Re: dash bug: double-quoted "\" breaks glob protection for next char

[Denys Vlasenko <vda.linux@xxxxxxxxxxxxxx>]

On Mon, Feb 19, 2018 at 11:13 PM, Harald van Dijk <harald@xxxxxxxxxxx> wrote:
> On 2/18/18 11:50 PM, Harald van Dijk wrote:
>> On 2/14/18 11:50 PM, Harald van Dijk wrote:
>>> On 2/14/18 10:44 PM, Harald van Dijk wrote:
>>>> On 2/14/18 9:03 PM, Harald van Dijk wrote:
>>>>> On 13/02/2018 14:53, Denys Vlasenko wrote:
>>>>>> $ >'\zzzz'
>>>>>> $ >'\wwww'
>>>>>> $ dash -c 'echo "\*"'
>>>>>> \wwww \zzzz
>>>>>
>>>>>
>>>>> [...]
>>>>>
>>>>> Currently:
>>>>>
>>>>> $ dash -c 'foo=a; echo "<${foo#[a\]]}>"'
>>>>> <>
>>>>>
>>>>> This is what I expect, and also what bash, ksh and posh do.
>>>>>
>>>>> With your patch:
>>>>>
>>>>> $ dash -c 'foo=a; echo "<${foo#[a\]]}>"'
>>>>> <a>
>>>>
>>>> Does the attached look right as an alternative? It treats a quoted
>>>> backslash the same way as if it were preceded by CTLESC in _rmescapes. It
>>>> passes your test case and mine, but I'll do more extensive testing.
>>>
>>> It causes preglob's string to potentially grow larger than the original.
>>> When called with RMESCAPE_ALLOC, that can be handled by increasing the
>>> buffer size, but preglob also gets called without RMESCAPE_ALLOC to modify a
>>> string in-place. That's never going to work with this approach. Back to the
>>> drawing board...
>>
>> There is a way to make it work: ensure sufficient memory is always
>> available. Instead of inserting CTLESC, which caused problems,
>> CTLQUOTEMARK+CTLQUOTEMARK can be inserted instead. It's effectively a no-op
>> here.
>
> It required one obvious additional trivial change to the CHECKSTRSPACE
> invocation, but with that added, the attached passed all testing I could
> think of. Does this look okay to include, did I miss something, or is there
> perhaps a better alternative?

I propose replacing this:

                if (*p == (char)CTLESC) {
                        p++;
+                       goto escape;
+               } else if (*p == '\\') {
+                       if (inquotes) {
+escape:
+                               if (notescaped)
+                                       *q++ = '\\';
+                       } else {
+                               /* naked back slash */
+                               notescaped = 0;
+                               goto copy;
+                       }

with equivalent

                if (*p == (char)CTLESC) {
                        p++;
+                       goto escape;
+               }
+               if (*p == '\\') {
+                       if (!inquotes) {
+                               /* naked back slash */
+                               notescaped = 0;
+                               goto copy;
+                       }
+escape:
+                       if (notescaped)
+                               *q++ = '\\';
--
To unsubscribe from this list: send the line "unsubscribe dash" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html