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Refactor new getcwd code

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Make sure that the "path_length *= 2" statement can't overflow.

Move the "malloc and getcwd" loop into its own function.
This commit is contained in:
Nick Mathewson 2012-05-10 14:20:15 -04:00
parent d916fc38b6
commit 57ed459b0d
1 changed files with 43 additions and 22 deletions
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65
src/common/compat.c
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@ -1630,6 +1630,38 @@ get_parent_directory(char *fname)
return -1;
}
#ifndef _WIN32
/** Return a newly allocated string containing the output of getcwd(). Return
* NULL on failure. (We can't just use getcwd() into a PATH_MAX buffer, since
* Hurd hasn't got a PATH_MAX.)
*/
static char *
alloc_getcwd(void)
{
int saved_errno = errno;
/* We use this as a starting path length. Not too large seems sane. */
#define START_PATH_LENGTH 128
/* Nobody has a maxpath longer than this, as far as I know. And if they
* do, they shouldn't. */
#define MAX_SANE_PATH_LENGTH 4096
size_t path_length = START_PATH_LENGTH;
char *path = tor_malloc(path_length);
errno = 0;
while (getcwd(path, path_length) == NULL) {
if (errno == ERANGE && path_length < MAX_SANE_PATH_LENGTH) {
path_length*=2;
path = tor_realloc(path, path_length);
} else {
tor_free(path);
return NULL;
}
}
errno = saved_errno;
return path;
}
#endif
/** Expand possibly relative path <b>fname</b> to an absolute path.
* Return a newly allocated string, possibly equal to <b>fname</b>. */
char *
@ -1645,36 +1677,25 @@ make_path_absolute(char *fname)
return absfname;
#else
/* We use this as a starting path length. Not too large seems sane. */
#define START_PATH_LENGTH 100
size_t path_length = START_PATH_LENGTH;
char *path = tor_malloc(path_length);
char *absfname = NULL;
char *absfname = NULL, *path = NULL;
tor_assert(fname);
if (fname[0] == '/') {
absfname = tor_strdup(fname);
} else {
int save_errno = errno;
errno = 0;
while (getcwd(path, path_length) == NULL) {
if (errno == ERANGE) {
path_length*=2;
path = tor_realloc(path, path_length);
} else {
/* If getcwd failed with an error other than ERANGE, the best we can
* do here is keep using the relative path. (Perhaps / isn't readable
* by this UID/GID.) */
absfname = tor_strdup(fname);
break;
}
path = alloc_getcwd();
if (path) {
tor_asprintf(&absfname, "%s/%s", path, fname);
tor_free(path);
} else {
/* If getcwd failed, the best we can do here is keep using the
* relative path. (Perhaps / isn't readable by this UID/GID.) */
log_warn(LD_GENERAL, "Unable to find current working directory: %s",
strerror(errno));
absfname = tor_strdup(fname);
}
errno = save_errno;
tor_asprintf(&absfname, "%s/%s", path, fname);
tor_free(path);
}
return absfname;
#endif
}