OAuth-Only MCP Login

Configure local MCP clients with OAuth device flow only. No static API keys are required. After user approval, the MCP receives a short-lived access token for API calls.

What the MCP stores locally

Ephemeral DPoP private key material for request proof signing.
Short-lived broker access token in memory only.
No long-lived static API key secrets.
Credential plaintext remains inaccessible to Aegis services without user-held key material.

Security defaults

Device flow token TTL defaults to 10 minutes and caps at 15 minutes.
Request only the operations your MCP integration needs.
Approval is bound to an authenticated user principal.
Every begin/approve/exchange action writes broker audit events.

Flow

MCP generates local DPoP keypair and `pop_key_id`.
Call `BeginMcpOauthDeviceAuthorization` to get `device_code` and `verification_uri`.
User completes login/consent in browser and approves the device code.
MCP polls `ExchangeMcpOauthDeviceAuthorization` until status `success`.
MCP uses returned broker token for lease RPCs with sender-constrained request proofs.

sequenceDiagram
  participant MCP as Local MCP Server
  participant Aegis as Aegis Identity API
  participant User as End User
  participant Browser as Authenticated Browser

  MCP->>Aegis: BeginMcpOauthDeviceAuthorization
  Aegis-->>MCP: device_code + user_code + verification_uri
  MCP-->>User: "Open URL and enter code"
  User->>Browser: Login + consent
  Browser->>Aegis: ApproveMcpOauthDeviceAuthorization
  loop poll every interval_seconds
    MCP->>Aegis: ExchangeMcpOauthDeviceAuthorization
    Aegis-->>MCP: authorization_pending or success
  end
  Aegis-->>MCP: broker_token (short-lived)

Begin Request

{
  "tenant_id": "business-default",
  "requested_ttl_seconds": 600,
  "pop_key_id": "mcp-key-2026-03",
  "client_display_name": "VS Code MCP"
}

Exchange Poll Request

{
  "device_code": "mdc_7f4f2b7c-7ac3-4e7f-a1c8-8f0ed6c0ddef"
}

Production Guardrails

Treat `access_denied` and `expired_token` as terminal states in MCP polling logic.
Rotate DPoP key material and enforce replay detection for lease requests.
Keep broker access tokens in memory only and clear them on process shutdown.
Allow outbound MCP token calls only to approved Aegis API hosts.

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