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Handle packing of empty RDATA correctly for EDNS0_EXPIRE (Resolves #1292) (#1293) 

* Change EDNS_EXPIRE field to support zero length option data (Resolves #1292)

As per [RFC7134](https://datatracker.ietf.org/doc/html/rfc7314#section-2) the Expire
Option in queries should be zero-length. In the current implementation the field is
uint32 which always instatiates 4bytes for that field when packing to wire format.
For that reason we change the field to []uint8 so it can support 0-length and 4-byte
length option data.

* addressed comments

* addressed comments

* make change backwards compatible

* add comment for Empty field
This commit is contained in:
Dimitris Mavrommatis 2022-03-12 08:42:42 +00:00 committed by GitHub
parent 05140a3136
commit d48e92a0e6
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1 changed files with 14 additions and 2 deletions
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16
edns.go
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@ -584,14 +584,17 @@ func (e *EDNS0_N3U) copy() EDNS0 { return &EDNS0_N3U{e.Code, e.AlgCode} }
type EDNS0_EXPIRE struct {
Code uint16 // Always EDNS0EXPIRE
Expire uint32
Empty bool // Empty is used to signal an empty Expire option in a backwards compatible way, it's not used on the wire.
}
// Option implements the EDNS0 interface.
func (e *EDNS0_EXPIRE) Option() uint16 { return EDNS0EXPIRE }
func (e *EDNS0_EXPIRE) String() string { return strconv.FormatUint(uint64(e.Expire), 10) }
func (e *EDNS0_EXPIRE) copy() EDNS0 { return &EDNS0_EXPIRE{e.Code, e.Expire} }
func (e *EDNS0_EXPIRE) copy() EDNS0 { return &EDNS0_EXPIRE{e.Code, e.Expire, e.Empty} }
func (e *EDNS0_EXPIRE) pack() ([]byte, error) {
if e.Empty {
return []byte{}, nil
}
b := make([]byte, 4)
binary.BigEndian.PutUint32(b, e.Expire)
return b, nil
@ -600,15 +603,24 @@ func (e *EDNS0_EXPIRE) pack() ([]byte, error) {
func (e *EDNS0_EXPIRE) unpack(b []byte) error {
if len(b) == 0 {
// zero-length EXPIRE query, see RFC 7314 Section 2
e.Empty = true
return nil
}
if len(b) < 4 {
return ErrBuf
}
e.Expire = binary.BigEndian.Uint32(b)
e.Empty = false
return nil
}
func (e *EDNS0_EXPIRE) String() (s string) {
if e.Empty {
return ""
}
return strconv.FormatUint(uint64(e.Expire), 10)
}
// The EDNS0_LOCAL option is used for local/experimental purposes. The option
// code is recommended to be within the range [EDNS0LOCALSTART, EDNS0LOCALEND]
// (RFC6891), although any unassigned code can actually be used. The content of