mirror of
https://github.com/go-gitea/gitea.git
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* use certmagic for more extensible/robust ACME cert handling * accept TOS based on config option Signed-off-by: Andrew Thornton <art27@cantab.net> Co-authored-by: zeripath <art27@cantab.net> Co-authored-by: Lauris BH <lauris@nix.lv>
1191 lines
32 KiB
Go
Vendored
1191 lines
32 KiB
Go
Vendored
// DNS packet assembly, see RFC 1035. Converting from - Unpack() -
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// and to - Pack() - wire format.
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// All the packers and unpackers take a (msg []byte, off int)
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// and return (off1 int, ok bool). If they return ok==false, they
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// also return off1==len(msg), so that the next unpacker will
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// also fail. This lets us avoid checks of ok until the end of a
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// packing sequence.
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package dns
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//go:generate go run msg_generate.go
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import (
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"crypto/rand"
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"encoding/binary"
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"fmt"
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"math/big"
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"strconv"
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"strings"
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)
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const (
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maxCompressionOffset = 2 << 13 // We have 14 bits for the compression pointer
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maxDomainNameWireOctets = 255 // See RFC 1035 section 2.3.4
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// This is the maximum number of compression pointers that should occur in a
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// semantically valid message. Each label in a domain name must be at least one
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// octet and is separated by a period. The root label won't be represented by a
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// compression pointer to a compression pointer, hence the -2 to exclude the
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// smallest valid root label.
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//
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// It is possible to construct a valid message that has more compression pointers
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// than this, and still doesn't loop, by pointing to a previous pointer. This is
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// not something a well written implementation should ever do, so we leave them
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// to trip the maximum compression pointer check.
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maxCompressionPointers = (maxDomainNameWireOctets+1)/2 - 2
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// This is the maximum length of a domain name in presentation format. The
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// maximum wire length of a domain name is 255 octets (see above), with the
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// maximum label length being 63. The wire format requires one extra byte over
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// the presentation format, reducing the number of octets by 1. Each label in
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// the name will be separated by a single period, with each octet in the label
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// expanding to at most 4 bytes (\DDD). If all other labels are of the maximum
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// length, then the final label can only be 61 octets long to not exceed the
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// maximum allowed wire length.
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maxDomainNamePresentationLength = 61*4 + 1 + 63*4 + 1 + 63*4 + 1 + 63*4 + 1
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)
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// Errors defined in this package.
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var (
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ErrAlg error = &Error{err: "bad algorithm"} // ErrAlg indicates an error with the (DNSSEC) algorithm.
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ErrAuth error = &Error{err: "bad authentication"} // ErrAuth indicates an error in the TSIG authentication.
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ErrBuf error = &Error{err: "buffer size too small"} // ErrBuf indicates that the buffer used is too small for the message.
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ErrConnEmpty error = &Error{err: "conn has no connection"} // ErrConnEmpty indicates a connection is being used before it is initialized.
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ErrExtendedRcode error = &Error{err: "bad extended rcode"} // ErrExtendedRcode ...
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ErrFqdn error = &Error{err: "domain must be fully qualified"} // ErrFqdn indicates that a domain name does not have a closing dot.
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ErrId error = &Error{err: "id mismatch"} // ErrId indicates there is a mismatch with the message's ID.
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ErrKeyAlg error = &Error{err: "bad key algorithm"} // ErrKeyAlg indicates that the algorithm in the key is not valid.
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ErrKey error = &Error{err: "bad key"}
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ErrKeySize error = &Error{err: "bad key size"}
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ErrLongDomain error = &Error{err: fmt.Sprintf("domain name exceeded %d wire-format octets", maxDomainNameWireOctets)}
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ErrNoSig error = &Error{err: "no signature found"}
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ErrPrivKey error = &Error{err: "bad private key"}
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ErrRcode error = &Error{err: "bad rcode"}
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ErrRdata error = &Error{err: "bad rdata"}
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ErrRRset error = &Error{err: "bad rrset"}
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ErrSecret error = &Error{err: "no secrets defined"}
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ErrShortRead error = &Error{err: "short read"}
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ErrSig error = &Error{err: "bad signature"} // ErrSig indicates that a signature can not be cryptographically validated.
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ErrSoa error = &Error{err: "no SOA"} // ErrSOA indicates that no SOA RR was seen when doing zone transfers.
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ErrTime error = &Error{err: "bad time"} // ErrTime indicates a timing error in TSIG authentication.
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)
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// Id by default returns a 16-bit random number to be used as a message id. The
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// number is drawn from a cryptographically secure random number generator.
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// This being a variable the function can be reassigned to a custom function.
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// For instance, to make it return a static value for testing:
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//
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// dns.Id = func() uint16 { return 3 }
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var Id = id
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// id returns a 16 bits random number to be used as a
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// message id. The random provided should be good enough.
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func id() uint16 {
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var output uint16
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err := binary.Read(rand.Reader, binary.BigEndian, &output)
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if err != nil {
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panic("dns: reading random id failed: " + err.Error())
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}
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return output
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}
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// MsgHdr is a a manually-unpacked version of (id, bits).
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type MsgHdr struct {
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Id uint16
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Response bool
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Opcode int
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Authoritative bool
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Truncated bool
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RecursionDesired bool
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RecursionAvailable bool
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Zero bool
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AuthenticatedData bool
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CheckingDisabled bool
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Rcode int
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}
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// Msg contains the layout of a DNS message.
