Principal Service: Add support for multiple user accounts

services/vanadium/security/principal.go

Index: services/vanadium/security/principal.go
diff --git a/services/vanadium/security/principal.go b/services/vanadium/security/principal.go
new file mode 100644
index 0000000000000000000000000000000000000000..e126b498606fca3b70b5b1c2b861ca02adb5b4a3
--- /dev/null
+++ b/services/vanadium/security/principal.go
@@ -0,0 +1,77 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package main
+
+import (
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"fmt"
+	"sync"
+
+	vpkg "mojo/services/vanadium/security/interfaces/principal"
+)
+
+type principal struct {
+	private   *ecdsa.PrivateKey
+	mu        sync.Mutex
+	blessings map[vpkg.User]*wireBlessings // GUARDED_BY(mu)
+	curr      *vpkg.User                   // GUARDED_BY(mu)
+}
+
+func (p *principal) publicKey() publicKey {
+	return newECDSAPublicKey(&p.private.PublicKey)
+}
+
+func (p *principal) currentBlessing() *wireBlessings {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	if p.curr == nil {
+		return nil
+	}
+	return p.blessings[*p.curr]
+}
+
+func (p *principal) users() ([]vpkg.User, *vpkg.User) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	var users []vpkg.User
+	for user, _ := range p.blessings {
+		users = append(users, user)
+	}
+	return users, p.curr
+}
+
+func (p *principal) addUser(user vpkg.User, blessing *wireBlessings) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	p.blessings[user] = blessing
+	p.curr = &user
+}
+
+func (p *principal) setCurrentUser(user vpkg.User) (err *string) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	if _, ok := p.blessings[user]; !ok {
+		str := fmt.Sprintf("User %v does not exist", user)
+		return &str
+	}
+	p.curr = &user
+	return
+}
+
+func (p *principal) unsetCurrentUser() {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+	p.curr = nil
+}
+
+func newPrincipal() (*principal, error) {
+	priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		return nil, err
+	}
+	return &principal{private: priv, blessings: make(map[vpkg.User]*wireBlessings)}, nil
+}