package dns
import (
"io"
"log"
"os"
"strconv"
"strings"
)
type debugging bool
const debug debugging = false
func (d debugging) Printf(format string, args ...interface{}) {
if d {
log.Printf(format, args...)
}
}
const maxTok = 2048 // Largest token we can return.
const maxUint16 = 1<<16 - 1
// Tokinize a RFC 1035 zone file. The tokenizer will normalize it:
// * Add ownernames if they are left blank;
// * Suppress sequences of spaces;
// * Make each RR fit on one line (_NEWLINE is send as last)
// * Handle comments: ;
// * Handle braces - anywhere.
const (
// Zonefile
zEOF = iota
zString
zBlank
zQuote
zNewline
zRrtpe
zOwner
zClass
zDirOrigin // $ORIGIN
zDirTtl // $TTL
zDirInclude // $INCLUDE
zDirGenerate // $GENERATE
// Privatekey file
zValue
zKey
zExpectOwnerDir // Ownername
zExpectOwnerBl // Whitespace after the ownername
zExpectAny // Expect rrtype, ttl or class
zExpectAnyNoClass // Expect rrtype or ttl
zExpectAnyNoClassBl // The whitespace after _EXPECT_ANY_NOCLASS
zExpectAnyNoTtl // Expect rrtype or class
zExpectAnyNoTtlBl // Whitespace after _EXPECT_ANY_NOTTL
zExpectRrtype // Expect rrtype
zExpectRrtypeBl // Whitespace BEFORE rrtype
zExpectRdata // The first element of the rdata
zExpectDirTtlBl // Space after directive $TTL
zExpectDirTtl // Directive $TTL
zExpectDirOriginBl // Space after directive $ORIGIN
zExpectDirOrigin // Directive $ORIGIN
zExpectDirIncludeBl // Space after directive $INCLUDE
zExpectDirInclude // Directive $INCLUDE
zExpectDirGenerate // Directive $GENERATE
zExpectDirGenerateBl // Space after directive $GENERATE
)
// ParseError is a parsing error. It contains the parse error and the location in the io.Reader
// where the error occurred.
type ParseError struct {
file string
err string
lex lex
}
func (e *ParseError) Error() (s string) {
if e.file != "" {
s = e.file + ": "
}
s += "dns: " + e.err + ": " + strconv.QuoteToASCII(e.lex.token) + " at line: " +
strconv.Itoa(e.lex.line) + ":" + strconv.Itoa(e.lex.column)
return
}
type lex struct {
token string // text of the token
tokenUpper string // uppercase text of the token
length int // length of the token
err bool // when true, token text has lexer error
value uint8 // value: zString, _BLANK, etc.
line int // line in the file
column int // column in the file
torc uint16 // type or class as parsed in the lexer, we only need to look this up in the grammar
comment string // any comment text seen
}
// Token holds the token that are returned when a zone file is parsed.
type Token struct {
// The scanned resource record when error is not nil.
RR
// When an error occurred, this has the error specifics.
Error *ParseError
// A potential comment positioned after the RR and on the same line.
Comment string
}
// NewRR reads the RR contained in the string s. Only the first RR is
// returned. If s contains no RR, return nil with no error. The class
// defaults to IN and TTL defaults to 3600. The full zone file syntax
// like $TTL, $ORIGIN, etc. is supported. All fields of the returned
// RR are set, except RR.Header().Rdlength which is set to 0.
func NewRR(s string) (RR, error) {
if len(s) > 0 && s[len(s)-1] != '\n' { // We need a closing newline
return ReadRR(strings.NewReader(s+"\n"), "")
}
return ReadRR(strings.NewReader(s), "")
}
// ReadRR reads the RR contained in q.
// See NewRR for more documentation.
func ReadRR(q io.Reader, filename string) (RR, error) {
r := <-parseZoneHelper(q, ".", filename, 1)
if r == nil {
return nil, nil
}
if r.Error != nil {
return nil, r.Error
}
return r.RR, nil
}
// ParseZone reads a RFC 1035 style zonefile from r. It returns *Tokens on the
// returned channel, which consist out the parsed RR, a potential comment or an error.
// If there is an error the RR is nil. The string file is only used
// in error reporting. The string origin is used as the initial origin, as
// if the file would start with: $ORIGIN origin .