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type Msg struct {
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MsgHdr
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Compress bool `json:"-"` // If true, the message will be compressed when converted to wire format.
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Question []Question // Holds the RR(s) of the question section.
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Answer []RR // Holds the RR(s) of the answer section.
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Ns []RR // Holds the RR(s) of the authority section.
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Extra []RR // Holds the RR(s) of the additional section.
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}
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// ClassToString is a maps Classes to strings for each CLASS wire type.
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var ClassToString = map[uint16]string{
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ClassINET: "IN",
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ClassCSNET: "CS",
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ClassCHAOS: "CH",
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ClassHESIOD: "HS",
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ClassNONE: "NONE",
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ClassANY: "ANY",
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}
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// OpcodeToString maps Opcodes to strings.
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var OpcodeToString = map[int]string{
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OpcodeQuery: "QUERY",
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OpcodeIQuery: "IQUERY",
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OpcodeStatus: "STATUS",
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OpcodeNotify: "NOTIFY",
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OpcodeUpdate: "UPDATE",
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}
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// RcodeToString maps Rcodes to strings.
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var RcodeToString = map[int]string{
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RcodeSuccess: "NOERROR",
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RcodeFormatError: "FORMERR",
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RcodeServerFailure: "SERVFAIL",
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RcodeNameError: "NXDOMAIN",
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RcodeNotImplemented: "NOTIMP",
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RcodeRefused: "REFUSED",
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RcodeYXDomain: "YXDOMAIN", // See RFC 2136
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RcodeYXRrset: "YXRRSET",
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RcodeNXRrset: "NXRRSET",
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RcodeNotAuth: "NOTAUTH",
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RcodeNotZone: "NOTZONE",
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RcodeBadSig: "BADSIG", // Also known as RcodeBadVers, see RFC 6891
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// RcodeBadVers: "BADVERS",
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RcodeBadKey: "BADKEY",
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RcodeBadTime: "BADTIME",
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RcodeBadMode: "BADMODE",
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RcodeBadName: "BADNAME",
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RcodeBadAlg: "BADALG",
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RcodeBadTrunc: "BADTRUNC",
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RcodeBadCookie: "BADCOOKIE",
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}
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// compressionMap is used to allow a more efficient compression map
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// to be used for internal packDomainName calls without changing the
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// signature or functionality of public API.
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//
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// In particular, map[string]uint16 uses 25% less per-entry memory
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// than does map[string]int.
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type compressionMap struct {
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ext map[string]int // external callers
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int map[string]uint16 // internal callers
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}
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func (m compressionMap) valid() bool {
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return m.int != nil || m.ext != nil
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}
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func (m compressionMap) insert(s string, pos int) {
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if m.ext != nil {
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m.ext[s] = pos
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} else {
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m.int[s] = uint16(pos)
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}
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}
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func (m compressionMap) find(s string) (int, bool) {
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if m.ext != nil {
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pos, ok := m.ext[s]
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return pos, ok
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}
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pos, ok := m.int[s]
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return int(pos), ok
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}
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// Domain names are a sequence of counted strings
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// split at the dots. They end with a zero-length string.
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// PackDomainName packs a domain name s into msg[off:].
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// If compression is wanted compress must be true and the compression
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// map needs to hold a mapping between domain names and offsets
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// pointing into msg.
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func PackDomainName(s string, msg []byte, off int, compression map[string]int, compress bool) (off1 int, err error) {
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return packDomainName(s, msg, off, compressionMap{ext: compression}, compress)
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}
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func packDomainName(s string, msg []byte, off int, compression compressionMap, compress bool) (off1 int, err error) {
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// XXX: A logical copy of this function exists in IsDomainName and
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// should be kept in sync with this function.
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ls := len(s)
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if ls == 0 { // Ok, for instance when dealing with update RR without any rdata.
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return off, nil
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}
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// If not fully qualified, error out.
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if !IsFqdn(s) {
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return len(msg), ErrFqdn
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}
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// Each dot ends a segment of the name.
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// We trade each dot byte for a length byte.
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// Except for escaped dots (\.), which are normal dots.
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// There is also a trailing zero.
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// Compression
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pointer := -1
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// Emit sequence of counted strings, chopping at dots.
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var (
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begin int
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compBegin int
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compOff int
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bs []byte
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wasDot bool
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)
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loop:
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for i := 0; i < ls; i++ {
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var c byte
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if bs == nil {
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c = s[i]
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} else {
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c = bs[i]
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}
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switch c {
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case '\\':
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if off+1 > len(msg) {
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return len(msg), ErrBuf
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}
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if bs == nil {
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bs = []byte(s)
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}
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// check for \DDD
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if i+3 < ls && isDigit(bs[i+1]) && isDigit(bs[i+2]) && isDigit(bs[i+3]) {
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bs[i] = dddToByte(bs[i+1:])
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copy(bs[i+1:ls-3], bs[i+4:])
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ls -= 3
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compOff += 3
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} else {
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copy(bs[i:ls-1], bs[i+1:])
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ls--
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compOff++
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}
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wasDot = false
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case '.':
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if wasDot {
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// two dots back to back is not legal
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return len(msg), ErrRdata
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}
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wasDot = true
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labelLen := i - begin
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if labelLen >= 1<<6 { // top two bits of length must be clear
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return len(msg), ErrRdata
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}
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// off can already (we're in a loop) be bigger than len(msg)
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// this happens when a name isn't fully qualified
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if off+1+labelLen > len(msg) {
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return len(msg), ErrBuf
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}
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// Don't try to compress '.'
