From 7d39ace96abb10c6740ba192ac6a7ded37dc1027 Mon Sep 17 00:00:00 2001
From: Renzo Davoli <renzo@cs.unibo.it>
Date: Sun, 7 Jan 2024 15:37:07 +0100
Subject: [PATCH] add no-pty-setowner option in authorized_keys

---
 src/auth.h                  |  3 +++
 src/svr-authpubkeyoptions.c | 14 ++++++++++++++
 src/svr-chansession.c       |  6 ++++--
 3 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/src/auth.h b/src/auth.h
index 0e854fbb8..9503192a2 100644
--- a/src/auth.h
+++ b/src/auth.h
@@ -46,6 +46,7 @@ int svr_pubkey_allows_agentfwd(void);
 int svr_pubkey_allows_tcpfwd(void);
 int svr_pubkey_allows_x11fwd(void);
 int svr_pubkey_allows_pty(void);
+int svr_pubkey_allows_pty_setowner(void);
 int svr_pubkey_allows_local_tcpfwd(const char *host, unsigned int port);
 void svr_pubkey_set_forced_command(struct ChanSess *chansess);
 void svr_pubkey_options_cleanup(void);
@@ -56,6 +57,7 @@ int svr_add_pubkey_options(buffer *options_buf, int line_num, const char* filena
 #define svr_pubkey_allows_tcpfwd() 1
 #define svr_pubkey_allows_x11fwd() 1
 #define svr_pubkey_allows_pty() 1
+#define svr_pubkey_allows_pty_setowner() 1
 static inline int svr_pubkey_allows_local_tcpfwd(const char *host, unsigned int port)
 	{ (void)host; (void)port; return 1; }
 
@@ -143,6 +145,7 @@ struct PubKeyOptions {
 	int no_agent_forwarding_flag;
 	int no_x11_forwarding_flag;
 	int no_pty_flag;
+	int no_pty_setowner_flag;
 	/* "command=" option. */
 	char * forced_command;
 	/* "permitopen=" option */
diff --git a/src/svr-authpubkeyoptions.c b/src/svr-authpubkeyoptions.c
index df9a7dfc7..c5c4dbfdf 100644
--- a/src/svr-authpubkeyoptions.c
+++ b/src/svr-authpubkeyoptions.c
@@ -89,6 +89,15 @@ int svr_pubkey_allows_pty() {
 	return 1;
 }
 
+/* Returns 1 if pubkey allows pty_setowner, 0 otherwise */
+int svr_pubkey_allows_pty_setowner() {
+	if (ses.authstate.pubkey_options
+		&& ses.authstate.pubkey_options->no_pty_setowner_flag) {
+		return 0;
+	}
+	return 1;
+}
+
 /* Returns 1 if pubkey allows local tcp fowarding to the provided destination,
  * 0 otherwise */
 int svr_pubkey_allows_local_tcpfwd(const char *host, unsigned int port) {
@@ -198,6 +207,11 @@ int svr_add_pubkey_options(buffer *options_buf, int line_num, const char* filena
 #endif
 			goto next_option;
 		}
+		if (match_option(options_buf, "no-pty-setowner") == DROPBEAR_SUCCESS) {
+			dropbear_log(LOG_WARNING, "Pty setowner disabled.");
+			ses.authstate.pubkey_options->no_pty_setowner_flag = 1;
+			goto next_option;
+		}
 		if (match_option(options_buf, "no-pty") == DROPBEAR_SUCCESS) {
 			dropbear_log(LOG_WARNING, "Pty allocation disabled.");
 			ses.authstate.pubkey_options->no_pty_flag = 1;
diff --git a/src/svr-chansession.c b/src/svr-chansession.c
index fced420fd..3719f4159 100644
--- a/src/svr-chansession.c
+++ b/src/svr-chansession.c
@@ -332,7 +332,8 @@ static void cleanupchansess(const struct Channel *channel) {
 		login_logout(li);
 		login_free_entry(li);
 
-		pty_release(chansess->tty);
+		if (svr_pubkey_allows_pty_setowner())
+			pty_release(chansess->tty);
 		m_free(chansess->tty);
 	}
 
@@ -614,7 +615,8 @@ static int sessionpty(struct ChanSess * chansess) {
 	pw = getpwnam(ses.authstate.pw_name);
 	if (!pw)
 		dropbear_exit("getpwnam failed after succeeding previously");
-	pty_setowner(pw, chansess->tty);
+	if (svr_pubkey_allows_pty_setowner())
+		pty_setowner(pw, chansess->tty);
 
 	/* Set up the rows/col counts */
 	sessionwinchange(chansess);