mirror of
https://github.com/slackhq/nebula.git
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Wade Simmons
118 lines
3.8 KiB
Go
118 lines
3.8 KiB
Go
package noiseutil
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import (
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"bytes"
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"crypto/cipher"
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"encoding/binary"
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"reflect"
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"unsafe"
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// unsafe needed for go:linkname
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_ "crypto/tls"
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_ "unsafe"
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"github.com/flynn/noise"
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)
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// TODO: Use NewGCMWithCounterNonce or NewGCMForQUIC once available:
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// - https://github.com/golang/go/issues/73110
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// - https://github.com/golang/go/issues/79219
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// Using tls.aeadAESGCMTLS13 gives us the TLS 1.3 GCM, which also verifies
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// that the nonce is strictly increasing. This works for both boringcrypto
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// and fips140.
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//
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//go:linkname aeadAESGCMTLS13 crypto/tls.aeadAESGCMTLS13
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func aeadAESGCMTLS13(key, noncePrefix []byte) cipher.AEAD
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type cipherFn struct {
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fn func([32]byte) noise.Cipher
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name string
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}
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func (c cipherFn) Cipher(k [32]byte) noise.Cipher { return c.fn(k) }
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func (c cipherFn) CipherName() string { return c.name }
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// CipherAESGCMFIPS140 is the AES256-GCM AEAD cipher (using aeadAESGCM when fips140 is enabled)
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var CipherAESGCMFIPS140 noise.CipherFunc = cipherFn{cipherAESGCMFIPS140, "AESGCM"}
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// tls.aeadAESGCMTLS13 uses a 4 byte static prefix and an 8 byte XOR mask
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var emptyNonce = []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
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func cipherAESGCMFIPS140(k [32]byte) noise.Cipher {
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gcm := aeadAESGCMTLS13(k[:], emptyNonce)
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gcm = extractFIPSAEAD(gcm)
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return &aeadGCMFIPS140Cipher{
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AEAD: gcm,
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}
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}
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type aeadGCMFIPS140Cipher struct {
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cipher.AEAD
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ready bool
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}
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// Extract the internal FIPS GCM implementation from the tls wrapper. The TLS
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// wrapper is not thread safe around Open, so instead of locking around it we
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// can grab the internal implementation that is thread safe. This is the FIPS
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// module implementation: `crypto/internal/fips140/aes/gcm.GCMWithXORCounterNonce`
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//
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// - https://github.com/golang/go/blob/go1.26.4/src/crypto/internal/fips140/aes/gcm/gcm_nonces.go#L212-L287
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//
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// The wrapper is struct `crypto/tls.xorNonceAEAD` , with field `aead`:
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//
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// - https://github.com/golang/go/blob/go1.26.4/src/crypto/tls/cipher_suites.go#L482-L487
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//
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// This can be cleaned up once these FIPS implementations are exposed directly:
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//
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// - https://github.com/golang/go/issues/73110
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func extractFIPSAEAD(xorNonceAEAD cipher.AEAD) cipher.AEAD {
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r := reflect.ValueOf(xorNonceAEAD)
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v := r.Elem().FieldByName("aead")
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v2 := reflect.NewAt(v.Type(), unsafe.Pointer(v.UnsafeAddr())).Elem()
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return v2.Interface().(cipher.AEAD)
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}
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func (c *aeadGCMFIPS140Cipher) init(nonce []byte) {
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// GCMWithXORCounterNonce expects that the first call to Seal
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// is with a counter of `0`, this is how it extracts the nonce mask.
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// We can clean this up in the future when NewGCMWithCounterNonce or
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// NewGCMForQUIC are available:
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if !bytes.Equal(emptyNonce, nonce) {
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c.AEAD.Seal([]byte{}, emptyNonce, []byte{}, []byte{})
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}
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c.ready = true
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}
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func (c *aeadGCMFIPS140Cipher) Seal(dst, nonce, plaintext, additionalData []byte) []byte {
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if !c.ready {
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c.init(nonce)
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}
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return c.AEAD.Seal(dst, nonce, plaintext, additionalData)
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}
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func (c *aeadGCMFIPS140Cipher) Encrypt(out []byte, n uint64, ad, plaintext []byte) []byte {
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return c.Seal(out, aeadGCMFIPS140CipherNonce(n), plaintext, ad)
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}
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func (c *aeadGCMFIPS140Cipher) Decrypt(out []byte, n uint64, ad, ciphertext []byte) ([]byte, error) {
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return c.Open(out, aeadGCMFIPS140CipherNonce(n), ciphertext, ad)
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}
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func (c *aeadGCMFIPS140Cipher) EncryptDanger(out, ad, plaintext []byte, n uint64, nb []byte) ([]byte, error) {
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binary.BigEndian.PutUint64(nb[4:], n)
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out = c.Seal(out, nb, plaintext, ad)
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return out, nil
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}
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func (c *aeadGCMFIPS140Cipher) DecryptDanger(out, ad, ciphertext []byte, n uint64, nb []byte) ([]byte, error) {
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binary.BigEndian.PutUint64(nb[4:], n)
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return c.Open(out, nb, ciphertext, ad)
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}
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func aeadGCMFIPS140CipherNonce(n uint64) []byte {
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// GCMWithXORCounterNonce uses a 4 byte static prefix and an 8 byte nonce
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var nonce [12]byte
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binary.BigEndian.PutUint64(nonce[4:], n)
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return nonce[:]
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}
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