diff options
Diffstat (limited to 'vendor/golang.org/x/crypto/otr/otr.go')
| -rw-r--r-- | vendor/golang.org/x/crypto/otr/otr.go | 1415 |
1 files changed, 0 insertions, 1415 deletions
diff --git a/vendor/golang.org/x/crypto/otr/otr.go b/vendor/golang.org/x/crypto/otr/otr.go deleted file mode 100644 index 173b753db..000000000 --- a/vendor/golang.org/x/crypto/otr/otr.go +++ /dev/null @@ -1,1415 +0,0 @@ -// Copyright 2012 The Go Authors. All rights reserved. -// Use of this source code is governed by a BSD-style -// license that can be found in the LICENSE file. - -// Package otr implements the Off The Record protocol as specified in -// http://www.cypherpunks.ca/otr/Protocol-v2-3.1.0.html -package otr // import "golang.org/x/crypto/otr" - -import ( - "bytes" - "crypto/aes" - "crypto/cipher" - "crypto/dsa" - "crypto/hmac" - "crypto/rand" - "crypto/sha1" - "crypto/sha256" - "crypto/subtle" - "encoding/base64" - "encoding/hex" - "errors" - "hash" - "io" - "math/big" - "strconv" -) - -// SecurityChange describes a change in the security state of a Conversation. -type SecurityChange int - -const ( - NoChange SecurityChange = iota - // NewKeys indicates that a key exchange has completed. This occurs - // when a conversation first becomes encrypted, and when the keys are - // renegotiated within an encrypted conversation. - NewKeys - // SMPSecretNeeded indicates that the peer has started an - // authentication and that we need to supply a secret. Call SMPQuestion - // to get the optional, human readable challenge and then Authenticate - // to supply the matching secret. - SMPSecretNeeded - // SMPComplete indicates that an authentication completed. The identity - // of the peer has now been confirmed. - SMPComplete - // SMPFailed indicates that an authentication failed. - SMPFailed - // ConversationEnded indicates that the peer ended the secure - // conversation. - ConversationEnded -) - -// QueryMessage can be sent to a peer to start an OTR conversation. -var QueryMessage = "?OTRv2?" - -// ErrorPrefix can be used to make an OTR error by appending an error message -// to it. -var ErrorPrefix = "?OTR Error:" - -var ( - fragmentPartSeparator = []byte(",") - fragmentPrefix = []byte("?OTR,") - msgPrefix = []byte("?OTR:") - queryMarker = []byte("?OTR") -) - -// isQuery attempts to parse an OTR query from msg and returns the greatest -// common version, or 0 if msg is not an OTR query. -func isQuery(msg []byte) (greatestCommonVersion int) { - pos := bytes.Index(msg, queryMarker) - if pos == -1 { - return 0 - } - for i, c := range msg[pos+len(queryMarker):] { - if i == 0 { - if c == '?' { - // Indicates support for version 1, but we don't - // implement that. - continue - } - - if c != 'v' { - // Invalid message - return 0 - } - - continue - } - - if c == '?' { - // End of message - return - } - - if c == ' ' || c == '\t' { - // Probably an invalid message - return 0 - } - - if c == '2' { - greatestCommonVersion = 2 - } - } - - return 0 -} - -const ( - statePlaintext = iota - stateEncrypted - stateFinished -) - -const ( - authStateNone = iota - authStateAwaitingDHKey - authStateAwaitingRevealSig - authStateAwaitingSig -) - -const ( - msgTypeDHCommit = 2 - msgTypeData = 3 - msgTypeDHKey = 10 - msgTypeRevealSig = 17 - msgTypeSig = 18 -) - -const ( - // If the requested fragment size is less than this, it will be ignored. - minFragmentSize = 18 - // Messages are padded to a multiple of this number of bytes. - paddingGranularity = 256 - // The number of bytes in a Diffie-Hellman private value (320-bits). - dhPrivateBytes = 40 - // The number of bytes needed to represent an element of the DSA - // subgroup (160-bits). - dsaSubgroupBytes = 20 - // The number of bytes of the MAC that are sent on the wire (160-bits). - macPrefixBytes = 20 -) - -// These are the global, common group parameters for OTR. -var ( - p *big.Int // group prime - g *big.Int // group generator - q *big.Int // group order - pMinus2 *big.Int -) - -func init() { - p, _ = new(big.Int).SetString("FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE649286651ECE45B3DC2007CB8A163BF0598DA48361C55D39A69163FA8FD24CF5F83655D23DCA3AD961C62F356208552BB9ED529077096966D670C354E4ABC9804F1746C08CA237327FFFFFFFFFFFFFFFF", 16) - q, _ = new(big.Int).SetString("7FFFFFFFFFFFFFFFE487ED5110B4611A62633145C06E0E68948127044533E63A0105DF531D89CD9128A5043CC71A026EF7CA8CD9E69D218D98158536F92F8A1BA7F09AB6B6A8E122F242DABB312F3F637A262174D31BF6B585FFAE5B7A035BF6F71C35FDAD44CFD2D74F9208BE258FF324943328F6722D9EE1003E5C50B1DF82CC6D241B0E2AE9CD348B1FD47E9267AFC1B2AE91EE51D6CB0E3179AB1042A95DCF6A9483B84B4B36B3861AA7255E4C0278BA36046511B993FFFFFFFFFFFFFFFF", 