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// We should only compress when compress is true, but we should also still pick
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// up names that can be used for *future* compression(s).
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if compression.valid() && !isRootLabel(s, bs, begin, ls) {
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if p, ok := compression.find(s[compBegin:]); ok {
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// The first hit is the longest matching dname
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// keep the pointer offset we get back and store
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// the offset of the current name, because that's
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// where we need to insert the pointer later
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// If compress is true, we're allowed to compress this dname
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if compress {
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pointer = p // Where to point to
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break loop
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}
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} else if off < maxCompressionOffset {
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// Only offsets smaller than maxCompressionOffset can be used.
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compression.insert(s[compBegin:], off)
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}
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}
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// The following is covered by the length check above.
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msg[off] = byte(labelLen)
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if bs == nil {
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copy(msg[off+1:], s[begin:i])
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} else {
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copy(msg[off+1:], bs[begin:i])
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}
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off += 1 + labelLen
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begin = i + 1
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compBegin = begin + compOff
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default:
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wasDot = false
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}
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}
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// Root label is special
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if isRootLabel(s, bs, 0, ls) {
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return off, nil
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}
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// If we did compression and we find something add the pointer here
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if pointer != -1 {
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// We have two bytes (14 bits) to put the pointer in
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binary.BigEndian.PutUint16(msg[off:], uint16(pointer^0xC000))
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return off + 2, nil
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}
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if off < len(msg) {
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msg[off] = 0
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}
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return off + 1, nil
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}
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// isRootLabel returns whether s or bs, from off to end, is the root
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// label ".".
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//
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// If bs is nil, s will be checked, otherwise bs will be checked.
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func isRootLabel(s string, bs []byte, off, end int) bool {
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if bs == nil {
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return s[off:end] == "."
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}
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return end-off == 1 && bs[off] == '.'
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}
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// Unpack a domain name.
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// In addition to the simple sequences of counted strings above,
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// domain names are allowed to refer to strings elsewhere in the
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// packet, to avoid repeating common suffixes when returning
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// many entries in a single domain. The pointers are marked
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// by a length byte with the top two bits set. Ignoring those
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// two bits, that byte and the next give a 14 bit offset from msg[0]
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// where we should pick up the trail.
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// Note that if we jump elsewhere in the packet,
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// we return off1 == the offset after the first pointer we found,
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// which is where the next record will start.
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// In theory, the pointers are only allowed to jump backward.
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// We let them jump anywhere and stop jumping after a while.
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// UnpackDomainName unpacks a domain name into a string. It returns
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// the name, the new offset into msg and any error that occurred.
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//
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// When an error is encountered, the unpacked name will be discarded
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// and len(msg) will be returned as the offset.
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func UnpackDomainName(msg []byte, off int) (string, int, error) {
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s := make([]byte, 0, maxDomainNamePresentationLength)
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off1 := 0
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lenmsg := len(msg)
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budget := maxDomainNameWireOctets
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ptr := 0 // number of pointers followed
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Loop:
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for {
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if off >= lenmsg {
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return "", lenmsg, ErrBuf
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}
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c := int(msg[off])
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off++
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switch c & 0xC0 {
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case 0x00:
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if c == 0x00 {
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// end of name
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break Loop
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}
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// literal string
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if off+c > lenmsg {
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return "", lenmsg, ErrBuf
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}
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budget -= c + 1 // +1 for the label separator
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if budget <= 0 {
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return "", lenmsg, ErrLongDomain
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}
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for _, b := range msg[off : off+c] {
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if isDomainNameLabelSpecial(b) {
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s = append(s, '\\', b)
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} else if b < ' ' || b > '~' {
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s = append(s, escapeByte(b)...)
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} else {
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s = append(s, b)
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}
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}
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s = append(s, '.')
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off += c
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case 0xC0:
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// pointer to somewhere else in msg.
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// remember location after first ptr,
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// since that's how many bytes we consumed.
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// also, don't follow too many pointers --
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// maybe there's a loop.
