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authorsiddharth <s@ricketyspace.net>2022-02-20 17:10:59 -0500
committersiddharth <s@ricketyspace.net>2022-02-20 17:10:59 -0500
commitd9c9edb96c2cd6e784a073894d65a843681006aa (patch)
tree5595c3586829428fa97658f26e6af4b4d0fdeca7
parent857d1ba18f3a458374e462db2a7ae3cb39e3e5db (diff)
challenge: do challenge 35 - part ii
-rw-r--r--challenge/c35.go340
1 files changed, 339 insertions, 1 deletions
diff --git a/challenge/c35.go b/challenge/c35.go
index cb2d166..b266e47 100644
--- a/challenge/c35.go
+++ b/challenge/c35.go
@@ -15,10 +15,15 @@ import (
func C35(args []string) {
if len(args) < 2 {
- fmt.Println("Usage: cryptopals -c 35 ENTITY PORT")
+ fmt.Println("Usage: cryptopals -c 35 ENTITY PORT [S-PORT] [G]")
return
}
entity := args[0]
+ if entity == "attacker" && len(args) != 4 {
+ fmt.Println("Usage: cryptopals -c 35 attacker PORT S-PORT G")
+ fmt.Println("\n G should be '1', 'p' or 'p-1'")
+ return
+ }
port, err := lib.StrToNum(args[1])
if err != nil {
fmt.Println("Port invalid")
@@ -28,6 +33,24 @@ func C35(args []string) {
fmt.Println("Error: port number must be >= 12000")
return
}
+ sport := 0
+ gtype := ""
+ if entity == "attacker" {
+ sport, err = lib.StrToNum(args[2])
+ if err != nil {
+ fmt.Println("S-Port invalid")
+ return
+ }
+ if sport < 12000 {
+ fmt.Println("Error: port number must be >= 12000")
+ return
+ }
+ gtype = lib.StripSpaceChars(args[3])
+ if gtype != "1" && gtype != "p" && gtype != "p-1" {
+ fmt.Println("Error: G is invalid")
+ return
+ }
+ }
// Cipher functions.
//
@@ -325,6 +348,257 @@ func C35(args []string) {
fmt.Printf("%s\n", smsg)
}
}
+ // Attacker handling.
+ //
+ // Slurp DH params from client.
+ attackerSlurpDHParams := func(conn net.Conn) ([]string, error) {
+ // Read DH packet from client.
+ packet, err := bufio.NewReader(conn).ReadString('\n')
+ if err != nil {
+ return []string{}, 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 []string{}, lib.CPError{"DH paramters invalid"}
+ }
+
+ // Try make a DH from params.
+ _, ok := lib.NewDH(params[0], params[1])
+ if !ok {
+ return []string{}, lib.CPError{"DH initialization failed"}
+ }
+ return params, nil
+ }
+ // Return DH param `g` based on gtype.
+ attackerGetDHG := func(p string) (string, *big.Int, bool) {
+ if gtype == "1" {
+ return "1", new(big.Int).SetInt64(1), true
+ }
+
+ // Convert string `p` to big.Int.
+ pi, ok := new(big.Int).SetString(p, 16)
+ if !ok {
+ return "", nil, false
+ }
+
+ if gtype == "p" {
+ return p, pi, true
+ }
+
+ if gtype != "p-1" {
+ return "", nil, false
+ }
+
+ // gtype is "p-1"; make it.
+ pi.Sub(pi, new(big.Int).SetInt64(1))
+ return fmt.Sprintf("%x", pi), pi, true
+ }
+ // Try to make a connection with the server using DH and
+ // return serve'rs DH public key.
+ attackerSecureConnToServer := func(p, g string) (net.Conn, *big.Int, error) {
+ // Try to connect to server.
+ addr := fmt.Sprintf(":%d", sport)
+ conn, err := net.Dial("tcp", addr)
+ if err != nil {
+ return conn, nil, err
+ }
+
+ // Initialize DH.
+ 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 server's DH public key.
+ return conn, dh.SharedSecret(sPub), nil
+ }
+ // Handle connection from a client.
+ attackerHandleConn := func(conn net.Conn) {
+ defer conn.Close()
+
+ // Read DH params from client.
+ dhParams, err := attackerSlurpDHParams(conn)
+ if err != nil {
+ fmt.Printf("Error: %v\n", err)
+ return
+ }
+
+ // DH params for the server.
+ p := dhParams[0]
+ g, gi, ok := attackerGetDHG(p)
+ if !ok {
+ fmt.Println("Error: Unable to get DH param 'g'")
+ return
+ }
+ sconn, skey, err := attackerSecureConnToServer(p, g)
+ if err != nil {
+ fmt.Printf("Error: %v\n", err)
+ return
+ }
+ defer sconn.Close()
+
+ // 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 {
+ fmt.Println("Error: Unable to read client's DH public key")
+ return
+ }
+ // Remove newline character.
+ packet = packet[:len(packet)-1]
+
+ // Parse client's DH public key.
+ _, ok = new(big.Int).SetString(lib.StripSpaceChars(packet), 10)
+ if !ok {
+ fmt.Println("Error: client DH public key invalid")
+ return
+ }
+
+ // Send server's session key as public key to client.
+ fmt.Fprintf(conn, "%v\n", skey)
+
+ // Client session key.
+ ckey := new(big.Int).Set(skey)
+ ckeyAlt := new(big.Int)
+ ckeyConfirmed := true
+ if gtype == "p-1" {
+ // ckey can be 1 or p-1. Set ckeyAlt to p-1 if
+ // ckey is 1; 1 otherwise.
