kc3-lang/pkgconf/libpkgconf/tuple.c

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• Hash : 628b2b2b
  Author :
  Date : 2023-01-20T22:07:03
  

  tuple: test for, and stop string processing, on truncation
  
  otherwise a buffer overflow occurs.
  this has been a bug in pkgconf since the beginning, it seems.
  instead of disclosing the bug correctly, a "hotshot" developer
  decided to blog about it instead.  sigh.
  
  https://nullprogram.com/blog/2023/01/18/
  

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• libpkgconf/tuple.c

• /*
   * tuple.c
   * management of key->value tuples
   *
   * Copyright (c) 2011, 2012 pkgconf authors (see AUTHORS).
   *
   * Permission to use, copy, modify, and/or distribute this software for any
   * purpose with or without fee is hereby granted, provided that the above
   * copyright notice and this permission notice appear in all copies.
   *
   * This software is provided 'as is' and without any warranty, express or
   * implied.  In no event shall the authors be liable for any damages arising
   * from the use of this software.
   */
  
  #include <libpkgconf/stdinc.h>
  #include <libpkgconf/libpkgconf.h>
  
  /*
   * !doc
   *
   * libpkgconf `tuple` module
   * =========================
   *
   * The `tuple` module provides key-value mappings backed by a linked list.  The key-value
   * mapping is mainly used for variable substitution when parsing .pc files.
   *
   * There are two sets of mappings: a ``pkgconf_pkg_t`` specific mapping, and a `global` mapping.
   * The `tuple` module provides convenience wrappers for managing the `global` mapping, which is
   * attached to a given client object.
   */
  
  /*
   * !doc
   *
   * .. c:function:: void pkgconf_tuple_add_global(pkgconf_client_t *client, const char *key, const char *value)
   *
   *    Defines a global variable, replacing the previous declaration if one was set.
   *
   *    :param pkgconf_client_t* client: The pkgconf client object to modify.
   *    :param char* key: The key for the mapping (variable name).
   *    :param char* value: The value for the mapped entry.
   *    :return: nothing
   */
  void
  pkgconf_tuple_add_global(pkgconf_client_t *client, const char *key, const char *value)
  {
  	pkgconf_tuple_add(client, &client->global_vars, key, value, false, 0);
  }
  
  static pkgconf_tuple_t *
  lookup_global_tuple(const pkgconf_client_t *client, const char *key)
  {
  	pkgconf_node_t *node;
  
  	PKGCONF_FOREACH_LIST_ENTRY(client->global_vars.head, node)
  	{
  		pkgconf_tuple_t *tuple = node->data;
  
  		if (!strcmp(tuple->key, key))
  			return tuple;
  	}
  
  	return NULL;
  }
  
  /*
   * !doc
   *
   * .. c:function:: void pkgconf_tuple_find_global(const pkgconf_client_t *client, const char *key)
   *
   *    Looks up a global variable.
   *
   *    :param pkgconf_client_t* client: The pkgconf client object to access.
   *    :param char* key: The key or variable name to look up.
   *    :return: the contents of the variable or ``NULL``
   *    :rtype: char *
   */
  char *
  pkgconf_tuple_find_global(const pkgconf_client_t *client, const char *key)
  {
  	pkgconf_tuple_t *tuple;
  
  	tuple = lookup_global_tuple(client, key);
  	if (tuple == NULL)
  		return NULL;
  
  	return tuple->value;
  }
  
  /*
   * !doc
   *
   * .. c:function:: void pkgconf_tuple_free_global(pkgconf_client_t *client)
   *
   *    Delete all global variables associated with a pkgconf client object.
   *
   *    :param pkgconf_client_t* client: The pkgconf client object to modify.
   *    :return: nothing
   */
  void
  pkgconf_tuple_free_global(pkgconf_client_t *client)
  {
  	pkgconf_tuple_free(&client->global_vars);
  }
  
  /*
   * !doc
   *
   * .. c:function:: void pkgconf_tuple_define_global(pkgconf_client_t *client, const char *kv)
   *
   *    Parse and define a global variable.
   *
   *    :param pkgconf_client_t* client: The pkgconf client object to modify.
   *    :param char* kv: The variable in the form of ``key=value``.
   *    :return: nothing
   */
  void
  pkgconf_tuple_define_global(pkgconf_client_t *client, const char *kv)
  {
  	char *workbuf = strdup(kv);
  	char *value;
  	pkgconf_tuple_t *tuple;
  
  	value = strchr(workbuf, '=');
  	if (value == NULL)
  		goto out;
  
