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Re: Genfscon 'dash' issue
From: Joshua Brindle <method_at_nospam>Date: Wed Oct 15 2008 - 15:08:39 GMT
To: Stephen Smalley <sds@tycho.nsa.gov>
Stephen Smalley wrote:
> On Tue, 2008-10-14 at 02:00 +0000, korkishko Tymur wrote:
>
>> I have checked policy_parse.y. It has following rule for genfscon:
>>
>> genfs_context_def : GENFSCON identifier path '-' identifier security_context_def
>> {if (define_genfs_context(1)) return -1;}
>> | GENFSCON identifier path '-' '-' {insert_id("-", 0);} security_context_def
>> {if (define_genfs_context(1)) return -1;}
>> | GENFSCON identifier path security_context_def
>> {if (define_genfs_context(0)) return -1;}
>>
>> The rule for path definition (in policy_scan.l) has already included '-' (dash):
>>
>> "/"({alnum}|[_.-/])* { return(PATH); }
>>
>> In my understanding (maybe wrong), path is parsed first (and path might include '-') and only then separate '-' is parsed.
>> But it still produces an error if path definition is correct and includes '-'.
>>
>> Any ideas/patches how to fix grammar rules are welcomed.
>>
>
> This looks like a bug in policy_scan.l - we are not escaping (via
> backslash) special characters in the pattern and thus the "-" (dash) is
> being interpreted rather than taken literally. The same would seemingly
> apply for "." (dot), and would seem relevant not only to PATH but also
> for IDENTIFIER. The patch below seems to fix this issue for me:
>
> diff --git a/checkpolicy/policy_scan.l b/checkpolicy/policy_scan.l
> index 9bc6e10..b55c659 100644
> --- a/checkpolicy/policy_scan.l
> +++ b/checkpolicy/policy_scan.l
> @@ -207,8 +207,8 @@ policycap |
> POLICYCAP { return(POLICYCAP); }
> permissive |
> PERMISSIVE { return(PERMISSIVE); }
> -"/"({alnum}|[_.-/])* { return(PATH); }
> -{letter}({alnum}|[_-])*([.]?({alnum}|[_-]))* { return(IDENTIFIER); }
> +"/"({alnum}|[_\.\-/])* { return(PATH); }
> +{letter}({alnum}|[_\-])*([\.]?({alnum}|[_\-]))* { return(IDENTIFIER); }
> {digit}+ { return(NUMBER); }
> {digit}{1,3}(\.{digit}{1,3}){3} { return(IPV4_ADDR); }
> {hexval}{0,4}":"{hexval}{0,4}":"({hexval}|[:.])* { return(IPV6_ADDR); }
>
>
It looks like I merged this a little hastily. According to the regex manual:
Character ranges can also be included in a character set, by writing two characters with a - between them. Thus, [a-z] matches any lower-case letter. Ranges may be intermixed freely with individual characters, as in [a-z$%.], which matches any lower case letter or $, % or period.
Note that the usual special characters are not special any more inside a character set. A completely different set of special characters exists inside character sets: ], - and ^
Therefore \. in a character set means both '\' and '.' are allowed. The standard way to add a dash to the character set is to put it last. I'll update the patch when I have a chance. -- This message was distributed to subscribers of the selinux mailing list. If you no longer wish to subscribe, send mail to majordomo@tycho.nsa.gov with the words "unsubscribe selinux" without quotes as the message.