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package dns
import (
"fmt"
"io"
"os"
"strconv"
"strings"
)
// Only used when debugging the parser itself.
var _DEBUG = false
// Complete unsure about the correctness of this value?
// Large blobs of base64 code might get longer than this....
const maxTok = 2048
// 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.
const (
// Zonefile
_EOF = iota
_STRING
_BLANK
_QUOTE
_NEWLINE
_RRTYPE
_OWNER
_CLASS
_DIRORIGIN // $ORIGIN
_DIRTTL // $TTL
_DIRINCLUDE // $INCLUDE
_DIRGENERATE // $GENERATE
// Privatekey file
_VALUE
_KEY
_EXPECT_OWNER_DIR // Ownername
_EXPECT_OWNER_BL // Whitespace after the ownername
_EXPECT_ANY // Expect rrtype, ttl or class
_EXPECT_ANY_NOCLASS // Expect rrtype or ttl
_EXPECT_ANY_NOCLASS_BL // The Whitespace after _EXPECT_ANY_NOCLASS
_EXPECT_ANY_NOTTL // Expect rrtype or class
_EXPECT_ANY_NOTTL_BL // Whitespace after _EXPECT_ANY_NOTTL
_EXPECT_RRTYPE // Expect rrtype
_EXPECT_RRTYPE_BL // Whitespace BEFORE rrtype
_EXPECT_RDATA // The first element of the rdata
_EXPECT_DIRTTL_BL // Space after directive $TTL
_EXPECT_DIRTTL // Directive $TTL
_EXPECT_DIRORIGIN_BL // Space after directive $ORIGIN
_EXPECT_DIRORIGIN // Directive $ORIGIN
_EXPECT_DIRINCLUDE_BL // Space after directive $INCLUDE
_EXPECT_DIRINCLUDE // Directive $INCLUDE
_EXPECT_DIRGENERATE // Directive $GENERATE
_EXPECT_DIRGENERATE_BL // Space after directive $GENERATE
)
// ParseError is a parsing error. It contains the parse error and the location in the io.Reader
// where the error occured.
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
err bool // When true, token text has lexer error
value uint8 // Value: _STRING, _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
}
// Tokens are returned when a zone file is parsed.
type Token struct {
RR // the scanned resource record when error is not nil
Error *ParseError // when an error occured, this has the error specifics
}
// NewRR reads the RR contained in the string s. Only the first RR is returned.
// The class defaults to IN and TTL defaults to 3600. The full zone file
// syntax like $TTL, $ORIGIN, etc. is supported.
func NewRR(s string) (RR, error) {
if 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. Only the first RR is returned.
// The class defaults to IN and TTL defaults to 3600.
func ReadRR(q io.Reader, filename string) (RR, error) {
r := <-parseZoneHelper(q, ".", filename, 1)
if r.Error != nil {
return nil, r.Error
}
return r.RR, nil
}
// ParseZone reads a RFC 1035 style one from r. It returns Tokens on the
// returned channel, which consist out the parsed RR 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 {
// // Do something with x.RR
// }
// }
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, 1000)
// Start the lexer
go zlexer(s, c)
// 6 possible beginnings of a line, _ is a space
// 0. _RRTYPE -> all omitted until the rrtype
// 1. _OWNER _ _RRTYPE -> class/ttl omitted
// 2. _OWNER _ _STRING _ _RRTYPE -> class omitted
// 3. _OWNER _ _STRING _ _CLASS _ _RRTYPE -> ttl/class
// 4. _OWNER _ _CLASS _ _RRTYPE -> ttl omitted
// 5. _OWNER _ _CLASS _ _STRING _ _RRTYPE -> class/ttl (reversed)
// After detecting these, we know the _RRTYPE so we can jump to functions
// handling the rdata for each of these types.
if origin == "" {
origin = "."