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if off >= lenmsg {
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return "", lenmsg, ErrBuf
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}
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c1 := msg[off]
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off++
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if ptr == 0 {
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off1 = off
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}
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if ptr++; ptr > maxCompressionPointers {
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return "", lenmsg, &Error{err: "too many compression pointers"}
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}
|
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// pointer should guarantee that it advances and points forwards at least
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// but the condition on previous three lines guarantees that it's
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// at least loop-free
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off = (c^0xC0)<<8 | int(c1)
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default:
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// 0x80 and 0x40 are reserved
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return "", lenmsg, ErrRdata
|
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}
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}
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if ptr == 0 {
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off1 = off
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}
|
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if len(s) == 0 {
|
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return ".", off1, nil
|
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}
|
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return string(s), off1, nil
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}
|
|
|
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func packTxt(txt []string, msg []byte, offset int, tmp []byte) (int, error) {
|
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if len(txt) == 0 {
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if offset >= len(msg) {
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return offset, ErrBuf
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}
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msg[offset] = 0
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return offset, nil
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}
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var err error
|
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for _, s := range txt {
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if len(s) > len(tmp) {
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return offset, ErrBuf
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}
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offset, err = packTxtString(s, msg, offset, tmp)
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if err != nil {
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return offset, err
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}
|
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}
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return offset, nil
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}
|
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|
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func packTxtString(s string, msg []byte, offset int, tmp []byte) (int, error) {
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lenByteOffset := offset
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if offset >= len(msg) || len(s) > len(tmp) {
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return offset, ErrBuf
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}
|
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offset++
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bs := tmp[:len(s)]
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copy(bs, s)
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for i := 0; i < len(bs); i++ {
|
|
if len(msg) <= offset {
|
|
return offset, ErrBuf
|
|
}
|
|
if bs[i] == '\\' {
|
|
i++
|
|
if i == len(bs) {
|
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break
|
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}
|
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// check for \DDD
|
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if i+2 < len(bs) && isDigit(bs[i]) && isDigit(bs[i+1]) && isDigit(bs[i+2]) {
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msg[offset] = dddToByte(bs[i:])
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i += 2
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} else {
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msg[offset] = bs[i]
|
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}
|
|
} else {
|
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msg[offset] = bs[i]
|
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}
|
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offset++
|
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}
|
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l := offset - lenByteOffset - 1
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if l > 255 {
|
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return offset, &Error{err: "string exceeded 255 bytes in txt"}
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|
}
|
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msg[lenByteOffset] = byte(l)
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return offset, nil
|
|
}
|
|
|
|
func packOctetString(s string, msg []byte, offset int, tmp []byte) (int, error) {
|
|
if offset >= len(msg) || len(s) > len(tmp) {
|
|
return offset, ErrBuf
|
|
}
|
|
bs := tmp[:len(s)]
|
|
copy(bs, s)
|
|
for i := 0; i < len(bs); i++ {
|
|
if len(msg) <= offset {
|
|
return offset, ErrBuf
|
|
}
|
|
if bs[i] == '\\' {
|
|
i++
|
|
if i == len(bs) {
|
|
break
|
|
}
|
|
// check for \DDD
|
|
if i+2 < len(bs) && isDigit(bs[i]) && isDigit(bs[i+1]) && isDigit(bs[i+2]) {
|
|
msg[offset] = dddToByte(bs[i:])
|
|
i += 2
|
|
} else {
|
|
msg[offset] = bs[i]
|
|
}
|
|
} else {
|
|
msg[offset] = bs[i]
|
|
}
|
|
offset++
|
|
}
|
|
return offset, nil
|
|
}
|
|
|
|
func unpackTxt(msg []byte, off0 int) (ss []string, off int, err error) {
|
|
off = off0
|
|
var s string
|
|
for off < len(msg) && err == nil {
|
|
s, off, err = unpackString(msg, off)
|
|
if err == nil {
|
|
ss = append(ss, s)
|
|
}
|
|
}
|
|
return
|
|
}
|
|
|
|
// Helpers for dealing with escaped bytes
|
|
func isDigit(b byte) bool { return b >= '0' && b <= '9' }
|
|
|
|
func dddToByte(s []byte) byte {
|
|
_ = s[2] // bounds check hint to compiler; see golang.org/issue/14808
|
|
return byte((s[0]-'0')*100 + (s[1]-'0')*10 + (s[2] - '0'))
|
|
}
|
|
|
|
func dddStringToByte(s string) byte {
|
|
_ = s[2] // bounds check hint to compiler; see golang.org/issue/14808
|
|
return byte((s[0]-'0')*100 + (s[1]-'0')*10 + (s[2] - '0'))
|
|
}
|
|
|
|
// Helper function for packing and unpacking
|
|
func intToBytes(i *big.Int, length int) []byte {
|
|
buf := i.Bytes()
|
|
if len(buf) < length {
|
|
b := make([]byte, length)
|
|
copy(b[length-len(buf):], buf)
|
|
return b
|
|
}
|
|
return buf
|
|
}
|
|
|
|
// PackRR packs a resource record rr into msg[off:].
|
|
// See PackDomainName for documentation about the compression.
|
|
func PackRR(rr RR, msg []byte, off int, compression map[string]int, compress bool) (off1 int, err error) {
|
|
headerEnd, off1, err := packRR(rr, msg, off, compressionMap{ext: compression}, compress)
|
|
if err == nil {
|
|
// packRR no longer sets the Rdlength field on the rr, but
|
|
// callers might be expecting it so we set it here.
|
|
rr.Header().Rdlength = uint16(off1 - headerEnd)
|
|
}
|
|
return off1, err
|
|
}
|
|
|
|
func packRR(rr RR, msg []byte, off int, compression compressionMap, compress bool) (headerEnd int, off1 int, err error) {
|
|
if rr == nil {
|
|
return len(msg), len(msg), &Error{err: "nil rr"}
|
|
}
|
|
|
|
headerEnd, err = rr.Header().packHeader(msg, off, compression, compress)
|
|
if err != nil {
|
|
return headerEnd, len(msg), err
|
|
}
|
|
|
|
off1, err = rr.pack(msg, headerEnd, compression, compress)
|
|
if err != nil {
|
|
return headerEnd, len(msg), err
|
|
}
|
|
|
|
rdlength := off1 - headerEnd
|
|
if int(uint16(rdlength)) != rdlength { // overflow
|
|
return headerEnd, len(msg), ErrRdata
|
|
}
|
|
|
|
// The RDLENGTH field is the last field in the header and we set it here.
|
|
binary.BigEndian.PutUint16(msg[headerEnd-2:], uint16(rdlength))
|
|
return headerEnd, off1, nil
|
|
}
|
|
|
|
// UnpackRR unpacks msg[off:] into an RR.
