_UTF8)
  		cfg->reader.read_ptr += bom_offset;
  
  	/* TODO: reference implementation is pretty stupid with BoM */
  
  	return 0;
  }
  
  /*
  	(* basic types *)
  	digit = "0".."9"
  	integer = digit { digit }
  	alphabet = "a".."z" + "A" .. "Z"
  
  	section_char = alphabet | "." | "-"
  	extension_char = (* any character except newline *)
  	any_char = (* any character *)
  	variable_char = "alphabet" | "-"
  
  
  	(* actual grammar *)
  	config = { section }
  
  	section = header { definition }
  
  	header = "[" section [subsection | subsection_ext] "]"
  
  	subsection = "." section
  	subsection_ext = "\"" extension "\""
  
  	section = section_char { section_char }
  	extension = extension_char { extension_char }
  
  	definition = variable_name ["=" variable_value] "\n"
  
  	variable_name = variable_char { variable_char }
  	variable_value = string | boolean | integer
  
  	string = quoted_string | plain_string
  	quoted_string = "\"" plain_string "\""
  	plain_string = { any_char }
  
  	boolean = boolean_true | boolean_false
  	boolean_true = "yes" | "1" | "true" | "on"
  	boolean_false = "no" | "0" | "false" | "off"
  */
  
  static int strip_comments(char *line, int in_quotes)
  {
  	int quote_count = in_quotes;
  	char *ptr;
  
  	for (ptr = line; *ptr; ++ptr) {
  		if (ptr[0] == '"' && ptr > line && ptr[-1] != '\\')
  			quote_count++;
  
  		if ((ptr[0] == ';' || ptr[0] == '#') && (quote_count % 2) == 0) {
  			ptr[0] = '\0';
  			break;
  		}
  	}
  
  	/* skip any space at the end */
  	if (ptr > line && git__isspace(ptr[-1])) {
  		ptr--;
  	}
  	ptr[0] = '\0';
  
  	return quote_count;
  }
  
  static int config_parse(diskfile_backend *cfg_file, unsigned int level)
  {
  	int c;
  	char *current_section = NULL;
  	char *var_name;
  	char *var_value;
  	cvar_t *var, *existing;
  	git_buf buf = GIT_BUF_INIT;
  	int result = 0;
  	khiter_t pos;
  
  	/* Initialize the reading position */
  	cfg_file->reader.read_ptr = cfg_file->reader.buffer.ptr;
  	cfg_file->reader.eof = 0;
  
  	/* If the file is empty, there's nothing for us to do */
  	if (*cfg_file->reader.read_ptr == '\0')
  		return 0;
  
  	skip_bom(cfg_file);
  
  	while (result == 0 && !cfg_file->reader.eof) {
  
  		c = cfg_peek(cfg_file, SKIP_WHITESPACE);
  
  		switch (c) {
  		case '\n': /* EOF when peeking, set EOF in the reader to exit the loop */
  			cfg_file->reader.eof = 1;
  			break;
  
  		case '[': /* section header, new section begins */
  			git__free(current_section);
  			current_section = NULL;
  			result = parse_section_header(cfg_file, &current_section);
  			break;
  
  		case ';':
  		case '#':
  			cfg_consume_line(cfg_file);
  			break;
  
  		default: /* assume variable declaration */
  			result = parse_variable(cfg_file, &var_name, &var_value);
  			if (result < 0)
  				break;
  
  			var = git__malloc(sizeof(cvar_t));
  			GITERR_CHECK_ALLOC(var);
  			memset(var, 0x0, sizeof(cvar_t));
  			var->entry = git__malloc(sizeof(git_config_entry));
  			GITERR_CHECK_ALLOC(var->entry);
  			memset(var->entry, 0x0, sizeof(git_config_entry));
  
  			git__strtolower(var_name);
  			git_buf_printf(&buf, "%s.%s", current_section, var_name);
  			git__free(var_name);
  
  			if (git_buf_oom(&buf))
  				return -1;
  
  			var->entry->name = git_buf_detach(&buf);
  			var->entry->value = var_value;
  			var->entry->level = level;
  
  			/* Add or append the new config option */
  			pos = git_strmap_lookup_index(cfg_file->values, var->entry->name);
  			if (!git_strmap_valid_index(cfg_file->values, pos)) {
  				git_strmap_insert(cfg_file->values, var->entry->name, var, result);
  				if (result < 0)
  					break;
  				result = 0;
  			} else {
  				existing = git_strmap_value_at(cfg_file->values, pos);
  				while (existing->next != NULL) {
  					existing = existing->next;
  				}
  				existing->next = var;
  			}
  
  			break;
  		}
  	}
  
  	git__free(current_section);
  	return result;
  }
  
  static int write_section(git_filebuf *file, const char *key)
  {
  	int result;
  	const char *dot;
  	git_buf buf = GIT_BUF_INIT;
  