}
if _, _, ok := IsDomainName(origin); !ok {
t <- Token{Error: &ParseError{f, "bad initial origin name", lex{}}}
return
}
origin = Fqdn(origin)
st := _EXPECT_OWNER_DIR // initial state
var h RR_Header
var defttl uint32 = defaultTtl
var prevName string
for l := range c {
if _DEBUG {
fmt.Printf("[%v]\n", l)
}
// Lexer spotted an error already
if l.err == true {
t <- Token{Error: &ParseError{f, l.token, l}}
return
}
switch st {
case _EXPECT_OWNER_DIR:
// We can also expect a directive, like $TTL or $ORIGIN
h.Ttl = defttl
h.Class = ClassINET
switch l.value {
case _NEWLINE: // Empty line
st = _EXPECT_OWNER_DIR
case _OWNER:
h.Name = l.token
if l.token[0] == '@' {
h.Name = origin
prevName = h.Name
st = _EXPECT_OWNER_BL
break
}
_, ld, ok := IsDomainName(l.token)
if !ok {
t <- Token{Error: &ParseError{f, "bad owner name", l}}
return
}
if h.Name[ld-1] != '.' {
h.Name = appendOrigin(h.Name, origin)
}
prevName = h.Name
st = _EXPECT_OWNER_BL
case _DIRTTL:
st = _EXPECT_DIRTTL_BL
case _DIRORIGIN:
st = _EXPECT_DIRORIGIN_BL
case _DIRINCLUDE:
st = _EXPECT_DIRINCLUDE_BL
case _DIRGENERATE:
st = _EXPECT_DIRGENERATE_BL
case _RRTYPE: // Everthing has been omitted, this is the first thing on the line
h.Name = prevName
h.Rrtype = l.torc
st = _EXPECT_RDATA
case _CLASS: // First thing on the line is the class
h.Name = prevName
h.Class = l.torc
st = _EXPECT_ANY_NOCLASS_BL
case _BLANK:
// Discard, can happen when there is nothing on the
// line except the RR type
case _STRING: // First thing on the is the ttl
if ttl, ok := stringToTtl(l.token); !ok {
t <- Token{Error: &ParseError{f, "not a TTL", l}}
return
} else {
h.Ttl = ttl
defttl = ttl
}
st = _EXPECT_ANY_NOTTL_BL
default:
t <- Token{Error: &ParseError{f, "syntax error at beginning", l}}
return
}
case _EXPECT_DIRINCLUDE_BL:
if l.value != _BLANK {
t <- Token{Error: &ParseError{f, "no blank after $INCLUDE-directive", l}}
return
}
st = _EXPECT_DIRINCLUDE
case _EXPECT_DIRINCLUDE:
if l.value != _STRING {
t <- Token{Error: &ParseError{f, "expecting $INCLUDE value, not this...", l}}
return
}
if e := slurpRemainder(c, f); e != nil {
t <- Token{Error: e}
}
// 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, origin, t, include+1)
st = _EXPECT_OWNER_DIR
case _EXPECT_DIRTTL_BL:
if l.value != _BLANK {
t <- Token{Error: &ParseError{f, "no blank after $TTL-directive", l}}
return
}
st = _EXPECT_DIRTTL
case _EXPECT_DIRTTL:
if l.value != _STRING {
t <- Token{Error: &ParseError{f, "expecting $TTL value, not this...", l}}
return
}
if e := slurpRemainder(c, f); e != nil {
t <- Token{Error: e}
return
}
if ttl, ok := stringToTtl(l.token); !ok {
t <- Token{Error: &ParseError{f, "expecting $TTL value, not this...", l}}
return
} else {
defttl = ttl
}
st = _EXPECT_OWNER_DIR
case _EXPECT_DIRORIGIN_BL:
if l.value != _BLANK {
t <- Token{Error: &ParseError{f, "no blank after $ORIGIN-directive", l}}
return
}
st = _EXPECT_DIRORIGIN
case _EXPECT_DIRORIGIN:
if l.value != _STRING {
t <- Token{Error: &ParseError{f, "expecting $ORIGIN value, not this...", l}}
return
}
if e := slurpRemainder(c, f); e != nil {
t <- Token{Error: e}
}
if !IsFqdn(l.token) {
if origin != "." { // Prevent .. endings
origin = l.token + "." + origin