|
|
func UnpackRR(msg []byte, off int) (rr RR, off1 int, err error) {
|
|
h, off, msg, err := unpackHeader(msg, off)
|
|
if err != nil {
|
|
return nil, len(msg), err
|
|
}
|
|
|
|
return UnpackRRWithHeader(h, msg, off)
|
|
}
|
|
|
|
// UnpackRRWithHeader unpacks the record type specific payload given an existing
|
|
// RR_Header.
|
|
func UnpackRRWithHeader(h RR_Header, msg []byte, off int) (rr RR, off1 int, err error) {
|
|
if newFn, ok := TypeToRR[h.Rrtype]; ok {
|
|
rr = newFn()
|
|
*rr.Header() = h
|
|
} else {
|
|
rr = &RFC3597{Hdr: h}
|
|
}
|
|
|
|
if noRdata(h) {
|
|
return rr, off, nil
|
|
}
|
|
|
|
end := off + int(h.Rdlength)
|
|
|
|
off, err = rr.unpack(msg, off)
|
|
if err != nil {
|
|
return nil, end, err
|
|
}
|
|
if off != end {
|
|
return &h, end, &Error{err: "bad rdlength"}
|
|
}
|
|
|
|
return rr, off, nil
|
|
}
|
|
|
|
// unpackRRslice unpacks msg[off:] into an []RR.
|
|
// If we cannot unpack the whole array, then it will return nil
|
|
func unpackRRslice(l int, msg []byte, off int) (dst1 []RR, off1 int, err error) {
|
|
var r RR
|
|
// Don't pre-allocate, l may be under attacker control
|
|
var dst []RR
|
|
for i := 0; i < l; i++ {
|
|
off1 := off
|
|
r, off, err = UnpackRR(msg, off)
|
|
if err != nil {
|
|
off = len(msg)
|
|
break
|
|
}
|
|
// If offset does not increase anymore, l is a lie
|
|
if off1 == off {
|
|
break
|
|
}
|
|
dst = append(dst, r)
|
|
}
|
|
if err != nil && off == len(msg) {
|
|
dst = nil
|
|
}
|
|
return dst, off, err
|
|
}
|
|
|
|
// Convert a MsgHdr to a string, with dig-like headers:
|
|
//
|
|
//;; opcode: QUERY, status: NOERROR, id: 48404
|
|
//
|
|
//;; flags: qr aa rd ra;
|
|
func (h *MsgHdr) String() string {
|
|
if h == nil {
|
|
return "<nil> MsgHdr"
|
|
}
|
|
|
|
s := ";; opcode: " + OpcodeToString[h.Opcode]
|
|
s += ", status: " + RcodeToString[h.Rcode]
|
|
s += ", id: " + strconv.Itoa(int(h.Id)) + "\n"
|
|
|
|
s += ";; flags:"
|
|
if h.Response {
|
|
s += " qr"
|
|
}
|
|
if h.Authoritative {
|
|
s += " aa"
|
|
}
|
|
if h.Truncated {
|
|
s += " tc"
|
|
}
|
|
if h.RecursionDesired {
|
|
s += " rd"
|
|
}
|
|
if h.RecursionAvailable {
|
|
s += " ra"
|
|
}
|
|
if h.Zero { // Hmm
|
|
s += " z"
|
|
}
|
|
if h.AuthenticatedData {
|
|
s += " ad"
|
|
}
|
|
if h.CheckingDisabled {
|
|
s += " cd"
|
|
}
|
|
|
|
s += ";"
|
|
return s
|
|
}
|
|
|
|
// Pack packs a Msg: it is converted to to wire format.
|
|
// If the dns.Compress is true the message will be in compressed wire format.
|
|
func (dns *Msg) Pack() (msg []byte, err error) {
|
|
return dns.PackBuffer(nil)
|
|
}
|
|
|
|
// PackBuffer packs a Msg, using the given buffer buf. If buf is too small a new buffer is allocated.
|
|
func (dns *Msg) PackBuffer(buf []byte) (msg []byte, err error) {
|
|
// If this message can't be compressed, avoid filling the
|
|
// compression map and creating garbage.
|
|
if dns.Compress && dns.isCompressible() {
|
|
compression := make(map[string]uint16) // Compression pointer mappings.
|
|
return dns.packBufferWithCompressionMap(buf, compressionMap{int: compression}, true)
|
|
}
|
|
|
|
return dns.packBufferWithCompressionMap(buf, compressionMap{}, false)
|
|
}
|
|
|
|
// packBufferWithCompressionMap packs a Msg, using the given buffer buf.
|
|
func (dns *Msg) packBufferWithCompressionMap(buf []byte, compression compressionMap, compress bool) (msg []byte, err error) {
|
|
if dns.Rcode < 0 || dns.Rcode > 0xFFF {
|
|
return nil, ErrRcode
|
|
}
|
|
|
|
// Set extended rcode unconditionally if we have an opt, this will allow
|
|
// reseting the extended rcode bits if they need to.
|
|
if opt := dns.IsEdns0(); opt != nil {
|
|
opt.SetExtendedRcode(uint16(dns.Rcode))
|
|
} else if dns.Rcode > 0xF {
|
|
// If Rcode is an extended one and opt is nil, error out.
|
|
return nil, ErrExtendedRcode
|
|
}
|
|
|
|
// Convert convenient Msg into wire-like Header.