  	*value++ = '\0';
  
  	tuple = pkgconf_tuple_add(client, &client->global_vars, workbuf, value, false, 0);
  	if (tuple != NULL)
  		tuple->flags = PKGCONF_PKG_TUPLEF_OVERRIDE;
  
  out:
  	free(workbuf);
  }
  
  static void
  pkgconf_tuple_find_delete(pkgconf_list_t *list, const char *key)
  {
  	pkgconf_node_t *node, *next;
  
  	PKGCONF_FOREACH_LIST_ENTRY_SAFE(list->head, next, node)
  	{
  		pkgconf_tuple_t *tuple = node->data;
  
  		if (!strcmp(tuple->key, key))
  		{
  			pkgconf_tuple_free_entry(tuple, list);
  			return;
  		}
  	}
  }
  
  static char *
  dequote(const char *value)
  {
  	char *buf = calloc((strlen(value) + 1) * 2, 1);
  	char *bptr = buf;
  	const char *i;
  	char quote = 0;
  
  	if (*value == '\'' || *value == '"')
  		quote = *value;
  
  	for (i = value; *i != '\0'; i++)
  	{
  		if (*i == '\\' && quote && *(i + 1) == quote)
  		{
  			i++;
  			*bptr++ = *i;
  		}
  		else if (*i != quote)
  			*bptr++ = *i;
  	}
  
  	return buf;
  }
  
  static const char *
  find_sysroot(const pkgconf_client_t *client, pkgconf_list_t *vars)
  {
  	const char *sysroot_dir;
  
  	sysroot_dir = pkgconf_tuple_find(client, vars, "pc_sysrootdir");
  	if (sysroot_dir == NULL)
  		sysroot_dir = client->sysroot_dir;
  
  	return sysroot_dir;
  }
  
  static bool
  should_rewrite_sysroot(const pkgconf_client_t *client, pkgconf_list_t *vars, const char *buf, unsigned int flags)
  {
  	const char *sysroot_dir;
  
  	if (flags & PKGCONF_PKG_PROPF_UNINSTALLED && !(client->flags & PKGCONF_PKG_PKGF_FDO_SYSROOT_RULES))
  		return false;
  
  	sysroot_dir = find_sysroot(client, vars);
  	if (sysroot_dir == NULL)
  		return false;
  
  	if (*buf != '/')
  		return false;
  
  	if (!strcmp(sysroot_dir, "/"))
  		return false;
  
  	if (strlen(buf) <= strlen(sysroot_dir))
  		return false;
  
  	if (strstr(buf + strlen(sysroot_dir), sysroot_dir) == NULL)
  		return false;
  
  	return true;
  }
  
  /*
   * !doc
   *
   * .. c:function:: pkgconf_tuple_t *pkgconf_tuple_add(const pkgconf_client_t *client, pkgconf_list_t *list, const char *key, const char *value, bool parse)
   *
   *    Optionally parse and then define a variable.
   *
   *    :param pkgconf_client_t* client: The pkgconf client object to access.
   *    :param pkgconf_list_t* list: The variable list to add the new variable to.
   *    :param char* key: The name of the variable being added.
   *    :param char* value: The value of the variable being added.
   *    :param bool parse: Whether or not to parse the value for variable substitution.
   *    :return: a variable object
   *    :rtype: pkgconf_tuple_t *
   */
  pkgconf_tuple_t *
  pkgconf_tuple_add(const pkgconf_client_t *client, pkgconf_list_t *list, const char *key, const char *value, bool parse, unsigned int flags)
  {
  	char *dequote_value;
  	pkgconf_tuple_t *tuple = calloc(sizeof(pkgconf_tuple_t), 1);
  
  	pkgconf_tuple_find_delete(list, key);
  
  	dequote_value = dequote(value);
  
  	tuple->key = strdup(key);
  	if (parse)
  		tuple->value = pkgconf_tuple_parse(client, list, dequote_value, flags);
  	else
  		tuple->value = strdup(dequote_value);
  
