Introduce a more granular, site-based allowlist (#14)

This PR updates the allowlist in a few ways:

1. Move from a comma-delimited list of domains to a structured JSON-formatted file
2. Adds support for allowlisting individual emails, in addition to domains
3. Adds support for allowlisting an entity (domain or email) for only a specific set of sites

It also removes the allowlists from the repo, as those will start containing more individual information.

.gitignore

@@ -3,3 +3,6 @@
 /test_ed25519.pub
 /test_server.key
 /test_server.pub
+
+/cmd/server/configs/allowlists/*.json
+!/cmd/server/configs/allowlists/example.json

README.md

@@ -14,9 +14,12 @@ The service currently has two main credential-exchanging endpoints:
 Things to note:
 
 - Only Azure AD B2C is supported as a source of exchangable user ID tokens at the moment, see [the server `main.go`](/cmd/server/main.go) and the [`azjwt` package](/azure/azjwt/azjwt.go) for more details.
+- The allowlists themselves (i.e. in `cmd/server/configs/allowlists/{local,dev}.json`, are **not** included in this repo. If you're deploying the actual RMI service, get these from one of the developers.
 
 ## Running the Credential Service
 
+Before running the service locally, you'll need an allowlist at `cmd/server/configs/allowlists/local.json`. You can create one based on the `example.json` in the same directory.
+
 Run the server against an Azure AD B2C instance:
 
 ```bash

allowlist/BUILD.bazel

@@ -11,4 +11,5 @@ go_test(
     name = "allowlist_test",
     srcs = ["allowlist_test.go"],
     embed = [":allowlist"],
+    deps = ["@com_github_google_go_cmp//cmp"],
 )

allowlist/allowlist.go

@@ -2,32 +2,143 @@
 package allowlist
 
 import (
+	"encoding/json"
+	"errors"
 	"fmt"
+	"os"
 	"strings"
 )
 
+type config struct {
+	Format    string            `json:"format"`
+	Allowlist []*AllowlistEntry `json:"allowlist"`
+}
+
+// AllowlistEntry maps some entity (a domain or email) to a list of authorized sites.
+type AllowlistEntry struct {
+	// Only one of Domain or Email may be set
+	Domain string `json:"domain"`
+	Email  string `json:"email"`
+
+	// If empty, all sites are allowed.
+	// This isn't a "fail closed" default, but I think that's fine at this stage.
+	Sites []string `json:"sites"`
+}
+
+type Site string
+
+const (
+	SiteOPGEE = Site("OPGEE")
+	SitePACTA = Site("PACTA")
+)
+
+type Entity struct {
+	// If true, AllowedSites is ignored
+	AllowAllSites bool
+	AllowedSites  []Site
+}
+
 type Checker struct {
-	allowedDomains map[string]bool
+	allowedDomains map[string]*Entity
+	allowedEmails  map[string]*Entity
 }
 
-func NewChecker(allowedDomains []string) *Checker {
-	m := make(map[string]bool)
-	for _, ad := range allowedDomains {
-		m[ad] = true
+func NewCheckerFromConfigFile(fn string) (*Checker, error) {
+	f, err := os.Open(fn)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open allowlist config file: %w", err)
+	}
+	defer f.Close()
+
+	var cfg config
+	if err := json.NewDecoder(f).Decode(&cfg); err != nil {
+		return nil, fmt.Errorf("failed to decode allowlist config: %w", err)
+	}
+
+	return newChecker(&cfg)
+}
+
+func newChecker(cfg *config) (*Checker, error) {
+	switch cfg.Format {
+	case "v1":
+		// Valid, continue
+	case "":
+		return nil, errors.New("config file had no 'format' field, which is required")
+	default:
+		return nil, fmt.Errorf("unknown format %q", cfg.Format)
+	}
+
+	allowedDomains := make(map[string]*Entity)
+	allowedEmails := make(map[string]*Entity)
+	for i, ae := range cfg.Allowlist {
+		if ae.Domain != "" && ae.Email != "" {
+			return nil, fmt.Errorf("allowlist entry specified both a domain (%q) and an email (%q), which isn't allowed", ae.Domain, ae.Email)
+		}
+		if ae.Domain == "" && ae.Email == "" {
+			return nil, fmt.Errorf("allowlist entry at index %d did not specify a domain or email", i)
+		}
+		entity, err := parseEntity(ae.Sites)
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse sites for entry at index %d: %w", i, err)
+		}
+		if ae.Domain != "" {
+			allowedDomains[strings.ToLower(ae.Domain)] = entity