|
|
var dh Header
|
|
dh.Id = dns.Id
|
|
dh.Bits = uint16(dns.Opcode)<<11 | uint16(dns.Rcode&0xF)
|
|
if dns.Response {
|
|
dh.Bits |= _QR
|
|
}
|
|
if dns.Authoritative {
|
|
dh.Bits |= _AA
|
|
}
|
|
if dns.Truncated {
|
|
dh.Bits |= _TC
|
|
}
|
|
if dns.RecursionDesired {
|
|
dh.Bits |= _RD
|
|
}
|
|
if dns.RecursionAvailable {
|
|
dh.Bits |= _RA
|
|
}
|
|
if dns.Zero {
|
|
dh.Bits |= _Z
|
|
}
|
|
if dns.AuthenticatedData {
|
|
dh.Bits |= _AD
|
|
}
|
|
if dns.CheckingDisabled {
|
|
dh.Bits |= _CD
|
|
}
|
|
|
|
dh.Qdcount = uint16(len(dns.Question))
|
|
dh.Ancount = uint16(len(dns.Answer))
|
|
dh.Nscount = uint16(len(dns.Ns))
|
|
dh.Arcount = uint16(len(dns.Extra))
|
|
|
|
// We need the uncompressed length here, because we first pack it and then compress it.
|
|
msg = buf
|
|
uncompressedLen := msgLenWithCompressionMap(dns, nil)
|
|
if packLen := uncompressedLen + 1; len(msg) < packLen {
|
|
msg = make([]byte, packLen)
|
|
}
|
|
|
|
// Pack it in: header and then the pieces.
|
|
off := 0
|
|
off, err = dh.pack(msg, off, compression, compress)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
for _, r := range dns.Question {
|
|
off, err = r.pack(msg, off, compression, compress)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
}
|
|
for _, r := range dns.Answer {
|
|
_, off, err = packRR(r, msg, off, compression, compress)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
}
|
|
for _, r := range dns.Ns {
|
|
_, off, err = packRR(r, msg, off, compression, compress)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
}
|
|
for _, r := range dns.Extra {
|
|
_, off, err = packRR(r, msg, off, compression, compress)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
}
|
|
return msg[:off], nil
|
|
}
|
|
|
|
func (dns *Msg) unpack(dh Header, msg []byte, off int) (err error) {
|
|
// If we are at the end of the message we should return *just* the
|
|
// header. This can still be useful to the caller. 9.9.9.9 sends these
|
|
// when responding with REFUSED for instance.
|
|
if off == len(msg) {
|
|
// reset sections before returning
|
|
dns.Question, dns.Answer, dns.Ns, dns.Extra = nil, nil, nil, nil
|
|
return nil
|
|
}
|
|
|
|
// Qdcount, Ancount, Nscount, Arcount can't be trusted, as they are
|
|
// attacker controlled. This means we can't use them to pre-allocate
|
|
// slices.
|
|
dns.Question = nil
|
|
for i := 0; i < int(dh.Qdcount); i++ {
|
|
off1 := off
|
|
var q Question
|
|
q, off, err = unpackQuestion(msg, off)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
if off1 == off { // Offset does not increase anymore, dh.Qdcount is a lie!
|
|
dh.Qdcount = uint16(i)
|
|
break
|
|
}
|
|
dns.Question = append(dns.Question, q)
|
|
}
|
|
|
|
dns.Answer, off, err = unpackRRslice(int(dh.Ancount), msg, off)
|
|
// The header counts might have been wrong so we need to update it
|
|
dh.Ancount = uint16(len(dns.Answer))
|
|
if err == nil {
|
|
dns.Ns, off, err = unpackRRslice(int(dh.Nscount), msg, off)
|
|
}
|
|
// The header counts might have been wrong so we need to update it
|
|
dh.Nscount = uint16(len(dns.Ns))
|
|
if err == nil {
|
|
dns.Extra, off, err = unpackRRslice(int(dh.Arcount), msg, off)
|
|
}
|
|
// The header counts might have been wrong so we need to update it
|
|
dh.Arcount = uint16(len(dns.Extra))
|
|
|
|
// Set extended Rcode
|
|
if opt := dns.IsEdns0(); opt != nil {
|
|
dns.Rcode |= opt.ExtendedRcode()
|
|
}
|
|
|
|
if off != len(msg) {
|
|
// TODO(miek) make this an error?
|
|
// use PackOpt to let people tell how detailed the error reporting should be?
|
|
// println("dns: extra bytes in dns packet", off, "<", len(msg))
|
|
}
|
|
return err
|
|
|
|
}
|
|
|
|
// Unpack unpacks a binary message to a Msg structure.
|
|
func (dns *Msg) Unpack(msg []byte) (err error) {
|
|
dh, off, err := unpackMsgHdr(msg, 0)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
dns.setHdr(dh)
|
|
return dns.unpack(dh, msg, off)
|
|
}
|
|
|
|
// Convert a complete message to a string with dig-like output.