// The directives $INCLUDE, $ORIGIN, $TTL and $GENERATE are supported.
// The channel t is closed by ParseZone when the end of r is reached.
//
// Basic usage pattern when reading from a string (z) containing the
// zone data:
//
// for x := range dns.ParseZone(strings.NewReader(z), "", "") {
// if x.Error != nil {
// // log.Println(x.Error)
// } else {
// // Do something with x.RR
// }
// }
//
// Comments specified after an RR (and on the same line!) are returned too:
//
// foo. IN A 10.0.0.1 ; this is a comment
//
// The text "; this is comment" is returned in Token.Comment. Comments inside the
// RR are discarded. Comments on a line by themselves are discarded too.
func ParseZone(r io.Reader, origin, file string) chan *Token {
return parseZoneHelper(r, origin, file, 10000)
}
func parseZoneHelper(r io.Reader, origin, file string, chansize int) chan *Token {
t := make(chan *Token, chansize)
go parseZone(r, origin, file, t, 0)
return t
}
func parseZone(r io.Reader, origin, f string, t chan *Token, include int) {
defer func() {
if include == 0 {
close(t)
}
}()
s := scanInit(r)
c := make(chan lex)
// Start the lexer
go zlexer(s, c)
// 6 possible beginnings of a line, _ is a space
// 0. zRRTYPE -> all omitted until the rrtype
// 1. zOwner _ zRrtype -> class/ttl omitted
// 2. zOwner _ zString _ zRrtype -> class omitted
// 3. zOwner _ zString _ zClass _ zRrtype -> ttl/class
// 4. zOwner _ zClass _ zRrtype -> ttl omitted
// 5. zOwner _ zClass _ zString _ zRrtype -> class/ttl (reversed)
// After detecting these, we know the zRrtype so we can jump to functions
// handling the rdata for each of these types.
if origin == "" {
origin = "."
}
origin = Fqdn(origin)
if _, ok := IsDomainName(origin); !ok {
t <- &Token{Error: &ParseError{f, "bad initial origin name", lex{}}}
return
}
st := zExpectOwnerDir // initial state
var h RR_Header
var defttl uint32 = defaultTtl
var prevName string
for l := range c {
// Lexer spotted an error already
if l.err == true {
t <- &Token{Error: &ParseError{f, l.token, l}}
return
}
switch st {
case zExpectOwnerDir:
// We can also expect a directive, like $TTL or $ORIGIN
h.Ttl = defttl
h.Class = ClassINET
switch l.value {
case zNewline:
st = zExpectOwnerDir
case zOwner:
h.Name = l.token
if l.token[0] == '@' {
h.Name = origin
prevName = h.Name
st = zExpectOwnerBl
break
}
if h.Name[l.length-1] != '.' {
h.Name = appendOrigin(h.Name, origin)
}
_, ok := IsDomainName(l.token)
if !ok {
t <- &Token{Error: &ParseError{f, "bad owner name", l}}
return
}
prevName = h.Name
st = zExpectOwnerBl
case zDirTtl:
st = zExpectDirTtlBl
case zDirOrigin:
st = zExpectDirOriginBl
case zDirInclude:
st = zExpectDirIncludeBl
case zDirGenerate:
st = zExpectDirGenerateBl
case zRrtpe:
h.Name = prevName
h.Rrtype = l.torc
st = zExpectRdata
case zClass:
h.Name = prevName
h.Class = l.torc
st = zExpectAnyNoClassBl
case zBlank:
// Discard, can happen when there is nothing on the
// line except the RR type
case zString:
ttl, ok := stringToTtl(l.token)
if !ok {
t <- &Token{Error: &ParseError{f, "not a TTL", l}}
return
}
h.Ttl = ttl
// Don't about the defttl, we should take the $TTL value
// defttl = ttl
st = zExpectAnyNoTtlBl
default:
t <- &Token{Error: &ParseError{f, "syntax error at beginning", l}}
return
}
case zExpectDirIncludeBl:
if l.value != zBlank {
t <- &Token{Error: &ParseError{f, "no blank after $INCLUDE-directive", l}}
return
}
st = zExpectDirInclude
case zExpectDirInclude:
if l.value != zString {
t <- &Token{Error: &ParseError{f, "expecting $INCLUDE value, not this...", l}}
return
}
neworigin := origin // There may be optionally a new origin set after the filename, if not use current one
l := <-c
switch l.value {
case zBlank:
l := <-c
if l.value == zString {
if _, ok := IsDomainName(l.token); !ok || l.length == 0 || l.err {
t <- &Token{Error: &ParseError{f, "bad origin name", l}}
return
}
// a new origin is specified.