  	/* All of this just for [section "subsection"] */
  	dot = strchr(key, '.');
  	git_buf_putc(&buf, '[');
  	if (dot == NULL) {
  		git_buf_puts(&buf, key);
  	} else {
  		char *escaped;
  		git_buf_put(&buf, key, dot - key);
  		escaped = escape_value(dot + 1);
  		GITERR_CHECK_ALLOC(escaped);
  		git_buf_printf(&buf, " \"%s\"", escaped);
  		git__free(escaped);
  	}
  	git_buf_puts(&buf, "]\n");
  
  	if (git_buf_oom(&buf))
  		return -1;
  
  	result = git_filebuf_write(file, git_buf_cstr(&buf), buf.size);
  	git_buf_free(&buf);
  
  	return result;
  }
  
  /*
   * This is pretty much the parsing, except we write out anything we don't have
   */
  static int config_write(diskfile_backend *cfg, const char *key, const regex_t *preg, const char* value)
  {
  	int result, c;
  	int section_matches = 0, last_section_matched = 0, preg_replaced = 0, write_trailer = 0;
  	const char *pre_end = NULL, *post_start = NULL, *data_start;
  	char *current_section = NULL, *section, *name, *ldot;
  	git_filebuf file = GIT_FILEBUF_INIT;
  
  	/* We need to read in our own config file */
  	result = git_futils_readbuffer(&cfg->reader.buffer, cfg->file_path);
  
  	/* Initialise the reading position */
  	if (result == GIT_ENOTFOUND) {
  		cfg->reader.read_ptr = NULL;
  		cfg->reader.eof = 1;
  		data_start = NULL;
  		git_buf_clear(&cfg->reader.buffer);
  	} else if (result == 0) {
  		cfg->reader.read_ptr = cfg->reader.buffer.ptr;
  		cfg->reader.eof = 0;
  		data_start = cfg->reader.read_ptr;
  	} else {
  		return -1; /* OS error when reading the file */
  	}
  
  	/* Lock the file */
  	if (git_filebuf_open(&file, cfg->file_path, 0) < 0)
  		return -1;
  
  	skip_bom(cfg);
  	ldot = strrchr(key, '.');
  	name = ldot + 1;
  	section = git__strndup(key, ldot - key);
  
  	while (!cfg->reader.eof) {
  		c = cfg_peek(cfg, SKIP_WHITESPACE);
  
  		if (c == '\0') { /* We've arrived at the end of the file */
  			break;
  
  		} else if (c == '[') { /* section header, new section begins */
  			/*
  			 * We set both positions to the current one in case we
  			 * need to add a variable to the end of a section. In that
  			 * case, we want both variables to point just before the
  			 * new section. If we actually want to replace it, the
  			 * default case will take care of updating them.
  			 */
  			pre_end = post_start = cfg->reader.read_ptr;
  
  			git__free(current_section);
  			current_section = NULL;
  			if (parse_section_header(cfg, &current_section) < 0)
  				goto rewrite_fail;
  
  			/* Keep track of when it stops matching */
  			last_section_matched = section_matches;
  			section_matches = !strcmp(current_section, section);
  		}
  
  		else if (c == ';' || c == '#') {
  			cfg_consume_line(cfg);
  		}
  
  		else {
  			/*
  			 * If the section doesn't match, but the last section did,
  			 * it means we need to add a variable (so skip the line
  			 * otherwise). If both the section and name match, we need
  			 * to overwrite the variable (so skip the line
  			 * otherwise). pre_end needs to be updated each time so we
  			 * don't loose that information, but we only need to
  			 * update post_start if we're going to use it in this
  			 * iteration.
  			 */
  			if (!section_matches) {
  				if (!last_section_matched) {
  					cfg_consume_line(cfg);
  					continue;
  				}
  			} else {
  				int has_matched = 0;
  				char *var_name, *var_value;
  
  				pre_end = cfg->reader.read_ptr;
  				if (parse_variable(cfg, &var_name, &var_value) < 0)
  					goto rewrite_fail;
  
  				/* First try to match the name of the variable */
  				if (strcasecmp(name, var_name) == 0)
  					has_matched = 1;
  
  				/* If the name matches, and we have a regex to match the
  				 * value, try to match it */
  				if (has_matched && preg != NULL)
  					has_matched = (regexec(preg, var_value, 0, NULL, 0) == 0);
  
  				git__free(var_name);
  				git__free(var_value);
  
