commit f90c9080ac86a871dcb2a14579222d514852c039 Author: erinn Date: Sat Oct 6 19:21:20 2018 -0700 initial commit diff --git a/.gitignore b/.gitignore new file mode 100644 index 0000000..2d4daa4 --- /dev/null +++ b/.gitignore @@ -0,0 +1 @@ +.idea* diff --git a/main.go b/main.go new file mode 100644 index 0000000..ef95a67 --- /dev/null +++ b/main.go @@ -0,0 +1,289 @@ +package main + +import ( + libpeer "cwtch.im/cwtch/peer" + "os" + "fmt" + "github.com/sethvargo/go-diceware/diceware" + "bufio" + "math/big" + "time" + "log" + "io/ioutil" + "cwtch.im/cwtch/model" +) + +func driftoff() { + time.Sleep(time.Second * 15) + os.Exit(1) +} + +func addContactEntry(peer libpeer.CwtchPeer, name string, onion string) { + pp := model.PublicProfile{ + name, + nil, + false, + false, + onion} + + if peer == nil { + fmt.Printf("peer is nil?!?!?\n") + } + + peer.GetProfile().Contacts[onion] = &pp + peer.GetProfile().SetCustomAttribute(onion+"_name", name) + peer.GetProfile().SetCustomAttribute(name+"_onion", onion) +} + +func printHelp() { + fmt.Println("usage: sendafriend [command] [options]\nCommands: help, setname, info, list, add, send, receive, hide, seek") +} + +func main() { + if len(os.Args) < 2 { + printHelp() + os.Exit(1) + } + + log.SetFlags(0) + log.SetOutput(ioutil.Discard) + inviteStr := "torv30I0zJgNiUz57gJlxFsp4PUq47WDoKNCL95GEadaLlEE=EsABCiA4MjViZTVjODU0ZDFhNGRhNjM3NmExNTBlYjM2ZjM2NxIgPAl3zAsMfauSZQyiGXlj7u6M6usYN/HqtPD2jafjwTAaOGloZDNlYXdhbjZ2aG1kaDdudDVicXh5aHVlM2k0aXgzb3kyZWZrcHdkaDZyNGptcTNhZXJ0dWlkIkDhF3Ko8nAtEJPvjpCjwFM4py0CeAhYCTc9l9H+Wah8traU15D/JzIHEAKhaDiIzmKqBOECk9Q+G40Y6pXPWKkI" + + peer, err := libpeer.LoadCwtchPeer("Whoami", "be gay do crime") + if err != nil { + fmt.Println("couldn't load your Whoami file, attempting to create a new one now") + + names, err := diceware.Generate(1) + peer, err = libpeer.NewCwtchPeer(names[0], "be gay do crime", "Whoami") + if err != nil { + fmt.Println("couldn't create one either :( exiting") + os.Exit(1) + } + } + + switch os.Args[1] { + default: + printHelp() + case "help": + printHelp() + case "iam": + if len(os.Args) != 3 { + fmt.Println("example: sendafriend iam alice") + os.Exit(1) + } + + peer.GetProfile().Name = os.Args[2] + fmt.Printf("hi, %v!\n", os.Args[2]) + case "setname": + if len(os.Args) == 3 { + fmt.Println("example: sendafriend setname alice xyz") + os.Exit(1) + } + + _, exists := peer.GetProfile().GetCustomAttribute(os.Args[3]+"_name") + if !exists { + fmt.Printf("um you don't have anyone with that onion address in your list") + os.Exit(1) + } + + peer.GetProfile().SetCustomAttribute(os.Args[3]+"_name", os.Args[2]) + peer.GetProfile().SetCustomAttribute(os.Args[2]+"_onion", os.Args[3]) + //todo: unset old one + fmt.Printf("okay, i'll remember that %v is named %v\n", os.Args[3], os.Args[2]) + case "info": + fmt.Printf("your name is currently %v and your address is currently %v\n", peer.GetProfile().Name, peer.GetProfile().Onion); + case "list": + contacts := peer.GetContacts() + for i := range contacts { + attr, _ := peer.GetProfile().GetCustomAttribute(contacts[i] + "_name") + fmt.Printf("%v <%v>\n", attr, contacts[i]) + } + case "add": + if len(os.Args) != 4 { + fmt.Println("example: sendafriend add bob xyz") + os.Exit(1) + } + + _, exists := peer.GetProfile().GetCustomAttribute(os.Args[3]+"_name") + if exists { + fmt.Printf("woah you already have someone named %v\n", os.Args[3]) + os.Exit(1) + } + + addContactEntry(peer, os.Args[2], os.Args[3]) + + fmt.Printf("okay, added %v <%v>\n", os.Args[2], os.Args[3]) + case "send": + if len(os.Args) != 3 { + fmt.Println("example: sendafriend send bob < file.txt") + os.Exit(1) + } + + onion, exists := peer.GetProfile().GetCustomAttribute(os.Args[2]+"_onion") + if !exists { + fmt.Printf("you don't seem to have a contact named %v\n", os.Args[2]) + } + + processData := func(onion string, data []byte) []byte { + return nil + } + + peer.SetPeerDataHandler(processData) + + fmt.Printf("connecting to %v...\n", os.Args[2]) + connection := peer.PeerWithOnion(onion) + + fmt.Printf("sending data...\n") + reader := bufio.NewReader(os.Stdin) + packet := make([]byte, 1024) + br, _ := reader.Read(packet) + + connection.SendPacket(packet[:br]) + case "receive": + if len(os.Args) != 3 { + fmt.Fprintf(os.Stderr, "example: sendafriend receive bob > file.txt\n") + os.Exit(1) + } + + _, exists := peer.GetProfile().GetCustomAttribute(os.Args[2]+"_name") + if exists { + fmt.Printf("woah you already have someone named %v\n", os.Args[2]) + os.Exit(1) + } + + verifyOnion, exists := peer.GetProfile().GetCustomAttribute(os.Args[2]+"_onion") + if !exists { + fmt.Fprintf(os.Stderr, "hmm you don't have a contact named %v\n", os.Args[2]) + os.Exit(1) + } + + processData := func(onion string, data []byte) []byte { + if onion != verifyOnion { + fmt.Fprintf(os.Stderr, "woah, got some unauthenticated data. discarding it!\n") + os.Exit(1) + } + + fmt.Printf("%s", data) + os.Exit(0) + return nil + } + + peer.SetPeerDataHandler(processData) + fmt.Fprintf(os.Stderr, "waiting for %v to send...\n", os.Args[2]) + peer.Listen() + case "hide": + if len(os.Args) != 3 { + fmt.Fprintf(os.Stderr, "example: sendafriend hide bob\n") + os.Exit(1) + } + + suggestedSecret, _ := diceware.Generate(1) + fmt.Printf("enter a secret that only the two of you would know [%v]: ", suggestedSecret[0]) + in := bufio.NewReader(os.Stdin) + secret, _ := in.ReadString('\n') + secret = secret[:len(secret) - 1] + + if secret == "" { + secret = suggestedSecret[0] + } + + ephemeralPeer, err := libpeer.NewCwtchPeer("Alice", "alicepass", "") + if err != nil { + fmt.Printf("couldn't create an ephemeral onion address: %v\n", err) + os.Exit(1) + } + + groupId, err := ephemeralPeer.ImportGroup(inviteStr) + if err != nil { + fmt.Printf("couldn't