  	PKGCONF_TRACE(client, "adding tuple to @%p: %s => %s (parsed? %d)", list, key, tuple->value, parse);
  
  	pkgconf_node_insert(&tuple->iter, tuple, list);
  
  	free(dequote_value);
  
  	return tuple;
  }
  
  /*
   * !doc
   *
   * .. c:function:: char *pkgconf_tuple_find(const pkgconf_client_t *client, pkgconf_list_t *list, const char *key)
   *
   *    Look up a variable in a variable list.
   *
   *    :param pkgconf_client_t* client: The pkgconf client object to access.
   *    :param pkgconf_list_t* list: The variable list to search.
   *    :param char* key: The variable name to search for.
   *    :return: the value of the variable or ``NULL``
   *    :rtype: char *
   */
  char *
  pkgconf_tuple_find(const pkgconf_client_t *client, pkgconf_list_t *list, const char *key)
  {
  	pkgconf_node_t *node;
  	pkgconf_tuple_t *global_tuple;
  
  	global_tuple = lookup_global_tuple(client, key);
  	if (global_tuple != NULL && global_tuple->flags & PKGCONF_PKG_TUPLEF_OVERRIDE)
  		return global_tuple->value;
  
  	PKGCONF_FOREACH_LIST_ENTRY(list->head, node)
  	{
  		pkgconf_tuple_t *tuple = node->data;
  
  		if (!strcmp(tuple->key, key))
  			return tuple->value;
  	}
  
  	if (global_tuple != NULL)
  		return global_tuple->value;
  
  	return NULL;
  }
  
  /*
   * !doc
   *
   * .. c:function:: char *pkgconf_tuple_parse(const pkgconf_client_t *client, pkgconf_list_t *vars, const char *value, unsigned int flags)
   *
   *    Parse an expression for variable substitution.
   *
   *    :param pkgconf_client_t* client: The pkgconf client object to access.
   *    :param pkgconf_list_t* list: The variable list to search for variables (along side the global variable list).
   *    :param char* value: The ``key=value`` string to parse.
   *    :param uint flags: Any flags to consider while parsing.
   *    :return: the variable data with any variables substituted
   *    :rtype: char *
   */
  char *
  pkgconf_tuple_parse(const pkgconf_client_t *client, pkgconf_list_t *vars, const char *value, unsigned int flags)
  {
  	char buf[PKGCONF_BUFSIZE];
  	const char *ptr;
  	char *bptr = buf;
  
  	if (!(client->flags & PKGCONF_PKG_PKGF_FDO_SYSROOT_RULES) &&
  		(!(flags & PKGCONF_PKG_PROPF_UNINSTALLED) || (client->flags & PKGCONF_PKG_PKGF_PKGCONF1_SYSROOT_RULES)))
  	{
  		if (*value == '/' && client->sysroot_dir != NULL && strncmp(value, client->sysroot_dir, strlen(client->sysroot_dir)))
  			bptr += pkgconf_strlcpy(buf, client->sysroot_dir, sizeof buf);
  	}
  
  	for (ptr = value; *ptr != '\0' && bptr - buf < PKGCONF_BUFSIZE; ptr++)
  	{
  		if (*ptr != '$' || (*ptr == '$' && *(ptr + 1) != '{'))
  			*bptr++ = *ptr;
  		else if (*(ptr + 1) == '{')
  		{
  			char varname[PKGCONF_ITEM_SIZE];
  			char *vend = varname + PKGCONF_ITEM_SIZE - 1;
  			char *vptr = varname;
  			const char *pptr;
  			char *kv, *parsekv;
  
  			*vptr = '\0';
  
  			for (pptr = ptr + 2; *pptr != '\0'; pptr++)
  			{
  				if (*pptr != '}')
  				{
  					if (vptr < vend)
  						*vptr++ = *pptr;
  					else
  					{
  						*vptr = '\0';
  						break;
  					}
  				}
  				else
  				{
  					*vptr = '\0';
  					break;
  				}
  			}
  