} else {
origin = l.token + origin
}
} else {
origin = l.token
}
st = _EXPECT_OWNER_DIR
case _EXPECT_DIRGENERATE_BL:
if l.value != _BLANK {
t <- Token{Error: &ParseError{f, "no blank after $GENERATE-directive", l}}
return
}
st = _EXPECT_DIRGENERATE
case _EXPECT_DIRGENERATE:
if l.value != _STRING {
t <- Token{Error: &ParseError{f, "expecting $GENERATE value, not this...", l}}
return
}
if e := generate(l, c, t, origin); e != "" {
t <- Token{Error: &ParseError{f, e, l}}
return
}
st = _EXPECT_OWNER_DIR
case _EXPECT_OWNER_BL:
if l.value != _BLANK {
t <- Token{Error: &ParseError{f, "no blank after owner", l}}
return
}
st = _EXPECT_ANY
case _EXPECT_ANY:
switch l.value {
case _RRTYPE:
h.Rrtype = l.torc
st = _EXPECT_RDATA
case _CLASS:
h.Class = l.torc
st = _EXPECT_ANY_NOCLASS_BL
case _STRING: // TTL is this case
if ttl, ok := stringToTtl(l.token); !ok {
t <- Token{Error: &ParseError{f, "not a TTL", l}}
return
} else {
h.Ttl = ttl
defttl = ttl
}
st = _EXPECT_ANY_NOTTL_BL
default:
t <- Token{Error: &ParseError{f, "expecting RR type, TTL or class, not this...", l}}
return
}
case _EXPECT_ANY_NOCLASS_BL:
if l.value != _BLANK {
t <- Token{Error: &ParseError{f, "no blank before class", l}}
return
}
st = _EXPECT_ANY_NOCLASS
case _EXPECT_ANY_NOTTL_BL:
if l.value != _BLANK {
t <- Token{Error: &ParseError{f, "no blank before TTL", l}}
return
}
st = _EXPECT_ANY_NOTTL
case _EXPECT_ANY_NOTTL:
switch l.value {
case _CLASS:
h.Class = l.torc
st = _EXPECT_RRTYPE_BL
case _RRTYPE:
h.Rrtype = l.torc
st = _EXPECT_RDATA
default:
t <- Token{Error: &ParseError{f, "expecting RR type or class, not this...", l}}
return
}
case _EXPECT_ANY_NOCLASS:
switch l.value {
case _STRING: // TTL
if ttl, ok := stringToTtl(l.token); !ok {
t <- Token{Error: &ParseError{f, "not a TTL", l}}
return
} else {
h.Ttl = ttl
defttl = ttl
}
st = _EXPECT_RRTYPE_BL
case _RRTYPE:
h.Rrtype = l.torc
st = _EXPECT_RDATA
default:
t <- Token{Error: &ParseError{f, "expecting RR type or TTL, not this...", l}}
return
}
case _EXPECT_RRTYPE_BL:
if l.value != _BLANK {
t <- Token{Error: &ParseError{f, "no blank before RR type", l}}
return
}
st = _EXPECT_RRTYPE
case _EXPECT_RRTYPE:
if l.value != _RRTYPE {
t <- Token{Error: &ParseError{f, "unknown RR type", l}}
return
}
h.Rrtype = l.torc
st = _EXPECT_RDATA
case _EXPECT_RDATA:
r, e := 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}
st = _EXPECT_OWNER_DIR
}
}
// 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)
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 = "tok length insufficient for parsing"
l.err = true
c <- l
return
}
switch x {
case ' ', '\t':
if quote {
// Inside quotes this is legal
str[stri] = x
stri++
break
}
escape = false
if commt {
break
}
if stri == 0 {
// Space directly as the beginnin, handled in the grammar
} else if owner {
// If we have a string and its the first, make it an owner
l.value = _OWNER
l.token = string(str[:stri])
// escape $... start with a \ not a $, so this will work
switch l.token {
case "$TTL":
l.value = _DIRTTL
case "$ORIGIN":
l.value = _DIRORIGIN
case "$INCLUDE":
l.value = _DIRINCLUDE
case "$GENERATE":
l.value = _DIRGENERATE
}
c <- l
} else {
l.value = _STRING