configure the bbs settings: %v\n", err) + os.Exit(1) + } + + group := ephemeralPeer.GetGroup(groupId) + ephemeralPeer.JoinServer(group.GroupServer) + time.Sleep(time.Second * 30) //TODO: can this be shorter? + + err = ephemeralPeer.SendMessageToGroup(groupId, "be gay do crimes") + if err != nil { + fmt.Printf("the hide-n-seek server is down or something? try again i guess\n") + os.Exit(1) + } + + fmt.Println("okay, now have your friend type \"sendafriend seek\" and enter the secret") + + convos := make(map[string]*Conversation) + processData := func(onion string, data []byte) []byte { + if _, contains := convos[onion]; !contains { + convos[onion] = new(Conversation) + secretInt := new(big.Int) + secretInt.SetBytes([]byte(secret)) + convos[onion].smp.secret = secretInt + } + + tlvPacket := arr2tlv(data) + if tlvPacket.typ == 42 { + fmt.Printf("you've been found! adding %v <%s> to contact list\n", os.Args[2], tlvPacket.data) + addContactEntry(peer, os.Args[2], string(tlvPacket.data)) + peer.Save() + finalPacket := tlv{42, uint16(len(peer.GetProfile().Onion)), []byte(peer.GetProfile().Onion)} + go driftoff() + return tlv2arr(finalPacket) + } + + out, _, _ := convos[onion].processSMP(tlvPacket) + return tlv2arr(out) + } + ephemeralPeer.SetPeerDataHandler(processData) + ephemeralPeer.Listen() + + fmt.Println("press enter to cancel the game and exit") + reader := bufio.NewReader(os.Stdin) + reader.ReadString('\n') + case "seek": + if len(os.Args) != 3 { + fmt.Fprintf(os.Stderr, "example: sendafriend seek alice\n") + os.Exit(1) + } + + fmt.Print("enter a secret that only the two of you would know: ") + in := bufio.NewReader(os.Stdin) + secret, _ := in.ReadString('\n') + secret = secret[:len(secret) - 1] + + ephemeralPeer, err := libpeer.NewCwtchPeer("Alice", "alicepass", "") + if err != nil { + fmt.Printf("couldn't create an ephemeral onion address: %v\n", err) + os.Exit(1) + } + + groupId, err := ephemeralPeer.ImportGroup(inviteStr) + if err != nil { + fmt.Printf("couldn't configure the bbs settings: %v\n", err) + os.Exit(1) + } + + group := ephemeralPeer.GetGroup(groupId) + ephemeralPeer.JoinServer(group.GroupServer) + time.Sleep(time.Second * 10) //TODO: can this be shorter? + + messages := group.GetTimeline() + + for i := len(messages) - 1; i >= 0; i-- { + fmt.Printf("checking advert %d/%d...\n", len(messages) - i, len(messages)) + //fmt.Printf("%v <%v> %v\n", messages[i].Timestamp, messages[i].PeerID, messages[i].Message) + + if messages[i].Message == "be gay do crimes" { + onion, success := doSMP(messages[i].PeerID, secret, os.Args[2], peer.GetProfile().Onion) + if success { + addContactEntry(peer, os.Args[2], onion) + peer.Save() + os.Exit(0) + } else { + fmt.Printf("debug:fail\n") + } + } + } + } + + peer.Save() +} \ No newline at end of file diff --git a/smp.go b/smp.go new file mode 100644 index 0000000..8ceba33 --- /dev/null +++ b/smp.go @@ -0,0 +1,2089 @@ +// 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. + +// This file implements the Socialist Millionaires Protocol as described in +// http://www.cypherpunks.ca/otr/Protocol-v2-3.1.0.html. The protocol +// specification is required in order to understand this code and, where +// possible, the variable names in the code match up with the spec. + +package main + +import ( + libpeer "cwtch.im/cwtch/peer" + "bytes" + "crypto/sha256" + "hash" + "math/big" + "errors" + "io" + "crypto/rand" + "encoding/base64" + "strconv" + "crypto/aes" + "crypto/cipher" + "crypto/hmac" + "crypto/subtle" + "crypto/sha1" + "crypto/dsa" + "encoding/hex" + "fmt" + "os" + "time" +) + + + + + +func arr2tlv(data[] byte) tlv { + var typ, len uint16 + typ = (uint16(data[0]) << 8) + uint16(data[1]) + len = (uint16(data[2]) << 8) + uint16(data[3]) + return tlv{typ, len, data[4:]} +} + +func tlv2arr(t tlv) []byte { + ret := make([]byte, 4 + len(t.data)) + ret[0] = byte(t.typ >> 8) + ret[1] = byte(t.typ & 0xFF) + ret[2] = byte(t.length >> 8) + ret[3] = byte(t.length & 0xFF) + for i := 0; i < len(t.data); i++ { + ret[4 + i] = t.data[i] + } + return ret +} + +func doSMP(onion string, secret string, friendname string, longtermonion string) (string, bool) { + var alice Conversation + secretInt := new(big.Int) + secretInt.SetBytes([]byte(secret)) + alice.smp.secret = secretInt + + peer, err := libpeer.NewCwtchPeer("doSMP", "doSMPpass", "") + if err != nil { + fmt.Println("couldn't create an ephemeral onion :(") + os.Exit(1) + } + + var wishandaprayer string + var success bool + processData := func(onion string, data []byte) []byte { + tlvPacket := arr2tlv(data) + out, complete, err := alice.processSMP(tlvPacket) + + if tlvPacket.typ == 42 { + fmt.Printf("found them! adding %v <%s> to contact list\n", friendname, tlvPacket.data) + wishandaprayer = string(tlvPacket.data) + success = true + return nil + } + + if err != nil { + os.Exit(1) + } else if complete { + finalPacket := tlv{42, uint16(len(longtermonion)), []byte(longtermonion)} + return tlv2arr(finalPacket) + } + + return tlv2arr(out) + } + peer.SetPeerDataHandler(processData) + connection := peer.PeerWithOnion(onion) + + tlvList := alice.startSMP("") + for i := range tlvList { + connection.SendPacket(tlv2arr(tlvList[i])) + } + + time.Sleep(time.Minute) + return wishandaprayer, success +} + + + + + + + +type smpFailure string + +func (s smpFailure) Error() string { + return string(s) +} + +var smpFailureError = smpFailure("otr: SMP protocol failed") +var smpSecretMissingError = smpFailure("otr: mutual secret needed") + +const smpVersion = 1 + +const ( + smpState1 = iota + smpState2 + smpState3 + smpState4 +) + +type smpState struct { + state int + a2, a3, b2, b3, pb, qb *big.Int + g2a, g3a *big.Int + g2, g3 *big.Int + g3b, papb, qaqb, ra *big.Int + saved *tlv + secret *big.Int + question string +} + +func (c *Conversation) startSMP(question string) (tlvs []tlv) { + if c.smp.state != smpState1 { + tlvs = append(tlvs, c.generateSMPAbort()) + } + tlvs = append(tlvs, c.generateSMP1(question)) + c.smp.question = "" + c.smp.state = smpState2 + return +} + +func (c *Conversation) resetSMP() { + c.smp.state = smpState1 + c.smp.secret = nil + c.smp.question = "" +} + +func (c *Conversation) processSMP(in tlv) (out tlv, complete bool, err error) { + data := in.data + + switch in.typ { + case tlvTypeSMPAbort: + if c.smp.state != smpState1 { + err = smpFailureError + } + c.resetSMP() + return + case tlvTypeSMP1WithQuestion: + // We preprocess this into a SMP1 message. + nulPos := bytes.IndexByte(data, 0) + if nulPos == -1 { + err = errors.New("otr: SMP message with question didn't contain a NUL byte") + return + } + c.smp.question = string(data[:nulPos]) + data = data[nulPos+1:] + } + + numMPIs, data, ok := getU32(data) + if !ok || numMPIs > 20 { + err = errors.New("otr: corrupt SMP message") + return + } + + mpis := make([]*big.Int, numMPIs) + for i := range mpis { + var ok bool + mpis[i], data, ok = getMPI(data) + if !ok { + err = errors.New("otr: corrupt SMP message") + return + } + } + + switch in.typ { + case tlvTypeSMP1, tlvTypeSMP1WithQuestion: + if c.smp.state != smpState1 { + c.resetSMP() + out = c.generateSMPAbort() + return + } + if c.smp.secret == nil { + err = smpSecretMissingError + return + } + if err = c.processSMP1(mpis); err != nil { + return + } + c.smp.state = smpState3 + out = c.generateSMP2() + case tlvTypeSMP2: + if c.smp.state != smpState2 { + c.resetSMP() + out = c.generateSMPAbort() + return + } + if out, err = c.processSMP2(mpis); err != nil { + out = c.generateSMPAbort() + return + } + c.smp.state = smpState4 + case tlvTypeSMP3: + if c.smp.state != smpState3 { + c.resetSMP() + out = c.generateSMPAbort() + return + } + if out, err = c.processSMP3(mpis); err != nil { + return + } + c.smp.state = smpState1 + c.smp.secret = nil + complete = true + case tlvTypeSMP4: + if c.smp.state != smpState4 { + c.resetSMP() + out = c.generateSMPAbort() + return + } + if err = c.processSMP4(mpis); err != nil { + out = c.generateSMPAbort() + return + } + c.smp.state = smpState1 + c.smp.secret = nil + complete = true + default: + panic("unknown SMP message") + } + + return +} + +func (c *Conversation) calcSMPSecret(mutualSecret []byte, weStarted bool) { + h := sha256.New() + h.Write([]byte{smpVersion}) + if weStarted { + h.Write(c.PrivateKey.PublicKey.Fingerprint()) + h.Write(c.TheirPublicKey.Fingerprint()) + } else { + h.Write(c.TheirPublicKey.Fingerprint()) + h.Write(c.PrivateKey.PublicKey.Fingerprint()) + } + h.Write(c.SSID[:]) + h.Write(mutualSecret) + c.smp.secret = new(big.Int).SetBytes(h.Sum(nil)) +} + +func (c *Conversation) generateSMP1(question string) tlv { + var randBuf [16]byte + c.smp.a2 = c.randMPI(randBuf[:]) + c.smp.a3 = c.randMPI(randBuf[:]) + g2a := new(big.Int).Exp(g, c.smp.a2, p) + g3a := new(big.Int).Exp(g, c.smp.a3, p) + h := sha256.New() + + r2 := c.randMPI(randBuf[:]) + r := new(big.Int).Exp(g, r2, p) + c2 := new(big.Int).SetBytes(hashMPIs(h, 1, r)) + d2 := new(big.Int).Mul(c.smp.a2, c2) + d2.Sub(r2, d2) + d2.Mod(d2, q) + if d2.Sign() < 0 { + d2.Add(d2, q) + } + + r3 := c.randMPI(randBuf[:]) + r.Exp(g, r3, p) + c3 := new(big.Int).SetBytes(hashMPIs(h, 2, r)) + d3 := new(big.Int).Mul(c.smp.a3, c3) + d3.Sub(r3, d3) + d3.Mod(d3, q) + if d3.Sign() < 0 { + d3.Add(d3, q) + } + + var ret tlv + if len(question) > 0 { + ret.typ = tlvTypeSMP1WithQuestion + ret.data = append(ret.data, question...) + ret.data = append(ret.data, 0) + } else { + ret.typ = tlvTypeSMP1 + } + ret.data = appendU32(ret.data, 6) + ret.data = appendMPIs(ret.data, g2a, c2, d2, g3a, c3, d3) + return ret +} + +func (c *Conversation) processSMP1(mpis []*big.Int) error { + if len(mpis) != 6 { + return errors.New("otr: incorrect number of arguments in SMP1 message") + } + g2a := mpis[0] + c2 := mpis[1] + d2 := mpis[2] + g3a := mpis[3] + c3 := mpis[4] + d3 := mpis[5] + h := sha256.New() + + r := new(big.Int).Exp(g, d2, p) + s := new(big.Int).Exp(g2a, c2, p) + r.Mul(r, s) + r.Mod(r, p) + t := new(big.Int).SetBytes(hashMPIs(h, 1, r)) + if c2.Cmp(t) != 0 { + return errors.New("otr: ZKP c2 incorrect in SMP1 message") + } + r.Exp(g, d3, p) + s.Exp(g3a, c3, p) + r.Mul(r, s) + r.Mod(r, p) + t.SetBytes(hashMPIs(h, 2, r)) + if c3.Cmp(t) != 0 { + return errors.New("otr: ZKP c3 incorrect in SMP1 message") + } + + c.smp.g2a = g2a + c.smp.g3a = g3a + return nil +} + +func (c *Conversation) generateSMP2() tlv { + var randBuf [16]byte + b2 := c.randMPI(randBuf[:]) + c.smp.b3 = c.randMPI(randBuf[:]) + r2 := c.randMPI(randBuf[:]) + r3 := c.randMPI(randBuf[:]) + r4 := c.randMPI(randBuf[:]) + r5 := c.randMPI(randBuf[:]) + r6 := c.randMPI(randBuf[:]) + + g2b := new(big.Int).Exp(g, b2, p) + g3b := new(big.Int).Exp(g, c.smp.b3, p) + + r := new(big.Int).Exp(g, r2, p) + h := sha256.New() + c2 := new(big.Int).SetBytes(hashMPIs(h, 3, r)) + d2 := new(big.Int).Mul(b2, c2) + d2.Sub(r2, d2) + d2.Mod(d2, q) + if d2.Sign() < 0 { + d2.Add(d2, q) + } + + r.Exp(g, r3, p) + c3 := new(big.Int).SetBytes(hashMPIs(h, 4, r)) + d3 := new(big.Int).Mul(c.smp.b3, c3) + d3.Sub(r3, d3) + d3.Mod(d3, q) + if d3.Sign() < 0 { + d3.Add(d3, q) + } + + c.smp.g2 = new(big.Int).Exp(c.smp.g2a, b2, p) + c.smp.g3 = new(big.Int).Exp(c.smp.g3a, c.smp.b3, p) + c.smp.pb = new(big.Int).Exp(c.smp.g3, r4, p) + c.smp.qb = new(big.Int).Exp(g, r4, p) + r.Exp(c.smp.g2, c.smp.secret, p) + c.smp.qb.Mul(c.smp.qb, r) + c.smp.qb.Mod(c.smp.qb, p) + + s := new(big.Int) + s.Exp(c.smp.g2, r6, p) + r.Exp(g, r5, p) + s.Mul(r, s) + s.Mod(s, p) + r.Exp(c.smp.g3, r5, p) + cp := new(big.Int).SetBytes(hashMPIs(h, 5, r, s)) + + // D5 = r5 - r4 cP mod q and D6 = r6 - y cP mod q + + s.Mul(r4, cp) + r.Sub(r5, s) + d5 := new(big.Int).Mod(r, q) + if d5.Sign() < 0 { + d5.Add(d5, q) + } + + s.Mul(c.smp.secret, cp) + r.Sub(r6, s) + d6 := new(big.Int).Mod(r, q) + if d6.Sign() < 0 { + d6.Add(d6, q) + } + + var ret tlv + ret.typ = tlvTypeSMP2 + ret.data = appendU32(ret.data, 11) + ret.data = appendMPIs(ret.data, g2b, c2, d2, g3b, c3, d3, c.smp.pb, c.smp.qb, cp, d5, d6) + return ret +} + +func (c *Conversation) processSMP2(mpis []*big.Int) (out tlv, err error) { + if len(mpis) != 11 { + err = errors.New("otr: incorrect number of arguments in SMP2 message") + return + } + g2b := mpis[0] + c2 := mpis[1] + d2 := mpis[2] + g3b := mpis[3] + c3 := mpis[4] + d3 := mpis[5] + pb := mpis[6] + qb := mpis[7] + cp := mpis[8] + d5 := mpis[9] + d6 := mpis[10] + h := sha256.New() + + r := new(big.Int).Exp(g, d2, p) + s := new(big.Int).Exp(g2b, c2, p) + r.Mul(r, s) + r.Mod(r, p) + s.SetBytes(hashMPIs(h, 3, r)) + if c2.Cmp(s) != 0 { + err = errors.New("otr: ZKP c2 failed in SMP2 message") + return + } + + r.Exp(g, d3, p) + s.Exp(g3b, c3, p) + r.Mul(r, s) + r.Mod(r, p) + s.SetBytes(hashMPIs(h, 4, r)) + if c3.Cmp(s) != 0 { + err = errors.New("otr: ZKP c3 failed in SMP2 message") + return + } + + c.smp.g2 = new(big.Int).Exp(g2b, c.smp.a2, p) + c.smp.g3 = new(big.Int).Exp(g3b, c.smp.a3, p) + + r.Exp(g, d5, p) + s.Exp(c.smp.g2, d6, p) + r.Mul(r, s) + s.Exp(qb, cp, p) + r.Mul(r, s) + r.Mod(r, p) + + s.Exp(c.smp.g3, d5, p) + t := new(big.Int).Exp(pb, cp, p) + s.Mul(s, t) + s.Mod(s, p) + t.SetBytes(hashMPIs(h, 5, s, r)) + if cp.Cmp(t) != 0 { + err = errors.New("otr: ZKP cP failed in SMP2 message") + return + } + + var randBuf [16]byte + r4 := c.randMPI(randBuf[:]) + r5 := c.randMPI(randBuf[:]) + r6 := c.randMPI(randBuf[:]) + r7 := c.randMPI(randBuf[:]) + + pa := new(big.Int).Exp(c.smp.g3, r4, p) + r.Exp(c.smp.g2, c.smp.secret, p) + qa := new(big.Int).Exp(g, r4, p) + qa.Mul(qa, r) + qa.Mod(qa, p) + + r.Exp(g, r5, p) + s.Exp(c.smp.g2, r6, p) + r.Mul(r, s) + r.Mod(r, p) + + s.Exp(c.smp.g3, r5, p) + cp.SetBytes(hashMPIs(h, 6, s, r)) + + r.Mul(r4, cp) + d5 = new(big.Int).Sub(r5, r) + d5.Mod(d5, q) + if d5.Sign() < 0 { + d5.Add(d5, q) + } + + r.Mul(c.smp.secret, cp) + d6 = new(big.Int).Sub(r6, r) + d6.Mod(d6, q) + if d6.Sign() < 0 { + d6.Add(d6, q) + } + + r.ModInverse(qb, p) + qaqb := new(big.Int).Mul(qa, r) + qaqb.Mod(qaqb, p) + + ra := new(big.Int).Exp(qaqb, c.smp.a3, p) + r.Exp(qaqb, r7, p) + s.Exp(g, r7, p) + cr := new(big.Int).SetBytes(hashMPIs(h, 7, s, r)) + + r.Mul(c.smp.a3, cr) + d7 := new(big.Int).Sub(r7, r) + d7.Mod(d7, q) + if d7.Sign() < 0 { + d7.Add(d7, q) + } + + c.smp.g3b = g3b + c.smp.qaqb = qaqb + + r.ModInverse(pb, p) + c.smp.papb = new(big.Int).Mul(pa, r) + c.smp.papb.Mod(c.smp.papb, p) + c.smp.ra = ra + + out.typ = tlvTypeSMP3 + out.data = appendU32(out.data, 8) + out.data = appendMPIs(out.data, pa, qa, cp, d5, d6, ra, cr, d7) + return +} + +func (c *Conversation) processSMP3(mpis []*big.Int) (out tlv, err error) { + if len(mpis) != 8 { + err = errors.New("otr: incorrect number of arguments in SMP3 message") + return + } + pa := mpis[0] + qa := mpis[1] + cp := mpis[2] + d5 := mpis[3] + d6 := mpis[4] + ra := mpis[5] + cr := mpis[6] + d7 := mpis[7] + h := sha256.New() + + r := new(big.Int).Exp(g, d5, p) + s := new(big.Int).Exp(c.smp.g2, d6, p) + r.Mul(r, s) + s.Exp(qa, cp, p) + r.Mul(r, s) + r.Mod(r, p) + + s.Exp(c.smp.g3, d5, p) + t := new(big.Int).Exp(pa, cp, p) + s.Mul(s, t) + s.Mod(s, p) + t.SetBytes(hashMPIs(h, 6, s, r)) + if t.Cmp(cp) != 0 { + err = errors.New("otr: ZKP cP failed in SMP3 message") + return + } + + r.ModInverse(c.smp.qb, p) + qaqb := new(big.Int).Mul(qa, r) + qaqb.Mod(qaqb, p) + + r.Exp(qaqb, d7, p) + s.Exp(ra, cr, p) + r.Mul(r, s) + r.Mod(r, p) + + s.Exp(g, d7, p) + t.Exp(c.smp.g3a, cr, p) + s.Mul(s, t) + s.Mod(s, p) + t.SetBytes(hashMPIs(h, 7, s, r)) + if t.Cmp(cr) != 0 { + err = errors.New("otr: ZKP cR failed in SMP3 message") + return + } + + var randBuf [16]byte + r7 := c.randMPI(randBuf[:]) + rb := new(big.Int).Exp(qaqb, c.smp.b3, p) + + r.Exp(qaqb, r7, p) + s.Exp(g, r7, p) + cr = new(big.Int).SetBytes(hashMPIs(h, 8, s, r)) + + r.Mul(c.smp.b3, cr) + d7 = new(big.Int).Sub(r7, r) + d7.Mod(d7, q) + if d7.Sign() < 0 { + d7.Add(d7, q) + } + + out.typ = tlvTypeSMP4 + out.data = appendU32(out.data, 3) + out.data = appendMPIs(out.data, rb, cr, d7) + + r.ModInverse(c.smp.pb, p) + r.Mul(pa, r) + r.Mod(r, p) + s.Exp(ra, c.smp.b3, p) + if r.Cmp(s) != 0 { + err = smpFailureError + } + + return +} + +func (c *Conversation) processSMP4(mpis []*big.Int) error { + if len(mpis) != 3 { + return errors.New("otr: incorrect number of arguments in SMP4 message") + } + rb := mpis[0] + cr := mpis[1] + d7 := mpis[2] + h := sha256.New() + + r := new(big.Int).Exp(c.smp.qaqb, d7, p) + s := new(big.Int).Exp(rb, cr, p) + r.Mul(r, s) + r.Mod(r, p) + + s.Exp(g, d7, p) + t := new(big.Int).Exp(c.smp.g3b, cr, p) + s.Mul(s, t) + s.Mod(s, p) + t.SetBytes(hashMPIs(h, 8, s, r)) + if t.Cmp(cr) != 0 { + return errors.New("otr: ZKP cR failed in SMP4 message") + } + + r.Exp(rb, c.smp.a3, p) + if r.Cmp(c.smp.papb) != 0 { + return smpFailureError + } + + return nil +} + +func (c *Conversation) generateSMPAbort() tlv { + return tlv{typ: tlvTypeSMPAbort} +} + +func hashMPIs(h hash.Hash, magic byte, mpis ...*big.Int) []byte { + if h != nil { + h.Reset() + } else { + h = sha256.New() + } + + h.Write([]byte{magic}) + for _, mpi := range mpis { + h.Write(appendMPI(nil, mpi)) + } + return h.Sum(nil) +} + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +// 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 + } +} diff --git a/test.txt b/test.txt new file mode 100644 index 0000000..f3cbd75 --- /dev/null +++ b/test.txt @@ -0,0 +1 @@ +hmph