[PATCH] [BUILTIN] Reject malformed printf specifications with digits after '*'

[Gioele Barabucci]

Hello,

I am forwarding a patch related to the bug described at
<https://bugs.debian.org/779618>.

You can find the same patch at
<https://github.com/gioele/dash/commit/ebdd2d7992c4b2bf49d9af2eed33e3c18c86dfc6>.

I refreshed the patch to be compatible with the current code, but left
the original author as the git author. I hope this is fine.

Regards,

--
Gioele Barabucci <gio...@svario.it>




>From ebdd2d7992c4b2bf49d9af2eed33e3c18c86dfc6 Mon Sep 17 00:00:00 2001
From: Patrick Brown <opensou...@whoopdedo.org>
Date: Mon, 2 Mar 2015 23:10:09 -0500
Subject: [PATCH] [BUILTIN] Reject malformed printf specifications with digits
 after '*'

Dash doesn't notice when a format string has digits following a * width
specifier.

    $ dash -c 'printf "%*0s  " 1 2 && echo FAIL || echo OK'
    %10s  FAIL

    $ bash -c 'printf "%*0s  " 1 2 && echo FAIL || echo OK'
    bash: line 0: printf: `0': invalid format character
    OK
    $ mksh -c 'printf "%*0s  " 1 2 && echo FAIL || echo OK'
    printf: %*0: invalid conversion specification
    OK

With this patch dash complains about the malformed specifications.

    $ ./src/dash -c 'printf "%*0s  " 1 2 && echo FAIL || echo OK'
    ./src/dash: 1: printf: %*0: invalid directive
    OK

Fixes: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=779618

Originally-by: Patrick Brown <opensou...@whoopdedo.org>
Forwarded-by: Gioele Barabucci <gio...@svario.it>
---
 src/bltin/printf.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/src/bltin/printf.c b/src/bltin/printf.c
index 9673e10..83077a7 100644
--- a/src/bltin/printf.c
+++ b/src/bltin/printf.c
@@ -175,17 +175,20 @@ pc:
 
 			/* skip to field width */
 			fmt += strspn(fmt, SKIP1);
-			if (*fmt == '*')
+			if (*fmt == '*') {
 				*param++ = getuintmax(1);
-
-			/* skip to possible '.', get following precision */
-			fmt += strspn(fmt, SKIP2);
-			if (*fmt == '.')
 				++fmt;
-			if (*fmt == '*')
-				*param++ = getuintmax(1);
-
-			fmt += strspn(fmt, SKIP2);
+			} else
+			   /* skip to possible '.', get following precision */
+			   fmt += strspn(fmt, SKIP2);
+			if (*fmt == '.') {
+				++fmt;
+				if (*fmt == '*') {
+					*param++ = getuintmax(1);
+					++fmt;
+				} else
+				   fmt += strspn(fmt, SKIP2);
+			}
 
 			ch = *fmt;
 			if (!ch)
-- 
2.6.2