feat: add secure agent enrollment

backend/app/agent_auth/service.py

@@ -0,0 +1,66 @@
+"""Per-Agent authentication with bounded legacy compatibility."""
+
+import hashlib
+import hmac
+
+from app.agent_auth.exceptions import (
+    AgentAuthenticationFailed,
+    AgentAuthenticationUnavailable,
+    AgentCredentialRevoked,
+    AgentIdentityUnauthorized,
+)
+from app.config import settings
+
+
+def hash_agent_secret(secret: str) -> str:
+    """Hash a high-entropy machine-generated Agent secret for persistence."""
+    return hashlib.sha256(secret.encode("utf-8")).hexdigest()
+
+
+class AgentAuthService:
+    def __init__(self, repository):
+        self.repository = repository
+
+    def authenticate(self, agent_id: str | None, provided_secret: str | None) -> str:
+        identity = (agent_id or "").strip()
+        secret = (provided_secret or "").strip()
+
+        if not identity:
+            raise AgentAuthenticationFailed("Missing Agent identity")
+        if not secret:
+            raise AgentAuthenticationFailed("Invalid or missing Agent secret")
+
+        credential = self.repository.get_credential(identity)
+
+        # Any Agent with a per-Agent credential is permanently on the new
+        # authentication path. The legacy shared secret must never authenticate
+        # that identity, even if the Agent later becomes revoked.
+        if credential and credential.get("agent_secret_hash"):
+            if credential.get("credential_revoked_at") is not None:
+                raise AgentCredentialRevoked("Agent credential has been revoked")
+
+            supplied_hash = hash_agent_secret(secret)
+            if not hmac.compare_digest(
+                supplied_hash,
+                str(credential["agent_secret_hash"]),
+            ):
+                raise AgentAuthenticationFailed("Invalid or missing Agent secret")
+
+            return identity
+
+        # Temporary compatibility for the single pre-enrollment Agent.
+        legacy_id = settings.minerops_agent_id.strip()
+        legacy_secret = settings.minerops_agent_shared_secret.strip()
+
+        if not legacy_id or not legacy_secret:
+            raise AgentAuthenticationUnavailable(
+                "Legacy Agent authentication is not configured"
+            )
+
+        if not hmac.compare_digest(identity, legacy_id):
+            raise AgentIdentityUnauthorized("Agent identity is not authorized")
+
+        if not hmac.compare_digest(secret, legacy_secret):
+            raise AgentAuthenticationFailed("Invalid or missing Agent secret")
+
+        return identity