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Stop using packDomainName in IsDomainName (#873) 

* Fork packDomainName for IsDomainName

* Eliminate msg buffer from packDomainName2

* Eliminate compression code from packDomainName2

* Remove off argument and return from packDomainName2

* Remove bs buffer from packDomainName2

* Merge packDomainName2 into IsDomainName

* Eliminate root label special case from IsDomainName

* Remove ls variable from IsDomainName

* Fixup comments in IsDomainName

* Remove msg == nil special cases from packDomainName

* Eliminate lenmsg variable from packDomainName

* Eliminate label counting from packDomainName

* Change off length check in IsDomainName

* Fix IsDomainName for escaped names

* Use strings.HasSuffix for IsFqdn

* Revert "Use strings.HasSuffix for IsFqdn"

I'll submit this as a seperate PR.

This reverts commit 80bf8c83700d121ea45edac0f00db52817498166.

* Cross reference IsDomainName and packDomainName

* Correct IsDomainName max length comment
This commit is contained in:
Tom Thorogood 2019-01-04 03:09:37 +10:30 committed by Miek Gieben
parent 1048d2bf96
commit 813bd39114
6 changed files with 135 additions and 82 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

71
defaults.go
View File

@ -164,11 +164,74 @@ func (dns *Msg) IsEdns0() *OPT {
// the number of labels. When false is returned the number of labels is not
// defined. Also note that this function is extremely liberal; almost any
// string is a valid domain name as the DNS is 8 bit protocol. It checks if each
// label fits in 63 characters, but there is no length check for the entire
// string s. I.e. a domain name longer than 255 characters is considered valid.
// label fits in 63 characters and that the entire name will fit into the 255
// octet wire format limit.
func IsDomainName(s string) (labels int, ok bool) {
_, labels, err := packDomainName(s, nil, 0, compressionMap{}, false)
return labels, err == nil
// XXX: The logic in this function was copied from packDomainName and
// should be kept in sync with that function.
const lenmsg = 256
if len(s) == 0 { // Ok, for instance when dealing with update RR without any rdata.
return 0, false
}
if !strings.HasSuffix(s, ".") {
s += "."
}
// Each dot ends a segment of the name. Except for escaped dots (\.), which
// are normal dots.
var (
off int
begin int
wasDot bool
)
for i := 0; i < len(s); i++ {
switch s[i] {
case '\\':
if off+1 > lenmsg {
return labels, false
}
// check for \DDD
if i+3 < len(s) && isDigit(s[i+1]) && isDigit(s[i+2]) && isDigit(s[i+3]) {
i += 3
begin += 3
} else {
i++
begin++
}
wasDot = false
case '.':
if wasDot {
// two dots back to back is not legal
return labels, false
}
wasDot = true
labelLen := i - begin
if labelLen >= 1<<6 { // top two bits of length must be clear
return labels, false
}
// off can already (we're in a loop) be bigger than lenmsg
// this happens when a name isn't fully qualified
off += 1 + labelLen
if off > lenmsg {
return labels, false
}
labels++
begin = i + 1
default:
wasDot = false
}
}
return labels, true
}
// IsSubDomain checks if child is indeed a child of the parent. If child and parent

16
labels_test.go
View File

@ -155,13 +155,15 @@ func TestIsDomainName(t *testing.T) {
lab int
}
names := map[string]*ret{
"..": {false, 1},
"@.": {true, 1},
"www.example.com": {true, 3},
"www.e%ample.com": {true, 3},
"www.example.com.": {true, 3},
"mi\\k.nl.": {true, 2},
"mi\\k.nl": {true, 2},
"..": {false, 1},
"@.": {true, 1},
"www.example.com": {true, 3},
"www.e%ample.com": {true, 3},
"www.example.com.": {true, 3},
"mi\\k.nl.": {true, 2},
"mi\\k.nl": {true, 2},
longestDomain: {true, 4},
longestUnprintableDomain: {true, 4},
}
for d, ok := range names {
l, k := IsDomainName(d)

