[apparmor] [PATCH] [parsers] allow for nested alternations expressions

[John Johansen]

On 09/05/2013 12:55 PM, John Johansen wrote:
> allow for nested alternations in regex patterns
> 
> Currently alternations are limited to a single level, make it so we can
> nest alternations.
> 
> Note: this is a temporary solution to the problem. Long term this routine
> to convert to pcre will go away when native parsing of aare is added to
> the backend.
> 
> Signed-off-by: John Johansen <john.johansen at canonical.com>

ping, or I'll commit

> 
> === modified file 'documentation/AppArmor Develper 1 - Kernel Notes.odt'
> Binary files documentation/AppArmor Develper 1 - Kernel Notes.odt	2013-05-02 17:57:23 +0000 and documentation/AppArmor Develper 1 - Kernel Notes.odt	2013-08-20 22:30:41 +0000 differ
> === modified file 'documentation/AppArmor Policy.odt'
> Binary files documentation/AppArmor Policy.odt	2013-06-14 19:35:51 +0000 and documentation/AppArmor Policy.odt	2013-07-26 13:10:32 +0000 differ
> === modified file 'parser/parser_regex.c'
> --- parser/parser_regex.c	2013-07-31 16:05:51 +0000
> +++ parser/parser_regex.c	2013-09-05 19:47:59 +0000
> @@ -91,7 +91,7 @@
>  		_dest += _len; \
>  	}
>  #define update_re_pos(X) if (!(*first_re_pos)) { *first_re_pos = (X); }
> -
> +#define MAX_ALT_DEPTH 50
>  	*first_re_pos = 0;
>  
>  	int ret = TRUE;
> @@ -105,6 +105,7 @@
>  	BOOL bEscape = 0;	/* flag to indicate escape */
>  	int ingrouping = 0;	/* flag to indicate {} context */
>  	int incharclass = 0;	/* flag to indicate [ ] context */
> +	int grouping_count[MAX_ALT_DEPTH];
>  
>  	error = e_no_error;
>  	ptype = ePatternBasic;	/* assume no regex */
> @@ -244,13 +245,14 @@
>  				/* { is a PCRE special character */
>  				STORE("\\{", dptr, 2);
>  			} else {
> -				if (ingrouping) {
> +				update_re_pos(sptr - aare);
> +				ingrouping++;
> +				if (ingrouping >= MAX_ALT_DEPTH) {
>  					error = e_parse_error;
> -					PERROR(_("%s: Illegal open {, nesting groupings not allowed\n"),
> -					       progname);
> +					PERROR(_("%s: Regex grouping error: Exceeded maximum nesting of {}\n"), progname);
> +
>  				} else {
> -					update_re_pos(sptr - aare);
> -					ingrouping = 1;
> +					grouping_count[ingrouping] = 0;
>  					ptype = ePatternRegex;
>  					STORE("(", dptr, 1);
>  				}
> @@ -262,24 +264,18 @@
>  				/* { is a PCRE special character */
>  				STORE("\\}", dptr, 2);
>  			} else {
> -				if (ingrouping <= 1) {
> -
> -					error = e_parse_error;
> -
> -					if (ingrouping == 1) {
> -						PERROR(_("%s: Regex grouping error: Invalid number of items between {}\n"),
> -						       progname);
> -
> -						ingrouping = 0;	/* prevent further errors */
> -
> -					} else {	/* ingrouping == 0 */
> -						PERROR(_("%s: Regex grouping error: Invalid close }, no matching open { detected\n"),
> -						       progname);
> -					}
> -				} else {	/* ingrouping > 1 */
> +				if (grouping_count[ingrouping] == 0) {
> +					error = e_parse_error;
> +					PERROR(_("%s: Regex grouping error: Invalid number of items between {}\n"), progname);
> +
> +				}
> +				ingrouping--;
> +				if (ingrouping < 0) {
> +					error = e_parse_error;
> +					PERROR(_("%s: Regex grouping error: Invalid close }, no matching open { detected\n"), progname);
>  					ingrouping = 0;
> -					STORE(")", dptr, 1);
>  				}
> +				STORE(")", dptr, 1);
>  			}	/* bEscape */
>  
>  			break;
> @@ -293,7 +289,7 @@
>  				STORE(sptr, dptr, 1);
>  			} else {
>  				if (ingrouping) {
> -					++ingrouping;
> +					grouping_count[ingrouping]++;
>  					STORE("|", dptr, 1);
>  				} else {
>  					STORE(sptr, dptr, 1);
> 
>