l.token = string(str[:stri])
if !rrtype {
if t, ok := Str_rr[strings.ToUpper(l.token)]; ok {
l.value = _RRTYPE
l.torc = t
rrtype = true
} else {
if strings.HasPrefix(l.token, "TYPE") {
if t, ok := typeToInt(l.token); !ok {
l.token = "unknown RR type"
l.err = true
c <- l
return
} else {
l.value = _RRTYPE
l.torc = t
}
}
}
if t, ok := Str_class[strings.ToUpper(l.token)]; ok {
l.value = _CLASS
l.torc = t
} else {
if strings.HasPrefix(l.token, "CLASS") {
if t, ok := classToInt(l.token); !ok {
l.token = "unknown class"
l.err = true
c <- l
return
} else {
l.value = _CLASS
l.torc = t
}
}
}
}
c <- l
}
stri = 0
// I reverse space stuff here
if !space && !commt {
l.value = _BLANK
l.token = " "
c <- l
}
owner = false
space = true
case ';':
if quote {
// Inside quotes this is legal
str[stri] = x
stri++
break
}
if escape {
escape = false
str[stri] = x
stri++
break
}
if stri > 0 {
l.value = _STRING
l.token = string(str[:stri])
c <- l
stri = 0
}
commt = true
case '\r':
// discard
// this means it can also not be used as rdata
case '\n':
// Escaped newline
if quote {
str[stri] = x
stri++
break
}
// inside quotes this is legal
escape = false
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 = _NEWLINE
l.token = "\n"
c <- l
}
break
}
if brace == 0 {
// If there is previous text, we should output it here
if stri != 0 {
l.value = _STRING
l.token = string(str[:stri])
if !rrtype {
if _, ok := Str_rr[strings.ToUpper(l.token)]; ok {
l.value = _RRTYPE
rrtype = true
}
}
c <- l
}
l.value = _NEWLINE
l.token = "\n"
c <- l
stri = 0
commt = false
rrtype = false
owner = true
}
case '\\':
// quote?
if commt {
break
}
if escape {
str[stri] = x
stri++
escape = false
break
}
str[stri] = x
stri++
escape = true
case '"':
if commt {
break
}
if escape {
str[stri] = x
stri++
escape = false
break
}
space = false
// send previous gathered text and the quote
if stri != 0 {
l.value = _STRING
l.token = string(str[:stri])
c <- l
stri = 0
}
l.value = _QUOTE
l.token = "\""
c <- l
quote = !quote
case '(', ')':
if quote {
str[stri] = x
stri++
break
}
if commt {
break
}
if escape {
str[stri] = x
stri++
escape = false
break
}
switch x {
case ')':
brace--
if brace < 0 {
l.token = "extra closing brace"
l.err = true
c <- l
return
}
case '(':
brace++
}
default:
if commt {
break
}
escape = false
str[stri] = x
stri++
space = false
}
x, err = s.tokenText()
}
// Hmm.
if stri > 0 {
// Send remainder
l.token = string(str[:stri])
l.value = _STRING
c <- l
}
}
// Extract the class number from CLASSxx
func classToInt(token string) (uint16, bool) {
class, ok := strconv.Atoi(token[5:])
if ok != nil {
return 0, false
}
return uint16(class), true
}
// Extract the rr number from TYPExxx
func typeToInt(token string) (uint16, bool) {
typ, ok := strconv.Atoi(token[4:])
if ok != 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"
func slurpRemainder(c chan lex, f string) *ParseError {
l := <-c
switch l.value {
case _BLANK:
l = <-c
if l.value != _NEWLINE && l.value != _EOF {
return &ParseError{f, "garbage after rdata", l}
}
// Ok
case _NEWLINE:
// Ok
case _EOF:
// Ok
default:
return &ParseError{f, "garbage after rdata", l}
}
return nil
}
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