[apparmor] [PATCH 3/6] parser: Create a label parsing function that doesn't exit or malloc

[John Johansen]

On 03/04/2016 12:16 AM, Tyler Hicks wrote:
> This patch separates the label parsing functionality from the program
> termination and memory allocation duties of parse_label(). This will
> ultimately help in creating simple helper functions that simply need to
> check if a label contains a namespace.
> 
> Signed-off-by: Tyler Hicks <tyhicks at canonical.com>

Acked-by: John Johansen <john.johansen at canonical.com>



> ---
>  parser/parser_misc.c | 94 +++++++++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 75 insertions(+), 19 deletions(-)
> 
> diff --git a/parser/parser_misc.c b/parser/parser_misc.c
> index 2348189..d0d8115 100644
> --- a/parser/parser_misc.c
> +++ b/parser/parser_misc.c
> @@ -569,24 +569,44 @@ int parse_X_mode(const char *X, int valid, const char *str_mode, int *mode, int
>  	return 1;
>  }
>  
> -void parse_label(char **ns, char **name, const char *label)
> +/**
> + * parse_label - break a label down to the namespace and profile name
> + * @ns: Will point to the first char in the namespace upon return or NULL
> + *      if no namespace is present
> + * @ns_len: Number of chars in the namespace string or 0 if no namespace
> + *          is present
> + * @name: Will point to the first char in the profile name upon return
> + * @name_len: Number of chars in the name string
> + * @label: The label to parse into namespace and profile name
> + *
> + * The returned pointers will point to locations within the original
> + * @label string. No new strings are allocated.
> + *
> + * Returns 0 upon success or non-zero with @ns, @ns_len, @name, and
> + * @name_len undefined upon error. Error codes are:
> + *
> + * 1) Namespace is not terminated despite @label starting with ':'
> + * 2) Namespace is empty meaning @label starts with "::"
> + * 3) Profile name is empty
> + */
> +static int _parse_label(char **ns, size_t *ns_len,
> +			char **name, size_t *name_len,
> +			const char *label)
>  {
>  	const char *name_start = NULL;
> -	char *_ns = NULL;
> -	char *_name = NULL;
> +	const char *ns_start = NULL;
> +	const char *ns_end = NULL;
>  
>  	if (label[0] != ':') {
>  		/* There is no namespace specified in the label */
>  		name_start = label;
>  	} else {
>  		/* A leading ':' indicates that a namespace is specified */
> -		const char *ns_start = label + 1;
> -		const char *ns_end = strstr(ns_start, ":");
> +		ns_start = label + 1;
> +		ns_end = strstr(ns_start, ":");
>  
>  		if (!ns_end)
> -			yyerror(_("Namespace not terminated: %s\n"), label);
> -		else if (ns_end - ns_start == 0)
> -			yyerror(_("Empty namespace: %s\n"), label);
> +			return 1;
>  
>  		/**
>  		 * Handle either of the two namespace formats:
> @@ -596,23 +616,59 @@ void parse_label(char **ns, char **name, const char *label)
>  		name_start = ns_end + 1;
>  		if (!strncmp(name_start, "//", 2))
>  			name_start += 2;
> -
> -		_ns = strndup(ns_start, ns_end - ns_start);
> -		if (!_ns)
> -			yyerror(_("Memory allocation error."));
>  	}
>  
> -	if (!strlen(name_start))
> +	/**
> +	 * The casts below are to allow @label to be const, signifying
> +	 * that this function doesn't modify it, while allowing callers to
> +	 * decide if they want to pass in pointers to const or non-const
> +	 * strings.
> +	 */
> +	*ns = (char *)ns_start;
> +	*name = (char *)name_start;
> +	*ns_len = ns_end - ns_start;
> +	*name_len = strlen(name_start);
> +
> +	if (*ns && *ns_len == 0)
> +		return 2;
> +	else if (*name_len == 0)
> +		return 3;
> +
> +	return 0;
> +}
> +
> +void parse_label(char **_ns, char **_name, const char *label)
> +{
> +	char *ns = NULL;
> +	char *name = NULL;
> +	size_t ns_len = 0;
> +	size_t name_len = 0;
> +	int res;
> +
> +	res = _parse_label(&ns, &ns_len, &name, &name_len, label);
> +	if (res == 1) {
> +		yyerror(_("Namespace not terminated: %s\n"), label);
> +	} else if (res == 2) {
> +		yyerror(_("Empty namespace: %s\n"), label);
> +	} else if (res == 3) {
>  		yyerror(_("Empty named transition profile name: %s\n"), label);
> +	} else if (res != 0) {
> +		yyerror(_("Unknown error while parsing label: %s\n"), label);
> +	}
>  
> -	_name = strdup(name_start);
> -	if (!_name) {
> -		free(_ns);
> -		yyerror(_("Memory allocation error."));
> +	if (ns) {
> +		*_ns = strndup(ns, ns_len);
> +		if (!*_ns)
> +			yyerror(_("Memory allocation error."));
> +	} else {
> +		*_ns = NULL;
>  	}
>  
> -	*ns = _ns;
> -	*name = _name;
> +	*_name = strndup(name, name_len);
> +	if (!*_name) {
> +		free(*_ns);
> +		yyerror(_("Memory allocation error."));
> +	}
>  }
>  
>  void parse_named_transition_target(struct named_transition *nt,
>