  			PKGCONF_TRACE(client, "lookup tuple %s", varname);
  
  			size_t remain = PKGCONF_BUFSIZE - (bptr - buf);
  			ptr += (pptr - ptr);
  			kv = pkgconf_tuple_find_global(client, varname);
  			if (kv != NULL)
  			{
  				size_t nlen = pkgconf_strlcpy(bptr, kv, remain);
  				if (nlen > remain)
  				{
  					pkgconf_warn(client, "warning: truncating very long variable to 64KB\n");
  
  					bptr = buf + (PKGCONF_BUFSIZE - 1);
  					break;
  				}
  
  				bptr += nlen;
  			}
  			else
  			{
  				kv = pkgconf_tuple_find(client, vars, varname);
  
  				if (kv != NULL)
  				{
  					size_t nlen;
  
  					parsekv = pkgconf_tuple_parse(client, vars, kv, flags);
  					nlen = pkgconf_strlcpy(bptr, parsekv, remain);
  					free(parsekv);
  
  					if (nlen > remain)
  					{
  						pkgconf_warn(client, "warning: truncating very long variable to 64KB\n");
  
  						bptr = buf + (PKGCONF_BUFSIZE - 1);
  						break;
  					}
  
  					bptr += nlen;
  				}
  			}
  		}
  	}
  
  	*bptr = '\0';
  
  	/*
  	 * Sigh.  Somebody actually attempted to use freedesktop.org pkg-config's broken sysroot support,
  	 * which was written by somebody who did not understand how sysroots are supposed to work.  This
  	 * results in an incorrect path being built as the sysroot will be prepended twice, once explicitly,
  	 * and once by variable expansion (the pkgconf approach).  We could simply make ${pc_sysrootdir} blank,
  	 * but sometimes it is necessary to know the explicit sysroot path for other reasons, so we can't really
  	 * do that.
  	 *
  	 * As a result, we check to see if ${pc_sysrootdir} is prepended as a duplicate, and if so, remove the
  	 * prepend.  This allows us to handle both our approach and the broken freedesktop.org implementation's
  	 * approach.  Because a path can be shorter than ${pc_sysrootdir}, we do some checks first to ensure it's
  	 * safe to skip ahead in the string to scan for our sysroot dir.
  	 *
  	 * Finally, we call pkgconf_path_relocate() to clean the path of spurious elements.
  	 *
  	 * New in 1.9: Only attempt to rewrite the sysroot if we are not processing an uninstalled package.
  	 */
  	if (should_rewrite_sysroot(client, vars, buf, flags))
  	{
  		char cleanpath[PKGCONF_ITEM_SIZE];
  		const char *sysroot_dir = find_sysroot(client, vars);
  
  		pkgconf_strlcpy(cleanpath, buf + strlen(sysroot_dir), sizeof cleanpath);
  		pkgconf_path_relocate(cleanpath, sizeof cleanpath);
  
  		return strdup(cleanpath);
  	}
  
  	return strdup(buf);
  }
  
  /*
   * !doc
   *
   * .. c:function:: void pkgconf_tuple_free_entry(pkgconf_tuple_t *tuple, pkgconf_list_t *list)
   *
   *    Deletes a variable object, removing it from any variable lists and releasing any memory associated
   *    with it.
   *
   *    :param pkgconf_tuple_t* tuple: The variable object to release.
   *    :param pkgconf_list_t* list: The variable list the variable object is attached to.
   *    :return: nothing
   */
  void
  pkgconf_tuple_free_entry(pkgconf_tuple_t *tuple, pkgconf_list_t *list)
  {
  	pkgconf_node_delete(&tuple->iter, list);
  
  	free(tuple->key);
  	free(tuple->value);
  	free(tuple);
  }
  
  /*
   * !doc
   *
   * .. c:function:: void pkgconf_tuple_free(pkgconf_list_t *list)
   *
   *    Deletes a variable list and any variables attached to it.
   *
   *    :param pkgconf_list_t* list: The variable list to delete.
   *    :return: nothing
   */
  void
  pkgconf_tuple_free(pkgconf_list_t *list)
  {
  	pkgconf_node_t *node, *next;
  
  	PKGCONF_FOREACH_LIST_ENTRY_SAFE(list->head, next, node)
  		pkgconf_tuple_free_entry(node->data, list);
  
  	pkgconf_list_zero(list);
  }
  

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