58
msg.go
View File

@ -231,29 +231,21 @@ func (m compressionMap) find(s string) (int, bool) {
// map needs to hold a mapping between domain names and offsets
// pointing into msg.
func PackDomainName(s string, msg []byte, off int, compression map[string]int, compress bool) (off1 int, err error) {
off1, _, err = packDomainName(s, msg, off, compressionMap{ext: compression}, compress)
return
return packDomainName(s, msg, off, compressionMap{ext: compression}, compress)
}
func packDomainName(s string, msg []byte, off int, compression compressionMap, compress bool) (off1 int, labels int, err error) {
// special case if msg == nil
lenmsg := 256
if msg != nil {
lenmsg = len(msg)
}
func packDomainName(s string, msg []byte, off int, compression compressionMap, compress bool) (off1 int, err error) {
// XXX: A logical copy of this function exists in IsDomainName and
// should be kept in sync with this function.
ls := len(s)
if ls == 0 { // Ok, for instance when dealing with update RR without any rdata.
return off, 0, nil
return off, nil
}
// If not fully qualified, error out, but only if msg != nil #ugly
// If not fully qualified, error out.
if s[ls-1] != '.' {
if msg != nil {
return lenmsg, 0, ErrFqdn
}
s += "."
ls++
return len(msg), ErrFqdn
}
// Each dot ends a segment of the name.
@ -283,8 +275,8 @@ loop:
switch c {
case '\\':
if off+1 > lenmsg {
return lenmsg, labels, ErrBuf
if off+1 > len(msg) {
return len(msg), ErrBuf
}
if bs == nil {
@ -307,19 +299,19 @@ loop:
case '.':
if wasDot {
// two dots back to back is not legal
return lenmsg, labels, ErrRdata
return len(msg), ErrRdata
}
wasDot = true
labelLen := i - begin
if labelLen >= 1<<6 { // top two bits of length must be clear
return lenmsg, labels, ErrRdata
return len(msg), ErrRdata
}
// off can already (we're in a loop) be bigger than len(msg)
// this happens when a name isn't fully qualified
if off+1+labelLen > lenmsg {
return lenmsg, labels, ErrBuf
if off+1+labelLen > len(msg) {
return len(msg), ErrBuf
}
// Don't try to compress '.'
@ -344,18 +336,15 @@ loop:
}
// The following is covered by the length check above.
if msg != nil {
msg[off] = byte(labelLen)
msg[off] = byte(labelLen)
if bs == nil {
copy(msg[off+1:], s[begin:i])
} else {
copy(msg[off+1:], bs[begin:i])
}
if bs == nil {
copy(msg[off+1:], s[begin:i])
} else {
copy(msg[off+1:], bs[begin:i])
}
off += 1 + labelLen
labels++
begin = i + 1
compBegin = begin + compOff
default:
@ -365,22 +354,21 @@ loop:
// Root label is special
if isRootLabel(s, bs, 0, ls) {
return off, labels, nil
return off, nil
}
// If we did compression and we find something add the pointer here
if pointer != -1 {
// We have two bytes (14 bits) to put the pointer in
// if msg == nil, we will never do compression
binary.BigEndian.PutUint16(msg[off:], uint16(pointer^0xC000))
return off + 2, labels, nil
return off + 2, nil
}
if msg != nil && off < lenmsg {
if off < len(msg) {
msg[off] = 0
}
return off + 1, labels, nil
return off + 1, nil
}
// isRootLabel returns whether s or bs, from off to end, is the root
@ -1131,7 +1119,7 @@ func (dns *Msg) CopyTo(r1 *Msg) *Msg {
}
func (q *Question) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
off, _, err := packDomainName(q.Name, msg, off, compression, compress)
off, err := packDomainName(q.Name, msg, off, compression, compress)
if err != nil {
return off, err
}

4
msg_generate.go
View File

@ -115,9 +115,9 @@ return headerEnd, off, err
switch {
case st.Tag(i) == `dns:"-"`: // ignored
case st.Tag(i) == `dns:"cdomain-name"`:
o("off, _, err = packDomainName(rr.%s, msg, off, compression, compress)\n")
o("off, err = packDomainName(rr.%s, msg, off, compression, compress)\n")
case st.Tag(i) == `dns:"domain-name"`:
o("off, _, err = packDomainName(rr.%s, msg, off, compression, false)\n")
o("off, err = packDomainName(rr.%s, msg, off, compression, false)\n")
case st.Tag(i) == `dns:"a"`:
o("off, err = packDataA(rr.%s, msg, off)\n")
case st.Tag(i) == `dns:"aaaa"`:

