/usr/share/gocode/src/github.com/jasonish/go-idsrules/parse.go is in golang-github-jasonish-go-idsrules-dev 0.0~git20170503.0.c646b91-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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// Copyright (c) 2016 Jason Ish
//
// Permission is hereby granted, free of charge, to any person
// obtaining a copy of this software and associated documentation
// files (the "Software"), to deal in the Software without
// restriction, including without limitation the rights to use, copy,
// modify, merge, publish, distribute, sublicense, and/or sell copies
// of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
// BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
// ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
// CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
package idsrules
import (
"bufio"
"fmt"
"io"
"strconv"
"strings"
)
// RuleParseError is the error returned when a parsing error occurs.
type RuleParseError struct {
// The rule that failed to parse.
Rule string
// Some message describing the parse error.
Message string
}
func (e *RuleParseError) Error() string {
return fmt.Sprintf("%s: %s", e.Message, e.Rule)
}
func newIcompleteRuleError(rule string) *RuleParseError {
return &RuleParseError{
Rule: rule,
Message: "incomplete",
}
}
// Remove leading and trailing quotes from a string.
func trimQuotes(buf string) string {
buflen := len(buf)
if buflen == 0 {
return buf
}
if buf[0:1] == "\"" && buf[buflen-1:buflen] == "\"" {
return buf[1: buflen-1]
}
return buf
}
// Remove leading white space from a string.
func trimLeadingWhiteSpace(buf string) string {
return strings.TrimLeft(buf, " ")
}
func splitAt(buf string, sep string) (string, string) {
var leading string
var trailing string
parts := strings.SplitN(buf, sep, 2)
if len(parts) > 1 {
trailing = strings.TrimSpace(parts[1])
}
leading = strings.TrimSpace(parts[0])
return leading, trailing
}
// Parse the next rule option from the provided rule.
//
// The option, argument and the remainder of the rule are returned.
func parseOption(rule string) (string, string, string, error) {
var option string
var arg string
// Strip any leading space.
rule = trimLeadingWhiteSpace(rule)
hasArg := false
optend := strings.IndexFunc(rule, func(r rune) bool {
switch r {
case ';':
return true
case ':':
hasArg = true
return true
}
return false
})
if optend < 0 {
return option, arg, rule, fmt.Errorf("unterminated option")
}
option = rule[0:optend]
rule = rule[optend+1:]
if hasArg {
if len(rule) == 0 {
return option, arg, rule, fmt.Errorf("no argument")
}
escaped := false
argend := strings.IndexFunc(rule, func(r rune) bool {
if escaped {
escaped = false
} else if r == '\\' {
escaped = true
} else if r == ';' {
return true
}
return false
})
if argend < 0 {
return option, arg, rule,
fmt.Errorf("unterminated option argument")
}
arg = rule[:argend]
rule = rule[argend+1:]
}
return option, trimQuotes(arg), rule, nil
}
// Parse an IDS rule from the provided string buffer.
func Parse(buf string) (Rule, error) {
rule := Rule{
Raw: buf,
}
// Removing leading space.
buf = trimLeadingWhiteSpace(buf)
// Check enable/disable status.
if !strings.HasPrefix(buf, "#") {
rule.Enabled = true
} else {
buf = strings.TrimPrefix(buf, "#")
buf = trimLeadingWhiteSpace(buf)
}
action, rem := splitAt(buf, " ")
rule.Action = action
if len(rem) == 0 {
return rule, newIcompleteRuleError(buf)
}
proto, rem := splitAt(rem, " ")
rule.Proto = proto
if len(rem) == 0 {
return rule, newIcompleteRuleError(buf)
}
sourceAddr, rem := splitAt(rem, " ")
rule.SourceAddr = sourceAddr
if len(rem) == 0 {
return rule, newIcompleteRuleError(buf)
}
sourcePort, rem := splitAt(rem, " ")
rule.SourcePort = sourcePort
if len(rem) == 0 {
return rule, newIcompleteRuleError(buf)
}
direction, rem := splitAt(rem, " ")
if !validateDirection(direction) {
return rule, fmt.Errorf("invalid direction: %s", direction)
}
rule.Direction = direction
if len(rem) == 0 {
return rule, newIcompleteRuleError(buf)
}
destAddr, rem := splitAt(rem, " ")
rule.DestAddr = destAddr
if len(rem) == 0 {
return rule, newIcompleteRuleError(buf)
}
destPort, rem := splitAt(rem, " ")
rule.DestPort = destPort
if len(rem) == 0 {
return rule, newIcompleteRuleError(buf)
}
offset := 0
// Check that then next char is a (.
if rem[offset:offset+1] != "(" {
return rule, fmt.Errorf("expected (, got %s", rem[0:1])
}
offset++
buf = rem[offset:]
// Parse options.
var option string
var arg string
var err error
for {
if len(buf) == 0 {
return rule, newIcompleteRuleError(buf)
}
buf = trimLeadingWhiteSpace(buf)
if strings.HasPrefix(buf, ")") {
// Done.
break
}
option, arg, buf, err = parseOption(buf)
if err != nil {
return rule, err
}
ruleOption := RuleOption{option, arg}
rule.Options = append(rule.Options, ruleOption)
switch option {
case "msg":
rule.Msg = arg
case "sid":
sid, err := strconv.ParseUint(arg, 10, 64)
if err != nil {
return rule, fmt.Errorf("failed to parse sid: %s", arg)
}
rule.Sid = sid
case "gid":
gid, err := strconv.ParseUint(arg, 10, 64)
if err != nil {
return rule, fmt.Errorf("failed to parse sid: %s", arg)
}
rule.Gid = gid
}
}
return rule, nil
}
// ParseReader parses multiple rules from a reader.
func ParseReader(reader io.Reader) ([]Rule, error) {
rules := make([]Rule, 0)
ruleReader := NewRuleReader(reader)
for {
rule, err := ruleReader.Next()
if err != nil {
if err == io.EOF {
break
}
continue
}
rules = append(rules, rule)
}
return rules, nil
}
// RuleReader parses rules one by from an underlying reader.
type RuleReader struct {
reader *bufio.Reader
}
// NewRuleReader creates a new RuleReader reading from a reader.
func NewRuleReader(reader io.Reader) *RuleReader {
ruleReader := &RuleReader{
reader: bufio.NewReader(reader),
}
return ruleReader
}
func (r *RuleReader) readLine() (string, error) {
bytes, err := r.reader.ReadBytes('\n')
if err != nil && len(bytes) == 0 {
return "", err
}
return strings.TrimSpace(string(bytes)), nil
}
// Next returns the next rule read from the reader. Empty lines and commented
// out lines are skipped. Any other line that doesn't parse as a rule is
// considered an error.
func (r *RuleReader) Next() (Rule, error) {
ruleString := ""
for {
line, err := r.readLine()
if err != nil && line == "" {
return Rule{}, err
}
if len(line) == 0 {
continue
}
if strings.HasSuffix(line, "\\") {
ruleString = fmt.Sprintf("%s%s",
ruleString, line[0:len(line)-1])
continue
}
ruleString = fmt.Sprintf("%s%s", ruleString, line)
rule, err := Parse(ruleString)
if err != nil {
if strings.HasPrefix(ruleString, "#") {
ruleString = ""
continue
}
return Rule{}, err
}
ruleString = ""
return rule, err
}
}
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