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package pt
import (
"bytes"
"fmt"
"sort"
"strings"
)
// Key–value mappings for the representation of client and server options.
// Args maps a string key to a list of values. It is similar to url.Values.
type Args map[string][]string
// Get the first value associated with the given key. If there are any values
// associated with the key, the value return has the value and ok is set to
// true. If there are no values for the given key, value is "" and ok is false.
// If you need access to multiple values, use the map directly.
func (args Args) Get(key string) (value string, ok bool) {
if args == nil {
return "", false
}
vals, ok := args[key]
if !ok || len(vals) == 0 {
return "", false
}
return vals[0], true
}
// Append value to the list of values for key.
func (args Args) Add(key, value string) {
args[key] = append(args[key], value)
}
// Return the index of the next unescaped byte in s that is in the term set, or
// else the length of the string if no terminators appear. Additionally return
// the unescaped string up to the returned index.
func indexUnescaped(s string, term []byte) (int, string, error) {
var i int
unesc := make([]byte, 0)
for i = 0; i < len(s); i++ {
b := s[i]
// A terminator byte?
if bytes.IndexByte(term, b) != -1 {
break
}
if b == '\\' {
i++
if i >= len(s) {
return 0, "", fmt.Errorf("nothing following final escape in %q", s)
}
b = s[i]
}
unesc = append(unesc, b)
}
return i, string(unesc), nil
}
// Parse a name–value mapping as from an encoded SOCKS username/password.
//
// "First the '<Key>=<Value>' formatted arguments MUST be escaped, such that all
// backslash, equal sign, and semicolon characters are escaped with a
// backslash."
func parseClientParameters(s string) (args Args, err error) {
args = make(Args)
if len(s) == 0 {
return
}
i := 0
for {
var key, value string
var offset, begin int
begin = i
// Read the key.
offset, key, err = indexUnescaped(s[i:], []byte{'=', ';'})
if err != nil {
return
}
i += offset
// End of string or no equals sign?
if i >= len(s) || s[i] != '=' {
err = fmt.Errorf("no equals sign in %q", s[begin:i])
return
}
// Skip the equals sign.
i++
// Read the value.
offset, value, err = indexUnescaped(s[i:], []byte{';'})
if err != nil {
return
}
i += offset
if len(key) == 0 {
err = fmt.Errorf("empty key in %q", s[begin:i])
return
}
args.Add(key, value)
if i >= len(s) {
break
}
// Skip the semicolon.
i++
}
return args, nil
}
// Parse a transport–name–value mapping as from TOR_PT_SERVER_TRANSPORT_OPTIONS.
//
// "...a semicolon-separated list of <key>:<value> pairs, where <key> is a PT
// name and <value> is a k=v string value with options that are to be passed to
// the transport. Colons, semicolons, equal signs and backslashes must be
// escaped with a backslash."
// Example: scramblesuit:key=banana;automata:rule=110;automata:depth=3
func parseServerTransportOptions(s string) (opts map[string]Args, err error) {
opts = make(map[string]Args)
if len(s) == 0 {
return
}
i := 0
for {
var methodName, key, value string
var offset, begin int
begin = i
// Read the method name.
offset, methodName, err = indexUnescaped(s[i:], []byte{':', '=', ';'})
if err != nil {
return
}
i += offset
// End of string or no colon?
if i >= len(s) || s[i] != ':' {
err = fmt.Errorf("no colon in %q", s[begin:i])
return
}
// Skip the colon.
i++
// Read the key.
offset, key, err = indexUnescaped(s[i:], []byte{'=', ';'})
if err != nil {
return
}
i += offset
// End of string or no equals sign?
if i >= len(s) || s[i] != '=' {
err = fmt.Errorf("no equals sign in %q", s[begin:i])
return
}
// Skip the equals sign.
i++
// Read the value.
offset, value, err = indexUnescaped(s[i:], []byte{';'})
if err != nil {
return
}
i += offset
if len(methodName) == 0 {
err = fmt.Errorf("empty method name in %q", s[begin:i])
return
}
if len(key) == 0 {
err = fmt.Errorf("empty key in %q", s[begin:i])
return
}
if opts[methodName] == nil {
opts[methodName] = make(Args)
}
opts[methodName].Add(key, value)
if i >= len(s) {
break
}
// Skip the semicolon.
i++
}
return opts, nil
}
// Escape backslashes and all the bytes that are in set.
func backslashEscape(s string, set []byte) string {
var buf bytes.Buffer
for _, b := range []byte(s) {
if b == '\\' || bytes.IndexByte(set, b) != -1 {
buf.WriteByte('\\')
}
buf.WriteByte(b)
}
return buf.String()
}
// Encode a name–value mapping so that it is suitable to go in the ARGS option
// of an SMETHOD line. The output is sorted by key. The "ARGS:" prefix is not
// added.
//
// "Equal signs and commas [and backslashes] MUST be escaped with a backslash."
func encodeSmethodArgs(args Args) string {
if args == nil {
return ""
}
keys := make([]string, 0, len(args))
for key := range args {
keys = append(keys, key)
}
sort.Strings(keys)
escape := func(s string) string {
return backslashEscape(s, []byte{'=', ','})
}
var pairs []string
for _, key := range keys {
for _, value := range args[key] {
pairs = append(pairs, escape(key)+"="+escape(value))
}
}
return strings.Join(pairs, ",")
}
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