* Re: mandoc -Tps aborts on <sp>\^h\n\n
2013-05-30 1:55 mandoc -Tps aborts on <sp>\^h\n\n Mike Small
@ 2013-05-30 4:13 ` Ingo Schwarze
2013-05-30 12:25 ` Mike Small
0 siblings, 1 reply; 3+ messages in thread
From: Ingo Schwarze @ 2013-05-30 4:13 UTC (permalink / raw)
To: Mike Small; +Cc: discuss
Hi Mike,
Mike Small wrote on Wed, May 29, 2013 at 09:55:59PM -0400:
> Not sure if this is covered under "clean up escape sequence handling"
> or another TODO I missed,
No, it isn't, you have found a so far unknown issue.
> but I see an abort in mandoc 1.12.1 from
> OpenBSD current from around May 3rd if I do the following:
>
> $ mandoc -Tps `man -w roff`
> ...
> 509.608 441.221 moveto
> (ASCII) show
> 490.358 425.832 moveto
> (characters) show
> 490.358 410.443 moveto
> (with) show
> assertion "8 != c" failed:
> file "/usr/src/usr.bin/mandoc/term_ps.c",
> line 997, function "ps_letter"
> Abort trap (core dumped)
Indeed, easily reproducible.
> $ man -w roff
> /usr/local/man/cat7/roff.0
> /usr/share/man/man7/roff.7
>
> So you also get it like this...
>
> $ mandoc -Tps /usr/local/man/cat7/roff.0
That doesn't make a lot of sense - you are handing an already formatted
document to the parsers again. Anyway, mandoc(1) is not supposed to
crash even when given garbage input.
[...]
> A minimal test file causing the same assertion...
>
> $ od -cb small_test_file.1
> 0000000 \ \b x \n \n
> 040 134 010 170 012 012
> 0000006
Indeed, that works as well.
It even works when you put a proper mdoc(7) or man(7) header
in front of the exploit code.
I have just committed a proper fix to both OpenBSD and bsd.lv,
see below for the patch.
Thanks for the perfect report!
Ingo
----- 8< ----- schnipp ----- >8 ----- 8< ----- schnapp ----- >8 -----
Log Message:
-----------
Reject non-printable characters found in the input stream even when
preceded by a backslash; otherwise, the escape sequence would later
be identified as invalid and the non-printable character would be
passed through to the output backends, sometimes triggering assertions.
Reported by Mike Small <smallm at panix dot com> on the mdocml discuss list.
Modified Files:
--------------
mdocml:
read.c
Revision Data
-------------
Index: read.c
===================================================================
RCS file: /usr/vhosts/mdocml.bsd.lv/cvs/mdocml/read.c,v
retrieving revision 1.34
retrieving revision 1.35
diff -Lread.c -Lread.c -u -p -r1.34 -r1.35
--- read.c
+++ read.c
@@ -1,7 +1,7 @@
/* $Id$ */
/*
* Copyright (c) 2008, 2009, 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
- * Copyright (c) 2010, 2011, 2012 Ingo Schwarze <schwarze@openbsd.org>
+ * Copyright (c) 2010, 2011, 2012, 2013 Ingo Schwarze <schwarze@openbsd.org>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
@@ -328,6 +328,15 @@ mparse_buf_r(struct mparse *curp, struct
break;
}
+ /*
+ * Make sure we have space for at least
+ * one backslash and one other character
+ * and the trailing NUL byte.
+ */
+
+ if (pos + 2 >= (int)ln.sz)
+ resize_buf(&ln, 256);
+
/*
* Warn about bogus characters. If you're using
* non-ASCII encoding, you're screwing your
@@ -344,8 +353,6 @@ mparse_buf_r(struct mparse *curp, struct
mandoc_msg(MANDOCERR_BADCHAR, curp,
curp->line, pos, NULL);
i++;
- if (pos >= (int)ln.sz)
- resize_buf(&ln, 256);
ln.buf[pos++] = '?';
continue;
}
@@ -353,8 +360,6 @@ mparse_buf_r(struct mparse *curp, struct
/* Trailing backslash = a plain char. */
if ('\\' != blk.buf[i] || i + 1 == (int)blk.sz) {
- if (pos >= (int)ln.sz)
- resize_buf(&ln, 256);
ln.buf[pos++] = blk.buf[i++];
continue;
}
@@ -396,10 +401,20 @@ mparse_buf_r(struct mparse *curp, struct
break;
}
- /* Some other escape sequence, copy & cont. */
+ /* Catch escaped bogus characters. */
- if (pos + 1 >= (int)ln.sz)
- resize_buf(&ln, 256);
+ c = (unsigned char) blk.buf[i+1];
+
+ if ( ! (isascii(c) &&
+ (isgraph(c) || isblank(c)))) {
+ mandoc_msg(MANDOCERR_BADCHAR, curp,
+ curp->line, pos, NULL);
+ i += 2;
+ ln.buf[pos++] = '?';
+ continue;
+ }
+
+ /* Some other escape sequence, copy & cont. */
ln.buf[pos++] = blk.buf[i++];
ln.buf[pos++] = blk.buf[i++];
--
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