16) - g = new(big.Int).SetInt64(2) - pMinus2 = new(big.Int).Sub(p, g) -} - -// Conversation represents a relation with a peer. The zero value is a valid -// Conversation, although PrivateKey must be set. -// -// When communicating with a peer, all inbound messages should be passed to -// Conversation.Receive and all outbound messages to Conversation.Send. The -// Conversation will take care of maintaining the encryption state and -// negotiating encryption as needed. -type Conversation struct { - // PrivateKey contains the private key to use to sign key exchanges. - PrivateKey *PrivateKey - - // Rand can be set to override the entropy source. Otherwise, - // crypto/rand will be used. - Rand io.Reader - // If FragmentSize is set, all messages produced by Receive and Send - // will be fragmented into messages of, at most, this number of bytes. - FragmentSize int - - // Once Receive has returned NewKeys once, the following fields are - // valid. - SSID [8]byte - TheirPublicKey PublicKey - - state, authState int - - r [16]byte - x, y *big.Int - gx, gy *big.Int - gxBytes []byte - digest [sha256.Size]byte - - revealKeys, sigKeys akeKeys - - myKeyId uint32 - myCurrentDHPub *big.Int - myCurrentDHPriv *big.Int - myLastDHPub *big.Int - myLastDHPriv *big.Int - - theirKeyId uint32 - theirCurrentDHPub *big.Int - theirLastDHPub *big.Int - - keySlots [4]keySlot - - myCounter [8]byte - theirLastCtr [8]byte - oldMACs []byte - - k, n int // fragment state - frag []byte - - smp smpState -} - -// A keySlot contains key material for a specific (their keyid, my keyid) pair. -type keySlot struct { - // used is true if this slot is valid. If false, it's free for reuse. - used bool - theirKeyId uint32 - myKeyId uint32 - sendAESKey, recvAESKey []byte - sendMACKey, recvMACKey []byte - theirLastCtr [8]byte -} - -// akeKeys are generated during key exchange. There's one set for the reveal -// signature message and another for the signature message. In the protocol -// spec the latter are indicated with a prime mark. -type akeKeys struct { - c [16]byte - m1, m2 [32]byte -} - -func (c *Conversation) rand() io.Reader { - if c.Rand != nil { - return c.Rand - } - return rand.Reader -} - -func (c *Conversation) randMPI(buf []byte) *big.Int { - _, err := io.ReadFull(c.rand(), buf) - if err != nil { - panic("otr: short read from random source") - } - - return new(big.Int).SetBytes(buf) -} - -// tlv represents the type-length value from the protocol. -type tlv struct { - typ, length uint16 - data []byte -} - -const ( - tlvTypePadding = 0 - tlvTypeDisconnected = 1 - tlvTypeSMP1 = 2 - tlvTypeSMP2 = 3 - tlvTypeSMP3 = 4 - tlvTypeSMP4 = 5 - tlvTypeSMPAbort = 6 - tlvTypeSMP1WithQuestion = 7 -) - -// Receive handles a message from a peer. It returns a human readable message, -// an indicator of whether that message was encrypted, a hint about the -// encryption state and zero or more messages to send back to the peer. -// These messages do not need to be passed to Send before transmission. -func (c *Conversation) Receive(in []byte) (out []byte, encrypted bool, change SecurityChange, toSend [][]byte, err error) { - if bytes.HasPrefix(in, fragmentPrefix) { - in, err = c.processFragment(in) - if in == nil || err != nil { - return - } - } - - if bytes.HasPrefix(in, msgPrefix) && in[len(in)-1] == '.' { - in = in[len(msgPrefix) : len(in)-1] - } else if version := isQuery(in); version > 0 { - c.authState = authStateAwaitingDHKey - c.reset() - toSend = c.encode(c.generateDHCommit()) - return - } else { - // plaintext message - out = in - return - } - - msg := make([]byte, base64.StdEncoding.DecodedLen(len(in))) - msgLen, err := base64.StdEncoding.Decode(msg, in) - if err != nil { - err = errors.New("otr: invalid base64 encoding in message") - return - } - msg = msg[:msgLen] - - // The first two bytes are the protocol version (2) - if len(msg) < 3 || msg[0] != 0 || msg[1] != 2 { - err = errors.New("otr: invalid OTR message") - return - } - - msgType := int(msg[2]) - msg = msg[3:] - - switch msgType { - case msgTypeDHCommit: - switch c.authState { - case authStateNone: - c.authState = authStateAwaitingRevealSig - if err = c.processDHCommit(msg); err != nil { - return - } - c.reset() - toSend = c.encode(c.generateDHKey()) - return - case authStateAwaitingDHKey: - // This is a 'SYN-crossing'. The greater digest wins. - var cmp int - if cmp, err = c.compareToDHCommit(msg); err != nil { - return - } - if cmp > 0 { - // We win. Retransmit DH commit. - toSend = c.encode(c.serializeDHCommit()) - return - } else { - // They win. We