  				/* if there is no match, keep going */
  				if (!has_matched)
  					continue;
  
  				post_start = cfg->reader.read_ptr;
  			}
  
  			/* We've found the variable we wanted to change, so
  			 * write anything up to it */
  			git_filebuf_write(&file, data_start, pre_end - data_start);
  			preg_replaced = 1;
  
  			/* Then replace the variable. If the value is NULL, it
  			 * means we want to delete it, so don't write anything. */
  			if (value != NULL) {
  				git_filebuf_printf(&file, "\t%s = %s\n", name, value);
  			}
  
  			/* multiline variable? we need to keep reading lines to match */
  			if (preg != NULL) {
  				data_start = post_start;
  				continue;
  			}
  
  			write_trailer = 1;
  			break; /* break from the loop */
  		}
  	}
  
  	/*
  	 * Being here can mean that
  	 *
  	 * 1) our section is the last one in the file and we're
  	 * adding a variable
  	 *
  	 * 2) we didn't find a section for us so we need to create it
  	 * ourselves.
  	 *
  	 * 3) we're setting a multivar with a regex, which means we
  	 * continue to search for matching values
  	 *
  	 * In the last case, if we've already replaced a value, we
  	 * want to write the rest of the file. Otherwise we need to write
  	 * out the whole file and then the new variable.
  	 */
  	if (write_trailer) {
  		/* Write out rest of the file */
  		git_filebuf_write(&file, post_start, cfg->reader.buffer.size - (post_start - data_start));
  	} else {
  		if (preg_replaced) {
  			git_filebuf_printf(&file, "\n%s", data_start);
  		} else {
  			git_filebuf_write(&file, cfg->reader.buffer.ptr, cfg->reader.buffer.size);
  
  			/* And now if we just need to add a variable */
  			if (!section_matches && write_section(&file, section) < 0)
  				goto rewrite_fail;
  
  			/* Sanity check: if we are here, and value is NULL, that means that somebody
  			 * touched the config file after our intial read. We should probably assert()
  			 * this, but instead we'll handle it gracefully with an error. */
  			if (value == NULL) {
  				giterr_set(GITERR_CONFIG,
  					"Race condition when writing a config file (a cvar has been removed)");
  				goto rewrite_fail;
  			}
  
  			/* If we are here, there is at least a section line */
  			if (cfg->reader.buffer.size > 0 && *(cfg->reader.buffer.ptr + cfg->reader.buffer.size - 1) != '\n')
  				git_filebuf_write(&file, "\n", 1);
  
  			git_filebuf_printf(&file, "\t%s = %s\n", name, value);
  		}
  	}
  
  	git__free(section);
  	git__free(current_section);
  
  	/* refresh stats - if this errors, then commit will error too */
  	(void)git_filebuf_stats(&cfg->file_mtime, &cfg->file_size, &file);
  
  	result = git_filebuf_commit(&file, GIT_CONFIG_FILE_MODE);
  	git_buf_free(&cfg->reader.buffer);
  
  	return result;
  
  rewrite_fail:
  	git__free(section);
  	git__free(current_section);
  
  	git_filebuf_cleanup(&file);
  	git_buf_free(&cfg->reader.buffer);
  	return -1;
  }
  
  static const char *escapes = "ntb\"\\";
  static const char *escaped = "\n\t\b\"\\";
  
  /* Escape the values to write them to the file */
  static char *escape_value(const char *ptr)
  {
  	git_buf buf = GIT_BUF_INIT;
  	size_t len;
  	const char *esc;
  
  	assert(ptr);
  
  	len = strlen(ptr);
  	git_buf_grow(&buf, len);
  
  	while (*ptr != '\0') {
  		if ((esc = strchr(escaped, *ptr)) != NULL) {
  			git_buf_putc(&buf, '\\');
  			git_buf_putc(&buf, escapes[esc - escaped]);
  		} else {
  			git_buf_putc(&buf, *ptr);
  		}
  		ptr++;
  	}
  
  	if (git_buf_oom(&buf)) {
  		git_buf_free(&buf);
  		return NULL;
  	}
  
  	return git_buf_detach(&buf);
  }
  
  /* '\"' -> '"' etc */
  static char *fixup_line(const char *ptr, int quote_count)
  {
  	char *str = git__malloc(strlen(ptr) + 1);
  	char *out = str, *esc;
  
  	if (str == NULL)
  		return NULL;
  
