File sudo-1.8.22-CVE-2019-18634.patch of Package sudo.17942

From fa8ffeb17523494f0e8bb49a25e53635f4509078 Mon Sep 17 00:00:00 2001
From: "Todd C. Miller" <Todd.Miller@sudo.ws>
Date: Wed, 29 Jan 2020 20:15:21 -0700
Subject: [PATCH] Fix a buffer overflow when pwfeedback is enabled and input is
 a not a tty. In getln() if the user enters ^U (erase line) and the write(2)
 fails, the remaining buffer size is reset but the current pointer is not.
 While here, fix an incorrect break for erase when write(2) fails. Also
 disable pwfeedback when input is not a tty as it cannot work. CVE-2019-18634
 Credit: Joe Vennix from Apple Information Security.

---
 src/tgetpass.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

Index: sudo-1.8.22/src/tgetpass.c
===================================================================
--- sudo-1.8.22.orig/src/tgetpass.c
+++ sudo-1.8.22/src/tgetpass.c
@@ -48,7 +48,7 @@ static volatile sig_atomic_t signo[NSIG]
 
 static bool tty_present(void);
 static void tgetpass_handler(int);
-static char *getln(int, char *, size_t, int);
+static char *getln(int, char *, size_t, bool);
 static char *sudo_askpass(const char *, const char *);
 
 static int
@@ -90,6 +90,7 @@ tgetpass(const char *prompt, int timeout
     static const char *askpass;
     static char buf[SUDO_CONV_REPL_MAX + 1];
     int i, input, output, save_errno, neednl = 0, need_restart;
+    bool feedback = ISSET(flags, TGP_MASK);
     debug_decl(tgetpass, SUDO_DEBUG_CONV)
 
     (void) fflush(stdout);
@@ -136,7 +137,7 @@ restart:
      */
     if (!ISSET(flags, TGP_ECHO)) {
 	for (;;) {
-	    if (ISSET(flags, TGP_MASK))
+	    if (feedback)
 		neednl = sudo_term_cbreak(input);
 	    else
 		neednl = sudo_term_noecho(input);
@@ -150,6 +151,9 @@ restart:
 	    }
 	}
     }
+    /* Only use feedback mode when we can disable echo. */
+    if (!neednl)
+	feedback = false;
 
     /*
      * Catch signals that would otherwise cause the user to end
@@ -175,7 +179,7 @@ restart:
 
     if (timeout > 0)
 	alarm(timeout);
-    pass = getln(input, buf, sizeof(buf), ISSET(flags, TGP_MASK));
+    pass = getln(input, buf, sizeof(buf), feedback);
     alarm(0);
     save_errno = errno;
 
@@ -305,7 +309,7 @@ sudo_askpass(const char *askpass, const
 extern int sudo_term_erase, sudo_term_kill;
 
 static char *
-getln(int fd, char *buf, size_t bufsiz, int feedback)
+getln(int fd, char *buf, size_t bufsiz, bool feedback)
 {
     size_t left = bufsiz;
     ssize_t nr = -1;
@@ -327,15 +331,15 @@ getln(int fd, char *buf, size_t bufsiz,
 		while (cp > buf) {
 		    if (write(fd, "\b \b", 3) == -1)
 			break;
-		    --cp;
+		    cp--;
 		}
+		cp = buf;
 		left = bufsiz;
 		continue;
 	    } else if (c == sudo_term_erase) {
 		if (cp > buf) {
-		    if (write(fd, "\b \b", 3) == -1)
-			break;
-		    --cp;
+		    ignore_result(write(fd, "\b \b", 3));
+		    cp--;
 		    left++;
 		}
 		continue;