facetec-api

README

facetec-api

A Go microservice that bridges the FaceTec biometric SDK (running on a mobile device) with a verifiable-credential (VC) issuer. It acts as a security gateway: biometric liveness and photo-ID scan results are validated against configurable SPOCP policy, and — only on acceptance — a verifiable credential is issued through a gRPC back-end.

Mobile SDK  →  facetec-api  →  FaceTec Server  (liveness + ID scan)
                   │
                   ├── SPOCP policy engine  (accept / reject)
                   │
                   └──  vc issuer (gRPC)  →  SD-JWT / mDoc / VC 2.0

Biometric data (FaceMaps, raw scan images) never leaves process memory and is never written to disk. See PRIVACY.md for a full data-flow and GDPR analysis.

Quickstart

# Build
make build

# Run with an example config (no TLS, no real FaceTec server)
cp configs/config.yaml configs/config.local.yaml
# Edit configs/config.local.yaml with your FaceTec Server URL and issuer address.
make run CONFIG=configs/config.local.yaml

Requirements

Tool	Version
Go	≥ 1.25
Make	any
Docker (optional)	≥ 25

Configuration

Configuration is loaded from a YAML file (default: configs/config.yaml) and can be overridden by environment variables. The full annotated reference is configs/config.yaml.

Core settings

YAML key	Env variable	Default	Description
server.host	SERVER_HOST	0.0.0.0	Listen address
server.port	SERVER_PORT	8080	Listen port
server.public_base_url	SERVER_PUBLIC_BASE_URL	(empty)	Externally reachable base URL; used for credentialOfferURI
server.max_concurrent_biometric	SERVER_MAX_CONCURRENT_BIOMETRIC	10	Max parallel biometric requests; excess get 503. Limits peak memory from large payloads. 0 = unlimited
server.tls.enabled	SERVER_TLS_ENABLED	false	Enable TLS on the HTTP listener
server.tls.cert_file	SERVER_TLS_CERT_FILE	(empty)	TLS certificate file
server.tls.key_file	SERVER_TLS_KEY_FILE	(empty)	TLS private key file
facetec.server_url	FACETEC_SERVER_URL	(required)	FaceTec Server base URL
facetec.device_key	FACETEC_DEVICE_KEY	(optional)	FaceTec device key; sent as X-Device-Key. Only required by the FaceTec Testing API — omit when using your own FaceTec Server (v10+)
facetec.device_key_path	FACETEC_DEVICE_KEY_PATH	(optional)	File containing the FaceTec device key (takes precedence over device_key)
facetec.timeout	FACETEC_TIMEOUT	30s	HTTP timeout for FaceTec Server requests
facetec.tls.skip_verify	FACETEC_TLS_SKIP_VERIFY	false	Disable cert verification — never use in production
facetec.tls.ca_file	FACETEC_TLS_CA_FILE	(optional)	CA certificate for outbound FaceTec TLS
facetec.tls.cert_file	FACETEC_TLS_CERT_FILE	(optional)	Client certificate for FaceTec mTLS
facetec.tls.key_file	FACETEC_TLS_KEY_FILE	(optional)	Client private key for FaceTec mTLS
issuer.addr	ISSUER_ADDR	(required)	gRPC address of the vc issuer (e.g. issuer:8090)
issuer.tls	ISSUER_TLS	false	Enable TLS on the gRPC issuer connection
issuer.ca_file	ISSUER_CA_FILE	(optional)	CA certificate for the issuer gRPC connection
issuer.cert_file	ISSUER_CERT_FILE	(optional)	Client certificate for issuer mTLS
issuer.key_file	ISSUER_KEY_FILE	(optional)	Client private key for issuer mTLS
issuer.scope	ISSUER_SCOPE	(required)	Default credential scope URI
issuer.format	ISSUER_FORMAT	sdjwt	Default credential format: sdjwt, mdoc, vc20
policy.rules_dir	POLICY_RULES_DIR	(empty)	Directory of .spoc rule files
session.liveness_ttl	SESSION_LIVENESS_TTL	2m	How long a FaceMap is held in memory
session.offer_ttl	SESSION_OFFER_TTL	5m	How long a credential offer is held in memory
logging.level	LOG_LEVEL	info	Log level: debug, info, warn, error
logging.production	LOG_PRODUCTION	false	Enable JSON structured logging (recommended in prod)

Numeric acceptance thresholds are encoded in the SPOCP rule files themselves rather than as separate config keys. This keeps deployment policy in one place and allows per-tenant rule sets to express score requirements such as liveness and face-match minima.