  	while (*ptr != '\0') {
  		if (*ptr == '"') {
  			quote_count++;
  		} else if (*ptr != '\\') {
  			*out++ = *ptr;
  		} else {
  			/* backslash, check the next char */
  			ptr++;
  			/* if we're at the end, it's a multiline, so keep the backslash */
  			if (*ptr == '\0') {
  				*out++ = '\\';
  				goto out;
  			}
  			if ((esc = strchr(escapes, *ptr)) != NULL) {
  				*out++ = escaped[esc - escapes];
  			} else {
  				git__free(str);
  				giterr_set(GITERR_CONFIG, "Invalid escape at %s", ptr);
  				return NULL;
  			}
  		}
  		ptr++;
  	}
  
  out:
  	*out = '\0';
  
  	return str;
  }
  
  static int is_multiline_var(const char *str)
  {
  	int count = 0;
  	const char *end = str + strlen(str);
  	while (end > str && end[-1] == '\\') {
  		count++;
  		end--;
  	}
  
  	/* An odd number means last backslash wasn't escaped, so it's multiline */
  	return (end > str) && (count & 1);
  }
  
  static int parse_multiline_variable(diskfile_backend *cfg, git_buf *value, int in_quotes)
  {
  	char *line = NULL, *proc_line = NULL;
  	int quote_count;
  
  	/* Check that the next line exists */
  	line = cfg_readline(cfg, false);
  	if (line == NULL)
  		return -1;
  
  	/* We've reached the end of the file, there is input missing */
  	if (line[0] == '\0') {
  		set_parse_error(cfg, 0, "Unexpected end of file while parsing multine var");
  		git__free(line);
  		return -1;
  	}
  
  	quote_count = strip_comments(line, !!in_quotes);
  
  	/* If it was just a comment, pretend it didn't exist */
  	if (line[0] == '\0') {
  		git__free(line);
  		return parse_multiline_variable(cfg, value, quote_count);
  		/* TODO: unbounded recursion. This **could** be exploitable */
  	}
  
  	/* Drop the continuation character '\': to closely follow the UNIX
  	 * standard, this character **has** to be last one in the buf, with
  	 * no whitespace after it */
  	assert(is_multiline_var(value->ptr));
  	git_buf_truncate(value, git_buf_len(value) - 1);
  
  	proc_line = fixup_line(line, in_quotes);
  	if (proc_line == NULL) {
  		git__free(line);
  		return -1;
  	}
  	/* add this line to the multiline var */
  	git_buf_puts(value, proc_line);
  	git__free(line);
  	git__free(proc_line);
  
  	/*
  	 * If we need to continue reading the next line, let's just
  	 * keep putting stuff in the buffer
  	 */
  	if (is_multiline_var(value->ptr))
  		return parse_multiline_variable(cfg, value, quote_count);
  
  	return 0;
  }
  
  static int parse_variable(diskfile_backend *cfg, char **var_name, char **var_value)
  {
  	const char *var_end = NULL;
  	const char *value_start = NULL;
  	char *line;
  	int quote_count;
  
  	line = cfg_readline(cfg, true);
  	if (line == NULL)
  		return -1;
  
  	quote_count = strip_comments(line, 0);
  
  	var_end = strchr(line, '=');
  
  	if (var_end == NULL)
  		var_end = strchr(line, '\0');
  	else
  		value_start = var_end + 1;
  
  	do var_end--;
  	while (var_end>line && git__isspace(*var_end));
  
  	*var_name = git__strndup(line, var_end - line + 1);
  	GITERR_CHECK_ALLOC(*var_name);
  
  	/* If there is no value, boolean true is assumed */
  	*var_value = NULL;
  
  	/*
  	 * Now, let's try to parse the value
  	 */
  	if (value_start != NULL) {
  		while (git__isspace(value_start[0]))
  			value_start++;
  
  		if (is_multiline_var(value_start)) {
  			git_buf multi_value = GIT_BUF_INIT;
  			char *proc_line = fixup_line(value_start, 0);
  			GITERR_CHECK_ALLOC(proc_line);
  			git_buf_puts(&multi_value, proc_line);
  			git__free(proc_line);
  			if (parse_multiline_variable(cfg, &multi_value, quote_count) < 0 || git_buf_oom(&multi_value)) {
  				git__free(*var_name);
  				git__free(line);
  				git_buf_free(&multi_value);
  				return -1;
  			}
  
  			*var_value = git_buf_detach(&multi_value);
  
  		}
  		else if (value_start[0] != '\0') {
  			*var_value = fixup_line(value_start, 0);
  			GITERR_CHECK_ALLOC(*var_value);
  		} else { /* equals sign but missing rhs */
  			*var_value = git__strdup("");
  			GITERR_CHECK_ALLOC(*var_value);
  		}
  	}
  
  	git__free(line);
  	return 0;
  }
  

Download