if l.token[l.length-1] != '.' {
if origin != "." { // Prevent .. endings
neworigin = l.token + "." + origin
} else {
neworigin = l.token + origin
}
} else {
neworigin = l.token
}
}
case zNewline, zEOF:
// Ok
default:
t <- &Token{Error: &ParseError{f, "garbage after $INCLUDE", l}}
return
}
// Start with the new file
r1, e1 := os.Open(l.token)
if e1 != nil {
t <- &Token{Error: &ParseError{f, "failed to open `" + l.token + "'", l}}
return
}
if include+1 > 7 {
t <- &Token{Error: &ParseError{f, "too deeply nested $INCLUDE", l}}
return
}
parseZone(r1, l.token, neworigin, t, include+1)
st = zExpectOwnerDir
case zExpectDirTtlBl:
if l.value != zBlank {
t <- &Token{Error: &ParseError{f, "no blank after $TTL-directive", l}}
return
}
st = zExpectDirTtl
case zExpectDirTtl:
if l.value != zString {
t <- &Token{Error: &ParseError{f, "expecting $TTL value, not this...", l}}
return
}
if e, _ := slurpRemainder(c, f); e != nil {
t <- &Token{Error: e}
return
}
ttl, ok := stringToTtl(l.token)
if !ok {
t <- &Token{Error: &ParseError{f, "expecting $TTL value, not this...", l}}
return
}
defttl = ttl
st = zExpectOwnerDir
case zExpectDirOriginBl:
if l.value != zBlank {
t <- &Token{Error: &ParseError{f, "no blank after $ORIGIN-directive", l}}
return
}
st = zExpectDirOrigin
case zExpectDirOrigin:
if l.value != zString {
t <- &Token{Error: &ParseError{f, "expecting $ORIGIN value, not this...", l}}
return
}
if e, _ := slurpRemainder(c, f); e != nil {
t <- &Token{Error: e}
}
if _, ok := IsDomainName(l.token); !ok {
t <- &Token{Error: &ParseError{f, "bad origin name", l}}
return
}
if l.token[l.length-1] != '.' {
if origin != "." { // Prevent .. endings
origin = l.token + "." + origin
} else {
origin = l.token + origin
}
} else {
origin = l.token
}
st = zExpectOwnerDir
case zExpectDirGenerateBl:
if l.value != zBlank {
t <- &Token{Error: &ParseError{f, "no blank after $GENERATE-directive", l}}
return
}
st = zExpectDirGenerate
case zExpectDirGenerate:
if l.value != zString {
t <- &Token{Error: &ParseError{f, "expecting $GENERATE value, not this...", l}}
return
}
if errMsg := generate(l, c, t, origin); errMsg != "" {
t <- &Token{Error: &ParseError{f, errMsg, l}}
return
}
st = zExpectOwnerDir
case zExpectOwnerBl:
if l.value != zBlank {
t <- &Token{Error: &ParseError{f, "no blank after owner", l}}
return
}
st = zExpectAny
case zExpectAny:
switch l.value {
case zRrtpe:
h.Rrtype = l.torc
st = zExpectRdata
case zClass:
h.Class = l.torc
st = zExpectAnyNoClassBl
case zString:
ttl, ok := stringToTtl(l.token)
if !ok {
t <- &Token{Error: &ParseError{f, "not a TTL", l}}
return
}
h.Ttl = ttl
// defttl = ttl // don't set the defttl here
st = zExpectAnyNoTtlBl
default:
t <- &Token{Error: &ParseError{f, "expecting RR type, TTL or class, not this...", l}}
return
}
case zExpectAnyNoClassBl:
if l.value != zBlank {
t <- &Token{Error: &ParseError{f, "no blank before class", l}}
return
}
st = zExpectAnyNoClass
case zExpectAnyNoTtlBl:
if l.value != zBlank {
t <- &Token{Error: &ParseError{f, "no blank before TTL", l}}
return
}
st = zExpectAnyNoTtl
case zExpectAnyNoTtl:
switch l.value {
case zClass:
h.Class = l.torc
st = zExpectRrtypeBl
case zRrtpe:
h.Rrtype = l.torc
st = zExpectRdata
default:
t <- &Token{Error: &ParseError{f, "expecting RR type or class, not this...", l}}
return
}
case zExpectAnyNoClass:
switch l.value {
case zString:
ttl, ok := stringToTtl(l.token)
if !ok {
t <- &Token{Error: &ParseError{f, "not a TTL", l}}
return
}
