php.lang.security.injection.tainted-url-host.tainted-url-host

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User data flows into the host portion of this manually-constructed URL. This could allow an attacker to send data to their own server, potentially exposing sensitive data such as cookies or authorization information sent with this request. They could also probe internal servers or other resources that the server runnig this code can access. (This is called server-side request forgery, or SSRF.) Do not allow arbitrary hosts. Instead, create an allowlist for approved hosts hardcode the correct host.

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Defintion

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rules:
  - id: tainted-url-host
    languages:
      - php
    severity: WARNING
    message: User data flows into the host portion of this manually-constructed URL.
      This could allow an attacker to send data to their own server, potentially
      exposing sensitive data such as cookies or authorization information sent
      with this request. They could also probe internal servers or other
      resources that the server runnig this code can access. (This is called
      server-side request forgery, or SSRF.) Do not allow arbitrary hosts.
      Instead, create an allowlist for approved hosts hardcode the correct host.
    metadata:
      cwe:
        - "CWE-918: Server-Side Request Forgery (SSRF)"
      owasp:
        - A10:2021 - Server-Side Request Forgery (SSRF)
      references:
        - https://cheatsheetseries.owasp.org/cheatsheets/Server_Side_Request_Forgery_Prevention_Cheat_Sheet.html
      category: security
      technology:
        - php
      license: Commons Clause License Condition v1.0[LGPL-2.1-only]
      cwe2022-top25: true
      cwe2021-top25: true
      subcategory:
        - vuln
      impact: MEDIUM
      likelihood: MEDIUM
      confidence: MEDIUM
      vulnerability_class:
        - Server-Side Request Forgery (SSRF)
    mode: taint
    pattern-sources:
      - patterns:
          - pattern-either:
              - pattern: $_GET
              - pattern: $_POST
              - pattern: $_COOKIE
              - pattern: $_REQUEST
    pattern-sinks:
      - pattern-either:
          - patterns:
              - pattern: |
                  sprintf($URLSTR, ...)
              - metavariable-pattern:
                  metavariable: $URLSTR
                  language: generic
                  pattern: $SCHEME://%s
          - patterns:
              - pattern: |
                  "...{$EXPR}..."
              - pattern-regex: |
                  .*://\{.*
          - patterns:
              - pattern: |
                  "...$EXPR..."
              - pattern-regex: |
                  .*://\$.*
          - patterns:
              - pattern: |
                  "...".$EXPR
              - pattern-regex: |
                  .*://["'].*

Examples

tainted-url-host.php

<?php

function make_request($url) {
    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_HEADER, 0);

    $data = curl_exec($ch);
    curl_close($ch);

    return $data;
}

// True Positives

function test1() {
    // ruleid: tainted-url-host
    $url = 'https://'.$_GET['url'].'/foobar';
    $info = make_request($url);
    return $info;
}

function test2() {
    $part = $_POST['url'];
    // ruleid: tainted-url-host
    $url = "https://$part/foobar";
    $info = make_request($url);
    return $info;
}

function test3() {
    // ruleid: tainted-url-host
    $url = "https://{$_REQUEST['url']}/foobar";
    $info = make_request($url);
    return $info;
}

function test4() {
    // ruleid: tainted-url-host
    $url = sprintf('https://%s/%s/', $_COOKIE['foo'], $bar);
    $info = make_request($url);
    return $info;
}

// True Negatives

function test1() {
    // ok: tainted-url-host
    $url = 'https://www.google.com/'.$_GET['url'].'/foobar';
    $info = make_request($url);
    return $info;
}

function test2() {
    $part = $_POST['url'];
    // ok: tainted-url-host
    $url = "some random text /$part/ foobar";
    $info = make_request($url);
    return $info;
}

function test3() {
    // ok: tainted-url-host
    $url = "https://www.google.com/{$_REQUEST['url']}/foobar";
    $info = make_request($url);
    return $info;
}

function test4() {
    // ok: tainted-url-host
    $url = sprintf('some random format string %s %s', $_COOKIE['foo'], $bar);
    $info = make_request($url);
    return $info;
}