Privilege Escalation from Zygote to Init

vendor:

Android

by:

Jann Horn

6.8

CVSS

MEDIUM

Privilege Escalation

269

CWE

Product Name: Android

Affected Version From: Android 8.0

Affected Version To: Android 8.1

Patch Exists: YES

Related CWE: CVE-2018-9445

CPE: o:google:android

Metasploit: N/A

Other Scripts: N/A

Platforms Tested: Android

2018

Privilege Escalation from Zygote to Init

The privilege escalation from zygote to init is possible because system/sepolicy/private/zygote.te contains the following rule: allow zygote self:capability sys_admin;. This rule allows processes in the zygote domain to use the CAP_SYS_ADMIN capability, if they have such a capability. The exploit for this issue is in zygote_exec_target.c, starting at 'if (unshare(CLONE_NEWNS))'. The attack is basically: 1. set up a new mount namespace with a root that is fully attacker-controlled 2. execute crash_dump64, causing an automatic transition to the crash_dump domain 3. the kernel tries to load the linker for crash_dump64 from the attacker-controlled filesystem, resulting in code execution in the context of the zygote.

Mitigation:

The mitigation for this vulnerability is to remove the rule from system/sepolicy/private/zygote.te that allows processes in the zygote domain to use the CAP_SYS_ADMIN capability.

Source

Exploit-DB raw data:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <meta name="robots" content="noindex, nofollow">
    <title>502 Hosting Server Connect Timeout | Sucuri Website Firewall</title>
    <!--
        Base origin-error page (502/504). lualibs/error_pages.lua fills the double-brace placeholders
        per $whitelabel at request time; init.lua substitutes the server id at load. Keep it
        self-contained: no external stylesheet, script, font, CSS import or remote image
        (tests/rules/71-error-pages-self-contained.sh).
    -->
    <style>
        :root {
            --accent: #3b7a26;
        }

        * {
            box-sizing: border-box;
        }

        html {
            -webkit-text-size-adjust: 100%;
        }

        body {
            margin: 0;
            background: #f4f5f7;
            color: #1d2330;
            font: 16px/1.55 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
        }

        a {
            color: var(--accent);
        }

        p {
            margin: 0 0 10px;
        }

        .wrap {
            max-width: 760px;
            margin: 0 auto;
            padding: 32px 16px 48px;
        }

        .product {
            margin: 0 0 20px;
            font-size: 14px;
            font-weight: 600;
            letter-spacing: .02em;
            color: var(--accent);
        }

        .card {
            padding: 28px 24px;
            background: #fff;
            border: 1px solid #e1e4ea;
            border-radius: 10px;
        }

        h1 {
            margin: 0 0 6px;
            font-size: 26px;
            line-height: 1.25;
        }

        h2 {
            margin: 24px 0 8px;
            font-size: 17px;
        }

        .lead {
            margin: 0 0 4px;
            font-size: 18px;
            color: #414a5a;
        }

        .retry {
            margin: 0;
            color: #5b6475;
        }

        /* You -> Firewall -> Hosting diagram */
        .flow {
            display: flex;
            align-items: flex-start;
            justify-content: space-between;
            gap: 8px;
            margin: 28px 0;
            padding: 0;
            list-style: none;
        }

        .node {
            flex: 0 0 auto;
            width: 132px;
            text-align: center;
            font-size: 14px;
            font-weight: 600;
        }

        .icon {
            position: relative;
            display: inline-flex;
            align-items: center;
            justify-content: center;
            width: 64px;
            height: 64px;
            margin-bottom: 6px;
            border-radius: 50%;
        }

        .icon svg {
            width: 32px;
            height: 32px;
            fill: none;
            stroke: currentColor;
            stroke-width: 1.8;
            stroke-linecap: round;
            stroke-linejoin: round;
        }

        .ok-node .icon {
            background: #e7f4ea;
            color: #2f7d3c;
        }

        .fail-node,
        .fail-node .icon {
            color: #c0362c;
        }

        .fail-node .icon {
            background: #fdebea;
        }

        .badge {
            position: absolute;
            right: -2px;
            bottom: -2px;
            width: 22px;
            height: 22px;
            border-radius: 50%;
            color: #fff;
            font-size: 13px;
            line-height: 22px;
        }

        .badge.ok {
            background: #2f7d3c;
        }

        .badge.fail {
            background: #c0362c;
        }

        /* Connector, vertically centred on the 64px icons */
        .link {
            flex: 1 1 auto;
            height: 2px;
            margin-top: 31px;
            background: #c9ced8;
        }