h.Ttl = ttl
// defttl = ttl // don't set the def ttl anymore
st = zExpectRrtypeBl
case zRrtpe:
h.Rrtype = l.torc
st = zExpectRdata
default:
t <- &Token{Error: &ParseError{f, "expecting RR type or TTL, not this...", l}}
return
}
case zExpectRrtypeBl:
if l.value != zBlank {
t <- &Token{Error: &ParseError{f, "no blank before RR type", l}}
return
}
st = zExpectRrtype
case zExpectRrtype:
if l.value != zRrtpe {
t <- &Token{Error: &ParseError{f, "unknown RR type", l}}
return
}
h.Rrtype = l.torc
st = zExpectRdata
case zExpectRdata:
r, e, c1 := setRR(h, c, origin, f)
if e != nil {
// If e.lex is nil than we have encounter a unknown RR type
// in that case we substitute our current lex token
if e.lex.token == "" && e.lex.value == 0 {
e.lex = l // Uh, dirty
}
t <- &Token{Error: e}
return
}
t <- &Token{RR: r, Comment: c1}
st = zExpectOwnerDir
}
}
// If we get here, we and the h.Rrtype is still zero, we haven't parsed anything, this
// is not an error, because an empty zone file is still a zone file.
}
// zlexer scans the sourcefile and returns tokens on the channel c.
func zlexer(s *scan, c chan lex) {
var l lex
str := make([]byte, maxTok) // Should be enough for any token
stri := 0 // Offset in str (0 means empty)
com := make([]byte, maxTok) // Hold comment text
comi := 0
quote := false
escape := false
space := false
commt := false
rrtype := false
owner := true
brace := 0
x, err := s.tokenText()
defer close(c)
for err == nil {
l.column = s.position.Column
l.line = s.position.Line
if stri >= maxTok {
l.token = "token length insufficient for parsing"
l.err = true
debug.Printf("[%+v]", l.token)
c <- l
return
}
if comi >= maxTok {
l.token = "comment length insufficient for parsing"
l.err = true
debug.Printf("[%+v]", l.token)
c <- l
return
}
switch x {
case ' ', '\t':
if escape {
escape = false
str[stri] = x
stri++
break
}
if quote {
// Inside quotes this is legal
str[stri] = x
stri++
break
}
if commt {
com[comi] = x
comi++
break
}
if stri == 0 {
// Space directly in the beginning, handled in the grammar
} else if owner {
// If we have a string and its the first, make it an owner
l.value = zOwner
l.token = string(str[:stri])
l.tokenUpper = strings.ToUpper(l.token)
l.length = stri
// escape $... start with a \ not a $, so this will work
switch l.tokenUpper {
case "$TTL":
l.value = zDirTtl
case "$ORIGIN":
l.value = zDirOrigin
case "$INCLUDE":
l.value = zDirInclude
case "$GENERATE":
l.value = zDirGenerate
}
debug.Printf("[7 %+v]", l.token)
c <- l
} else {
l.value = zString
l.token = string(str[:stri])
l.tokenUpper = strings.ToUpper(l.token)
l.length = stri
if !rrtype {
if t, ok := StringToType[l.tokenUpper]; ok {
l.value = zRrtpe
l.torc = t
rrtype = true
} else {
if strings.HasPrefix(l.tokenUpper, "TYPE") {
t, ok := typeToInt(l.token)
if !ok {
l.token = "unknown RR type"
l.err = true
c <- l
return
}
l.value = zRrtpe
l.torc = t
}
}
if t, ok := StringToClass[l.tokenUpper]; ok {
l.value = zClass
l.torc = t
} else {
if strings.HasPrefix(l.tokenUpper, "CLASS") {
t, ok := classToInt(l.token)
if !ok {
l.token = "unknown class"
l.err = true
c <- l
return
}
l.value = zClass
l.torc = t
}
}
}
debug.Printf("[6 %+v]", l.token)
c <- l
}
stri = 0
// I reverse space stuff here
if !space && !commt {
l.value = zBlank
l.token = " "
l.length = 1
debug.Printf("[5 %+v]", l.token)
c <- l
}
owner = false
space = true
case ';':
if escape {
escape = false
str[stri] = x
stri++
break
}
if quote {
// Inside quotes this is legal
