diff options
Diffstat (limited to 'challenge/c35.go')
| -rw-r--r-- | challenge/c35.go | 358 |
1 files changed, 358 insertions, 0 deletions
diff --git a/challenge/c35.go b/challenge/c35.go new file mode 100644 index 0000000..cb2d166 --- /dev/null +++ b/challenge/c35.go @@ -0,0 +1,358 @@ +// Copyright © 2022 siddharth <s@ricketyspace.net> +// SPDX-License-Identifier: ISC + +package challenge + +import ( + "bufio" + "fmt" + "math/big" + "net" + "os" + + "ricketyspace.net/cryptopals/lib" +) + +func C35(args []string) { + if len(args) < 2 { + fmt.Println("Usage: cryptopals -c 35 ENTITY PORT") + return + } + entity := args[0] + port, err := lib.StrToNum(args[1]) + if err != nil { + fmt.Println("Port invalid") + return + } + if port < 12000 { + fmt.Println("Error: port number must be >= 12000") + return + } + + // Cipher functions. + // + // Pack a cipher and it's iv into packet. + cipherPacketEncode := func(cipher, iv []byte) string { + packet := append(cipher, iv...) + return lib.BytesToHexStr(packet) + } + // Unpack packet into cipher and iv. + cipherPacketDecode := func(packet string) (cipher, iv []byte) { + stream := lib.HexStrToBytes(packet) + cipher = stream[0 : len(stream)-16] + iv = stream[len(stream)-16:] + + return cipher, iv + } + // Encipher using AES-CBC. + encipher := func(skey *big.Int, msg string) (string, error) { + // Make key out of DH sesssion key. + sha1 := lib.Sha1{} + sha1.Init([]uint32{}) + sha1.Message(skey.Bytes()) + skeyb := sha1.Hash() + if len(skeyb) < 16 { + // Pad it to 16 bytes. + skeyb = append(skeyb, make([]byte, 16-len(skeyb))...) + } + k := skeyb[0:16] + + // Make initialization vector. + iv, err := lib.RandomBytes(16) + if err != nil { + return "", err + } + + // Encrypt msg using AES-CBC + cipher := lib.AESEncryptCBC([]byte(msg), k, iv) + + // Pack encrypted message in a format that can be sent + // over the wire. + packet := cipherPacketEncode(cipher, iv) + + // Return packed encrypted message. + return packet, nil + } + // Decipher using AES-CBC. + decipher := func(skey *big.Int, packet string) (string, error) { + // Make key out of DH sesssion key. + sha1 := lib.Sha1{} + sha1.Init([]uint32{}) + sha1.Message(skey.Bytes()) + skeyb := sha1.Hash() + if len(skeyb) < 16 { + // Pad it to 16 bytes. + skeyb = append(skeyb, make([]byte, 16-len(skeyb))...) + } + k := skeyb[0:16] + + // Decode packet + cipher, iv := cipherPacketDecode(packet) + + // Decrypt message. + msg, err := lib.AESDecryptCBC(cipher, k, iv) + if err != nil { + return "", err + } + + return string(msg), nil + } + // Server handling. + // + // Do DH handshake with client and return DH session key. + serverDHHandshake := func(conn net.Conn) (*big.Int, error) { + // Read p+g packet from client. + packet, err := bufio.NewReader(conn).ReadString('\n') + if err != nil { + return nil, err + } + // Remove newline character from packet. + packet = packet[:len(packet)-1] + + // Try to read DH paramters from packet. + params := lib.StrSplitAt('+', packet) + if len(params) != 2 { + return nil, lib.CPError{"DH paramters invalid"} + } + + // Try make DH for this client connection. + dh, ok := lib.NewDH(params[0], params[1]) + if !ok { + return nil, lib.CPError{"DH initialization failed"} + } + + // Send ACK to client. + fmt.Fprintf(conn, "ACK\n") + + // Wait and get client's DH public key + packet, err = bufio.NewReader(conn).ReadString('\n') + if err != nil { + return nil, err + } + // Remove newline character. + packet = packet[:len(packet)-1] + + // Parse client's DH public key. + cPub, ok := new(big.Int).SetString(lib.StripSpaceChars(packet), 10) + if !ok { + return nil, lib.CPError{"DH public key invalid"} + } + + // Send server's DH public key for this connection. + fmt.Fprintf(conn, "%v\n", dh.Pub()) + + // Return DH session key. + return dh.SharedSecret(cPub), nil + } + // Handle connection from a client. + serverHandleConn := func(conn net.Conn) { + defer conn.Close() + + // Do DH handshake. + skey, err := serverDHHandshake(conn) + if err != nil { + fmt.Printf("DH Handshake failed [%v]: %v\n", + conn.RemoteAddr(), err) + return + } + fmt.Printf("Made secure connection with %v\n", conn.RemoteAddr()) + + // Enter read-echo loop. + for { + packet, err := bufio.NewReader(conn).ReadString('\n') + if err != nil { + fmt.Printf("Closed connection to [%v]\n", + conn.RemoteAddr()) + return + } + // Remove newline character. + packet = packet[:len(packet)-1] + + // Decipher packet. + msg, err := decipher(skey, packet) + if err != nil { + fmt.Printf("Message decryption failed for [%v]: %v\n", + conn.RemoteAddr(), err) + return + } + fmt.Printf("Received from [%v]: '%v'\n", conn.RemoteAddr(), msg) + + // Make msg to client. + msg = fmt.Sprintf("-> %s", msg) + + // Encrypt and echo back message. + cpacket, err := encipher(skey, msg) + if err != nil { + fmt.Printf("Message encryption failed for [%v]: %v\n", + conn.RemoteAddr(), err) + return + } + // Send message to client. + fmt.Fprintf(conn, "%s\n", cpacket) + } + } + // Start "secure" echo server. + serverSpawn := func() { + p := fmt.Sprintf(":%d", port) + ln, err := net.Listen("tcp", p) + if err != nil { + fmt.Printf("Server listen error: %v\n", err) + return + } + for { + fmt.Println("Waiting for connection...") + conn, err := ln.Accept() + if err != nil { + fmt.Printf("Server accept error: %v", err) + } + go serverHandleConn(conn) + } + } + // Client handling. + // + // Try to make secure connection with server using DH and + // return server's DH public key. + clientSecureConnToServer := func() (net.Conn, *big.Int, error) { + // Try to connect to server. + addr := fmt.Sprintf(":%d", port) + conn, err := net.Dial("tcp", addr) + if err != nil { + return conn, nil, err + } + + // Initialize DH. + p := lib.StripSpaceChars( + `ffffffffffffffffc90fdaa22168c234c4c6628b80dc1cd129024 + e088a67cc74020bbea63b139b22514a08798e3404ddef9519b3cd + 3a431b302b0a6df25f14374fe1356d6d51c245e485b576625e7ec + 6f44c42e9a637ed6b0bff5cb6f406b7edee386bfb5a899fa5ae9f + 24117c4b1fe649286651ece45b3dc2007cb8a163bf0598da48361 + c55d39a69163fa8fd24cf5f83655d23dca3ad961c62f356208552 + bb9ed529077096966d670c354e4abc9804f1746c08ca237327fff + fffffffffffff`) + g := "2" + dh, ok := lib.NewDH(p, g) + if !ok { + return conn, nil, lib.CPError{"DH initialization failed"} + } + + // Make DH packet: p+g + packet := fmt.Sprintf("%v+%v", p, g) + + // Sent DH packet to server. + fmt.Fprintf(conn, "%s\n", packet) + + // Wait and try to get ACK from server. + spacket, err := bufio.NewReader(conn).ReadString('\n') + if err != nil { + return conn, nil, err + } + // Remove newline character. + spacket = spacket[:len(spacket)-1] + if spacket != "ACK" { + return conn, nil, lib.CPError{"ACK failed"} + } + + // Send DH public key to server. + fmt.Fprintf(conn, "%v\n", dh.Pub()) + + // Get server's DH public key. + spacket, err = bufio.NewReader(conn).ReadString('\n') + if err != nil { + return conn, nil, err + } + // Remove newline character. + spacket = spacket[:len(spacket)-1] + + // Parse server's DH public key. + sPub, ok := new(big.Int).SetString(lib.StripSpaceChars(spacket), 10) + if !ok { + return conn, nil, lib.CPError{"Server's DH key invalid"} + } + + // Return server connection and DH session key. + return conn, dh.SharedSecret(sPub), nil + } + // Start the client. + clientSpawn := func() { + // Make a secure connection to server. + conn, skey, err := clientSecureConnToServer() + if err != nil { + fmt.Printf("Unable to establish secure connection: %v\n", err) + return + } + defer conn.Close() + fmt.Printf("Made secure connection with %v\n", conn.RemoteAddr()) + + // Enter write loop. + for { + // Read message from stdin. + fmt.Printf("> ") + msg, err := bufio.NewReader(os.Stdin).ReadString('\n') + if err != nil { + fmt.Printf("Read error: %v\n", err) + return + } + // Remove newline character. + msg = msg[:len(msg)-1] + + // Encrypt message. + packet, err := encipher(skey, msg) + if err != nil { + fmt.Printf("Encryption error: %v\n", err) + return + } + + // Send message to server. + fmt.Fprintf(conn, "%s\n", packet) + + // Read response from server. + spacket, err := bufio.NewReader(conn).ReadString('\n') + if err != nil { + fmt.Printf("Server closed connection\n") + return + } + // Remove newline character. + spacket = spacket[:len(spacket)-1] + + // Decipher packet from server. + smsg, err := decipher(skey, spacket) + if err != nil { + fmt.Printf("Message decryption failed: %v\n", err) + return + } + // Barf server's response. + fmt.Printf("%s\n", smsg) + } + } + + // Take action based on entity. + switch { + case entity == "server": + serverSpawn() + case entity == "client": + clientSpawn() + default: + fmt.Println("Error: Uknown entity") + } +} + +// Output: +// +// Part I: +// +// $ ./cryptopals -c 35 server 12000 +// Waiting for connection... +// Waiting for connection... +// Made secure connection with 127.0.0.1:40557 +// Received from [127.0.0.1:40557]: 'Put this together while listening to' +// Received from [127.0.0.1:40557]: 'Kara Swisher's Sway.' +// +// $ ./cryptopals -c 35 client 12000 +// Made secure connection with 127.0.0.1:12000 +// > Put this together while listening to +// -> Put this together while listening to +// > Kara Swisher's Sway. +// -> Kara Swisher's Sway. +// > ^C +// |