forget about our DH commit. - c.authState = authStateAwaitingRevealSig - if err = c.processDHCommit(msg); err != nil { - return - } - c.reset() - toSend = c.encode(c.generateDHKey()) - return - } - case authStateAwaitingRevealSig: - if err = c.processDHCommit(msg); err != nil { - return - } - toSend = c.encode(c.serializeDHKey()) - case authStateAwaitingSig: - if err = c.processDHCommit(msg); err != nil { - return - } - c.reset() - toSend = c.encode(c.generateDHKey()) - c.authState = authStateAwaitingRevealSig - default: - panic("bad state") - } - case msgTypeDHKey: - switch c.authState { - case authStateAwaitingDHKey: - var isSame bool - if isSame, err = c.processDHKey(msg); err != nil { - return - } - if isSame { - err = errors.New("otr: unexpected duplicate DH key") - return - } - toSend = c.encode(c.generateRevealSig()) - c.authState = authStateAwaitingSig - case authStateAwaitingSig: - var isSame bool - if isSame, err = c.processDHKey(msg); err != nil { - return - } - if isSame { - toSend = c.encode(c.serializeDHKey()) - } - } - case msgTypeRevealSig: - if c.authState != authStateAwaitingRevealSig { - return - } - if err = c.processRevealSig(msg); err != nil { - return - } - toSend = c.encode(c.generateSig()) - c.authState = authStateNone - c.state = stateEncrypted - change = NewKeys - case msgTypeSig: - if c.authState != authStateAwaitingSig { - return - } - if err = c.processSig(msg); err != nil { - return - } - c.authState = authStateNone - c.state = stateEncrypted - change = NewKeys - case msgTypeData: - if c.state != stateEncrypted { - err = errors.New("otr: encrypted message received without encrypted session established") - return - } - var tlvs []tlv - out, tlvs, err = c.processData(msg) - encrypted = true - - EachTLV: - for _, inTLV := range tlvs { - switch inTLV.typ { - case tlvTypeDisconnected: - change = ConversationEnded - c.state = stateFinished - break EachTLV - case tlvTypeSMP1, tlvTypeSMP2, tlvTypeSMP3, tlvTypeSMP4, tlvTypeSMPAbort, tlvTypeSMP1WithQuestion: - var reply tlv - var complete bool - reply, complete, err = c.processSMP(inTLV) - if err == smpSecretMissingError { - err = nil - change = SMPSecretNeeded - c.smp.saved = &inTLV - return - } - if err == smpFailureError { - err = nil - change = SMPFailed - } else if complete { - change = SMPComplete - } - if reply.typ != 0 { - toSend = c.encode(c.generateData(nil, &reply)) - } - break EachTLV - default: - // skip unknown TLVs - } - } - default: - err = errors.New("otr: unknown message type " + strconv.Itoa(msgType)) - } - - return -} - -// Send takes a human readable message from the local user, possibly encrypts -// it and returns zero one or more messages to send to the peer. -func (c *Conversation) Send(msg []byte) ([][]byte, error) { - switch c.state { - case statePlaintext: - return [][]byte{msg}, nil - case stateEncrypted: - return c.encode(c.generateData(msg, nil)), nil - case stateFinished: - return nil, errors.New("otr: cannot send message because secure conversation has finished") - } - - return nil, errors.New("otr: cannot send message in current state") -} - -// SMPQuestion returns the human readable challenge question from the peer. -// It's only valid after Receive has returned SMPSecretNeeded. -func (c *Conversation) SMPQuestion() string { - return c.smp.question -} - -// Authenticate begins an authentication with the peer. Authentication involves -// an optional challenge message and a shared secret. The authentication -// proceeds until either Receive returns SMPComplete, SMPSecretNeeded (which -// indicates that a new authentication is happening and thus this one was -// aborted) or SMPFailed. -func (c *Conversation) Authenticate(question string, mutualSecret []byte) (toSend [][]byte, err error) { - if c.state != stateEncrypted { - err = errors.New("otr: can't authenticate a peer without a secure conversation established") - return - } - - if c.smp.saved != nil { - c.calcSMPSecret(mutualSecret, false /* they started it */) - - var out tlv - var complete bool - out, complete, err = c.processSMP(*c.smp.saved) - if complete { - panic("SMP completed on the first message") - } - c.smp.saved = nil - if out.typ != 0 { - toSend = c.encode(c.generateData(nil, &out)) - } - return - } - - c.calcSMPSecret(mutualSecret, true /* we started it */) - outs := c.startSMP(question) - for _, out := range outs { - toSend = append(toSend, c.encode(c.generateData(nil, &out))...) - } - return -} - -// End ends a secure conversation by generating a termination message for -// the peer and switches to unencrypted communication. -func (c *Conversation) End() (toSend [][]byte) { - switch c.state { - case statePlaintext: - return nil - case stateEncrypted: - c.state = statePlaintext - return c.encode(c.generateData(nil, &tlv{typ: tlvTypeDisconnected})) - case stateFinished: - c.state = statePlaintext - return nil - } - panic("unreachable") -} - -// IsEncrypted returns true if a message passed to Send would be encrypted -// before transmission. This result remains valid until the next call to -// Receive or End, which may change the state of the Conversation. -func (c *Conversation) IsEncrypted() bool { - return c.state == stateEncrypted -} - -var fragmentError = errors.New("otr: invalid OTR fragment") - -// processFragment processes a fragmented OTR message and possibly returns a -// complete message. Fragmented messages look like "?OTR,k,n,msg," where k is -// the fragment number (starting from 1), n is the number of fragments in this -// message and msg is a substring of the base64 encoded message. -func (c *Conversation) processFragment(in []byte) (out []byte, err error) { - in = in[len(fragmentPrefix):] // remove "?OTR," - parts := bytes.Split(in, fragmentPartSeparator) - if len(parts) != 4 || len(parts[3]) != 0 { - return nil, fragmentError - } - - k, err := strconv.Atoi(string(parts[0])) - if err != nil { - return nil, fragmentError - } - - n, err := strconv.Atoi(string(parts[1])) - if err != nil { - return nil, fragmentError - } - - if k < 1 || n < 1 || k > n { - return nil, fragmentError - } - - if k == 1 { - c.frag = append(c.frag[:0], parts[2]...) - c.k, c.n = k, n - } else if n == c.n && k == c.k+1 { - c.frag = append(c.frag, parts[2]...) - c.k++ - } else { - c.frag = c.frag[:0] - c.n, c.k = 0, 0 - } - - if c.n > 0 && c.k == c.n { - c.n, c.k = 0, 0 - return c.frag, nil - } - - return nil, nil -} - -func (c *Conversation) generateDHCommit() []byte { - _, err := io.ReadFull(c.rand(), c.r[:]) - if err != nil { - panic("otr: short read from random source") - } - - var xBytes [dhPrivateBytes]byte - c.x = c.randMPI(xBytes[:]) - c.gx = new(big.Int).Exp(g, c.x, p) - c.gy = nil - c.gxBytes = appendMPI(nil, c.gx) - - h := sha256.New() - h.Write(c.gxBytes) - h.Sum(c.digest[:0]) - - aesCipher, err := aes.NewCipher(c.r[:]) - if err != nil { - panic(err.Error()) - } - - var iv [aes.BlockSize]byte - ctr := cipher.NewCTR(aesCipher, iv[:]) - ctr.XORKeyStream(c.gxBytes, c.gxBytes) - - return c.serializeDHCommit() -} - -func (c *Conversation) serializeDHCommit() []byte { - var ret []byte - ret = appendU16(ret, 2) // protocol version - ret = append(ret, msgTypeDHCommit) - ret = appendData(ret, c.gxBytes) - ret = appendData(ret, c.digest[:]) - return ret -} - -func (c *Conversation) processDHCommit(in []byte) error { - var ok1, ok2 bool - c.gxBytes, in, ok1 = getData(in) - digest, in, ok2 := getData(in) - if !ok1 || !ok2 || len(in) > 0 { - return errors.New("otr: corrupt DH commit message") - } - copy(c.digest[:], digest) - return nil -} - -func (c *Conversation) compareToDHCommit(in []byte) (int, error) { - _, in, ok1 := getData(in) - digest, in, ok2 := getData(in) - if !ok1 || !ok2 || len(in) > 0 { - return 0, errors.New("otr: corrupt DH commit message") - } - return bytes.Compare(c.digest[:], digest), nil -} - -func (c *Conversation) generateDHKey() []byte { - var yBytes [dhPrivateBytes]byte - c.y = c.randMPI(yBytes[:]) - c.gy = new(big.Int).Exp(g, c.y, p) - return c.serializeDHKey() -} - -func (c *Conversation) serializeDHKey() []byte { - var ret []byte - ret = appendU16(ret, 2) // protocol version - ret = append(ret, msgTypeDHKey) - ret = appendMPI(ret, c.gy) - return ret -} - -func (c *Conversation) processDHKey(in []byte) (isSame bool, err error) { - gy, in, ok := getMPI(in) - if !ok { - err = errors.New("otr: corrupt DH key message") - return - } - if gy.Cmp(g) < 0 || gy.Cmp(pMinus2) > 0 { - err = errors.New("otr: DH value out of range") - return - } - if c.gy != nil { - isSame = c.gy.Cmp(gy) == 0 - return - } - c.gy = gy - return -} - -func (c *Conversation) generateEncryptedSignature(keys *akeKeys, xFirst bool) ([]byte, []byte) { - var xb []byte - xb = c.PrivateKey.PublicKey.Serialize(xb) - - var verifyData []byte - if xFirst { - verifyData = appendMPI(verifyData, c.gx) - verifyData = appendMPI(verifyData, c.gy) - } else { - verifyData = appendMPI(verifyData, c.gy) - verifyData = appendMPI(verifyData, c.gx) - } - verifyData = append(verifyData, xb...) - verifyData = appendU32(verifyData, c.myKeyId) - - mac := hmac.New(sha256.New, keys.m1[:]) - mac.Write(verifyData) - mb := mac.Sum(nil) - - xb = appendU32(xb, c.myKeyId) - xb = append(xb, c.PrivateKey.Sign(c.rand(), mb)...) - - aesCipher, err := aes.NewCipher(keys.c[:]) - if err != nil { - panic(err.Error()) - } - var iv [aes.BlockSize]byte - ctr := cipher.NewCTR(aesCipher, iv[:]) - ctr.XORKeyStream(xb, xb) - - mac = hmac.New(sha256.New, keys.m2[:]) - encryptedSig := appendData(nil, xb) - mac.Write(encryptedSig) - - return encryptedSig, mac.Sum(nil) -} - -func (c *Conversation) generateRevealSig() []byte { - s := new(big.Int).Exp(c.gy, c.x, p) - c.calcAKEKeys(s) - c.myKeyId++ - - encryptedSig, mac := c.generateEncryptedSignature(&c.revealKeys, true /* gx comes first */) - - c.myCurrentDHPub = c.gx - c.myCurrentDHPriv = c.x - c.rotateDHKeys() - incCounter(&c.myCounter) - - var ret []byte - ret = appendU16(ret, 2) - ret = append(ret, msgTypeRevealSig) - ret = appendData(ret, c.r[:]) - ret = append(ret, encryptedSig...) - ret = append(ret, mac[:20]...) - return ret -} - -func (c *Conversation) processEncryptedSig(encryptedSig, theirMAC []byte, keys *akeKeys, xFirst bool) error { - mac := hmac.New(sha256.New, keys.m2[:]) - mac.Write(appendData(nil, encryptedSig)) - myMAC := mac.Sum(nil)[:20] - - if len(myMAC) != len(theirMAC) || subtle.ConstantTimeCompare(myMAC, theirMAC) == 0 { - return errors.New("bad signature MAC in encrypted signature") - } - - aesCipher, err := aes.NewCipher(keys.c[:]) - if err != nil { - panic(err.Error()) - } - var iv [aes.BlockSize]byte - ctr := cipher.NewCTR(aesCipher, iv[:]) - ctr.XORKeyStream(encryptedSig, encryptedSig) - - sig := encryptedSig - sig, ok1 := c.TheirPublicKey.Parse(sig) - keyId, sig, ok2 := getU32(sig) - if !ok1 || !ok2 { - return errors.New("otr: corrupt encrypted signature") - } - - var verifyData []byte - if xFirst { - verifyData = appendMPI(verifyData, c.gx) - verifyData = appendMPI(verifyData, c.gy) - } else { - verifyData = appendMPI(verifyData, c.gy) - verifyData = appendMPI(verifyData, c.gx) - } - verifyData = c.TheirPublicKey.Serialize(verifyData) - verifyData = appendU32(verifyData, keyId) - - mac = hmac.New(sha256.New, keys.m1[:]) - mac.Write(verifyData) - mb := mac.Sum(nil) - - sig, ok1 = c.TheirPublicKey.Verify(mb, sig) - if !ok1 { - return errors.New("bad signature in encrypted signature") - } - if len(sig) > 0 { - return errors.New("corrupt encrypted signature") - } - - c.theirKeyId = keyId - zero(c.theirLastCtr[:]) - return nil -} - -func (c *Conversation) processRevealSig(in []byte) error { - r, in, ok1 := getData(in) - encryptedSig, in, ok2 := getData(in) - theirMAC := in - if !ok1 || !ok2 || len(theirMAC) != 20 { - return errors.New("otr: corrupt reveal signature message") - } - - aesCipher, err := aes.NewCipher(r) - if err != nil { - return errors.New("otr: cannot create AES cipher from reveal signature message: " + err.Error()) - } - var iv [aes.BlockSize]byte - ctr := cipher.NewCTR(aesCipher, iv[:]) - ctr.XORKeyStream(c.gxBytes, c.gxBytes) - h := sha256.New() - h.Write(c.gxBytes) - digest := h.Sum(nil) - if len(digest) != len(c.digest) || subtle.ConstantTimeCompare(digest, c.digest[:]) == 0 { - return errors.New("otr: bad commit MAC in reveal signature message") - } - var rest []byte - c.gx, rest, ok1 = getMPI(c.gxBytes) - if !ok1 || len(rest) > 0 { - return errors.New("otr: gx corrupt after decryption") - } - if c.gx.Cmp(g) < 0 || c.gx.Cmp(pMinus2) > 0 { - return errors.New("otr: DH value out of range") - } - s := new(big.Int).Exp(c.gx, c.y, p) - c.calcAKEKeys(s) - - if err := c.processEncryptedSig(encryptedSig, theirMAC, &c.revealKeys, true /* gx comes first */); err != nil { - return errors.New("otr: in reveal signature message: " + err.Error()) - } - - c.theirCurrentDHPub = c.gx - c.theirLastDHPub = nil - - return nil -} - -func (c *Conversation) generateSig() []byte { - c.myKeyId++ - - encryptedSig, mac := c.generateEncryptedSignature(&c.sigKeys, false /* gy comes first */) - - c.myCurrentDHPub = c.gy - c.myCurrentDHPriv = c.y - c.rotateDHKeys() - incCounter(&c.myCounter) - - var ret []byte - ret = appendU16(ret, 2) - ret = append(ret, msgTypeSig) - ret = append(ret, encryptedSig...) - ret = append(ret, mac[:macPrefixBytes]...) - return ret -} - -func (c *Conversation) processSig(in []byte) error { - encryptedSig, in, ok1 := getData(in) - theirMAC := in - if !ok1 || len(theirMAC) != macPrefixBytes { - return errors.New("otr: corrupt signature message") - } - - if err := c.processEncryptedSig(encryptedSig, theirMAC, &c.sigKeys, false /* gy comes first */); err != nil { - return errors.New("otr: in signature message: " + err.Error()) - } - - c.theirCurrentDHPub = c.gy - c.theirLastDHPub = nil - - return nil -} - -func (c *Conversation) rotateDHKeys() { - // evict slots