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apply(1): Fix magic number substitution with magic character ' '

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Using a space as the magic character would result in problems if the command
started with a number:

- For a 'valid' number n, n < size of argv, it would erroneously get
  replaced with that argument; e.g. `apply -a ' ' -d 1rm x => `execxrm x`

- For an 'invalid' number n, n >= size of argv, it would segfault.
  e.g. `apply -a ' ' 2to3 test.py` would try to access argv[2]

This problem occurred because apply(1) would prepend "exec " to the command
string before doing the actual magic number replacements, so it would come
across "exec 2to3 1" and assume that the " 2" is also a magic number to be
replaced.

Re-work this to instead just append "exec " to the command sbuf and
workaround the ugliness. This also simplifies stuff in the process.

PR:		226948
Submitted by:	Tobias Stoeckmann <tobias@stoeckmann.org>
MFC after:	1 week
This commit is contained in:
kevans 2018-08-08 21:21:28 +00:00
parent f0f5552f39
commit f0f01aabba
1 changed files with 17 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
usr.bin/apply/apply.c
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@ -55,7 +55,8 @@ __FBSDID("$FreeBSD$");
#include <string.h>
#include <unistd.h>
#define EXEC "exec "
#define ISMAGICNO(p) \
(p)[0] == magic && isdigit((unsigned char)(p)[1]) && (p)[1] != '0'
static int exec_shell(const char *, const char *, const char *);
static void usage(void);
@ -65,8 +66,9 @@ main(int argc, char *argv[])
{
struct sbuf *cmdbuf;
long arg_max;
int ch, debug, i, magic, n, nargs, offset, rval;
int ch, debug, i, magic, n, nargs, rval;
size_t cmdsize;
char buf[4];
char *cmd, *name, *p, *shell, *slashp, *tmpshell;
debug = 0;
@ -75,7 +77,7 @@ main(int argc, char *argv[])
while ((ch = getopt(argc, argv, "a:d0123456789")) != -1)
switch (ch) {
case 'a':
if (optarg[1] != '\0')
if (optarg[0] == '\0' || optarg[1] != '\0')
errx(1,
"illegal magic character specification");
magic = optarg[0];
@ -105,7 +107,7 @@ main(int argc, char *argv[])
* largest one.
*/
for (n = 0, p = argv[0]; *p != '\0'; ++p)
if (p[0] == magic && isdigit(p[1]) && p[1] != '0') {
if (ISMAGICNO(p)) {
++p;
if (p[0] - '0' > n)
n = p[0] - '0';
@ -134,28 +136,19 @@ main(int argc, char *argv[])
* Allocate enough space to hold the maximum command. Save the
* size to pass to snprintf().
*/
cmdsize = sizeof(EXEC) - 1 + strlen(argv[0])
+ 9 * (sizeof(" %1") - 1) + 1;
if (n == 0) {
cmdsize = strlen(argv[0]) + 9 * (sizeof(" %1") - 1) + 1;
if ((cmd = malloc(cmdsize)) == NULL)
err(1, NULL);
strlcpy(cmd, argv[0], cmdsize);
if (n == 0) {
/* If nargs not set, default to a single argument. */
if (nargs == -1)
nargs = 1;
p = cmd;
offset = snprintf(cmd, cmdsize, EXEC "%s", argv[0]);
if ((size_t)offset >= cmdsize)
errx(1, "snprintf() failed");
p += offset;
cmdsize -= offset;
for (i = 1; i <= nargs; i++) {
offset = snprintf(p, cmdsize, " %c%d", magic, i);
if ((size_t)offset >= cmdsize)
errx(1, "snprintf() failed");
p += offset;
cmdsize -= offset;
snprintf(buf, sizeof(buf), " %c%d", magic, i);
strlcat(cmd, buf, cmdsize);
}
/*
@ -165,9 +158,8 @@ main(int argc, char *argv[])
if (nargs == 0)
nargs = 1;
} else {
offset = snprintf(cmd, cmdsize, EXEC "%s", argv[0]);
if ((size_t)offset >= cmdsize)
errx(1, "snprintf() failed");
if ((cmd = strdup(argv[0])) == NULL)
err(1, NULL);
nargs = n;
}
@ -184,9 +176,10 @@ main(int argc, char *argv[])
*/
for (rval = 0; argc > nargs; argc -= nargs, argv += nargs) {
sbuf_clear(cmdbuf);
sbuf_cat(cmdbuf, "exec ");
/* Expand command argv references. */
for (p = cmd; *p != '\0'; ++p) {
if (p[0] == magic && isdigit(p[1]) && p[1] != '0') {
if (ISMAGICNO(p)) {
if (sbuf_cat(cmdbuf, argv[(++p)[0] - '0'])
== -1)
errc(1, ENOMEM, "sbuf");