+ ckeyConfirmed = false
+ if ckey.Cmp(new(big.Int).SetInt64(1)) == 0 {
+ ckeyAlt.Set(gi)
+ } else {
+ ckeyAlt.Set(new(big.Int).SetInt64(1))
+ }
+ }
+
+ // Enter mitm loop
+ for {
+ // Read from client.
+ 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.
+ if !ckeyConfirmed {
+ _, err = decipher(ckey, packet)
+ if err != nil {
+ ckey = ckeyAlt
+ ckeyConfirmed = true
+ }
+ }
+ msg, err := decipher(ckey, packet)
+ if err != nil {
+ fmt.Printf("Message decryption failed for [%v]: %v\n",
+ conn.RemoteAddr(), err)
+ return
+ }
+ fmt.Printf("Received from client [%v]: '%v'\n",
+ conn.RemoteAddr(), msg)
+
+ // Encrypt and forward message to server.
+ spacket, err := encipher(skey, msg)
+ if err != nil {
+ fmt.Printf("Message encryption failed for [%v]: %v\n",
+ sconn.RemoteAddr(), err)
+ return
+ }
+ // Send message to server.
+ fmt.Fprintf(sconn, "%s\n", spacket)
+
+ // Read encrypted message from server.
+ spacket, err = bufio.NewReader(sconn).ReadString('\n')
+ if err != nil {
+ fmt.Printf("Closed connection to [%v]\n",
+ sconn.RemoteAddr())
+ return
+ }
+ // Remove newline character.
+ spacket = spacket[:len(spacket)-1]
+
+ // Decipher packet.
+ msg, err = decipher(skey, spacket)
+ if err != nil {
+ fmt.Printf("Message decryption failed for [%v]: %v\n",
+ sconn.RemoteAddr(), err)
+ return
+ }
+ fmt.Printf("Received from server [%v]: '%v'\n",
+ sconn.RemoteAddr(), msg)
+
+ // Encrypt and echo back message.
+ cpacket, err := encipher(ckey, 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 (mitm) attacker server.
+ attackerSpawn := func() {
+ p := fmt.Sprintf(":%d", port)
+ ln, err := net.Listen("tcp", p)
+ if err != nil {
+ fmt.Printf("Attacker listen error: %v\n", err)
+ return
+ }
+ for {
+ fmt.Println("Waiting for connection...")
+ conn, err := ln.Accept()
+ if err != nil {
+ fmt.Printf("Attacker accept error: %v", err)
+ }
+ go attackerHandleConn(conn)
+ }
+ }
// Take action based on entity.
switch {
@@ -332,6 +606,8 @@ func C35(args []string) {
serverSpawn()
case entity == "client":
clientSpawn()
+ case entity == "attacker":
+ attackerSpawn()
default:
fmt.Println("Error: Uknown entity")
}
@@ -356,3 +632,65 @@ func C35(args []string) {
// -> Kara Swisher's Sway.
// > ^C
//
+// Part II:
+//
+// https://ricketyspace.net/cryptopals/c35.webm
+//
+// $ ./cryptopals -c 35 server 12000
+// Waiting for connection...
+// Waiting for connection...
+// Made secure connection with 127.0.0.1:27477
+// Received from [127.0.0.1:27477]: 'If the red slayer think he slays,'
+// Closed connection to [127.0.0.1:27477]
+// Waiting for connection...
+// Made secure connection with 127.0.0.1:46947
+// Received from [127.0.0.1:46947]: 'Or if the slain think he is slain,'
+// Closed connection to [127.0.0.1:46947]
+// Waiting for connection...
+// Made secure connection with 127.0.0.1:42735
+// Received from [127.0.0.1:42735]: 'They know not well the subtle ways'
+// Received from [127.0.0.1:42735]: 'I keep, and pass, and turn again.'
+// Closed connection to [127.0.0.1:42735]
+// ^C
+//
+// $ ./cryptopals -c 35 attacker 12001 12000 1
+// Waiting for connection...
+// Waiting for connection...
+// Received from client [127.0.0.1:12597]: 'If the red slayer think he slays,'
+// Received from server [127.0.0.1:12000]: '-> If the red slayer think he slays,'
+// Closed connection to [127.0.0.1:12597]
+// ^C
+// ada$ ./cryptopals -c 35 attacker 12001 12000 p
+// Waiting for connection...
+// Waiting for connection...
+// Received from client [127.0.0.1:47227]: 'Or if the slain think he is slain,'
+// Received from server [127.0.0.1:12000]: '-> Or if the slain think he is slain,'
+// Closed connection to [127.0.0.1:47227]
+// ^C
+// ada$ ./cryptopals -c 35 attacker 12001 12000 p-1
+// Waiting for connection...
+// Waiting for connection...
+// Received from client [127.0.0.1:9193]: 'They know not well the subtle ways'
+// Received from server [127.0.0.1:12000]: '-> They know not well the subtle ways'
+// Received from client [127.0.0.1:9193]: 'I keep, and pass, and turn again.'
+// Received from server [127.0.0.1:12000]: '-> I keep, and pass, and turn again.'
+// Closed connection to [127.0.0.1:9193]
+// ^C
+//
+// $ ./cryptopals -c 35 client 12001
+// Made secure connection with 127.0.0.1:12001
+// > If the red slayer think he slays,
+// -> If the red slayer think he slays,
+// > ^C
+// ada$ ./cryptopals -c 35 client 12001
+// Made secure connection with 127.0.0.1:12001
+// > Or if the slain think he is slain,
+// -> Or if the slain think he is slain,
+// > ^C
+// ada$ ./cryptopals -c 35 client 12001
+// Made secure connection with 127.0.0.1:12001
+// > They know not well the subtle ways
+// -> They know not well the subtle ways
+// > I keep, and pass, and turn again.
+// -> I keep, and pass, and turn again.
+// > ^C