[hackers] [sbase] Audit readlink(1) || FRIGN

From: <git_AT_suckless.org>
Date: Mon, 23 Mar 2015 18:35:49 +0100 (CET)

commit 33a57bd620ae62f2df04d4dd1bc2b2d674bdf84e
Author: FRIGN <dev_AT_frign.de>
Date: Fri Mar 20 22:09:47 2015 +0100

    Audit readlink(1)
    
    1) Properly document e, f and m-flags in the manpage.
    2) Clear up the code for the m-flag-handling. Add idiomatic
       '/'-path-traversal as already seen in mkdir(1).
    3) Unwrap the SWAP_BUF()-macro.
    4) BUGFIX: Actually handle the f-flag properly. Only resolve
       the dirname and append the basename later.
    5) Use fputs() instead of printf("%s", ...).

diff --git a/README b/README
index f6c7fe5..1d9186d 100644
--- a/README
+++ b/README
_AT_@ -55,7 +55,7 @@ The following tools are implemented ('*' == finished, '#' == UTF-8 support,
 =*| printenv non-posix none
 #*| printf yes none
 =*| pwd yes none
-= readlink non-posix none
+=*| readlink non-posix none
 =*| renice yes none
 =*| rm yes none (-i)
 =*| rmdir yes none
diff --git a/readlink.1 b/readlink.1
index 8b4a9d2..7d28969 100644
--- a/readlink.1
+++ b/readlink.1
_AT_@ -1,4 +1,4 @@
-.Dd January 31, 2015
+.Dd March 20, 2015
 .Dt READLINK 1
 .Os sbase
 .Sh NAME
_AT_@ -6,30 +6,27 @@
 .Nd print symbolic link target or canonical file name
 .Sh SYNOPSIS
 .Nm
-.Op Fl fn
-.Ar name
+.Op Fl e | Fl f | Fl m
+.Op Fl n
+.Ar path
 .Sh DESCRIPTION
-If
-.Ar name
-is a symbolic link,
 .Nm
-writes its target to stdout.
-If
-.Fl f
-is not set and
-.Ar name
-is not a symbolic link,
+writes the target of
+.Ar path ,
+if it is a symbolic link, to stdout.
+If not,
 .Nm
-exits with a nonzero exit code without printing anything.
+exits with a non-zero return value.
 .Sh OPTIONS
 .Bl -tag -width Ds
-.It Fl f
+.It Fl e | Fl f | Fl m
 Canonicalize
 .Ar name ,
-which does not need to be a symlink,
-by recursively following every symlink in its components.
+which needn't be a symlink,
+by recursively following every symlink in its path components.
+All | All but the last | No path components must exist.
 .It Fl n
-Do not output the trailing newline.
+Do not print the terminating newline.
 .El
 .Sh SEE ALSO
 .Xr readlink 2 ,
diff --git a/readlink.c b/readlink.c
index 9c6c789..e80767f 100644
--- a/readlink.c
+++ b/readlink.c
_AT_@ -1,6 +1,7 @@
 /* See LICENSE file for copyright and license details. */
 #include <sys/stat.h>
 
+#include <libgen.h>
 #include <unistd.h>
 #include <stdio.h>
 #include <stdlib.h>
_AT_@ -11,18 +12,17 @@
 static void
 usage(void)
 {
- eprintf("usage: %s [-efmn] name\n", argv0);
+ eprintf("usage: %s [-e | -f | -m] [-n] path\n", argv0);
 }
 
 int
 main(int argc, char *argv[])
 {
- char buf1[PATH_MAX], buf2[PATH_MAX], arg[PATH_MAX];
- int nflag = 0;
- int mefflag = 0;
- ssize_t n;
         struct stat st;
- char *p = arg, *lp = NULL, *b = buf1;
+ ssize_t n;
+ int nflag = 0, mefflag = 0;
+ char buf1[PATH_MAX], buf2[PATH_MAX], arg[PATH_MAX],
+ *p, *slash, *prefix, *lp, *b = buf1;
 
         ARGBEGIN {
         case 'm':
_AT_@ -40,57 +40,54 @@ main(int argc, char *argv[])
         if (argc != 1)
                 usage();
 
- if (strlen(argv[0]) > PATH_MAX - 1)
+ if (strlen(argv[0]) >= PATH_MAX)
                 eprintf("path too long\n");
 
-#define SWAP_BUF() (b = (b == buf1 ? buf2 : buf1));
         switch (mefflag) {
         case 'm':
- if (argv[0][0] == '/') { /* case when path is on '/' */
- arg[0] = '/';
- arg[1] = '\0';
- p++;
- } else if (!strchr(argv[0], '/')) { /* relative path */
- arg[0] = '.';
- arg[1] = '/';
- arg[2] = '\0';
- } else
- arg[0] = '\0';
+ slash = strchr(argv[0], '/');
+ prefix = (slash == argv[0]) ? "/" : (!slash) ? "./" : "";
+
+ estrlcpy(arg, prefix, sizeof(arg));
                 estrlcat(arg, argv[0], sizeof(arg));
- while ((p = strchr(p, '/'))) {
+
+ for (lp = "", p = arg + (argv[0][0] == '/'); *p; p++) {
+ if (*p != '/')
+ continue;
                         *p = '\0';
                         if (!realpath(arg, b)) {
                                 *p = '/';
                                 goto mdone;
                         }
- SWAP_BUF();
+ b = (b == buf1) ? buf2 : buf1;
                         lp = p;
- *p++ = '/';
+ *p = '/';
                 }
                 if (!realpath(arg, b)) {
 mdone:
- SWAP_BUF();
- if (lp) {
- /* drop the extra '/' on root */
- lp += (argv[0][0] == '/' &&
- lp - arg == 1);
- estrlcat(b, lp, sizeof(arg));
- }
+ b = (b == buf1) ? buf2 : buf1;
+ estrlcat(b, lp, sizeof(arg));
                 }
                 break;
         case 'e':
                 if (stat(argv[0], &st) < 0)
                         eprintf("stat %s:", argv[0]);
- case 'f': /* fallthrough */
                 if (!realpath(argv[0], b))
                         eprintf("realpath %s:", argv[0]);
                 break;
+ case 'f':
+ p = dirname(estrdup(argv[0]));
+ if (!realpath(p, b))
+ eprintf("realpath %s:", p);
+ estrlcat(b, "/", sizeof(arg));
+ estrlcat(b, basename(estrdup(argv[0])), sizeof(arg));
+ break;
         default:
                 if ((n = readlink(argv[0], b, PATH_MAX - 1)) < 0)
                         eprintf("readlink %s:", argv[0]);
                 b[n] = '\0';
         }
- printf("%s", b);
+ fputs(b, stdout);
         if (!nflag)
                 putchar('\n');
 
Received on Mon Mar 23 2015 - 18:35:49 CET