[apparmor] [PATCH] parser - fix trailing \\ in regex (was Re: [PATCH] [parsers] allow for nested alternations expressions)

[Steve Beattie]

On Tue, Nov 05, 2013 at 12:29:56PM -0800, John Johansen wrote:
> On 11/05/2013 11:33 AM, Steve Beattie wrote:
> > On Mon, Nov 04, 2013 at 05:28:22PM -0800, John Johansen wrote:
> >> On 11/04/2013 04:34 PM, Steve Beattie wrote:
> >>> Well, part of the slowdown was me writing some unit tests for that
> >>> function. Here's the patch that does that:
> > [SNIP]
> >>> +	//MY_REGEX_TEST("\\", "\\", ePatternBasic);
> >>> +	MY_REGEX_TEST("\\\\", "\\\\", ePatternBasic);
> >>> +	//MY_REGEX_TEST("\\blort", "\\blort", ePatternBasic);
> >>> +	MY_REGEX_TEST("\\\\blort", "\\\\blort", ePatternBasic);
> >>> +	//MY_REGEX_TEST("blort\\", "blort\\", ePatternBasic);
> >> why are these 3 commented out?
> > 
> > Ah, right, I'd forgotten about these. They're commented out
> > because as-is, they fail; however I wasn't sure if that was the
> > correct expected output. Basically, what happens is that if whatever
> > follows isn't expecting an escape character, then the escaping '\' is
> > dropped. Thus, the current behavior is that '\\' becomes '' and both
> > '\\blort' and 'blort\\' become 'blort'.
> > 
> > The question is, is this a bug? I think so... but I'm willing to hear
> > countering arguments.
> > 
> O_o  Its a bug

Alright, here's a patch that fixes the issue:

Signed-off-by: Steve Beattie <steve at nxnw.org>
---
 parser/parser_regex.c |  140 +++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 110 insertions(+), 30 deletions(-)

Index: b/parser/parser_regex.c
===================================================================
--- a/parser/parser_regex.c
+++ b/parser/parser_regex.c
@@ -326,9 +347,14 @@ static pattern_t convert_aaregex_to_pcre
 		case '(':
 		case ')':
 			STORE("\\", dptr, 1);
-			// fall through to default
+			STORE(sptr, dptr, 1);
+			break;
 
 		default:
+			if (bEscape) {
+				/* just a regular backslash */
+				STORE("\\", dptr, 1);
+			}
 			STORE(sptr, dptr, 1);
 			break;
 		}	/* switch (*sptr) */
@@ -344,6 +370,10 @@ static pattern_t convert_aaregex_to_pcre
 		       progname);
 	}
 
+	if ((error == e_no_error) && bEscape) {
+		/* just a regular backslash */
+		STORE("\\", dptr, 1);
+	}
 	/* anchor end and terminate pattern string */
 	if ((error == e_no_error) && anchor) {
 		STORE("$" , dptr, 1);


-- 
Steve Beattie
<sbeattie at ubuntu.com>
http://NxNW.org/~steve/
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