feature: the web service is an OpenID Provider, which signs the directory's users in to other systems, the clients being service accounts with redirect URIs.

debian-package/src/usr/share/vpn-router/sql/oidc.sql

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+-- The state of the router's OpenID Provider (vpnrouter_oidc) in the database of web.database.
+-- Codes, tokens and sessions are kept as the SHA-256 of their values; expired rows are purged when new ones are saved.
+-- The whole file runs as one transaction, serialized by an advisory lock, so that two processes can load it at once.
+
+SELECT pg_advisory_xact_lock(hashtext('vpn-router oidc schema'));
+
+-- An authorization code, valid until it is exchanged for tokens or expires.
+CREATE TABLE IF NOT EXISTS oidc_codes (
+    hash text PRIMARY KEY,
+    client_id text NOT NULL,
+    name text NOT NULL,
+    redirect_uri text NOT NULL,
+    scopes text[] NOT NULL,
+    nonce text,
+    code_challenge text NOT NULL,
+    code_challenge_method text NOT NULL,
+    auth_time timestamptz NOT NULL,
+    amr text[] NOT NULL,
+    expires timestamptz NOT NULL
+);
+
+-- An access token or a refresh token (kind) a client was issued for a user.
+CREATE TABLE IF NOT EXISTS oidc_tokens (
+    hash text PRIMARY KEY,
+    kind text NOT NULL CHECK (kind IN ('access', 'refresh')),
+    client_id text NOT NULL,
+    name text NOT NULL,
+    scopes text[] NOT NULL,
+    auth_time timestamptz NOT NULL,
+    amr text[] NOT NULL,
+    expires timestamptz NOT NULL
+);
+CREATE INDEX IF NOT EXISTS oidc_tokens_name ON oidc_tokens (name);
+
+-- A user's sign-in at the OpenID Provider, which the session cookie names.
+CREATE TABLE IF NOT EXISTS oidc_sessions (
+    hash text PRIMARY KEY,
+    name text NOT NULL,
+    auth_time timestamptz NOT NULL,
+    amr text[] NOT NULL,
+    expires timestamptz NOT NULL
+);
+
+CREATE OR REPLACE PROCEDURE oidc_code_save(p_hash text, p_client_id text, p_name text, p_redirect_uri text,
+                                           p_scopes text[], p_nonce text, p_code_challenge text,
+                                           p_code_challenge_method text, p_auth_time timestamptz, p_amr text[],
+                                           p_seconds integer)
+LANGUAGE sql AS $$
+    DELETE FROM oidc_codes WHERE expires < now();
+    INSERT INTO oidc_codes VALUES (p_hash, p_client_id, p_name, p_redirect_uri, p_scopes, p_nonce, p_code_challenge,
+                                   p_code_challenge_method, p_auth_time, p_amr, now() + make_interval(secs => p_seconds));
+$$;
+
+-- The unexpired code.
+CREATE OR REPLACE FUNCTION oidc_code_get(p_hash text)
+RETURNS TABLE (client_id text, name text, redirect_uri text, scopes text[], nonce text, code_challenge text,
+               code_challenge_method text, auth_time timestamptz, amr text[])
+LANGUAGE sql STABLE AS $$
+    SELECT client_id, name, redirect_uri, scopes, nonce, code_challenge, code_challenge_method, auth_time, amr
+    FROM oidc_codes WHERE hash = p_hash AND expires > now();
+$$;
+
+CREATE OR REPLACE PROCEDURE oidc_code_delete(p_hash text)
+LANGUAGE sql AS $$
+    DELETE FROM oidc_codes WHERE hash = p_hash;
+$$;
+
+CREATE OR REPLACE PROCEDURE oidc_token_save(p_hash text, p_kind text, p_client_id text, p_name text, p_scopes text[],
+                                            p_auth_time timestamptz, p_amr text[], p_seconds integer)
+LANGUAGE sql AS $$
+    DELETE FROM oidc_tokens WHERE expires < now();
+    INSERT INTO oidc_tokens VALUES (p_hash, p_kind, p_client_id, p_name, p_scopes, p_auth_time, p_amr,
+                                    now() + make_interval(secs => p_seconds));
+$$;
+
+-- The unexpired token of the kind.
+CREATE OR REPLACE FUNCTION oidc_token_get(p_hash text, p_kind text)
+RETURNS TABLE (client_id text, name text, scopes text[], auth_time timestamptz, amr text[])
+LANGUAGE sql STABLE AS $$
+    SELECT client_id, name, scopes, auth_time, amr FROM oidc_tokens
+    WHERE hash = p_hash AND kind = p_kind AND expires > now();
+$$;
+
+CREATE OR REPLACE PROCEDURE oidc_token_delete(p_hash text)
+LANGUAGE sql AS $$
+    DELETE FROM oidc_tokens WHERE hash = p_hash;
+$$;
+
+CREATE OR REPLACE PROCEDURE oidc_session_save(p_hash text, p_name text, p_amr text[], p_seconds integer)
+LANGUAGE sql AS $$
+    DELETE FROM oidc_sessions WHERE expires < now();
+    INSERT INTO oidc_sessions VALUES (p_hash, p_name, now(), p_amr, now() + make_interval(secs => p_seconds));
+$$;
+
+-- The unexpired session.
+CREATE OR REPLACE FUNCTION oidc_session_get(p_hash text)
+RETURNS TABLE (name text, auth_time timestamptz, amr text[])
+LANGUAGE sql STABLE AS $$
+    SELECT name, auth_time, amr FROM oidc_sessions WHERE hash = p_hash AND expires > now();
+$$;
+
+CREATE OR REPLACE PROCEDURE oidc_session_delete(p_hash text)
+LANGUAGE sql AS $$
+    DELETE FROM oidc_sessions WHERE hash = p_hash;
+$$;
+
+-- Remove every code, token and session of the user.
+CREATE OR REPLACE PROCEDURE oidc_revoke(p_name text)
+LANGUAGE sql AS $$
+    DELETE FROM oidc_codes WHERE name = p_name;
+    DELETE FROM oidc_tokens WHERE name = p_name;
+    DELETE FROM oidc_sessions WHERE name = p_name;
+$$;