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When trying to determine the tty, fall back on /proc/ppid/fd/{0,1,2}

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if the main process's fds 0-2 are not hooked up to a tty.  Adapted
from a diff by Zdenek Behan.
This commit is contained in:
Todd C. Miller
2012-01-03 10:47:33 -05:00
parent 5bc0756406
commit 4da65677bd
1 changed files with 34 additions and 2 deletions
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36
src/sudo.c
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@@ -421,6 +421,39 @@ get_user_groups(struct user_details *ud)
debug_return_str(gid_list);
}
/*
* Return a string from ttyname() containing the tty to which the process is
* attached or NULL if there is no tty associated with the process (or its
* parent). First tries std{in,out,err} then falls back to the parent's /proc
* entry. We could try following the parent all the way to pid 1 but
* /proc/%d/status is system-specific (text on Linux, a struct on Solaris).
*/
static char *
get_process_tty(void)
{
char path[PATH_MAX], *tty = NULL;
pid_t ppid;
int i, fd;
debug_decl(get_process_tty, SUDO_DEBUG_UTIL)
if ((tty = ttyname(STDIN_FILENO)) == NULL &&
(tty = ttyname(STDOUT_FILENO)) == NULL &&
(tty = ttyname(STDERR_FILENO)) == NULL) {
/* No tty for child, check the parent via /proc. */
ppid = getppid();
for (i = STDIN_FILENO; i < STDERR_FILENO && tty == NULL; i++) {
snprintf(path, sizeof(path), "/proc/%d/fd/%d", ppid, i);
fd = open(path, O_RDONLY|O_NOCTTY, 0);
if (fd != -1) {
tty = ttyname(fd);
close(fd);
}
}
}
debug_return_str(tty);
}
/*
* Return user information as an array of name=value pairs.
* and fill in struct user_details (which shares the same strings).
@@ -471,8 +504,7 @@ get_user_info(struct user_details *ud)
ud->cwd = user_info[i] + sizeof("cwd=") - 1;
}
if ((cp = ttyname(STDIN_FILENO)) || (cp = ttyname(STDOUT_FILENO)) ||
(cp = ttyname(STDERR_FILENO))) {
if ((cp = get_process_tty()) != NULL) {
user_info[++i] = fmt_string("tty", cp);
if (user_info[i] == NULL)
errorx(1, _("unable to allocate memory"));