        .link.broken {
            background: repeating-linear-gradient(90deg, #c0362c 0 6px, transparent 6px 11px);
        }

        dl {
            display: grid;
            grid-template-columns: max-content 1fr;
            gap: 4px 16px;
            margin: 0;
            padding: 14px 16px;
            background: #f7f8fa;
            border-radius: 8px;
            font-size: 15px;
        }

        dt {
            color: #5b6475;
        }

        dd {
            margin: 0;
            font-weight: 600;
            overflow-wrap: anywhere;
        }

        ul.causes {
            margin: 0;
            padding-left: 20px;
        }

        footer {
            margin-top: 20px;
            font-size: 13px;
            color: #6b7383;
            text-align: center;
        }

        @media (max-width: 520px) {
            .wrap {
                padding: 20px 16px 32px;
            }

            .card {
                padding: 20px 16px;
            }

            h1 {
                font-size: 22px;
            }

            .flow {
                gap: 4px;
            }

            .node {
                flex: 1 1 0;
                width: auto;
                min-width: 0;
                font-size: 12px;
                line-height: 1.3;
            }

            /* Connector, vertically centred on the 52px icons */
            .link {
                flex: 0 0 14px;
                margin-top: 25px;
            }

            .icon {
                width: 52px;
                height: 52px;
            }

            .icon svg {
                width: 26px;
                height: 26px;
            }
        }
    </style>
</head>
<body>
    <main class="wrap">
        <p class="product">Sucuri Website Firewall</p>

        <div class="card">
            <h1>Hosting Server Connect Timeout</h1>
            <p class="lead">HTTP 502 &mdash; Unable to Connect to the Origin Server</p>
            <p class="retry">Please try again in a few minutes.</p>

            <ol class="flow" aria-label="Connection path">
                <li class="node ok-node">
                    <span class="icon">
                        <svg viewBox="0 0 24 24" aria-hidden="true">
                            <circle cx="12" cy="8" r="4"/>
                            <path d="M4 21c0-4.4 3.6-8 8-8s8 3.6 8 8"/>
                        </svg>
                        <span class="badge ok" aria-hidden="true">&#10003;</span>
                    </span><br>
                    You
                </li>
                <li class="link" aria-hidden="true"></li>
                <li class="node ok-node">
                    <span class="icon">
                        <svg viewBox="0 0 24 24" aria-hidden="true">
                            <path d="M12 2 4 5v6c0 5 3.4 9.3 8 11 4.6-1.7 8-6 8-11V5z"/>
                        </svg>
                        <span class="badge ok" aria-hidden="true">&#10003;</span>
                    </span><br>
                    Sucuri Firewall
                </li>
                <li class="link broken" aria-hidden="true"></li>
                <li class="node fail-node">
                    <span class="icon">
                        <svg viewBox="0 0 24 24" aria-hidden="true">
                            <rect x="4" y="3" width="16" height="7" rx="1.5"/>
                            <rect x="4" y="14" width="16" height="7" rx="1.5"/>
                            <path d="M8 6.5h.01M8 17.5h.01"/>
                        </svg>
                        <span class="badge fail" aria-hidden="true">&#10005;</span>
                    </span><br>
                    Hosting Timeout
                </li>
            </ol>

            <h2>Error details</h2>
            <dl>
                <dt>Error code</dt>
                <dd>HTTP 502</dd>
                <dt>Error message</dt>
                <dd>Backend or gateway connection timeout.</dd>
                <dt>Server ID</dt>
                <dd>14012</dd>
            </dl>

            <h2>What's going on?</h2>
            <ul class="causes">
                <li>The origin server might be down</li>
                <li>The Sucuri network might be blocked by the origin&#39;s firewall</li>
            </ul>

            <h2>What can I do to fix it?</h2>
            <p>
                If you are just visiting the site, wait a bit and it should be back soon.
                We apologize for the inconvenience.
            </p>
            <p>
                If you own the website, check with your hosting company that your server is up and
                running and that they have <a href="https://docs.sucuri.net/website-firewall/troubleshooting/backend-timeout-message/">our firewall IPs allowlisted</a>.
            </p>
            <p>If the problem persists, open a ticket on our <a href="https://support.sucuri.net">support page</a> and we will help you troubleshoot.</p>
        </div>

        <footer>&copy; Sucuri Inc. All rights reserved. &middot; <a href="https://sucuri.net/privacy/">Privacy Policy</a></footer>
    </main>
</body>
</html>