|
|
func (dns *Msg) String() string {
|
|
if dns == nil {
|
|
return "<nil> MsgHdr"
|
|
}
|
|
s := dns.MsgHdr.String() + " "
|
|
s += "QUERY: " + strconv.Itoa(len(dns.Question)) + ", "
|
|
s += "ANSWER: " + strconv.Itoa(len(dns.Answer)) + ", "
|
|
s += "AUTHORITY: " + strconv.Itoa(len(dns.Ns)) + ", "
|
|
s += "ADDITIONAL: " + strconv.Itoa(len(dns.Extra)) + "\n"
|
|
if len(dns.Question) > 0 {
|
|
s += "\n;; QUESTION SECTION:\n"
|
|
for _, r := range dns.Question {
|
|
s += r.String() + "\n"
|
|
}
|
|
}
|
|
if len(dns.Answer) > 0 {
|
|
s += "\n;; ANSWER SECTION:\n"
|
|
for _, r := range dns.Answer {
|
|
if r != nil {
|
|
s += r.String() + "\n"
|
|
}
|
|
}
|
|
}
|
|
if len(dns.Ns) > 0 {
|
|
s += "\n;; AUTHORITY SECTION:\n"
|
|
for _, r := range dns.Ns {
|
|
if r != nil {
|
|
s += r.String() + "\n"
|
|
}
|
|
}
|
|
}
|
|
if len(dns.Extra) > 0 {
|
|
s += "\n;; ADDITIONAL SECTION:\n"
|
|
for _, r := range dns.Extra {
|
|
if r != nil {
|
|
s += r.String() + "\n"
|
|
}
|
|
}
|
|
}
|
|
return s
|
|
}
|
|
|
|
// isCompressible returns whether the msg may be compressible.
|
|
func (dns *Msg) isCompressible() bool {
|
|
// If we only have one question, there is nothing we can ever compress.
|
|
return len(dns.Question) > 1 || len(dns.Answer) > 0 ||
|
|
len(dns.Ns) > 0 || len(dns.Extra) > 0
|
|
}
|
|
|
|
// Len returns the message length when in (un)compressed wire format.
|
|
// If dns.Compress is true compression it is taken into account. Len()
|
|
// is provided to be a faster way to get the size of the resulting packet,
|
|
// than packing it, measuring the size and discarding the buffer.
|
|
func (dns *Msg) Len() int {
|
|
// If this message can't be compressed, avoid filling the
|
|
// compression map and creating garbage.
|
|
if dns.Compress && dns.isCompressible() {
|
|
compression := make(map[string]struct{})
|
|
return msgLenWithCompressionMap(dns, compression)
|
|
}
|
|
|
|
return msgLenWithCompressionMap(dns, nil)
|
|
}
|
|
|
|
func msgLenWithCompressionMap(dns *Msg, compression map[string]struct{}) int {
|
|
l := headerSize
|
|
|
|
for _, r := range dns.Question {
|
|
l += r.len(l, compression)
|
|
}
|
|
for _, r := range dns.Answer {
|
|
if r != nil {
|
|
l += r.len(l, compression)
|
|
}
|
|
}
|
|
for _, r := range dns.Ns {
|
|
if r != nil {
|
|
l += r.len(l, compression)
|
|
}
|
|
}
|
|
for _, r := range dns.Extra {
|
|
if r != nil {
|
|
l += r.len(l, compression)
|
|
}
|
|
}
|
|
|
|
return l
|
|
}
|
|
|
|
func domainNameLen(s string, off int, compression map[string]struct{}, compress bool) int {
|
|
if s == "" || s == "." {
|
|
return 1
|
|
}
|
|
|
|
escaped := strings.Contains(s, "\\")
|
|
|
|
if compression != nil && (compress || off < maxCompressionOffset) {
|
|
// compressionLenSearch will insert the entry into the compression
|
|
// map if it doesn't contain it.
|
|
if l, ok := compressionLenSearch(compression, s, off); ok && compress {
|
|
if escaped {
|
|
return escapedNameLen(s[:l]) + 2
|
|
}
|
|
|
|
return l + 2
|
|
}
|
|
}
|
|
|
|
if escaped {
|
|
return escapedNameLen(s) + 1
|
|
}
|
|
|
|
return len(s) + 1
|
|
}
|
|
|
|
func escapedNameLen(s string) int {
|
|
nameLen := len(s)
|
|
for i := 0; i < len(s); i++ {
|
|
if s[i] != '\\' {
|
|
continue
|
|
}
|
|
|
|
if i+3 < len(s) && isDigit(s[i+1]) && isDigit(s[i+2]) && isDigit(s[i+3]) {
|
|
nameLen -= 3
|
|
i += 3
|
|
} else {
|
|
nameLen--
|
|
i++
|
|
}
|
|
}
|
|
|
|
return nameLen
|
|
}
|
|
|
|
func compressionLenSearch(c map[string]struct{}, s string, msgOff int) (int, bool) {
|
|
for off, end := 0, false; !end; off, end = NextLabel(s, off) {
|
|
if _, ok := c[s[off:]]; ok {
|
|
return off, true
|
|
}
|
|
|
|
if msgOff+off < maxCompressionOffset {
|
|
c[s[off:]] = struct{}{}
|
|
}
|
|
}
|
|
|
|
return 0, false
|
|
}
|
|
|
|
// Copy returns a new RR which is a deep-copy of r.
|
|
func Copy(r RR) RR { return r.copy() }
|
|
|
|
// Len returns the length (in octets) of the uncompressed RR in wire format.
|
|
func Len(r RR) int { return r.len(0, nil) }
|
|
|
|
// Copy returns a new *Msg which is a deep-copy of dns.
|
|
func (dns *Msg) Copy() *Msg { return dns.CopyTo(new(Msg)) }
|
|
|
|
// CopyTo copies the contents to the provided message using a deep-copy and returns the copy.