Authentication

Three modes are selected automatically based on which keys are present:

Mode	Config keys	Behaviour
JWT (recommended)	jwt.secret	Validates HMAC-signed JWTs. The tenant_id claim selects the per-tenant policy; tokens without it use the default tenant.
Legacy Bearer	security.app_key (no JWT secret)	Constant-time comparison of a raw token. Single-tenant only.
Dev / unauthenticated	neither set	All requests are accepted. Never use in production.

JWT settings:

YAML key	Env variable	Default	Description
jwt.secret	JWT_SECRET	(empty)	HMAC shared secret for HS256/384/512
jwt.secret_path	JWT_SECRET_PATH	(optional)	File containing the JWT secret
jwt.issuer	JWT_ISSUER	(empty)	Expected iss claim; leave empty to skip validation
jwt.require_auth	JWT_REQUIRE_AUTH	false	Reject requests without a valid JWT
security.app_key	SECURITY_APP_KEY	(optional)	Legacy Bearer token (set directly or via app_key_path)
security.app_key_path	SECURITY_APP_KEY_PATH	(optional)	File containing a legacy Bearer token
security.rate_limit.enabled	SECURITY_RATE_LIMIT_ENABLED	true	Enable per-IP rate limiting on biometric endpoints
security.rate_limit.requests_per_minute	SECURITY_RATE_LIMIT_RPM	10	Per-IP rate limit on biometric endpoints

Multi-tenant operation

When no tenants: block is present, a single default tenant is synthesised from the global policy and issuer settings — existing deployments need no change.

When the tenants: block is present, each tenant is selected by the tenant_id JWT claim. A missing or unconfigured tenant_id falls back to the default tenant (i.e., global settings), so onboarding new tenants incrementally is safe.

Per-tenant overrides:

tenants:
  - id: acme                          # must match JWT tenant_id claim
    issuer:
      scope: "https://credentials.acme.example.org/photo-id"
      format: sdjwt
    policy:
      rules_dir: "/etc/facetec-api/rules/acme"

  - id: gov
    issuer:
      scope: "https://credentials.gov.example.org/id-document"
      format: mdoc
    policy:
      rules_dir: "/etc/facetec-api/rules/gov"

API

All /v1/* endpoints require a valid Authorization: Bearer <token> header when authentication is configured. /livez and /readyz are always unauthenticated.

Probes (unauthenticated)

Method	Path	Response
GET	/livez	200 {"status":"ok"} — process is alive
GET	/readyz	200 {"status":"ok"} when policy rules are loaded; 503 otherwise

v1 API (authenticated)

Method	Path	Description
GET	/v1/health	Returns 200 {"status":"ok"} — useful as a credential smoke-test
POST	/process-request	FaceTec-compatible requestBlob/responseBlob endpoint; augments successful matches with offer metadata
POST	/v1/process-request	Versioned alias of /process-request
POST	/v1/session-token	Obtain a short-lived FaceTec session token
POST	/v1/liveness	Submit a liveness FaceScan; returns livenessSessionId
POST	/v1/id-scan	Submit a photo ID scan; returns transactionId + credentialOfferURI
GET	/v1/offer/:txid	Redeem a one-time credential offer (wallet pull)

Biometric flow

Two mobile-facing contracts are supported:

1. FaceTec-native processor flow via /process-request or /v1/process-request
2. Legacy split flow via /v1/session-token, /v1/liveness, and /v1/id-scan

The FaceTec-native flow is the recommended integration for mobile SDKs that already use the sample SessionRequestProcessor pattern.

FaceTec-native flow

1. POST /process-request
  → { "requestBlob": "...", "externalDatabaseRefID": "..." }
  ← { "responseBlob": "...", "result": { ... }, "transactionId": "...",
     "credentialOfferURI": "openid-credential-offer://?..." }

2. GET /v1/offer/:transactionId
  ← { "credentials": ["<signed-token>"], "scope": "..." }

/process-request preserves FaceTec's upstream response JSON. When the upstream payload represents a successful photo-ID match and local policy accepts it, facetec-api augments that response with transactionId and credentialOfferURI. If policy or issuance fails, the response still contains the upstream responseBlob and instead adds credentialIssueError.

Legacy split flow

1. POST /v1/session-token
   ← { "sessionToken": "…" }

2. POST /v1/liveness
   → { "sessionToken": "…", "faceScan": "<base64>", "auditTrail": […] }
   ← { "livenessSessionId": "…" }

3. POST /v1/id-scan
   → { "sessionToken": "…", "livenessSessionId": "…", "idScan": "<base64>",
       "idScanFrontImagesCompressedBase64": […], … }
   ← { "transactionId": "…", "credentialOfferURI": "openid-credential-offer://…" }

4. GET /v1/offer/:transactionId
   ← { "credentials": ["<signed-token>"], "scope": "…" }

Steps 2 and 3 are independently rate-limited per source IP.

