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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2021 Canonical Ltd
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package utils
import (
"fmt"
"regexp"
)
type PathPattern struct {
pattern string
regex *regexp.Regexp
}
const maxGroupDepth = 50
type GlobFlags int
const (
globDefault GlobFlags = 1 << iota
globNull
)
// createRegex converts the apparmor-like glob sequence into a regex. Loosely
// using this as reference:
// https://gitlab.com/apparmor/apparmor/-/blob/master/parser/parser_regex.c#L107
func createRegex(pattern string, glob GlobFlags, allowCommas bool) (string, error) {
regex := "^"
appendGlob := func(defaultGlob, nullGlob string) {
var pattern string
switch glob {
case globDefault:
pattern = defaultGlob
case globNull:
pattern = nullGlob
}
regex += pattern
}
const (
noSlashOrNull = `[^/\x00]`
noSlash = `[^/]`
)
escapeNext := false
currentGroupLevel := 0
inCharClass := false
skipNext := false
itemCountInGroup := new([maxGroupDepth + 1]int)
for i, ch := range pattern {
if escapeNext {
regex += regexp.QuoteMeta(string(ch))
escapeNext = false
continue
}
if skipNext {
skipNext = false
continue
}
if inCharClass && ch != '\\' && ch != ']' {
// no characters are special other than '\' and ']'
regex += string(ch)
continue
}
switch ch {
case '\\':
escapeNext = true
case '*':
if regex[len(regex)-1] == '/' {
// if the * is at the end of the pattern or is followed by a
// '/' we don't want it to match an empty string:
// /foo/* -> should not match /foo/
// /foo/*bar -> should match /foo/bar
// /*/foo -> should not match //foo
pos := i + 1
for len(pattern) > pos && pattern[pos] == '*' {
pos++
}
if len(pattern) <= pos || pattern[pos] == '/' {
appendGlob(noSlashOrNull, noSlash)
}
}
if len(pattern) > i+1 && pattern[i+1] == '*' {
// Handle **
appendGlob("[^\\x00]*", ".*")
skipNext = true
} else {
appendGlob(noSlashOrNull+"*", noSlash+"*")
}
case '?':
appendGlob(noSlashOrNull, noSlash)
case '[':
inCharClass = true
regex += string(ch)
case ']':
if !inCharClass {
return "", fmt.Errorf("pattern contains unmatching ']': %q", pattern)
}
inCharClass = false
regex += string(ch)
case '{':
currentGroupLevel++
if currentGroupLevel > maxGroupDepth {
return "", fmt.Errorf("maximum group depth exceeded: %q", pattern)
}
itemCountInGroup[currentGroupLevel] = 0
regex += "("
case '}':
if currentGroupLevel <= 0 {
return "", fmt.Errorf("invalid closing brace, no matching open { found: %q", pattern)
}
if itemCountInGroup[currentGroupLevel] == 0 {
return "", fmt.Errorf("invalid number of items between {}: %q", pattern)
}
currentGroupLevel--
regex += ")"
case ',':
if currentGroupLevel > 0 {
itemCountInGroup[currentGroupLevel]++
regex += "|"
} else if allowCommas {
// treat commas outside of groups as literal commas
regex += ","
} else {
return "", fmt.Errorf("cannot use ',' outside of group or character class")
}
default:
// take literal character (with quoting if needed)
regex += regexp.QuoteMeta(string(ch))
}
}
if currentGroupLevel > 0 {
return "", fmt.Errorf("missing %d closing brace(s): %q", currentGroupLevel, pattern)
}
if inCharClass {
return "", fmt.Errorf("missing closing bracket ']': %q", pattern)
}
if escapeNext {
return "", fmt.Errorf("expected character after '\\': %q", pattern)
}
regex += "$"
return regex, nil
}
func NewPathPattern(pattern string, allowCommas bool) (*PathPattern, error) {
regexPattern, err := createRegex(pattern, globDefault, allowCommas)
if err != nil {
return nil, err
}
regex := regexp.MustCompile(regexPattern)
pp := &PathPattern{pattern, regex}
return pp, nil
}
func (pp *PathPattern) Matches(path string) bool {
return pp.regex.MatchString(path)
}
|
