If two config writes collide, file corruption could result. Use a mkstemp() file...

Reported by: paravoid
Patch by: tilghman
Closes issue #10781

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@89191 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/main/config.c b/main/config.c
index 4055b34e2becdf59314b10e57a508d18c124a76e..bb9037cdf4f2cca77bc939ee4006117e4f9c03b6 100644 (file)
--- a/main/config.c
+++ b/main/config.c
@@ -990,27 +990,27 @@ static struct ast_config *config_text_file_load(const char *database, const char
 
 int config_text_file_save(const char *configfile, const struct ast_config *cfg, const char *generator)
 {
-       FILE *f;
-       char fn[256];
+       FILE *f = NULL;
+       int fd = -1;
+       char fn[256], fntmp[256];
        char date[256]="";
        time_t t;
        struct ast_variable *var;
        struct ast_category *cat;
        struct ast_comment *cmt;
+       struct stat s;
        int blanklines = 0;
 
        if (configfile[0] == '/') {
+               snprintf(fntmp, sizeof(fntmp), "%s.XXXXXX", configfile);
                ast_copy_string(fn, configfile, sizeof(fn));
        } else {
+               snprintf(fntmp, sizeof(fntmp), "%s/%s.XXXXXX", ast_config_AST_CONFIG_DIR, configfile);
                snprintf(fn, sizeof(fn), "%s/%s", ast_config_AST_CONFIG_DIR, configfile);
        }
        time(&t);
        ast_copy_string(date, ctime(&t), sizeof(date));
-#ifdef __CYGWIN__      
-       if ((f = fopen(fn, "w+"))) {
-#else
-       if ((f = fopen(fn, "w"))) {
-#endif     
+       if ((fd = mkstemp(fntmp)) > 0 && (f = fdopen(fd, "w")) != NULL) {
                if (option_verbose > 1)
                        ast_verbose(VERBOSE_PREFIX_2 "Saving '%s': ", fn);
                fprintf(f, ";!\n");
@@ -1093,12 +1093,25 @@ int config_text_file_save(const char *configfile, const struct ast_config *cfg,
                        ast_verbose("Saved\n");
        } else {
                if (option_debug)
-                       ast_log(LOG_DEBUG, "Unable to open for writing: %s\n", fn);
+                       ast_log(LOG_DEBUG, "Unable to open for writing: %s (%s)\n", fn, strerror(errno));
                if (option_verbose > 1)
-                       ast_verbose(VERBOSE_PREFIX_2 "Unable to write (%s)", strerror(errno));
+                       ast_verbose(VERBOSE_PREFIX_2 "Unable to write %s (%s)", fn, strerror(errno));
+               if (fd > -1)
+                       close(fd);
                return -1;
        }
+       stat(fn, &s);
+       fchmod(fd, s.st_mode);
        fclose(f);
+       if (unlink(fn) || link(fntmp, fn)) {
+               if (option_debug)
+                       ast_log(LOG_DEBUG, "Unable to open for writing: %s (%s)\n", fn, strerror(errno));
+               if (option_verbose > 1)
+                       ast_verbose(VERBOSE_PREFIX_2 "Unable to write %s (%s)", fn, strerror(errno));
+               unlink(fntmp);
+               return -1;
+       }
+       unlink(fntmp);
        return 0;
 }