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-rw-r--r--hurd/hurdlookup.c79
1 files changed, 67 insertions, 12 deletions
diff --git a/hurd/hurdlookup.c b/hurd/hurdlookup.c
index 6ca84ce..6ba89b9 100644
--- a/hurd/hurdlookup.c
+++ b/hurd/hurdlookup.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 1992, 93, 94, 95, 96, 97 Free Software Foundation, Inc.
+/* Copyright (C) 1992, 93, 94, 95, 96, 97, 99 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
@@ -55,12 +55,10 @@ __hurd_file_name_lookup (error_t (*use_init_port)
error_t err;
enum retry_type doretry;
char retryname[1024]; /* XXX string_t LOSES! */
+ int startport;
error_t lookup_op (mach_port_t startdir)
{
- while (file_name[0] == '/')
- file_name++;
-
return lookup_error ((*lookup) (startdir, file_name, flags, mode,
&doretry, retryname, result));
}
@@ -68,13 +66,40 @@ __hurd_file_name_lookup (error_t (*use_init_port)
if (! lookup)
lookup = __dir_lookup;
- err = (*use_init_port) (file_name[0] == '/'
- ? INIT_PORT_CRDIR : INIT_PORT_CWDIR,
- &lookup_op);
+ startport = (file_name[0] == '/') ? INIT_PORT_CRDIR : INIT_PORT_CWDIR;
+ while (file_name[0] == '/')
+ file_name++;
+
+#if 0 /* ?? XXX Linux 2.2.1 does this. */
+ if ((flags & (O_CREAT|O_EXCL)) == (O_CREAT|O_EXCL))
+ flags |= O_NOFOLLOW;
+#endif
+ if (flags & O_NOFOLLOW) /* See comments below about O_NOFOLLOW. */
+ flags |= O_NOTRANS;
+
+ if (flags & O_DIRECTORY)
+ {
+ /* The caller wants to require that the file we look up is a directory.
+ We can do this without an extra RPC by appending a trailing slash
+ to the file name we look up. */
+ size_t len = strlen (file_name);
+ if (len == 0)
+ file_name = "/";
+ else if (file_name[len - 1] != '/')
+ {
+ char *n = alloca (len + 2);
+ memcpy (n, file_name, len);
+ n[len] = '/';
+ n[len + 1] = '\0';
+ file_name = n;
+ }
+ }
+
+ err = (*use_init_port) (startport, &lookup_op);
if (! err)
- err = __hurd_file_name_lookup_retry (use_init_port, get_dtable_port, lookup,
- doretry, retryname, flags, mode,
- result);
+ err = __hurd_file_name_lookup_retry (use_init_port, get_dtable_port,
+ lookup, doretry, retryname,
+ flags, mode, result);
return err;
}
@@ -85,7 +110,8 @@ __hurd_file_name_lookup_retry (error_t (*use_init_port)
(int which, error_t (*operate) (file_t)),
file_t (*get_dtable_port) (int fd),
error_t (*lookup)
- (file_t dir, char *name, int flags, mode_t mode,
+ (file_t dir, char *name,
+ int flags, mode_t mode,
retry_type *do_retry, string_t retry_name,
mach_port_t *result),
enum retry_type doretry,
@@ -152,9 +178,38 @@ __hurd_file_name_lookup_retry (error_t (*use_init_port)
translator a chance to make a new port for us. */
doretry == FS_RETRY_NORMAL)
{
+ if (flags & O_NOFOLLOW)
+ {
+ /* In Linux, O_NOFOLLOW means to reject symlinks. If we
+ did an O_NOLINK lookup above and io_stat here to check
+ for S_IFLNK, a translator like firmlink could easily
+ spoof this check by not showing S_IFLNK, but in fact
+ redirecting the lookup to some other name
+ (i.e. opening the very same holes a symlink would).
+
+ Instead we do an O_NOTRANS lookup above, and stat the
+ underlying node: if it has a translator set, and its
+ owner is not root (st_uid 0) then we reject it.
+ Since the motivation for this feature is security, and
+ that security presumes we trust the containing
+ directory, this check approximates the security of
+ refusing symlinks while accepting mount points.
+ Note that we actually permit something Linux doesn't:
+ we follow root-owned symlinks; if that is deemed
+ undesireable, we can add a final check for that
+ one exception to our general translator-based rule. */
+ struct stat st;
+ err = __io_stat (*result, &st);
+ if (!err
+ && st.st_uid != 0
+ && (st.st_mode & (S_IPTRANS|S_IATRANS)))
+ err = ENOENT;
+ }
+
/* We got a successful translation. Now apply any open-time
action flags we were passed. */
- if (flags & O_TRUNC)
+
+ if (!err && (flags & O_TRUNC)) /* Asked to truncate the file. */
err = __file_set_size (*result, 0);
if (err)