Re: [BUG] Two vulnerabilities in zsh

[Peter Stephenson <p.w.stephenson@xxxxxxxxxxxx>]

On Wed, 2020-05-20 at 00:45 +0000, Daniel Shahaf wrote:
> Peter Stephenson wrote on Tue, 19 May 2020 21:38 +0100:
> > The BUG message simplifies to this:
> > 
> > (127)9:32% zsh -fc '$\
> > ('
> > 1: BUG: parse error in command substitution
> > zsh:1: no such file or directory: pws/.
> > 
> > The other output shows it's doing something it shouldn't even if there
> > isn't a crash as a result.  Adding a command in front does produce a
> > crash.
> > 
> > I think the backslashed newline is valid, and it looks like it's usually
> > correctly handled; apparently its presence is disguising the bad input
> > in this case.
> 
> Test cases:

This seems to be doing the right thing.  It's a bit hairy, but I think
it just *is* a bit hairy --- we do need to re-input the multi-character
special sequence if there's something to ignore in the middle.  I can't
see an obvious problem with how I've done it as it can't be triggered by
anythign else that I can see.

There may be other sequences like this.

I believe inlined patches work from this version of Evolution...

pws

diff --git a/Src/lex.c b/Src/lex.c
index a541defe6..5382a5309 100644
--- a/Src/lex.c
+++ b/Src/lex.c
@@ -1237,6 +1237,19 @@ gettokstr(int c, int sub)
 	case LX2_BKSLASH:
 	    c = hgetc();
 	    if (c == '\n') {
+		if (lexbuf.len && !lexstop &&
+		    (lexbuf.ptr[-1] == String ||
+		     lexbuf.ptr[-1] == Qstring))
+		{
+		    /*
+		     * $-prefixed expression interrupted by \\\n.
+		     * This is valid --- reparse.
+		     */
+		    --lexbuf.len;
+		    --lexbuf.ptr;
+		    c = '$';
+		    continue;
+		}
 		c = hgetc();
 		if (!lexstop)
 		    continue;
diff --git a/Test/D04parameter.ztst b/Test/D04parameter.ztst
index 6d2dd0d99..a3661f5da 100644
--- a/Test/D04parameter.ztst
+++ b/Test/D04parameter.ztst
@@ -2662,7 +2662,6 @@ F:behavior, see http://austingroupbugs.net/view.php?id=888
 -f:regression test for workers/45843#1
 ?(eval):1: bad substitution
 
-# Temporarily using the 'D' flag because it generates a "BUG:" message in
-# debug builds only.
  $ZTST_testdir/../Src/zsh -fc $'$\\\n('
-1Df:regression test for workers/45843#2: escaped newline in command substitution start token
+1f:regression test for workers/45843#2: escaped newline in command substitution start token
+?(eval):1: parse error near `$('