str[stri] = x
stri++
break
}
if stri > 0 {
l.value = zString
l.token = string(str[:stri])
l.tokenUpper = strings.ToUpper(l.token)
l.length = stri
debug.Printf("[4 %+v]", l.token)
c <- l
stri = 0
}
commt = true
com[comi] = ';'
comi++
case '\r':
escape = false
if quote {
str[stri] = x
stri++
break
}
// discard if outside of quotes
case '\n':
escape = false
// Escaped newline
if quote {
str[stri] = x
stri++
break
}
// inside quotes this is legal
if commt {
// Reset a comment
commt = false
rrtype = false
stri = 0
// If not in a brace this ends the comment AND the RR
if brace == 0 {
owner = true
owner = true
l.value = zNewline
l.token = "\n"
l.tokenUpper = l.token
l.length = 1
l.comment = string(com[:comi])
debug.Printf("[3 %+v %+v]", l.token, l.comment)
c <- l
l.comment = ""
comi = 0
break
}
com[comi] = ' ' // convert newline to space
comi++
break
}
if brace == 0 {
// If there is previous text, we should output it here
if stri != 0 {
l.value = zString
l.token = string(str[:stri])
l.tokenUpper = strings.ToUpper(l.token)
l.length = stri
if !rrtype {
if t, ok := StringToType[l.tokenUpper]; ok {
l.value = zRrtpe
l.torc = t
rrtype = true
}
}
debug.Printf("[2 %+v]", l.token)
c <- l
}
l.value = zNewline
l.token = "\n"
l.tokenUpper = l.token
l.length = 1
debug.Printf("[1 %+v]", l.token)
c <- l
stri = 0
commt = false
rrtype = false
owner = true
comi = 0
}
case '\\':
// comments do not get escaped chars, everything is copied
if commt {
com[comi] = x
comi++
break
}
// something already escaped must be in string
if escape {
str[stri] = x
stri++
escape = false
break
}
// something escaped outside of string gets added to string
str[stri] = x
stri++
escape = true
case '"':
if commt {
com[comi] = x
comi++
break
}
if escape {
str[stri] = x
stri++
escape = false
break
}
space = false
// send previous gathered text and the quote
if stri != 0 {
l.value = zString
l.token = string(str[:stri])
l.tokenUpper = strings.ToUpper(l.token)
l.length = stri
debug.Printf("[%+v]", l.token)
c <- l
stri = 0
}
// send quote itself as separate token
l.value = zQuote
l.token = "\""
l.tokenUpper = l.token
l.length = 1
c <- l
quote = !quote
case '(', ')':
if commt {
com[comi] = x
comi++
break
}
if escape {
str[stri] = x
stri++
escape = false
break
}
if quote {
str[stri] = x
stri++
break
}
switch x {
case ')':
brace--
if brace < 0 {
l.token = "extra closing brace"
l.tokenUpper = l.token
l.err = true
debug.Printf("[%+v]", l.token)
c <- l
return
}
case '(':
brace++
}
default:
escape = false
if commt {
com[comi] = x
comi++
break
}
str[stri] = x
stri++
space = false
}
x, err = s.tokenText()
}
if stri > 0 {
// Send remainder
l.token = string(str[:stri])
l.tokenUpper = strings.ToUpper(l.token)
l.length = stri
l.value = zString
debug.Printf("[%+v]", l.token)
c <- l
}
if brace != 0 {
l.token = "unbalanced brace"
l.tokenUpper = l.token
l.err = true
c <- l
}
}
// Extract the class number from CLASSxx
func classToInt(token string) (uint16, bool) {
offset := 5
if len(token) < offset+1 {
return 0, false
}
class, err := strconv.ParseUint(token[offset:], 10, 16)
if err != nil {
return 0, false
}
return uint16(class), true
}
// Extract the rr number from TYPExxx
func typeToInt(token string) (uint16, bool) {
offset := 4
if len(token) < offset+1 {
return 0, false
}
typ, err := strconv.ParseUint(token[offset:], 10, 16)
if err != nil {
return 0, false
}
return uint16(typ), true
}
// Parse things like 2w, 2m, etc, Return the time in seconds.
