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diff -up ./src/tgetpass.c.CVE-2019-18634 ./src/tgetpass.c
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--- ./src/tgetpass.c.CVE-2019-18634	2020-02-05 17:16:07.601420697 +0100
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+++ ./src/tgetpass.c	2020-02-05 17:22:34.206301510 +0100
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@@ -55,7 +55,7 @@ static volatile sig_atomic_t signo[NSIG]
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 static bool tty_present(void);
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 static void tgetpass_handler(int);
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-static char *getln(int, char *, size_t, int, enum tgetpass_errval *);
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+static char *getln(int, char *, size_t, bool, enum tgetpass_errval *);
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 static char *sudo_askpass(const char *, const char *);
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 static int
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@@ -118,6 +118,7 @@ tgetpass(const char *prompt, int timeout
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     static const char *askpass;
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     static char buf[SUDO_CONV_REPL_MAX + 1];
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     int i, input, output, save_errno, neednl = 0, need_restart;
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+    bool feedback = ISSET(flags, TGP_MASK);
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     enum tgetpass_errval errval;
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     debug_decl(tgetpass, SUDO_DEBUG_CONV)
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@@ -165,7 +166,7 @@ restart:
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      */
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     if (!ISSET(flags, TGP_ECHO)) {
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 	for (;;) {
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-	    if (ISSET(flags, TGP_MASK))
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+	    if (feedback)
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 		neednl = sudo_term_cbreak(input);
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 	    else
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 		neednl = sudo_term_noecho(input);
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@@ -179,6 +180,9 @@ restart:
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 	    }
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 	}
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     }
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+    /* Only use feedback mode when we can disable echo. */
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+    if (!neednl)
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+	feedback = false;
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     /*
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      * Catch signals that would otherwise cause the user to end
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@@ -204,7 +208,7 @@ restart:
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     if (timeout > 0)
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 	alarm(timeout);
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-    pass = getln(input, buf, sizeof(buf), ISSET(flags, TGP_MASK), &errval);
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+    pass = getln(input, buf, sizeof(buf), feedback, &errval);
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     alarm(0);
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     save_errno = errno;
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@@ -340,7 +344,7 @@ sudo_askpass(const char *askpass, const
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 extern int sudo_term_erase, sudo_term_kill;
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 static char *
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-getln(int fd, char *buf, size_t bufsiz, int feedback,
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+getln(int fd, char *buf, size_t bufsiz, bool feedback,
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       enum tgetpass_errval *errval)
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 {
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     size_t left = bufsiz;
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@@ -366,15 +370,15 @@ getln(int fd, char *buf, size_t bufsiz,
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 		while (cp > buf) {
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 		    if (write(fd, "\b \b", 3) == -1)
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 			break;
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-		    --cp;
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+		    cp--;
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 		}
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+		cp = buf;
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 		left = bufsiz;
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 		continue;
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 	    } else if (c == sudo_term_erase) {
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 		if (cp > buf) {
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-		    if (write(fd, "\b \b", 3) == -1)
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-			break;
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-		    --cp;
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+		    ignore_result(write(fd, "\b \b", 3));
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+		    cp--;
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 		    left++;
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 		}
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 		continue;