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", ...).
This commit is contained in:
FRIGN 2015-03-20 22:09:47 +01:00
parent e6c20fe367
commit a531865fe5
3 changed files with 42 additions and 48 deletions

2
README
View File

@ -55,7 +55,7 @@ The following tools are implemented ('*' == finished, '#' == UTF-8 support,
=*| printenv non-posix none =*| printenv non-posix none
#*| printf yes none #*| printf yes none
=*| pwd yes none =*| pwd yes none
= readlink non-posix none =*| readlink non-posix none
=*| renice yes none =*| renice yes none
=*| rm yes none (-i) =*| rm yes none (-i)
=*| rmdir yes none =*| rmdir yes none

View File

@ -1,4 +1,4 @@
.Dd January 31, 2015 .Dd March 20, 2015
.Dt READLINK 1 .Dt READLINK 1
.Os sbase .Os sbase
.Sh NAME .Sh NAME
@ -6,30 +6,27 @@
.Nd print symbolic link target or canonical file name .Nd print symbolic link target or canonical file name
.Sh SYNOPSIS .Sh SYNOPSIS
.Nm .Nm
.Op Fl fn .Op Fl e | Fl f | Fl m
.Ar name .Op Fl n
.Ar path
.Sh DESCRIPTION .Sh DESCRIPTION
If
.Ar name
is a symbolic link,
.Nm .Nm
writes its target to stdout. writes the target of
If .Ar path ,
.Fl f if it is a symbolic link, to stdout.
is not set and If not,
.Ar name
is not a symbolic link,
.Nm .Nm
exits with a nonzero exit code without printing anything. exits with a non-zero return value.
.Sh OPTIONS .Sh OPTIONS
.Bl -tag -width Ds .Bl -tag -width Ds
.It Fl f .It Fl e | Fl f | Fl m
Canonicalize Canonicalize
.Ar name , .Ar name ,
which does not need to be a symlink, which needn't be a symlink,
by recursively following every symlink in its components. by recursively following every symlink in its path components.
All | All but the last | No path components must exist.
.It Fl n .It Fl n
Do not output the trailing newline. Do not print the terminating newline.
.El .El
.Sh SEE ALSO .Sh SEE ALSO
.Xr readlink 2 , .Xr readlink 2 ,

View File

@ -1,6 +1,7 @@
/* See LICENSE file for copyright and license details. */ /* See LICENSE file for copyright and license details. */
#include <sys/stat.h> #include <sys/stat.h>
#include <libgen.h>
#include <unistd.h> #include <unistd.h>
#include <stdio.h> #include <stdio.h>
#include <stdlib.h> #include <stdlib.h>
@ -11,18 +12,17 @@
static void static void
usage(void) usage(void)
{ {
eprintf("usage: %s [-efmn] name\n", argv0); eprintf("usage: %s [-e | -f | -m] [-n] path\n", argv0);
} }
int int
main(int argc, char *argv[]) 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; 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 { ARGBEGIN {
case 'm': case 'm':
@ -40,57 +40,54 @@ main(int argc, char *argv[])
if (argc != 1) if (argc != 1)
usage(); usage();
if (strlen(argv[0]) > PATH_MAX - 1) if (strlen(argv[0]) >= PATH_MAX)
eprintf("path too long\n"); eprintf("path too long\n");
#define SWAP_BUF() (b = (b == buf1 ? buf2 : buf1));
switch (mefflag) { switch (mefflag) {
case 'm': case 'm':
if (argv[0][0] == '/') { /* case when path is on '/' */ slash = strchr(argv[0], '/');
arg[0] = '/'; prefix = (slash == argv[0]) ? "/" : (!slash) ? "./" : "";
arg[1] = '\0';
p++; estrlcpy(arg, prefix, sizeof(arg));
} else if (!strchr(argv[0], '/')) { /* relative path */
arg[0] = '.';
arg[1] = '/';
arg[2] = '\0';
} else
arg[0] = '\0';
estrlcat(arg, argv[0], 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'; *p = '\0';
if (!realpath(arg, b)) { if (!realpath(arg, b)) {
*p = '/'; *p = '/';
goto mdone; goto mdone;
} }
SWAP_BUF(); b = (b == buf1) ? buf2 : buf1;
lp = p; lp = p;
*p++ = '/'; *p = '/';
} }
if (!realpath(arg, b)) { if (!realpath(arg, b)) {
mdone: mdone:
SWAP_BUF(); b = (b == buf1) ? buf2 : buf1;
if (lp) { estrlcat(b, lp, sizeof(arg));
/* drop the extra '/' on root */
lp += (argv[0][0] == '/' &&
lp - arg == 1);
estrlcat(b, lp, sizeof(arg));
}
} }
break; break;
case 'e': case 'e':
if (stat(argv[0], &st) < 0) if (stat(argv[0], &st) < 0)
eprintf("stat %s:", argv[0]); eprintf("stat %s:", argv[0]);
case 'f': /* fallthrough */
if (!realpath(argv[0], b)) if (!realpath(argv[0], b))
eprintf("realpath %s:", argv[0]); eprintf("realpath %s:", argv[0]);
break; 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: default:
if ((n = readlink(argv[0], b, PATH_MAX - 1)) < 0) if ((n = readlink(argv[0], b, PATH_MAX - 1)) < 0)
eprintf("readlink %s:", argv[0]); eprintf("readlink %s:", argv[0]);
b[n] = '\0'; b[n] = '\0';
} }
printf("%s", b); fputs(b, stdout);
if (!nflag) if (!nflag)
putchar('\n'); putchar('\n');