4
msg_helpers.go
View File

@ -106,7 +106,7 @@ func (hdr RR_Header) pack(msg []byte, off int, compression compressionMap, compr
return off, off, nil
}
off, _, err := packDomainName(hdr.Name, msg, off, compression, compress)
off, err := packDomainName(hdr.Name, msg, off, compression, compress)
if err != nil {
return off, len(msg), err
}
@ -640,7 +640,7 @@ func unpackDataDomainNames(msg []byte, off, end int) ([]string, int, error) {
func packDataDomainNames(names []string, msg []byte, off int, compression compressionMap, compress bool) (int, error) {
var err error
for j := 0; j < len(names); j++ {
off, _, err = packDomainName(names[j], msg, off, compression, compress)
off, err = packDomainName(names[j], msg, off, compression, compress)
if err != nil {
return len(msg), err
}

64
zmsg.go
View File

@ -37,7 +37,7 @@ func (rr *AFSDB) pack(msg []byte, off int, compression compressionMap, compress
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Hostname, msg, off, compression, false)
off, err = packDomainName(rr.Hostname, msg, off, compression, false)
if err != nil {
return headerEnd, off, err
}
@ -161,7 +161,7 @@ func (rr *CNAME) pack(msg []byte, off int, compression compressionMap, compress
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Target, msg, off, compression, compress)
off, err = packDomainName(rr.Target, msg, off, compression, compress)
if err != nil {
return headerEnd, off, err
}
@ -229,7 +229,7 @@ func (rr *DNAME) pack(msg []byte, off int, compression compressionMap, compress
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Target, msg, off, compression, false)
off, err = packDomainName(rr.Target, msg, off, compression, false)
if err != nil {
return headerEnd, off, err
}
@ -433,7 +433,7 @@ func (rr *KX) pack(msg []byte, off int, compression compressionMap, compress boo
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Exchanger, msg, off, compression, false)
off, err = packDomainName(rr.Exchanger, msg, off, compression, false)
if err != nil {
return headerEnd, off, err
}
@ -517,7 +517,7 @@ func (rr *LP) pack(msg []byte, off int, compression compressionMap, compress boo
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Fqdn, msg, off, compression, false)
off, err = packDomainName(rr.Fqdn, msg, off, compression, false)
if err != nil {
return headerEnd, off, err
}
@ -529,7 +529,7 @@ func (rr *MB) pack(msg []byte, off int, compression compressionMap, compress boo
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Mb, msg, off, compression, compress)
off, err = packDomainName(rr.Mb, msg, off, compression, compress)
if err != nil {
return headerEnd, off, err
}
@ -541,7 +541,7 @@ func (rr *MD) pack(msg []byte, off int, compression compressionMap, compress boo
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Md, msg, off, compression, compress)
off, err = packDomainName(rr.Md, msg, off, compression, compress)
if err != nil {
return headerEnd, off, err
}
@ -553,7 +553,7 @@ func (rr *MF) pack(msg []byte, off int, compression compressionMap, compress boo
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Mf, msg, off, compression, compress)
off, err = packDomainName(rr.Mf, msg, off, compression, compress)
if err != nil {
return headerEnd, off, err
}
@ -565,7 +565,7 @@ func (rr *MG) pack(msg []byte, off int, compression compressionMap, compress boo
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Mg, msg, off, compression, compress)
off, err = packDomainName(rr.Mg, msg, off, compression, compress)
if err != nil {
return headerEnd, off, err
}
@ -577,11 +577,11 @@ func (rr *MINFO) pack(msg []byte, off int, compression compressionMap, compress
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Rmail, msg, off, compression, compress)
off, err = packDomainName(rr.Rmail, msg, off, compression, compress)
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Email, msg, off, compression, compress)
off, err = packDomainName(rr.Email, msg, off, compression, compress)
if err != nil {
return headerEnd, off, err
}
@ -593,7 +593,7 @@ func (rr *MR) pack(msg []byte, off int, compression compressionMap, compress boo
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Mr, msg, off, compression, compress)
off, err = packDomainName(rr.Mr, msg, off, compression, compress)
if err != nil {
return headerEnd, off, err
}
@ -609,7 +609,7 @@ func (rr *MX) pack(msg []byte, off int, compression compressionMap, compress boo
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Mx, msg, off, compression, compress)
off, err = packDomainName(rr.Mx, msg, off, compression, compress)
if err != nil {
return headerEnd, off, err
}
@ -641,7 +641,7 @@ func (rr *NAPTR) pack(msg []byte, off int, compression compressionMap, compress
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Replacement, msg, off, compression, false)
off, err = packDomainName(rr.Replacement, msg, off, compression, false)
if err != nil {
return headerEnd, off, err
}