func stringToTtl(token string) (uint32, bool) {
s := uint32(0)
i := uint32(0)
for _, c := range token {
switch c {
case 's', 'S':
s += i
i = 0
case 'm', 'M':
s += i * 60
i = 0
case 'h', 'H':
s += i * 60 * 60
i = 0
case 'd', 'D':
s += i * 60 * 60 * 24
i = 0
case 'w', 'W':
s += i * 60 * 60 * 24 * 7
i = 0
case '0', '1', '2', '3', '4', '5', '6', '7', '8', '9':
i *= 10
i += uint32(c) - '0'
default:
return 0, false
}
}
return s + i, true
}
// Parse LOC records' <digits>[.<digits>][mM] into a
// mantissa exponent format. Token should contain the entire
// string (i.e. no spaces allowed)
func stringToCm(token string) (e, m uint8, ok bool) {
if token[len(token)-1] == 'M' || token[len(token)-1] == 'm' {
token = token[0 : len(token)-1]
}
s := strings.SplitN(token, ".", 2)
var meters, cmeters, val int
var err error
switch len(s) {
case 2:
if cmeters, err = strconv.Atoi(s[1]); err != nil {
return
}
fallthrough
case 1:
if meters, err = strconv.Atoi(s[0]); err != nil {
return
}
case 0:
// huh?
return 0, 0, false
}
ok = true
if meters > 0 {
e = 2
val = meters
} else {
e = 0
val = cmeters
}
for val > 10 {
e++
val /= 10
}
if e > 9 {
ok = false
}
m = uint8(val)
return
}
func appendOrigin(name, origin string) string {
if origin == "." {
return name + origin
}
return name + "." + origin
}
// LOC record helper function
func locCheckNorth(token string, latitude uint32) (uint32, bool) {
switch token {
case "n", "N":
return LOC_EQUATOR + latitude, true
case "s", "S":
return LOC_EQUATOR - latitude, true
}
return latitude, false
}
// LOC record helper function
func locCheckEast(token string, longitude uint32) (uint32, bool) {
switch token {
case "e", "E":
return LOC_EQUATOR + longitude, true
case "w", "W":
return LOC_EQUATOR - longitude, true
}
return longitude, false
}
// "Eat" the rest of the "line". Return potential comments
func slurpRemainder(c chan lex, f string) (*ParseError, string) {
l := <-c
com := ""
switch l.value {
case zBlank:
l = <-c
com = l.comment
if l.value != zNewline && l.value != zEOF {
return &ParseError{f, "garbage after rdata", l}, ""
}
case zNewline:
com = l.comment
case zEOF:
default:
return &ParseError{f, "garbage after rdata", l}, ""
}
return nil, com
}
// Parse a 64 bit-like ipv6 address: "0014:4fff:ff20:ee64"
// Used for NID and L64 record.
func stringToNodeID(l lex) (uint64, *ParseError) {
if len(l.token) < 19 {
return 0, &ParseError{l.token, "bad NID/L64 NodeID/Locator64", l}
}
// There must be three colons at fixes postitions, if not its a parse error
if l.token[4] != ':' && l.token[9] != ':' && l.token[14] != ':' {
return 0, &ParseError{l.token, "bad NID/L64 NodeID/Locator64", l}
}
s := l.token[0:4] + l.token[5:9] + l.token[10:14] + l.token[15:19]
u, err := strconv.ParseUint(s, 16, 64)
if err != nil {
return 0, &ParseError{l.token, "bad NID/L64 NodeID/Locator64", l}
}
return u, nil
}