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sip utils callee


Wait for calls and handle them

What it does

Listen for a call and handle incoming calls. If the register flag is specified, it will register against that target otherwise it will listen on the specified target address. In that case, the address would need to be assigned to the local machine.

Tool functionality

This tool receives calls (i.e. incoming INVITE messages) and handles them according to the behaviour specified by the callee-mode flag. By default, the tool accepts the call and plays an internal audio file music.raw, if the file does not exist in the current directory and hangup if the tool is terminated. It handles the normal SIP traffic, including SIP Re-INVITE and other in-dialog traffic.

This tool is useful when simulating a system that automatically handles calls (e.g. auto-answer or auto-answer and then hangup after 1 second), perhaps as part of a security test that requires that functionality.

By default, the tool will attempt to listen on the target address that is specified unless the register flag is used. This means that the target address needs to be associated with the local machine. When the register flag is used, the tool will register against the specified target (a SIP registrar) and listen on a random port which is advertised in the SIP Contact header per the SIP standard.

Video demonstration

sipvicious sip utils callee

Command format

sipvicious sip utils callee [target1] [flags]


      --auth-config strings   Specify SIP authentication configuration. See documentation for details e.g. algorithm:sha-256
      --callee-mode string    Specify how to behave during the call attempt; format: action or action:duration or action:duration:destination; (ignore|hangup-call|never-hangup|refer) (default "never-hangup")
      --codec strings         Specify the codec that should be used for the RTP stream (ulaw|alaw|opus) (default [ulaw,alaw,opus])
  -u, --credentials string    Set the username and password in the following format: username:password[:realm] (e.g. 1000:test123:snowflake). Realm is optional
  -D, --domain string         Override domain name for the SIP address
  -f, --from string           Specify the from header address; if not specified, the from address is constructed from the credentials, otherwise a random numeric extension is used
      --max-calls int32       Set the maximum number of calls to handle before quitting
      --register              Register with the specified target
      --rtp-payload string    Specify the RTP payload for the audio (e.g. music.wav or 2600hz.raw) (default "music.wav")

Flags inherited from parent commands

      --ca-cert string       TLS CA Certificate
      --client-cert string   TLS client certificate
      --client-key string    TLS client private key
  -C, --config string        configuration file to use (may be JSON, TOML or YAML)
      --debug                set log level to debug
  -T, --duration duration    
      --logfile string       specify a log filename
      --results string       specify the filename for the result output, defaults to standard output. See documentation for information on file extension meanings
      --srtp string          Specify if either none, dtls or sdes to enforce SRTP for calls; format: method or method:parameters; see full documentation for details (default "none")
      --templates string     Directory to search for template overrides (default ".")
      --tls-key-log string   TLS key log


sipvicious sip utils callee
sipvicious sip utils callee tcp://target:5060 --register --credentials username:password
sipvicious sip utils callee tcp://target:5060 --callee-mode hangup-call:10s
sipvicious sip utils callee udp:// --callee-mode hangup-call -T 5s

Advanced examples

# register with target with given credentials and a duration
sipvicious sip utils callee tcp:// --register -u 1000:1500 --duration 20s

# listen on on the TCP port 5060, and hangup incoming calls after 10 seconds while only allowing the alaw codec
sipvicious sip utils callee tcp:// --callee-mode hangup-call:10s --codec alaw --max-calls 10

# listen on on the UDP port 5060 and use a specific rtp payload for incoming calls along with a custom from address
sipvicious sip utils callee udp:// --rtp-payload 2600hz.raw -f sip:0000@danksip.tld 

Exit codes

Code Description
40 Security issues cannot be detected with this tool since it is a SIP utility and not an attack tool
30 A network connectivity issue is raised when the connection fails or when no response is received

Full flag documentation

Flag: --auth-config

Specify SIP authentication configuration. This flag accepts the following values:

  • algorithm:value where value may be md5, md5-sess, sha-256, sha-256-sess, sha-512-256 or sha-512-256-sess. This value will force the tool to calculate the authorization response based on the first WWW-Authenticate or Proxy-Authenticate header field that matches this algorithm. If no match is found then the first WWW-Authenticate or Proxy-Authenticate header is selected.

Flag: --ca-cert

The CA cert can be passed when making use of client certificate authentication. The file should be formatted as PEM.

Flag: --callee-mode

The flag callee-mode allows one to specify how to behave during a call. The value of this flag could be one of the following actions:

  • ignore which does not respond to SIP INVITE requests
  • hangup-call which hangs up (by sending a BYE) after picking up the incoming call (i.e. when a 200 OK is sent)
  • never-hangup which handles the call flow normally without hanging up
  • refer which transfers the call to another SIP URI

Additionally, the action value may be preceded by a colon and a duration value. This duration should be specified when the action should be taken after a specific time (e.g. 2s or 300ms). For example, hangup-ringing:300ms. To hangup a call after 30 seconds, the value of callee-mode should be hangup-call:30s. When refer is specified, the parameters take a SIP address after the duration value. This is the address to refer the call to. For example:

Flag: --client-cert

The client certificate must be passed when making use of client certificate authentication. The file should be formatted as PEM.

Flag: --client-key

The client key must be passed when making use of client certificate authentication. The file should be formatted as PEM.