|
|
func (dns *Msg) CopyTo(r1 *Msg) *Msg {
|
|
r1.MsgHdr = dns.MsgHdr
|
|
r1.Compress = dns.Compress
|
|
|
|
if len(dns.Question) > 0 {
|
|
r1.Question = make([]Question, len(dns.Question))
|
|
copy(r1.Question, dns.Question) // TODO(miek): Question is an immutable value, ok to do a shallow-copy
|
|
}
|
|
|
|
rrArr := make([]RR, len(dns.Answer)+len(dns.Ns)+len(dns.Extra))
|
|
r1.Answer, rrArr = rrArr[:0:len(dns.Answer)], rrArr[len(dns.Answer):]
|
|
r1.Ns, rrArr = rrArr[:0:len(dns.Ns)], rrArr[len(dns.Ns):]
|
|
r1.Extra = rrArr[:0:len(dns.Extra)]
|
|
|
|
for _, r := range dns.Answer {
|
|
r1.Answer = append(r1.Answer, r.copy())
|
|
}
|
|
|
|
for _, r := range dns.Ns {
|
|
r1.Ns = append(r1.Ns, r.copy())
|
|
}
|
|
|
|
for _, r := range dns.Extra {
|
|
r1.Extra = append(r1.Extra, r.copy())
|
|
}
|
|
|
|
return r1
|
|
}
|
|
|
|
func (q *Question) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
|
|
off, err := packDomainName(q.Name, msg, off, compression, compress)
|
|
if err != nil {
|
|
return off, err
|
|
}
|
|
off, err = packUint16(q.Qtype, msg, off)
|
|
if err != nil {
|
|
return off, err
|
|
}
|
|
off, err = packUint16(q.Qclass, msg, off)
|
|
if err != nil {
|
|
return off, err
|
|
}
|
|
return off, nil
|
|
}
|
|
|
|
func unpackQuestion(msg []byte, off int) (Question, int, error) {
|
|
var (
|
|
q Question
|
|
err error
|
|
)
|
|
q.Name, off, err = UnpackDomainName(msg, off)
|
|
if err != nil {
|
|
return q, off, err
|
|
}
|
|
if off == len(msg) {
|
|
return q, off, nil
|
|
}
|
|
q.Qtype, off, err = unpackUint16(msg, off)
|
|
if err != nil {
|
|
return q, off, err
|
|
}
|
|
if off == len(msg) {
|
|
return q, off, nil
|
|
}
|
|
q.Qclass, off, err = unpackUint16(msg, off)
|
|
if off == len(msg) {
|
|
return q, off, nil
|
|
}
|
|
return q, off, err
|
|
}
|
|
|
|
func (dh *Header) pack(msg []byte, off int, compression compressionMap, compress bool) (int, error) {
|
|
off, err := packUint16(dh.Id, msg, off)
|
|
if err != nil {
|
|
return off, err
|
|
}
|
|
off, err = packUint16(dh.Bits, msg, off)
|
|
if err != nil {
|
|
return off, err
|
|
}
|
|
off, err = packUint16(dh.Qdcount, msg, off)
|
|
if err != nil {
|
|
return off, err
|
|
}
|
|
off, err = packUint16(dh.Ancount, msg, off)
|
|
if err != nil {
|
|
return off, err
|
|
}
|
|
off, err = packUint16(dh.Nscount, msg, off)
|
|
if err != nil {
|
|
return off, err
|
|
}
|
|
off, err = packUint16(dh.Arcount, msg, off)
|
|
if err != nil {
|
|
return off, err
|
|
}
|
|
return off, nil
|
|
}
|
|
|
|
func unpackMsgHdr(msg []byte, off int) (Header, int, error) {
|
|
var (
|
|
dh Header
|
|
err error
|
|
)
|
|
dh.Id, off, err = unpackUint16(msg, off)
|
|
if err != nil {
|
|
return dh, off, err
|
|
}
|
|
dh.Bits, off, err = unpackUint16(msg, off)
|
|
if err != nil {
|
|
return dh, off, err
|
|
}
|
|
dh.Qdcount, off, err = unpackUint16(msg, off)
|
|
if err != nil {
|
|
return dh, off, err
|
|
}
|
|
dh.Ancount, off, err = unpackUint16(msg, off)
|
|
if err != nil {
|
|
return dh, off, err
|
|
}
|
|
dh.Nscount, off, err = unpackUint16(msg, off)
|
|
if err != nil {
|
|
return dh, off, err
|
|
}
|
|
dh.Arcount, off, err = unpackUint16(msg, off)
|
|
if err != nil {
|
|
return dh, off, err
|
|
}
|
|
return dh, off, nil
|
|
}
|
|
|
|
// setHdr set the header in the dns using the binary data in dh.
|
|
func (dns *Msg) setHdr(dh Header) {
|
|
dns.Id = dh.Id
|
|
dns.Response = dh.Bits&_QR != 0
|
|
dns.Opcode = int(dh.Bits>>11) & 0xF
|
|
dns.Authoritative = dh.Bits&_AA != 0
|
|
dns.Truncated = dh.Bits&_TC != 0
|
|
dns.RecursionDesired = dh.Bits&_RD != 0
|
|
dns.RecursionAvailable = dh.Bits&_RA != 0
|
|
dns.Zero = dh.Bits&_Z != 0 // _Z covers the zero bit, which should be zero; not sure why we set it to the opposite.
|
|
dns.AuthenticatedData = dh.Bits&_AD != 0
|
|
dns.CheckingDisabled = dh.Bits&_CD != 0
|
|
dns.Rcode = int(dh.Bits & 0xF)
|
|
}
|