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-rw-r--r--challenge/c36.go202
1 files changed, 202 insertions, 0 deletions
diff --git a/challenge/c36.go b/challenge/c36.go
new file mode 100644
index 0000000..dc4456b
--- /dev/null
+++ b/challenge/c36.go
@@ -0,0 +1,202 @@
+// Copyright © 2022 siddharth <s@ricketyspace.net>
+// SPDX-License-Identifier: ISC
+
+package challenge
+
+import (
+ "bufio"
+ "fmt"
+ "net"
+ "os"
+
+ "ricketyspace.net/cryptopals/lib"
+)
+
+// Usage:
+//
+func C36(args []string) {
+ if len(args) < 2 {
+ fmt.Println("Usage: cryptopals -c 36 [ client | server ] PORT")
+ return
+ }
+ entity := args[0]
+ port, err := lib.StrToNum(args[1])
+ if err != nil {
+ fmt.Println("port invalid")
+ return
+ }
+ if port < 12000 {
+ fmt.Println("port number must be >= 12000")
+ return
+ }
+
+ // Register user on the server.
+ serverRegisterUser := func(server *lib.SRPServer, info []string) error {
+ if len(info) != 5 {
+ return fmt.Errorf("regiser user: info valid")
+ }
+ n := info[0]
+ g := info[1]
+ k := info[2]
+ ident := info[3]
+ pass := info[4]
+ user, err := lib.NewSRPUser(n, g, k, ident, pass)
+ if err != nil {
+ return fmt.Errorf("register user: %v", err)
+ }
+ if err = server.RegisterUser(user); err != nil {
+ return fmt.Errorf("register user: %v", err)
+ }
+ return nil
+ }
+ // Handle connection from a client.
+ serverHandleConn := func(server *lib.SRPServer, conn net.Conn) {
+ defer conn.Close()
+ fmt.Printf("Got connection from %v\n", conn.RemoteAddr())
+
+ // Read packet from client.
+ packet, err := bufio.NewReader(conn).ReadString('\n')
+ if err != nil {
+ fmt.Printf("Unable to read from client %v\n",
+ conn.RemoteAddr())
+ return
+ }
+
+ // Remove newline character from packet.
+ packet = packet[:len(packet)-1]
+
+ parts := lib.StrSplitAt('+', packet)
+ if len(parts) < 2 {
+ fmt.Fprintf(conn, "invalid request\n")
+ return
+ }
+
+ switch {
+ case parts[0] == "register":
+ err = serverRegisterUser(server, parts[1:])
+ if err != nil {
+ fmt.Fprintf(conn, "%v\n", err)
+ return
+ } else {
+ fmt.Fprintf(conn, "OK\n")
+ }
+ return
+ default:
+ fmt.Fprintf(conn, "invalid action")
+ return
+ }
+
+ }
+ // Start SRP server.
+ serverSpawn := func() {
+ server := new(lib.SRPServer)
+
+ 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\n", err)
+ }
+ go serverHandleConn(server, conn)
+ }
+ }
+ // Register user with server.
+ clientRegisterUser := func(client *lib.SRPClient, ident string) error {
+ n := lib.StripSpaceChars(
+ `ffffffffffffffffc90fdaa22168c234c4c6628b80dc1cd129024
+ e088a67cc74020bbea63b139b22514a08798e3404ddef9519b3cd
+ 3a431b302b0a6df25f14374fe1356d6d51c245e485b576625e7ec
+ 6f44c42e9a637ed6b0bff5cb6f406b7edee386bfb5a899fa5ae9f
+ 24117c4b1fe649286651ece45b3dc2007cb8a163bf0598da48361
+ c55d39a69163fa8fd24cf5f83655d23dca3ad961c62f356208552
+ bb9ed529077096966d670c354e4abc9804f1746c08ca237327fff
+ fffffffffffff`)
+ g := "2"
+ k := "3"
+
+ // Prompt for password.
+ fmt.Printf("password> ")
+ pass, err := bufio.NewReader(os.Stdin).ReadString('\n')
+ if err != nil {
+ return fmt.Errorf("unable to read password: %v", err)
+ }
+
+ // Create session for user.
+ client.Session, err = lib.NewSRPClientSession(n, g, k, ident)
+ if err != nil {
+ return fmt.Errorf("unable to create session: %v", err)
+ }
+
+ // Make SRP registration packet.
+ packet := fmt.Sprintf("%s+%s+%s+%s+%s+%s", "register",
+ n, g, k, ident, pass)
+
+ // Try to connect to server.
+ conn, err := net.Dial("tcp", fmt.Sprintf(":%d", port))
+ if err != nil {
+ return fmt.Errorf("unable connect to server: %v", err)
+ }
+ defer conn.Close()
+
+ // Send packet to server.
+ _, err = fmt.Fprintf(conn, "%s", packet)
+ if err != nil {
+ return fmt.Errorf("unable communicate with server: %v", err)
+ }
+
+ // Wait and try to get registration ACK from server.
+ spacket, err := bufio.NewReader(conn).ReadString('\n')
+ if err != nil {
+ return fmt.Errorf("server did not respond: %v", err)
+ }
+ // Remove newline character.
+ spacket = spacket[:len(spacket)-1]
+ if spacket != "OK" {
+ return fmt.Errorf("server registration failed: %s", spacket)
+ }
+ return nil
+ }
+ // Start SRP client.
+ clientSpawn := func() {
+ client := new(lib.SRPClient)
+ // Enter repl.
+ 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]
+
+ msg_parts := lib.StrSplitAt(' ', msg)
+ switch {
+ case msg_parts[0] == "register" && len(msg_parts) == 2:
+ err := clientRegisterUser(client, msg_parts[1])
+ if err != nil {
+ fmt.Printf("Registration failed: %v\n", err)
+ } else {
+ fmt.Printf("Registered!\n")
+ }
+ }
+ }
+ }
+
+ // Take action based on entity.
+ switch {
+ case entity == "server":
+ serverSpawn()
+ case entity == "client":
+ clientSpawn()
+ default:
+ fmt.Println("uknown entity")
+ }
+}