Add SUDO_TTY environment variable if the user has a tty

This can be used to find the user's original tty device when sudo
runs the command in its own pty.  GitHub issue #447.

Author: millert

docs/sudo.man.in

@@ -2,7 +2,7 @@
 .\"
 .\" SPDX-License-Identifier: ISC
 .\"
-.\" Copyright (c) 1994-1996, 1998-2005, 2007-2024
+.\" Copyright (c) 1994-1996, 1998-2005, 2007-2025
 .\"	Todd C. Miller <[email protected]>
 .\"
 .\" Permission to use, copy, modify, and distribute this software for any
@@ -25,7 +25,7 @@
 .nr BA @BAMAN@
 .nr LC @LCMAN@
 .nr PS @PSMAN@
-.TH "SUDO" "@mansectsu@" "December 20, 2024" "Sudo @PACKAGE_VERSION@" "System Manager's Manual"
+.TH "SUDO" "@mansectsu@" "June 7, 2025" "Sudo @PACKAGE_VERSION@" "System Manager's Manual"
 .nh
 .if n .ad l
 .SH "NAME"
@@ -1436,6 +1436,9 @@ If set,
 \fRPS1\fR
 will be set to its value for the program being run.
 .TP 17n
+\fRSUDO_TTY\fR
+Set to the terminal device of the user who invoked sudo, if one is present.
+.TP 17n
 \fRSUDO_UID\fR
 Set to the user-ID of the user who invoked sudo.
 .TP 17n

docs/sudo.mdoc.in

@@ -1,7 +1,7 @@
 .\"
 .\" SPDX-License-Identifier: ISC
 .\"
-.\" Copyright (c) 1994-1996, 1998-2005, 2007-2024
+.\" Copyright (c) 1994-1996, 1998-2005, 2007-2025
 .\"	Todd C. Miller <[email protected]>
 .\"
 .\" Permission to use, copy, modify, and distribute this software for any
@@ -24,7 +24,7 @@
 .nr BA @BAMAN@
 .nr LC @LCMAN@
 .nr PS @PSMAN@
-.Dd December 20, 2024
+.Dd June 7, 2025
 .Dt SUDO @mansectsu@
 .Os Sudo @PACKAGE_VERSION@
 .Sh NAME
@@ -1355,6 +1355,8 @@ option was specified.
 If set,
 .Ev PS1
 will be set to its value for the program being run.
+.It Ev SUDO_TTY
+Set to the terminal device of the user who invoked sudo, if one is present.
 .It Ev SUDO_UID
 Set to the user-ID of the user who invoked sudo.
 .It Ev SUDO_USER

plugins/sudoers/env.c

@@ -1123,13 +1123,15 @@ rebuild_env(const struct sudoers_context *ctx)
 	CHECK_SETENV2("SUDO_COMMAND", ctx->user.cmnd, true, true);
     }
 
-    /* Add the SUDO_{USER,UID,GID,HOME} environment variables. */
+    /* Add the SUDO_{USER,UID,GID,HOME,TTY,TTY} environment variables. */
     CHECK_SETENV2("SUDO_USER", ctx->user.name, true, true);
     (void)snprintf(idbuf, sizeof(idbuf), "%u", (unsigned int) ctx->user.uid);
     CHECK_SETENV2("SUDO_UID", idbuf, true, true);
     (void)snprintf(idbuf, sizeof(idbuf), "%u", (unsigned int) ctx->user.gid);
     CHECK_SETENV2("SUDO_GID", idbuf, true, true);
     CHECK_SETENV2("SUDO_HOME", ctx->user.pw->pw_dir, true, true);
+    if (ctx->user.ttypath != NULL)
+	CHECK_SETENV2("SUDO_TTY", ctx->user.ttypath, true, true);
 
     debug_return_bool(true);