/**
 * @name Binding a socket to all network interfaces
 * @description Binding a socket to all interfaces opens it up to traffic from any IPv4 address
 * and is therefore associated with security risks.
 * @kind path-problem
 * @tags security
 *       external/cwe/cwe-200
 * @problem.severity error
 * @security-severity 6.5
 * @sub-severity low
 * @precision high
 * @id py/bind-socket-all-network-interfaces
 */

import python
import semmle.python.dataflow.new.DataFlow
import semmle.python.dataflow.new.TaintTracking
private import semmle.python.frameworks.data.ModelsAsData
import BindToAllInterfacesFlow::PathGraph

/** Gets a hostname that can be used to bind to all interfaces. */
private string vulnerableHostname() {
  result in [
      // IPv4
      "0.0.0.0", "",
      // IPv6
      "::", "::0"
    ]
}

private module BindToAllInterfacesConfig implements DataFlow::ConfigSig {
  predicate isSource(DataFlow::Node source) {
    source.asExpr().(StringLiteral).getText() = vulnerableHostname()
  }

  predicate isSink(DataFlow::Node sink) {
    ModelOutput::sinkNode(sink, "bind-socket-all-interfaces")
  }
}

private module BindToAllInterfacesFlow = TaintTracking::Global<BindToAllInterfacesConfig>;

private import BindToAllInterfacesFlow

/**
 * Holds if `sink` is the address argument of a `bind()` call on a
 * network socket (AF_INET or AF_INET6), as opposed to a Unix domain
 * socket (AF_UNIX) which takes a plain string path.
 *
 * Network socket addresses are tuples like `(host, port)`, so we check
 * that the sink argument is a tuple, by looking for flow from a tuple expression.
 */
private predicate isNetworkBind(DataFlow::Node sink) {
  any(DataFlow::LocalSourceNode n | n.asExpr() instanceof Tuple).flowsTo(sink)
}

from PathNode source, PathNode sink
where flowPath(source, sink) and isNetworkBind(sink.getNode())
select sink.getNode(), source, sink,
  "Binding a socket to all interfaces (using $@) is a security risk.", source.getNode(),
  "'" + source.getNode().asExpr().(StringLiteral).getText() + "'"