Flag: --codec

Specify the codec to be supported for the SDP and also in the RTP stream. Currently supported are ulaw, alaw and opus. You may pass multiple codecs by delimiting using a comma, as follows: ulaw,alaw,opus.

When rates and channels need to be passed, they can be provided after the codec name, separated by a slash. For example: opus/48000/2.

Flag: -C, --config

Specify a configuration file which may be a JSON, TOML and YAML config format. To get the default settings and figure out which settings are available, one may run the sipvicious utils dump config command. This is typically used to create a template configuration that can then be edited as need be.

These settings may be overwritten when the corresponding flag is explicitly set, if one is present.

Flag: -u, --credentials

Specify valid credentials so that the registration can be done authenticated. The following format is used username:password (e.g. 1000:test123).

Additionally, a realm may be specified as a third parameter (e.g. 1000:test123:snowflake).

Flag: --debug

Tells the logger to print out debug messages.

Flag: -D, --domain

A domain name can be specified so that the SIP URI contains that particular domain rather than the one specified as the target. This is useful for targets that expect a particular domain name.

Flag: -T, --duration

Specify how long to keep the tool going. Example: 1m.

Flag: -f, --from

This flag allows users to set the From address, overriding the default behaviour of setting a random extension or the username in the credentials when one is provided. The value can be either just the SIP extension/username (e.g. 1234) or a SIP URI (e.g.

Flag: --logfile

When the logfile flag is specified, a log file is created in the location specified and logs are generated in this file instead of being sent to standard output. If the filename ends with a .json file extension, then the output format is in JSON, otherwise it defaults to text format.

Flag: --max-calls

Set the maximum number of calls to handle (according to the callee-mode setting) before the tool exits. This is useful when using the tool as part of automation.

Flag: --register

Register may use credentials to be passed so that a REGISTER message is sent to authenticate with a registrar server before starting the call. The registration is maintained as per SIP standards, so that authentication does not time out.

Flag: --results

When the results flag is specified, upon completing the test, it outputs the results to the specified filename. The format for this output file is text unless the filename ends with a .json file extension. In that case, the result output is that of JSON.

The schema for the JSON output for this submodule can be found here.

Flag: --rtp-payload

The rtp-payload parameter allows the setting of a file that is used for the RTP stream. The following file types are supported:

  • .raw, for raw audio to be passed to the RTP stream without any transcoding
  • .wav, for wave files to be transcoded for the RTP stream
  • .rtp, for payload files containing the whole RTP packet to be sent as is

The audio is looped unless a noloop parameter is passed after a comma, e.g. audio.wav,noloop.

If a blank filename, i.e. "", is passed, then no RTP is sent during the call and no SDP is set.

If the value of rtp-payload starts with dtmf:, then the RTP stream will consist of a sequence of DTMF tones instead of audio stream.

The supported alphabet in the DTMF string is 0-9, A-D, *, #, F (flash), and , (comma) for a pause equivalent to one digit in length. The other side may not support all of these.

Example: When Asterisk is configured to allow call forwarding with feature code #1, the following value to rtp-payload will forward the call to 123456: dtmf:#1,,,123456.

Flag: --srtp

The srtp flag when specified, allows users to set the SRTP mode. By default, outgoing calls do not make use of SRTP, while incoming calls automatically handle SRTP depending on the SDP body of the incoming INVITE message. When the srtp flag is set to none, incoming calls do not make use of SRTP, regardless of the SDP body in an incoming INVITE. The srtp mode can also be either dtls or sdes. In both dtls and sdes modes, the parameters are not required and will be generated randomly as need be.

Options for both dtls and sdes mode may be passed after a colon. For example:

  • --srtp dtls:cert.crt:cert.key[:ca.crt] where the first argument after the mode (dtls) is the public certificate cert.crt, then the private key cert.key and finally, the optional certificate authority file ca.crt
  • --srtp sdes:d0RmdmcmVCspeEc3QGZiNWpVLFJhQX1cfHAwJSoj where the argument is the base64 encoded cryptographic master key appended with the master salt.

Note that in the case of sdes key, the master key needs to be a valid length, which is 30 octets, for the default crypto-suite AES_CM_128_HMAC_SHA1_80.

Flag: --templates

Allows one to set the template directory which is used to load (or save) the SIP templates.

To get the default SIP templates, make use of the sipvicious sip utils dump templates command.

Flag: --tls-key-log

The TLS key log creates a file with the TLS key that can then be used to decrypt the TLS stream in tools that support it, such as Wireshark.

Future enhancements

  • DTLS SRTP support, especially useful in WebRTC environments
  • STUN and TURN support, also especially useful in WebRTC environments

JSON schema

The following is the JSON schema for the JSON output of this tool:

  "type": "object",
  "properties": {
    "status": {
      "type": "object",
      "properties": {
        "returncode": { "type": "integer" },
        "description": { "type": "string" }
    "targets": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "target": { "type": "string" },
          "status": {
            "type": "object",
            "properties": {
              "returncode": { "type": "integer" },
              "description": { "type": "string" }
          "results": {
            "type": "object",
            "properties": {
          "issues": {
            "type": "object",
            "properties": {