using our retired key id - for i := range c.keySlots { - slot := &c.keySlots[i] - if slot.used && slot.myKeyId == c.myKeyId-1 { - slot.used = false - c.oldMACs = append(c.oldMACs, slot.recvMACKey...) - } - } - - c.myLastDHPriv = c.myCurrentDHPriv - c.myLastDHPub = c.myCurrentDHPub - - var xBytes [dhPrivateBytes]byte - c.myCurrentDHPriv = c.randMPI(xBytes[:]) - c.myCurrentDHPub = new(big.Int).Exp(g, c.myCurrentDHPriv, p) - c.myKeyId++ -} - -func (c *Conversation) processData(in []byte) (out []byte, tlvs []tlv, err error) { - origIn := in - flags, in, ok1 := getU8(in) - theirKeyId, in, ok2 := getU32(in) - myKeyId, in, ok3 := getU32(in) - y, in, ok4 := getMPI(in) - counter, in, ok5 := getNBytes(in, 8) - encrypted, in, ok6 := getData(in) - macedData := origIn[:len(origIn)-len(in)] - theirMAC, in, ok7 := getNBytes(in, macPrefixBytes) - _, in, ok8 := getData(in) - if !ok1 || !ok2 || !ok3 || !ok4 || !ok5 || !ok6 || !ok7 || !ok8 || len(in) > 0 { - err = errors.New("otr: corrupt data message") - return - } - - ignoreErrors := flags&1 != 0 - - slot, err := c.calcDataKeys(myKeyId, theirKeyId) - if err != nil { - if ignoreErrors { - err = nil - } - return - } - - mac := hmac.New(sha1.New, slot.recvMACKey) - mac.Write([]byte{0, 2, 3}) - mac.Write(macedData) - myMAC := mac.Sum(nil) - if len(myMAC) != len(theirMAC) || subtle.ConstantTimeCompare(myMAC, theirMAC) == 0 { - if !ignoreErrors { - err = errors.New("otr: bad MAC on data message") - } - return - } - - if bytes.Compare(counter, slot.theirLastCtr[:]) <= 0 { - err = errors.New("otr: counter regressed") - return - } - copy(slot.theirLastCtr[:], counter) - - var iv [aes.BlockSize]byte - copy(iv[:], counter) - aesCipher, err := aes.NewCipher(slot.recvAESKey) - if err != nil { - panic(err.Error()) - } - ctr := cipher.NewCTR(aesCipher, iv[:]) - ctr.XORKeyStream(encrypted, encrypted) - decrypted := encrypted - - if myKeyId == c.myKeyId { - c.rotateDHKeys() - } - if theirKeyId == c.theirKeyId { - // evict slots using their retired key id - for i := range c.keySlots { - slot := &c.keySlots[i] - if slot.used && slot.theirKeyId == theirKeyId-1 { - slot.used = false - c.oldMACs = append(c.oldMACs, slot.recvMACKey...) - } - } - - c.theirLastDHPub = c.theirCurrentDHPub - c.theirKeyId++ - c.theirCurrentDHPub = y - } - - if nulPos := bytes.IndexByte(decrypted, 0); nulPos >= 0 { - out = decrypted[:nulPos] - tlvData := decrypted[nulPos+1:] - for len(tlvData) > 0 { - var t tlv - var ok1, ok2, ok3 bool - - t.typ, tlvData, ok1 = getU16(tlvData) - t.length, tlvData, ok2 = getU16(tlvData) - t.data, tlvData, ok3 = getNBytes(tlvData, int(t.length)) - if !ok1 || !ok2 || !ok3 { - err = errors.New("otr: corrupt tlv data") - return - } - tlvs = append(tlvs, t) - } - } else { - out = decrypted - } - - return -} - -func (c *Conversation) generateData(msg []byte, extra *tlv) []byte { - slot, err := c.calcDataKeys(c.myKeyId-1, c.theirKeyId) - if err != nil { - panic("otr: failed to generate sending keys: " + err.Error()) - } - - var plaintext []byte - plaintext = append(plaintext, msg...) - plaintext = append(plaintext, 0) - - padding := paddingGranularity - ((len(plaintext) + 4) % paddingGranularity) - plaintext = appendU16(plaintext, tlvTypePadding) - plaintext = appendU16(plaintext, uint16(padding)) - for i := 0; i < padding; i++ { - plaintext = append(plaintext, 0) - } - - if extra != nil { - plaintext = appendU16(plaintext, extra.typ) - plaintext = appendU16(plaintext, uint16(len(extra.data))) - plaintext = append(plaintext, extra.data...) - } - - encrypted := make([]byte, len(plaintext)) - - var iv [aes.BlockSize]byte - copy(iv[:], c.myCounter[:]) - aesCipher, err := aes.NewCipher(slot.sendAESKey) - if err != nil { - panic(err.Error()) - } - ctr := cipher.NewCTR(aesCipher, iv[:]) - ctr.XORKeyStream(encrypted, plaintext) - - var ret []byte - ret = appendU16(ret, 2) - ret = append(ret, msgTypeData) - ret = append(ret, 0 /* flags */) - ret = appendU32(ret, c.myKeyId-1) - ret = appendU32(ret, c.theirKeyId) - ret = appendMPI(ret, c.myCurrentDHPub) - ret = append(ret, c.myCounter[:]...) - ret = appendData(ret, encrypted) - - mac := hmac.New(sha1.New, slot.sendMACKey) - mac.Write(ret) - ret = append(ret, mac.Sum(nil)[:macPrefixBytes]...) - ret = appendData(ret, c.oldMACs) - c.oldMACs = nil - incCounter(&c.myCounter) - - return ret -} - -func incCounter(counter *[8]byte) { - for i := 7; i >= 0; i-- { - counter[i]++ - if counter[i] > 0 { - break - } - } -} - -// calcDataKeys computes the keys used to encrypt a data message given the key -// IDs. -func (c *Conversation) calcDataKeys(myKeyId, theirKeyId uint32) (slot *keySlot, err error) { - // Check for a cache hit. - for i := range c.keySlots { - slot = &c.keySlots[i] - if slot.used && slot.theirKeyId == theirKeyId && slot.myKeyId == myKeyId { - return - } - } - - // Find an empty slot to write into. - slot = nil - for i := range c.keySlots { - if !c.keySlots[i].used { - slot = &c.keySlots[i] - break - } - } - if slot == nil { - return nil, errors.New("otr: internal error: no more key slots") - } - - var myPriv, myPub, theirPub *big.Int - - if myKeyId == c.myKeyId { - myPriv = c.myCurrentDHPriv - myPub = c.myCurrentDHPub - } else if myKeyId == c.myKeyId-1 { - myPriv = c.myLastDHPriv - myPub = c.myLastDHPub - } else { - err = errors.New("otr: peer requested keyid " + strconv.FormatUint(uint64(myKeyId), 10) + " when I'm on " + strconv.FormatUint(uint64(c.myKeyId), 10)) - return - } - - if theirKeyId == c.theirKeyId { - theirPub = c.theirCurrentDHPub - } else if theirKeyId == c.theirKeyId-1 && c.theirLastDHPub != nil { - theirPub = c.theirLastDHPub - } else { - err = errors.New("otr: peer requested keyid " + strconv.FormatUint(uint64(myKeyId), 10) + " when they're on " + strconv.FormatUint(uint64(c.myKeyId), 10)) - return - } - - var sendPrefixByte, recvPrefixByte [1]byte - - if myPub.Cmp(theirPub) > 0 { - // we're the high end - sendPrefixByte[0], recvPrefixByte[0] = 1, 2 - } else { - // we're the low end - sendPrefixByte[0], recvPrefixByte[0] = 2, 1 - } - - s := new(big.Int).Exp(theirPub, myPriv, p) - sBytes := appendMPI(nil, s) - - h := sha1.New() - h.Write(sendPrefixByte[:]) - h.Write(sBytes) - slot.sendAESKey = h.Sum(slot.sendAESKey[:0])[:16] - - h.Reset() - h.Write(slot.sendAESKey) - slot.sendMACKey = h.Sum(slot.sendMACKey[:0]) - - h.Reset() - h.Write(recvPrefixByte[:]) - h.Write(sBytes) - slot.recvAESKey = h.Sum(slot.recvAESKey[:0])[:16] - - h.Reset() - h.Write(slot.recvAESKey) - slot.recvMACKey = h.Sum(slot.recvMACKey[:0]) - - slot.theirKeyId = theirKeyId - slot.myKeyId = myKeyId - slot.used = true - - zero(slot.theirLastCtr[:]) - return -} - -func (c *Conversation) calcAKEKeys(s *big.Int) { - mpi := appendMPI(nil, s) - h := sha256.New() - - var cBytes [32]byte - hashWithPrefix(c.SSID[:], 0, mpi, h) - - hashWithPrefix(cBytes[:], 1, mpi, h) - copy(c.revealKeys.c[:], cBytes[:16]) - copy(c.sigKeys.c[:], cBytes[16:]) - - hashWithPrefix(c.revealKeys.m1[:], 2, mpi, h) - hashWithPrefix(c.revealKeys.m2[:], 3, mpi, h) - hashWithPrefix(c.sigKeys.m1[:], 4, mpi, h) - hashWithPrefix(c.sigKeys.m2[:], 5, mpi, h) -} - -func hashWithPrefix(out []byte, prefix byte, in []byte, h hash.Hash) { - h.Reset() - var p [1]byte - p[0] = prefix - h.Write(p[:]) - h.Write(in) - if len(out) == h.Size() { - h.Sum(out[:0]) - } else { - digest := h.Sum(nil) - copy(out, digest) - } -} - -func (c *Conversation) encode(msg []byte) [][]byte { - b64 := make([]byte, base64.StdEncoding.EncodedLen(len(msg))+len(msgPrefix)+1) - base64.StdEncoding.Encode(b64[len(msgPrefix):], msg) - copy(b64, msgPrefix) - b64[len(b64)-1] = '.' - - if c.FragmentSize < minFragmentSize || len(b64) <= c.FragmentSize { - // We can encode this in a single fragment. - return [][]byte{b64} - } - - // We have to fragment this message. - var ret [][]byte - bytesPerFragment := c.FragmentSize - minFragmentSize - numFragments := (len(b64) + bytesPerFragment) / bytesPerFragment - - for i := 0; i < numFragments; i++ { - frag := []byte("?OTR," + strconv.Itoa(i+1) + "," + strconv.Itoa(numFragments) + ",") - todo := bytesPerFragment - if todo > len(b64) { - todo = len(b64) - } - frag = append(frag, b64[:todo]...) - b64 = b64[todo:] - frag = append(frag, ',') - ret = append(ret, frag) - } - - return ret -} - -func (c *Conversation) reset() { - c.myKeyId = 0 - - for i := range c.keySlots { - c.keySlots[i].used = false - } -} - -type PublicKey struct { - dsa.PublicKey -} - -func (pk *PublicKey) Parse(in []byte) ([]byte, bool) { - var ok bool - var pubKeyType uint16 - - if pubKeyType, in, ok = getU16(in); !ok || pubKeyType != 0 { - return nil, false - } - if pk.P, in, ok = getMPI(in); !ok { - return nil, false - } - if pk.Q, in, ok = getMPI(in); !ok { - return nil, false - } - if pk.G, in, ok = getMPI(in); !ok { - return nil, false - } - if pk.Y, in, ok = getMPI(in); !ok { - return nil, false - } - - return in, true -} - -func (pk *PublicKey) Serialize(in []byte) []byte { - in = appendU16(in, 0) - in = appendMPI(in, pk.P) - in = appendMPI(in, pk.Q) - in = appendMPI(in, pk.G) - in = appendMPI(in, pk.Y) - return in -} - -// Fingerprint returns the 20-byte, binary fingerprint of the PublicKey. -func (pk *PublicKey) Fingerprint() []byte { - b := pk.Serialize(nil) - h := sha1.New() - h.Write(b[2:]) - return h.Sum(nil) -} - -func (pk *PublicKey) Verify(hashed, sig []byte) ([]byte, bool) { - if len(sig) != 2*dsaSubgroupBytes { - return nil, false - } - r := new(big.Int).SetBytes(sig[:dsaSubgroupBytes]) - s := new(big.Int).SetBytes(sig[dsaSubgroupBytes:]) - ok := dsa.Verify(&pk.PublicKey, hashed, r, s) - return sig[dsaSubgroupBytes*2:], ok -} - -type PrivateKey struct { - PublicKey - dsa.PrivateKey -} - -func (priv *PrivateKey) Sign(rand io.Reader, hashed []byte) []byte { - r, s, err := dsa.Sign(rand, &priv.PrivateKey, hashed) - if err != nil { - panic(err.Error()) - } - rBytes := r.Bytes() - sBytes := s.Bytes() - if len(rBytes) > dsaSubgroupBytes || len(sBytes) > dsaSubgroupBytes { - panic("DSA signature too large") - } - - out := make([]byte, 2*dsaSubgroupBytes) - copy(out[dsaSubgroupBytes-len(rBytes):], rBytes) - copy(out[len(out)-len(sBytes):], sBytes) - return out -} - -func (priv *PrivateKey) Serialize(in []byte) []byte { - in = priv.PublicKey.Serialize(in) - in = appendMPI(in, priv.PrivateKey.X) - return in -} - -func (priv *PrivateKey) Parse(in []byte) ([]byte, bool) { - in, ok := priv.PublicKey.Parse(in) - if !ok { - return in, ok - } - priv.PrivateKey.PublicKey = priv.PublicKey.PublicKey - priv.PrivateKey.X, in, ok = getMPI(in) - return in, ok -} - -func (priv *PrivateKey) Generate(rand io.Reader) { - if err := dsa.GenerateParameters(&priv.PrivateKey.PublicKey.Parameters, rand, dsa.L1024N160); err != nil { - panic(err.Error()) - } - if err := dsa.GenerateKey(&priv.PrivateKey, rand); err != nil { - panic(err.Error()) - } - priv.PublicKey.PublicKey = priv.PrivateKey.PublicKey -} - -func notHex(r rune) bool { - if r >= '0' && r <= '9' || - r >= 'a' && r <= 'f' || - r >= 'A' && r <= 'F' { - return false - } - - return true -} - -// Import parses the contents of a libotr private key file. -func (priv *PrivateKey) Import(in []byte) bool { - mpiStart := []byte(" #") - - mpis := make([]*big.Int, 5) - - for i := 0; i < len(mpis); i++ { - start := bytes.Index(in, mpiStart) - if start == -1 { - return false - } - in = in[start+len(mpiStart):] - end := bytes.IndexFunc(in, notHex) - if end == -1 { - return false - } - hexBytes := in[:end] - in = in[end:] - - if len(hexBytes)&1 != 0 { - return false - } - - mpiBytes := make([]byte, len(hexBytes)/2) - if _, err := hex.Decode(mpiBytes, hexBytes); err != nil { - return false - } - - mpis[i] = new(big.Int).SetBytes(mpiBytes) - } - - for _, mpi := range mpis { - if mpi.Sign() <= 0 { - return false - } - } - - priv.PrivateKey.P = mpis[0] - priv.PrivateKey.Q = mpis[1] - priv.PrivateKey.G = mpis[2] - priv.PrivateKey.Y = mpis[3] - priv.PrivateKey.X = mpis[4] - priv.PublicKey.PublicKey = priv.PrivateKey.PublicKey - - a := new(big.Int).Exp(priv.PrivateKey.G, priv.PrivateKey.X, priv.PrivateKey.P) - return a.Cmp(priv.PrivateKey.Y) == 0 -} - -func getU8(in []byte) (uint8, []byte, bool) { - if len(in) < 1 { - return 0, in, false - } - return in[0], in[1:], true -} - -func getU16(in []byte) (uint16, []byte, bool) { - if len(in) < 2 { - return 0, in, false - } - r := uint16(in[0])<<8 | uint16(in[1]) - return r, in[2:], true -} - -func getU32(in []byte) (uint32, []byte, bool) { - if len(in) < 4 { - return 0, in, false - } - r := uint32(in[0])<<24 | uint32(in[1])<<16 | uint32(in[2])<<8 | uint32(in[3]) - return r, in[4:], true -} - -func getMPI(in []byte) (*big.Int, []byte, bool) { - l, in, ok := getU32(in) - if !ok || uint32(len(in)) < l { - return nil, in, false - } - r := new(big.Int).SetBytes(in[:l]) - return r, in[l:], true -} - -func getData(in []byte) ([]byte, []byte, bool) { - l, in, ok := getU32(in) - if !ok || uint32(len(in)) < l { - return nil, in, false - } - return in[:l], in[l:], true -} - -func getNBytes(in []byte, n int) ([]byte, []byte, bool) { - if len(in) < n { - return nil, in, false - } - return in[:n], in[n:], true -} - -func appendU16(out []byte, v uint16) []byte { - out = append(out, byte(v>>8), byte(v)) - return out -} - -func appendU32(out []byte, v uint32) []byte { - out = append(out, byte(v>>24), byte(v>>16), byte(v>>8), byte(v)) - return out -} - -func appendData(out, v []byte) []byte { - out = appendU32(out, uint32(len(v))) - out = append(out, v...) - return out -} - -func appendMPI(out []byte, v *big.Int) []byte { - vBytes := v.Bytes() - out = appendU32(out, uint32(len(vBytes))) - out = append(out, vBytes...) - return out -} - -func appendMPIs(out []byte, mpis ...*big.Int) []byte { - for _, mpi := range mpis { - out = appendMPI(out, mpi) - } - return out -} - -func zero(b []byte) { - for i := range b { - b[i] = 0 - } -} |