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Check the controlling tty to determine if a tty belongs to the user.

Browse Source 
Previously, we compared the terminal device number returned by
get_process_ttyname() with that of stdin, stdout and stderr.  This
causes problems on Linux if the user is logged in on the console,
which is a virtual device that may correspond to one of several
different terminal devices.  In this specific case, there is a
mismatch between the controlling terminal listed in /proc/self/stat
(which corresponds to the underlying terminal device) and the device
number of stdin, stdout and stderr (which is that of /dev/console).
This commit is contained in:
Todd C. Miller
2025-01-15 20:00:46 -07:00
parent a3cd820d21
commit fd3ff3a0bd
4 changed files with 20 additions and 28 deletions
Download Patch File Download Diff File Expand all files Collapse all files

23
src/exec.c
View File

@@ -377,26 +377,23 @@ sudo_needs_pty(const struct command_details *details)
}
/*
* Check whether the specified fd matches the device file that
* corresponds to tty_sb. If tty_sb is NULL, just check whether
* fd is a tty. Always fills in fd_sb (zeroed on error).
* Check whether the specified fd is a terminal with the specified
* controlling process group. Always fills in sb (zeroed on error).
* Returns true on match, else false.
*/
bool
fd_matches_tty(int fd, struct stat *tty_sb, struct stat *fd_sb)
fd_matches_pgrp(int fd, pid_t pgrp, struct stat *sb)
{
debug_decl(fd_is_user_tty, SUDO_DEBUG_EXEC);
debug_decl(fd_matches_pgrp, SUDO_DEBUG_EXEC);
if (fstat(fd, fd_sb) == -1) {
/* Always initialize fd_sb. */
memset(fd_sb, 0, sizeof(*fd_sb));
if (!sudo_isatty(fd, sb))
debug_return_bool(false);
if (pgrp != -1) {
if (pgrp != tcgetpgrp(fd))
debug_return_bool(false);
}
if (!S_ISCHR(fd_sb->st_mode))
debug_return_bool(false);
/* Compare with tty_sb if available, else just check that fd is a tty. */
debug_return_bool(tty_sb ? tty_sb->st_rdev == fd_sb->st_rdev : isatty(fd));
debug_return_bool(true);
}
/*

12
src/exec_nopty.c
View File

@@ -470,9 +470,10 @@ static void
interpose_pipes(struct exec_closure *ec, const char *tty, int io_pipe[3][2])
{
bool interpose[3] = { false, false, false };
struct stat sb, tty_sbuf, *tty_sb = NULL;
struct plugin_container *plugin;
const pid_t pgrp = getpgrp();
bool want_winch = false;
struct stat sb;
debug_decl(interpose_pipes, SUDO_DEBUG_EXEC);
/*
@@ -496,11 +497,8 @@ interpose_pipes(struct exec_closure *ec, const char *tty, int io_pipe[3][2])
* If stdin, stdout or stderr is not the user's tty and logging is
* enabled, use a pipe to interpose ourselves.
*/
if (tty != NULL && stat(tty, &tty_sbuf) != -1)
tty_sb = &tty_sbuf;
if (interpose[STDIN_FILENO]) {
if (!fd_matches_tty(STDIN_FILENO, tty_sb, &sb)) {
if (!fd_matches_pgrp(STDIN_FILENO, pgrp, &sb)) {
sudo_debug_printf(SUDO_DEBUG_INFO,
"stdin not user's tty, creating a pipe");
if (pipe2(io_pipe[STDIN_FILENO], O_CLOEXEC) != 0)
@@ -510,7 +508,7 @@ interpose_pipes(struct exec_closure *ec, const char *tty, int io_pipe[3][2])
}
}
if (interpose[STDOUT_FILENO]) {
if (!fd_matches_tty(STDOUT_FILENO, tty_sb, &sb)) {
if (!fd_matches_pgrp(STDOUT_FILENO, pgrp, &sb)) {
sudo_debug_printf(SUDO_DEBUG_INFO,
"stdout not user's tty, creating a pipe");
if (pipe2(io_pipe[STDOUT_FILENO], O_CLOEXEC) != 0)
@@ -520,7 +518,7 @@ interpose_pipes(struct exec_closure *ec, const char *tty, int io_pipe[3][2])
}
}
if (interpose[STDERR_FILENO]) {
if (!fd_matches_tty(STDERR_FILENO, tty_sb, &sb)) {
if (!fd_matches_pgrp(STDERR_FILENO, pgrp, &sb)) {
sudo_debug_printf(SUDO_DEBUG_INFO,
"stderr not user's tty, creating a pipe");
if (pipe2(io_pipe[STDERR_FILENO], O_CLOEXEC) != 0)

11
src/exec_pty.c
View File

@@ -1095,7 +1095,7 @@ exec_pty(struct command_details *details,
{
int io_pipe[3][2] = { { -1, -1 }, { -1, -1 }, { -1, -1 } };
bool interpose[3] = { false, false, false };
struct stat sb, tty_sbuf, *tty_sb = NULL;
struct stat sb;
int sv[2], intercept_sv[2] = { -1, -1 };
struct exec_closure *ec = &pty_ec;
struct plugin_container *plugin;
@@ -1203,10 +1203,7 @@ exec_pty(struct command_details *details,
* enabled, use a pipe to interpose ourselves instead of using the
* pty fd. We always use a pipe for stdin when in background mode.
*/
if (user_details->tty != NULL && stat(user_details->tty, &tty_sbuf) != -1)
tty_sb = &tty_sbuf;
if (!fd_matches_tty(STDIN_FILENO, tty_sb, &sb)) {
if (!fd_matches_pgrp(STDIN_FILENO, ppgrp, &sb)) {
if (!interpose[STDIN_FILENO]) {
/* Not logging stdin, do not interpose. */
sudo_debug_printf(SUDO_DEBUG_INFO,
@@ -1253,7 +1250,7 @@ exec_pty(struct command_details *details,
close(io_pipe[STDIN_FILENO][1]);
io_pipe[STDIN_FILENO][1] = -1;
}
if (!fd_matches_tty(STDOUT_FILENO, tty_sb, &sb)) {
if (!fd_matches_pgrp(STDOUT_FILENO, ppgrp, &sb)) {
if (!interpose[STDOUT_FILENO]) {
/* Not logging stdout, do not interpose. */
sudo_debug_printf(SUDO_DEBUG_INFO,
@@ -1277,7 +1274,7 @@ exec_pty(struct command_details *details,
io_fds[SFD_STDOUT] = io_pipe[STDOUT_FILENO][1];
}
}
if (!fd_matches_tty(STDERR_FILENO, tty_sb, &sb)) {
if (!fd_matches_pgrp(STDERR_FILENO, ppgrp, &sb)) {
if (!interpose[STDERR_FILENO]) {
/* Not logging stderr, do not interpose. */
sudo_debug_printf(SUDO_DEBUG_INFO,

2
src/sudo_exec.h
View File

@@ -179,7 +179,7 @@ void exec_cmnd(struct command_details *details, sigset_t *mask, int intercept_fd
void terminate_command(pid_t pid, bool use_pgrp);
bool sudo_terminated(struct command_status *cstat);
void free_exec_closure(struct exec_closure *ec);
bool fd_matches_tty(int fd, struct stat *tty_sb, struct stat *fd_sb);
bool fd_matches_pgrp(int fd, pid_t pgrp, struct stat *sb);
/* exec_common.c */
int sudo_execve(int fd, const char *path, char *const argv[], char *envp[], int intercept_fd, unsigned int flags);