SimpleBouncer is an open source (Apache License, Version 2.0) Java network proxy. Do not require any external lib.

1. Machine-A (Client) init connection to Machine-B (Bouncer)
2. Machine-B init connection to Machine-C (Server)
3. Done: Machine-A is able to speak with Machine-C

• Machine-A (Client) may be in Internal network.
• Machine-B (Bouncer) may be in DMZ.
• Machine-C (Server) may be in External network.

1. Machine-A (MUX-OUT) init connection to Machine-B (MUX-IN)
2. Machine-D (Client) init connection to Machine-B
3. Machine-B request to Machine-A new SubChannel over MUX (Tunnel).
4. Machine-A open connection to Machine-C (Server).
5. Done: Machine-D is able to speak with Machine-C

• Machine-B (MUX-IN) should be in DMZ.
• Machine-A (MUX-OUT) and Machine-C (Server) may be in internal network.

# To redir stdout/stderr to (auto-daily-rotated) files you can use:
-Dlog.stdOutFile=/var/log/bouncer.out -Dlog.stdErrFile=/var/log/bouncer.err
# To log to stdout too:
-Dlog.stdToo=true 

Config file must be in class-path, general format is:

# <left-addr> <left-port> <right-addr> <right-port> [options]

• Options for outgoing connections
  • Loadbalancing/Failover (only one option can be used)
    • LB=ORDER: active failover-only in DNS order
    • LB=RR: active LoadBalancing in DNS order (round-robin)
    • LB=RAND: activate LoadBalancing in DNS random order
• Options for Simple Forward (rinetd)
  • TUN=SSL: activate SSL tunneling (origin is plain, destination is SSL)
• Options for Reverse Tunneling (MUX)
  • Select operation of MUX (only one option can be used)
    • MUX=IN: activate input-terminator multiplexor
    • MUX=OUT: activate output-initiator multiplexor
  • Options for encryption (optional -AES or SSL or NONE-):
    • MUX=AES: activate AES encryption in multiplexor (see AES=key)
      • AES=key: specify the key for AES (no white spaces, no comma sign, no equals sign)
    • MUX=SSL: activate SSL encryption in multiplexor (see SSL=xxx)
      • SSL=server.crt:server.key:client.crt: specify files for SSL config (server/mux-in)
      • SSL=client.crt:client.key:server.crt: specify files for SSL config (client/mux-out)

• If use MUX=SSL
  • Keys/Certificates are pairs, must be configured in the two ends (MUX-IN & MUX-OUT)
  • files.crt are X.509 public certificates
  • files.key are RSA Keys in PKCS#8 format (no encrypted)
  • files.crt/.key must be in class-path like "bouncer.conf"
  • be careful about permissions of "files.key" (unix permission 600 may be good)
• If use MUX=AES, you need to protect the "bouncer.conf" from indiscrete eyes (unix permission 600 may be good)

# <listen-addr> <listen-port> <remote-addr> <remote-port> [options]
0.0.0.0 1234 127.1.2.3 9876
127.0.0.1 5678 encrypted.google.com 443 LB=RR,TUN=SSL

# <remote-addr> <remote-port> <remote-tun-addr> <remote-tun-port> MUX-OUT
192.168.1.1 80 192.168.2.1 5555 MUX=OUT

# <listen-tun-addr> <listen-tun-port> <listen-addr> <listen-port> MUX-IN
192.168.2.1 5555 127.0.0.1 8080 MUX=IN

# <remote-addr> <remote-port> <remote-tun-addr> <remote-tun-port> MUX-OUT
192.168.1.1 80 192.168.2.1 5555 MUX=OUT,MUX=SSL,SSL=peerA.crt:peerA.key:peerB.crt

# <listen-tun-addr> <listen-tun-port> <listen-addr> <listen-port> MUX-IN
192.168.2.1 5555 127.0.0.1 8080 MUX=IN,MUX=SSL,SSL=peerB.crt:peerB.key:peerA.crt

mkdir classes
javac -d classes/ src/net/bouncer/SimpleBouncer.java
# KeyGenerator compilation can output warnings about Sun proprietary API (you can safely ignore it)
javac -d classes/ src/net/bouncer/KeyGenerator.java
jar cvf bouncer-x.y.z.jar -C classes/ .

java -cp .:bouncer-x.y.z.jar net.bouncer.KeyGenerator <bits> <days> <CommonName> <filename-without-extension>

java -cp .:bouncer-x.y.z.jar net.bouncer.SimpleBouncer

• NIO?
• JMX?
• Multiple remote-addr (not only multi DNS A-record)?
• Use Log4J
• Limit number of connections
• Limit absolute timeout/TTL of a connection
• Configurable retry-sleeps
• Allow different tunnels over same MUX(IN/OUT)

• Reload config (v1.1)
• Thread pool/control (v1.2)
• Reverse tunnels (like ssh -R) over MUX (multiplexed channels) (v1.2)
• FlowControl in MUX (v1.3)
• Custom timeout by binding (v1.4)
• Encryption MUX/Tunnel (AES+PreSharedSecret) (v1.4)
• Manage better the read timeouts (full-duplex) (v1.4)
• Encryption MUX/Tunnel (SSL/TLS) (v1.5)
• Key Generator for MUX-SSL/TLS (v1.5)
• Audit threads / connections (v1.5)
• Improved FlowControl in MUX (v1.5)
• Allow redir stdout/stderr to File, with auto daily-rotate (v1.5.1)

Current harcoded values:

• Buffer length for I/O: 4096bytes
• IO-Buffers: 8
• TCP SO_SNDBUF/SO_RCVBUF: BufferLength * IO-Buffers
• Connection timeout: 30seconds
• Read timeout: 5minutes
• MUX Read timeout / keep-alive: 30seconds
• MUX-IN Error retry sleep: 0.5/1seconds
• MUX-OUT Error retry sleep: 5seconds
• Reload config check time interval: 10seconds
• Reset Initialization Vector (IV) for MUX-AES: { Iterations: 64K, Data: 16MB }
• For MUX-AES encryption/transformation are AES/CBC/PKCS5Padding
• For MUX-SSL supported Asymmetric Keys are RSA
• For MUX-SSL enabled Protocols are:
  • TLSv1
  • SSLv3
• For MUX-SSL enabled CipherSuites are:
  • TLS_RSA_WITH_AES_256_CBC_SHA
    • For AES-256 you need JCE Unlimited Strength
  • TLS_RSA_WITH_AES_128_CBC_SHA
  • SSL_RSA_WITH_3DES_EDE_CBC_SHA
  • SSL_RSA_WITH_RC4_128_SHA
• Shutdown/Reload timeout: 30seconds

Inspired in rinetd, stunnel and openssh, this bouncer is Java-minimalistic version.