diff -up ./src/tgetpass.c.bla ./src/tgetpass.c

--- ./src/tgetpass.c.bla	2018-08-18 16:10:15.000000000 +0200

+++ ./src/tgetpass.c	2020-02-05 17:15:16.216904891 +0100

@@ -44,11 +44,18 @@

 #include "sudo.h"

 #include "sudo_plugin.h"

+enum tgetpass_errval {

+    TGP_ERRVAL_NOERROR,

+    TGP_ERRVAL_TIMEOUT,

+    TGP_ERRVAL_NOPASSWORD,

+    TGP_ERRVAL_READERROR

+};

+

 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, int, enum tgetpass_errval *);

 static char *sudo_askpass(const char *, const char *);

 static int

@@ -77,6 +84,27 @@ suspend(int signo, struct sudo_conv_call

     debug_return_int(ret);

 }

+static void

+tgetpass_display_error(enum tgetpass_errval errval)

+{

+    debug_decl(tgetpass_display_error, SUDO_DEBUG_CONV)

+

+    switch (errval) {

+    case TGP_ERRVAL_NOERROR:

+	break;

+    case TGP_ERRVAL_TIMEOUT:

+	sudo_warnx(U_("timed out reading password"));

+	break;

+    case TGP_ERRVAL_NOPASSWORD:

+	sudo_warnx(U_("no password was provided"));

+	break;

+    case TGP_ERRVAL_READERROR:

+	sudo_warn(U_("unable to read password"));

+	break;

+    }

+    debug_return;

+}

+

 /*

  * Like getpass(3) but with timeout and echo flags.

  */

@@ -90,6 +118,7 @@ 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;

+    enum tgetpass_errval errval;

     debug_decl(tgetpass, SUDO_DEBUG_CONV)

     (void) fflush(stdout);

@@ -175,7 +204,7 @@ restart:

     if (timeout > 0)

 	alarm(timeout);

-    pass = getln(input, buf, sizeof(buf), ISSET(flags, TGP_MASK));

+    pass = getln(input, buf, sizeof(buf), ISSET(flags, TGP_MASK), &errval);

     alarm(0);

     save_errno = errno;

@@ -183,6 +212,7 @@ restart:

 	if (write(output, "\n", 1) == -1)

 	    goto restore;

     }

+    tgetpass_display_error(errval);

 restore:

     /* Restore old signal handlers. */

@@ -210,6 +240,8 @@ restore:

     for (i = 0; i < NSIG; i++) {

 	if (signo[i]) {

 	    switch (i) {

+		case SIGALRM:

+		    break;

 		case SIGTSTP:

 		case SIGTTIN:

 		case SIGTTOU:

@@ -239,6 +271,7 @@ sudo_askpass(const char *askpass, const

 {

     static char buf[SUDO_CONV_REPL_MAX + 1], *pass;

     struct sigaction sa, savechld;

+    enum tgetpass_errval errval;

     int pfd[2], status;

     pid_t child;

     debug_decl(sudo_askpass, SUDO_DEBUG_CONV)

@@ -281,9 +314,11 @@ sudo_askpass(const char *askpass, const

     /* Get response from child (askpass). */

     (void) close(pfd[1]);

-    pass = getln(pfd[0], buf, sizeof(buf), 0);

+    pass = getln(pfd[0], buf, sizeof(buf), 0, &errval);

     (void) close(pfd[0]);

+    tgetpass_display_error(errval);

+

     /* Wait for child to exit. */

     for (;;) {

 	pid_t rv = waitpid(child, &status, 0);

@@ -305,7 +340,8 @@ 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, int feedback,

+      enum tgetpass_errval *errval)

 {

     size_t left = bufsiz;

     ssize_t nr = -1;

@@ -313,7 +349,10 @@ getln(int fd, char *buf, size_t bufsiz,

     char c = '\0';

     debug_decl(getln, SUDO_DEBUG_CONV)

+    *errval = TGP_ERRVAL_NOERROR;

+

     if (left == 0) {

+	*errval = TGP_ERRVAL_READERROR;

 	errno = EINVAL;

 	debug_return_str(NULL);		/* sanity */

     }

@@ -354,14 +393,27 @@ getln(int fd, char *buf, size_t bufsiz,

 	}

     }

-    debug_return_str_masked(nr == 1 ? buf : NULL);

+    if (nr != 1) {

+	if (nr == 0) {

+	    *errval = TGP_ERRVAL_NOPASSWORD;

+	} else if (nr == -1) {

+	    if (errno == EINTR) {

+		if (signo[SIGALRM] == 1)

+		    *errval = TGP_ERRVAL_TIMEOUT;

+	    } else {

+		*errval = TGP_ERRVAL_READERROR;

+	    }

+	}

+	debug_return_str(NULL);

+    }

+

+    debug_return_str_masked(buf);

 }

 static void

 tgetpass_handler(int s)

 {

-    if (s != SIGALRM)

-	signo[s] = 1;

+    signo[s] = 1;

 }

 static bool