For FaceTec sample-app style integrations, use /process-request and send the SDK-generated requestBlob unchanged. The service returns FaceTec's response JSON unchanged, and on successful photo-ID matches also attaches transactionId and credentialOfferURI so the wallet can redeem the issued credential.

SPOCP Policy Rules

Scan acceptance is a two-stage process:

1. Score thresholds — encoded directly in SPOCP range predicates such as (liveness-score (* range numeric ge 080)) and (face-match-level (* range numeric ge 06)).
2. Categorical rules (.spoc files in policy.rules_dir) — S-expressions that encode which combinations of document type and verification flags are acceptable.

Rules are loaded at startup (and re-loaded on SIGHUP). If the rules directory is empty or policy.rules_dir is unset, the service starts but rejects all scans and reports not-ready.

; rules/default.spoc
; Accept passports with MRZ verification.
(facetec-scan (doc-type passport) (mrz-verified true))

; Accept e-passports with NFC chip verification.
(facetec-scan (doc-type passport) (mrz-verified true) (nfc-verified true))

; Accept driving licences with barcode verification.
(facetec-scan (doc-type dl) (mrz-verified false) (nfc-verified false) (barcode-verified true))

; Accept national ID cards (numeric thresholds from config still apply).
(facetec-scan (doc-type id_card))

Query fields available in every SPOCP query:

Field	Values
doc-type	passport, dl, id_card, unknown
mrz-verified	true, false
nfc-verified	true, false
barcode-verified	true, false

Security

• Biometric data never touches disk. FaceMap templates are held exclusively in process memory for the duration of the liveness→id-scan window (default 2 min); backing bytes are zeroed with clear() immediately after use and again on graceful shutdown.
• MRZ lines stripped before forwarding. Raw MRZ lines (encoding the full identity in machine-readable form) are removed before any data is sent to the VC issuer.
• No request/response body logging. Gin runs in gin.New() mode; the panic-recovery handler is bound to nil to suppress recovery body dumps. RequestLogger records only method, path, status, latency, client IP, and user agent.
• JWT authentication with HMAC HS256/384/512; signing method is explicitly validated to prevent algorithm-confusion attacks. Legacy Bearer fallback uses constant-time comparison.
• Rate limiting. Biometric endpoints are rate-limited per source IP (default 10 rpm); stale IP buckets are evicted every 5 minutes to prevent unbounded memory growth.
• Concurrency cap. Biometric requests amplify payload size ~3-4× in memory (decoded blob, re-encoded forward buffer, upstream response, JSON output). max_concurrent_biometric (default 10) limits the number of in-flight biometric requests; excess callers receive 503 immediately instead of queuing. Combined with GOMEMLIMIT, this prevents OOM under sustained load.
• Upstream response cap. All FaceTec Server responses are capped at 15 MB via io.LimitReader to prevent memory exhaustion from unexpectedly large payloads.
• Eager payload release. Request payloads (requestBlob, faceScan, idScan) are zeroed immediately after forwarding to the FaceTec Server so the GC can reclaim them while the upstream response is still in flight.
• Security response headers. X-Content-Type-Options: nosniff, X-Frame-Options: DENY, Cache-Control: no-store on every response.
• HTTP timeouts. ReadHeaderTimeout: 10s, WriteTimeout: 90s, IdleTimeout: 120s.
• Production safety guard. With logging.production: true, startup fails unless at least one of jwt.secret or security.app_key is set.
• Atomic SIGHUP reload. The tenant registry is swapped atomically on SIGHUP; in-flight requests are unaffected.

See PRIVACY.md for a full data-flow description and GDPR analysis.

Development

make tools          # install golangci-lint, protoc plugins
make dev            # build and run with hot config reload
make test           # run all tests
make test-coverage  # run tests with coverage profile + HTML report
make lint           # run golangci-lint
make fmt            # gofmt
make vet            # go vet

Regenerating gRPC client code

The gRPC stubs under internal/gen/issuer/apiv1_issuer/ are copied from the vc workspace sibling. Regenerate them after updating the vc proto source:

./scripts/generate-proto.sh

If protoc is available and you want to regenerate from the proto source directly:

REGEN=1 ./scripts/generate-proto.sh

Docker

make docker                        # build image
make docker-push                   # push to registry
docker compose up -d               # run with compose.yaml

The Docker image is built on gcr.io/distroless/static-debian12 and runs as UID 65532 (non-root). Mount configuration and secrets as volumes or Docker secrets.

License

Apache-2.0 — see LICENSE.