Improve "stdin vs. keyboard vs. message"

Add option --force-keys for enabling it even if we're not the
foreground process, for use with pipes and inside frontend scripts.
Ensure the "Press 'q' to abort (...)" message really reflects whether
we have the terminal set up for reading keystrokes or not.

Closes openwall#4403

doc/NEWS

@@ -136,6 +136,11 @@ Major changes from 1.9.0-jumbo-1 (May 2019) in this bleeding-edge version:
   a legacy internal codepage, convert them to that codepage.  Mask mode already
   had the corresponding feature.  [magnum; 2020]
 
+- Improve handling of using stdin or pipe vs. reading keystrokes.  This
+  includes a new option --force-keys that will set the terminal up for
+  reading status/quit keystrokes even if we're not the foreground process.
+  [magnum; 2020]
+
 
 Major changes from 1.8.0-jumbo-1 (December 2014) to 1.9.0-jumbo-1 (May 2019):
 

doc/OPTIONS

@@ -57,6 +57,12 @@ very large, sorting it will speed up loading.
 These are used to enable the wordlist mode.  If FILE is not specified,
 the one defined in john.conf will be used.
 
+--force-keys
+
+Set the terminal up for reading status/quit keystrokes even if we're not
+the foreground process.  The downside is we might get race conditions so
+you may end up with strange problems hard to reproduce.
+
 --dupe-suppression		suppress all duplicates from wordlist
 
 Normally, consecutive duplicates are ignored when reading a wordlist file.

src/cracker.c

@@ -66,6 +66,7 @@
 #include "gpu_common.h"
 #endif
 #include "rules.h"
+#include "tty.h"
 
 #ifdef index
 #undef index
@@ -125,9 +126,13 @@ static void crk_init_salt(void)
 static void crk_help(void)
 {
 	static int printed = 0;
-	if (!john_main_process || printed ||
-	    ((options.flags & FLG_STDOUT) && isatty(fileno(stdout))))
+
+	if (!john_main_process || printed)
+		return;
+
+	if ((options.flags & FLG_STDOUT) && isatty(fileno(stdout)))
 		return;
+
 #ifdef HAVE_MPI
 	if (mpi_p > 1 || getenv("OMPI_COMM_WORLD_SIZE"))
 #ifdef SIGUSR1
@@ -137,16 +142,16 @@ static void crk_help(void)
 #endif
 	else
 #endif
-	if ((options.flags & FLG_STDIN_CHK) || (options.flags & FLG_PIPE_CHK))
+	if (tty_has_keyboard())
+		fprintf(stderr, "Press 'q' or Ctrl-C to abort, almost any other key for status\n");
+	else
 		fprintf(stderr, "Press Ctrl-C to abort, "
 #ifdef SIGUSR1
 		        "or send SIGUSR1 to john process for status\n");
 #else
 		        "or send SIGHUP to john process for status\n");
 #endif
-	else
-	fprintf(stderr, "Press 'q' or Ctrl-C to abort, "
-	    "almost any other key for status\n");
+
 	printed = 1;
 }
 

src/options.c

@@ -290,6 +290,7 @@ static struct opt_entry opt_list[] = {
 		~FLG_MASK_CHK & ~OPT_REQ_PARAM, "%d", &benchmark_time},
 	{"tune", FLG_ZERO, 0, 0, OPT_REQ_PARAM,
 		OPT_FMT_STR_ALLOC, &options.tune},
+	{"force-keys", FLG_FORCE_KEYS},
 	{NULL}
 };
 
@@ -441,7 +442,9 @@ JOHN_USAGE_FORK \
 "--input-encoding=NAME      input encoding (alias for --encoding)\n" \
 "--internal-codepage=NAME   codepage used in rules/masks (see doc/ENCODINGS)\n" \
 "--target-encoding=NAME     output encoding (used by format, see doc/ENCODINGS)\n" \
-"--tune=HOW                 tuning options (auto/report/N)\n"
+"--tune=HOW                 tuning options (auto/report/N)\n" \
+"--force-keys               set up terminal for reading keystrokes even if we're\n" \
+"                           not the foreground process\n"
 
