diff options
Diffstat (limited to 'vendor/github.com/pion/stun/fingerprint.go')
-rw-r--r-- | vendor/github.com/pion/stun/fingerprint.go | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/vendor/github.com/pion/stun/fingerprint.go b/vendor/github.com/pion/stun/fingerprint.go new file mode 100644 index 0000000..aef80a2 --- /dev/null +++ b/vendor/github.com/pion/stun/fingerprint.go @@ -0,0 +1,67 @@ +package stun + +import ( + "errors" + "hash/crc32" +) + +// FingerprintAttr represents FINGERPRINT attribute. +// +// RFC 5389 Section 15.5 +type FingerprintAttr struct{} + +// ErrFingerprintMismatch means that computed fingerprint differs from expected. +var ErrFingerprintMismatch = errors.New("fingerprint check failed") + +// Fingerprint is shorthand for FingerprintAttr. +// +// Example: +// +// m := New() +// Fingerprint.AddTo(m) +var Fingerprint FingerprintAttr + +const ( + fingerprintXORValue uint32 = 0x5354554e //nolint:staticcheck + fingerprintSize = 4 // 32 bit +) + +// FingerprintValue returns CRC-32 of b XOR-ed by 0x5354554e. +// +// The value of the attribute is computed as the CRC-32 of the STUN message +// up to (but excluding) the FINGERPRINT attribute itself, XOR'ed with +// the 32-bit value 0x5354554e (the XOR helps in cases where an +// application packet is also using CRC-32 in it). +func FingerprintValue(b []byte) uint32 { + return crc32.ChecksumIEEE(b) ^ fingerprintXORValue // XOR +} + +// AddTo adds fingerprint to message. +func (FingerprintAttr) AddTo(m *Message) error { + l := m.Length + // length in header should include size of fingerprint attribute + m.Length += fingerprintSize + attributeHeaderSize // increasing length + m.WriteLength() // writing Length to Raw + b := make([]byte, fingerprintSize) + val := FingerprintValue(m.Raw) + bin.PutUint32(b, val) + m.Length = l + m.Add(AttrFingerprint, b) + return nil +} + +// Check reads fingerprint value from m and checks it, returning error if any. +// Can return *AttrLengthErr, ErrAttributeNotFound, and *CRCMismatch. +func (FingerprintAttr) Check(m *Message) error { + b, err := m.Get(AttrFingerprint) + if err != nil { + return err + } + if err = CheckSize(AttrFingerprint, len(b), fingerprintSize); err != nil { + return err + } + val := bin.Uint32(b) + attrStart := len(m.Raw) - (fingerprintSize + attributeHeaderSize) + expected := FingerprintValue(m.Raw[:attrStart]) + return checkFingerprint(val, expected) +} |