@ -693,7 +693,7 @@ func (rr *NS) pack(msg []byte, off int, compression compressionMap, compress boo
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Ns, msg, off, compression, compress)
off, err = packDomainName(rr.Ns, msg, off, compression, compress)
if err != nil {
return headerEnd, off, err
}
@ -705,7 +705,7 @@ func (rr *NSAPPTR) pack(msg []byte, off int, compression compressionMap, compres
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Ptr, msg, off, compression, false)
off, err = packDomainName(rr.Ptr, msg, off, compression, false)
if err != nil {
return headerEnd, off, err
}
@ -717,7 +717,7 @@ func (rr *NSEC) pack(msg []byte, off int, compression compressionMap, compress b
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.NextDomain, msg, off, compression, false)
off, err = packDomainName(rr.NextDomain, msg, off, compression, false)
if err != nil {
return headerEnd, off, err
}
@ -843,7 +843,7 @@ func (rr *PTR) pack(msg []byte, off int, compression compressionMap, compress bo
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Ptr, msg, off, compression, compress)
off, err = packDomainName(rr.Ptr, msg, off, compression, compress)
if err != nil {
return headerEnd, off, err
}
@ -859,11 +859,11 @@ func (rr *PX) pack(msg []byte, off int, compression compressionMap, compress boo
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Map822, msg, off, compression, false)
off, err = packDomainName(rr.Map822, msg, off, compression, false)
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Mapx400, msg, off, compression, false)
off, err = packDomainName(rr.Mapx400, msg, off, compression, false)
if err != nil {
return headerEnd, off, err
}
@ -911,11 +911,11 @@ func (rr *RP) pack(msg []byte, off int, compression compressionMap, compress boo
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Mbox, msg, off, compression, false)
off, err = packDomainName(rr.Mbox, msg, off, compression, false)
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Txt, msg, off, compression, false)
off, err = packDomainName(rr.Txt, msg, off, compression, false)
if err != nil {
return headerEnd, off, err
}
@ -955,7 +955,7 @@ func (rr *RRSIG) pack(msg []byte, off int, compression compressionMap, compress
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.SignerName, msg, off, compression, false)
off, err = packDomainName(rr.SignerName, msg, off, compression, false)
if err != nil {
return headerEnd, off, err
}
@ -975,7 +975,7 @@ func (rr *RT) pack(msg []byte, off int, compression compressionMap, compress boo
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Host, msg, off, compression, false)
off, err = packDomainName(rr.Host, msg, off, compression, false)
if err != nil {
return headerEnd, off, err
}
@ -1015,7 +1015,7 @@ func (rr *SIG) pack(msg []byte, off int, compression compressionMap, compress bo
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.SignerName, msg, off, compression, false)
off, err = packDomainName(rr.SignerName, msg, off, compression, false)
if err != nil {
return headerEnd, off, err
}
@ -1055,11 +1055,11 @@ func (rr *SOA) pack(msg []byte, off int, compression compressionMap, compress bo
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Ns, msg, off, compression, compress)
off, err = packDomainName(rr.Ns, msg, off, compression, compress)
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Mbox, msg, off, compression, compress)
off, err = packDomainName(rr.Mbox, msg, off, compression, compress)
if err != nil {
return headerEnd, off, err
}
@ -1115,7 +1115,7 @@ func (rr *SRV) pack(msg []byte, off int, compression compressionMap, compress bo
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Target, msg, off, compression, false)
off, err = packDomainName(rr.Target, msg, off, compression, false)
if err != nil {
return headerEnd, off, err
}
@ -1171,11 +1171,11 @@ func (rr *TALINK) pack(msg []byte, off int, compression compressionMap, compress
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.PreviousName, msg, off, compression, false)
off, err = packDomainName(rr.PreviousName, msg, off, compression, false)
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.NextName, msg, off, compression, false)
off, err = packDomainName(rr.NextName, msg, off, compression, false)
if err != nil {
return headerEnd, off, err
}
@ -1187,7 +1187,7 @@ func (rr *TKEY) pack(msg []byte, off int, compression compressionMap, compress b
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Algorithm, msg, off, compression, false)
off, err = packDomainName(rr.Algorithm, msg, off, compression, false)
if err != nil {
return headerEnd, off, err
}
@ -1255,7 +1255,7 @@ func (rr *TSIG) pack(msg []byte, off int, compression compressionMap, compress b
if err != nil {
return headerEnd, off, err
}
off, _, err = packDomainName(rr.Algorithm, msg, off, compression, false)
off, err = packDomainName(rr.Algorithm, msg, off, compression, false)
if err != nil {
return headerEnd, off, err
}