+		}
+		if ae.Email != "" {
+			allowedEmails[strings.ToLower(ae.Email)] = entity
+		}
 	}
 	return &Checker{
-		allowedDomains: m,
+		allowedDomains: allowedDomains,
+		allowedEmails:  allowedEmails,
+	}, nil
+}
+
+func parseEntity(inp []string) (*Entity, error) {
+	if len(inp) == 0 {
+		return &Entity{AllowAllSites: true}, nil
+	}
+	var sites []Site
+	for _, s := range inp {
+		st, err := parseSite(s)
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse entity %q: %w", s, err)
+		}
+		sites = append(sites, st)
+	}
+	return &Entity{AllowedSites: sites}, nil
+}
+
+func parseSite(inp string) (Site, error) {
+	switch inp {
+	case "OPGEE":
+		return SiteOPGEE, nil
+	case "PACTA":
+		return SitePACTA, nil
+	default:
+		return "", errors.New("unknown site")
 	}
 }
 
 // Check returns if the email is of an allowlisted domain, and errors if the
 // email is incorrectly formatted. Subdomains are not handled specially, only
 // exact matches are allowed.
-func (c *Checker) Check(email string) (bool, error) {
+func (c *Checker) Check(email string) (*Entity, error) {
+	email = strings.ToLower(email)
+
+	// First, check the email
+	if tmp, ok := c.allowedEmails[email]; ok {
+		return tmp, nil
+	}
+
 	_, domain, ok := strings.Cut(email, "@")
 	if !ok {
-		return false, fmt.Errorf("email %q was missing '@'", email)
+		return nil, fmt.Errorf("email %q was missing '@'", email)
+	}
+
+	if tmp, ok := c.allowedDomains[domain]; ok {
+		return tmp, nil
 	}
 
-	return c.allowedDomains[domain], nil
+	return nil, nil
 }

allowlist/allowlist_test.go

@@ -1,33 +1,82 @@
 package allowlist
 
-import "testing"
+import (
+	"testing"
 
-func TestCheck(t *testing.T) {
-	allowedDomain := "example.com"
+	"github.com/google/go-cmp/cmp"
+)
 
-	c := NewChecker([]string{allowedDomain})
+var exampleConfig = &config{
+	Format: "v1",
+	Allowlist: []*AllowlistEntry{
+		&AllowlistEntry{Domain: "example.com"},                                  // Can access any site
+		&AllowlistEntry{Domain: "only-opgee.com", Sites: []string{"OPGEE"}},     // Can only access OPGEE
+		&AllowlistEntry{Email: "test@only-pacta.com", Sites: []string{"PACTA"}}, // Only test@ can access PACTA
+	},
+}
 
-	allowed, err := c.Check("allowed@example.com")
+func TestCheck(t *testing.T) {
+	c, err := newChecker(exampleConfig)
 	if err != nil {
-		t.Fatalf("Check: %v", err)
+		t.Fatalf("failed to init checker: %v", err)
+	}
+
+	tests := []struct {
+		desc  string
+		email string
+		want  *Entity
+	}{
+		{
+			desc:  "allowed on any site",
+			email: "allowed@example.com",
+			want:  &Entity{AllowAllSites: true},
+		},
+		{
+			desc:  "domain not in the allowlist",
+			email: "denied@example.net",
+			want:  nil,
+		},
+		{
+			desc:  "domain allowlisted for OPGEE",
+			email: "any-email@only-opgee.com",
+			want:  &Entity{AllowedSites: []Site{SiteOPGEE}},
+		},
+		{
+			desc:  "email allowlisted for PACTA",
+			email: "test@only-pacta.com",
+			want:  &Entity{AllowedSites: []Site{SitePACTA}},
+		},
+		{
+			desc:  "different email allowlisted for PACTA",
+			email: "not-allowed@only-pacta.com",
+			want:  nil,
+		},
 	}
-	if !allowed {
-		t.Error("Check said email was not allowed, expected allowed")
+
+	for _, test := range tests {
+		t.Run(test.desc, func(t *testing.T) {
+			got, err := c.Check(test.email)
+			if err != nil {
+				t.Fatalf("Check: %v", err)
+			}
+			if diff := cmp.Diff(test.want, got); diff != "" {
+				t.Errorf("unexpected Check() results (-want +got)\n%s", diff)
+			}
+		})
 	}
+}
 
-	allowed, err = c.Check("denied@example.net")
+func TestCheck_Error(t *testing.T) {
+	c, err := newChecker(exampleConfig)
 	if err != nil {
-		t.Fatalf("Check: %v", err)
-	}
-	if allowed {
-		t.Error("Check said email was allowed, expected not allowed")
+		t.Fatalf("failed to init checker: %v", err)
 	}
 
-	allowed, err = c.Check("malformed.biz")
+	entity, err := c.Check("malformed.biz")
 	if err == nil {
 		t.Fatal("Check returned no error for invalid email address")
 	}
-	if allowed {
-		t.Error("Check said invalid email was allowed")
+	if entity != nil {
