shells: do not allow bare "read" in non-bash compat configs

On Sat, Feb 9, 2019 Cristian Ionescu-Idbohrn wrote:
    > In my case (at work), I have to watch and prevent people from doing
    > unportable things.  For me, that's a burden.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

libbb/getopt32.c

@@ -89,6 +89,12 @@ getopt32(char **argv, const char *applet_opts, ...)
         root:x:0:0:root:/root:/bin/bash
         user:x:500:500::/home/user:/bin/bash
 
+ "^"    options string is "^optchars""\0""opt_complementary".
+
+ "!"    If the first character in the applet_opts string is a '!',
+        report bad options, missing required options,
+        inconsistent options with all-ones return value (instead of abort.
+
  "+"    If the first character in the applet_opts string is a plus,
         then option processing will stop as soon as a non-option is
         encountered in the argv array.  Useful for applets like env
@@ -96,10 +102,7 @@ getopt32(char **argv, const char *applet_opts, ...)
         env -i ls -d /
         Here we want env to process just the '-i', not the '-d'.
 
- "!"    Report bad options, missing required options,
-        inconsistent options with all-ones return value (instead of abort).
-
- "^"    options string is "^optchars""\0""opt_complementary".
+        (The order of multiple prefixes must be "^!+...")
 
 uint32_t
 getopt32long(char **argv, const char *applet_opts, const char *logopts...)

shell/ash.c

@@ -14161,6 +14161,10 @@ readcmd(int argc UNUSED_PARAM, char **argv UNUSED_PARAM)
 		}
 	}
 
+	if (!ENABLE_ASH_BASH_COMPAT && !argptr) {
+		bb_simple_error_msg("read: need variable name");
+		return 1;
+	}
 	params.argv = argptr;
 	params.setvar = setvar0;
 	params.ifs = bltinlookup("IFS"); /* can be NULL */

shell/hush.c

@@ -4251,7 +4251,7 @@ static int done_word(struct parse_context *ctx)
 		 || endofname(command->argv[0])[0] != '\0'
 		) {
 			/* bash says just "not a valid identifier" */
-			syntax_error("not a valid identifier in for");
+			syntax_error("bad variable name in for");
 			return 1;
 		}
 		/* Force FOR to have just one word (variable name) */
@@ -10799,10 +10799,17 @@ static int FAST_FUNC builtin_read(char **argv)
 	 */
 	params.read_flags = getopt32(argv,
 # if BASH_READ_D
-		"!srn:p:t:u:d:", &params.opt_n, &params.opt_p, &params.opt_t, &params.opt_u, &params.opt_d
+		IF_NOT_HUSH_BASH_COMPAT("^")
+		"!srn:p:t:u:d:" IF_NOT_HUSH_BASH_COMPAT("\0" "-1"/*min 1 arg*/),
+		&params.opt_n, &params.opt_p, &params.opt_t, &params.opt_u, &params.opt_d
 # else
-		"!srn:p:t:u:", &params.opt_n, &params.opt_p, &params.opt_t, &params.opt_u
+		IF_NOT_HUSH_BASH_COMPAT("^")
+		"!srn:p:t:u:" IF_NOT_HUSH_BASH_COMPAT("\0" "-1"/*min 1 arg*/),
+		&params.opt_n, &params.opt_p, &params.opt_t, &params.opt_u
 # endif
+//TODO: print "read: need variable name"
+//for the case of !BASH "read" with no args (now it fails silently)
+//(or maybe extend getopt32() to emit a message if "-1" fails)
 	);
 	if ((uint32_t)params.read_flags == (uint32_t)-1)
 		return EXIT_FAILURE;

shell/shell_common.c

@@ -59,7 +59,7 @@ shell_builtin_read(struct builtin_read_params *params)
 	while (*pp) {
 		if (endofname(*pp)[0] != '\0') {
 			/* Mimic bash message */
-			bb_error_msg("read: '%s': not a valid identifier", *pp);
+			bb_error_msg("read: '%s': bad variable name", *pp);
 			return (const char *)(uintptr_t)1;
 		}
 		pp++;