 #define JOHN_USAGE_FORMAT \
 "--format=[NAME|CLASS][,..] force hash of type NAME. The supported formats can\n" \

src/options.h

@@ -189,6 +189,8 @@
 /* Ignore NOP rules */
 #define FLG_RULE_SKIP_NOP		0x0800000000000000ULL
 #define FLG_NO_MASK_BENCH		0x1000000000000000ULL
+/* Configure terminal for reading keystrokes even if we're not the foreground process */
+#define FLG_FORCE_KEYS			0x2000000000000000ULL
 
 /*
  * Macro for getting correct node number regardless of if MPI or not

src/tty.c

@@ -44,33 +44,53 @@
 #if !defined(__DJGPP__) && !defined(__MINGW32__) && !defined (_MSC_VER)
 static int tty_fd = -1;
 static struct termios saved_ti;
+#else
+static int in_stdin_mode;
+#endif
+
+int tty_has_keyboard(void)
+{
+#if !defined(__DJGPP__) && !defined(__MINGW32__) && !defined (_MSC_VER)
+	return (tty_fd >= 0);
+#else
+	return !(in_stdin_mode && isatty(fileno(stdin)));
 #endif
+}
 
 void tty_init(opt_flags stdin_mode)
 {
 #if !defined(__DJGPP__) && !defined(__MINGW32__) && !defined (_MSC_VER)
 	int fd;
 	struct termios ti;
 
-	if (tty_fd >= 0) return;
-
+	if (tty_fd >= 0)
+		return;
 /*
  * If we're in "--stdin" mode (reading candidate passwords from stdin), then
  * only initialize the tty if stdin is not a tty.  Otherwise it could be the
  * same tty, in which case we'd interfere with the user's ability to type
  * candidate passwords directly to John.
  */
-	if (stdin_mode && !tcgetattr(0, &ti))
+	if (stdin_mode && isatty(fileno(stdin)))
 		return;
 
-	if ((fd = open("/dev/tty", O_RDONLY | O_NONBLOCK)) < 0) return;
+	if ((fd = open("/dev/tty", O_RDONLY | O_NONBLOCK)) < 0)
+		return;
 
-	if (tcgetpgrp(fd) != getpid()) {
-		close(fd); return;
+/*
+ * Give up the keyboard if we're not the foreground process.  This can be
+ * overridden with --force-keys option.
+ */
+	if (!(options.flags & FLG_FORCE_KEYS) && tcgetpgrp(fd) != getpid()) {
+		close(fd);
+		return;
 	}
 
 	tcgetattr(fd, &ti);
 	saved_ti = ti;
+/*
+ * Set up terminal for reading keystrokes, and no echo.
+ */
 	ti.c_lflag &= ~(ICANON | ECHO);
 	ti.c_cc[VMIN] = 1;
 	ti.c_cc[VTIME] = 0;
@@ -79,6 +99,8 @@ void tty_init(opt_flags stdin_mode)
 	tty_fd = fd;
 
 	atexit(tty_done);
+#else
+	in_stdin_mode = stdin_mode;
 #endif
 }
 
@@ -101,7 +123,8 @@ int tty_getchar(void)
 			return -1;
 #endif
 		c = 0;
-		if (read(tty_fd, &c, 1) > 0) return c;
+		if (read(tty_fd, &c, 1) > 0)
+			return c;
 	}
 #elif defined(__DJGPP__)
 	if (_bios_keybrd(_KEYBRD_READY))
@@ -119,9 +142,15 @@ void tty_done(void)
 #if !defined(__DJGPP__) && !defined(__MINGW32__) && !defined (_MSC_VER)
 	int fd;
 
-	if (tty_fd < 0) return;
+	if (tty_fd < 0)
+		return;
 
 	fd = tty_fd; tty_fd = -1;
+
+/* Do the usually-best-thing in the race condition sometimes caused by --force-keys */
+	if (options.flags & FLG_FORCE_KEYS)
+		saved_ti.c_lflag |= (ICANON | ECHO);
+
 	tcsetattr(fd, TCSANOW, &saved_ti);
 
 	close(fd);

src/tty.h

@@ -16,6 +16,11 @@
 #define _JOHN_TTY_H
 #include "options.h"
 
+/*
+ * Returns true if we set up terminal for reading keystrokes
+ */
+extern int tty_has_keyboard(void);
+
 /*
  * Initializes the terminal for unbuffered non-blocking input. Also registers
  * tty_done() via atexit().