+		t.Errorf("Check said invalid email was allowed: %+v", entity)
 	}
 }

azure/azjwt/BUILD.bazel

@@ -7,7 +7,7 @@ go_library(
     visibility = ["//visibility:public"],
     deps = [
         "//allowlist",
-        "//emailctx",
+        "//tokenctx",
         "@com_github_go_chi_jwtauth_v5//:jwtauth",
         "@com_github_lestrrat_go_jwx_v2//jwk",
         "@com_github_lestrrat_go_jwx_v2//jwt",

azure/azjwt/azjwt.go

@@ -10,7 +10,7 @@ import (
 	"net/http"
 
 	"github.com/RMI/credential-service/allowlist"
-	"github.com/RMI/credential-service/emailctx"
+	"github.com/RMI/credential-service/tokenctx"
 	"github.com/go-chi/jwtauth/v5"
 	"github.com/lestrrat-go/jwx/v2/jwk"
 	"github.com/lestrrat-go/jwx/v2/jwt"
@@ -138,7 +138,7 @@ func (a *Auth) Authenticator(next http.Handler) http.Handler {
 		}
 
 		// Now, check against the allowlist
-		allowedEmails, err := a.checkEmailAllowed(token)
+		allowedEmails, entity, err := a.checkEmailAllowed(token)
 		if err != nil {
 			a.logger.Warn("token failed allowlist check", zap.Error(err))
 			if errors.Is(err, errNotAllowlisted) {
@@ -150,7 +150,8 @@ func (a *Auth) Authenticator(next http.Handler) http.Handler {
 		}
 
 		// Add the email to the context so that it can be used by the handler
-		ctx := emailctx.AddEmailsToContext(r.Context(), allowedEmails)
+		ctx := tokenctx.AddEmailsToContext(r.Context(), allowedEmails)
+		ctx = tokenctx.AddAllowlistEntityToContext(ctx, entity)
 		// Token is authenticated, pass it through
 		next.ServeHTTP(w, r.WithContext(ctx))
 	}
@@ -212,47 +213,61 @@ func (a *Auth) parseAndVerify(ctx context.Context, r *http.Request) (jwt.Token,
 
 var errNotAllowlisted = errors.New("email isn't allowlisted")
 
-func (a *Auth) checkEmailAllowed(tkn jwt.Token) ([]string, error) {
+func (a *Auth) checkEmailAllowed(tkn jwt.Token) ([]string, *allowlist.Entity, error) {
 	// See https://learn.microsoft.com/en-us/azure/active-directory/develop/id-token-claims-reference
 	emailsVal, ok := tkn.Get("emails")
 	if !ok {
-		return nil, errors.New("token didn't contain an 'emails' claim")
+		return nil, nil, errors.New("token didn't contain an 'emails' claim")
 	}
 	emailsI, ok := emailsVal.([]any)
 	if !ok {
-		return nil, fmt.Errorf("'emails' claim in token had unexpected type %T", emailsVal)
+		return nil, nil, fmt.Errorf("'emails' claim in token had unexpected type %T", emailsVal)
 	}
 
 	var emails []string
 	for i, ei := range emailsI {
 		email, ok := ei.(string)
 		if !ok {
-			return nil, fmt.Errorf("email %d from 'emails' claim in token had unexpected type %T", i, ei)
+			return nil, nil, fmt.Errorf("email %d from 'emails' claim in token had unexpected type %T", i, ei)
 		}
 		emails = append(emails, email)
 	}
 
 	// If one of their emails is allowed, consider them allowed.
-	allowed := a.allowedEmails(emails)
+	allowed, entity := a.allowedEmails(emails)
 	if len(allowed) == 0 {
-		return nil, errNotAllowlisted
+		return nil, nil, errNotAllowlisted
 	}
 
-	return allowed, nil
+	return allowed, entity, nil
 }
 
-func (a *Auth) allowedEmails(emails []string) []string {
-	var result []string
+func (a *Auth) allowedEmails(emails []string) ([]string, *allowlist.Entity) {
+	var (
+		outEmails     []string
+		allowAllSites bool
+		sites         []allowlist.Site
+	)
 	for _, email := range emails {
-		allowed, err := a.allowlist.Check(email)
+		entity, err := a.allowlist.Check(email)
 		if err != nil {
 			a.logger.Warn("failed to check allowlist", zap.String("email", email), zap.Error(err))
 			continue
 		}
-		// We don't return early on success, just to parse and validate all emails in the token.
-		if allowed {
-			result = append(result, email)
+		if entity == nil {
+			continue
+		}
+		if entity.AllowAllSites {
+			allowAllSites = true
 		}
+		sites = append(sites, entity.AllowedSites...)
+		outEmails = append(outEmails, email)
+	}
+	var entity *allowlist.Entity
+	if allowAllSites {
+		entity = &allowlist.Entity{AllowAllSites: true}
+	} else {
+		entity = &allowlist.Entity{AllowedSites: sites}
 	}
-	return result
+	return outEmails, entity
 }