tokenserver: Validate and parse service_accounts.cfg rules.

tokenserver/appengine/impl/serviceaccounts/config_validation.go

Index: tokenserver/appengine/impl/serviceaccounts/config_validation.go
diff --git a/tokenserver/appengine/impl/serviceaccounts/config_validation.go b/tokenserver/appengine/impl/serviceaccounts/config_validation.go
index 907e33c085a2b8d79a0fbc7cc60e50446c48d826..98d6ee748399c205d9a4b381057c63224c897883 100644
--- a/tokenserver/appengine/impl/serviceaccounts/config_validation.go
+++ b/tokenserver/appengine/impl/serviceaccounts/config_validation.go
@@ -15,7 +15,12 @@
 package serviceaccounts
 
 import (
+	"fmt"
+	"strings"
+
 	"github.com/luci/luci-go/common/config/validation"
+	"github.com/luci/luci-go/common/data/stringset"
+	"github.com/luci/luci-go/server/auth/identity"
 
 	"github.com/luci/luci-go/tokenserver/api/admin/v1"
 	"github.com/luci/luci-go/tokenserver/appengine/impl/utils/policy"
@@ -30,5 +35,89 @@ func validateConfigs(bundle policy.ConfigBundle, ctx *validation.Context) {
 		return
 	}
 
-	// TODO(vadimsh): Validate cfg.Rules.
+	names := stringset.New(0)
+	accounts := map[string]string{} // service account -> rule name where its defined
+	for i, rule := range cfg.Rules {
+		// Rule name must be unique.
+		if rule.Name != "" {
+			if names.Has(rule.Name) {
+				ctx.Error("two rules with identical name %q", rule.Name)
+			} else {
+				names.Add(rule.Name)
+			}
+		}

[smut, 2017/08/04 23:07:37]

Add comment that we don't bother handling the else because rule.Name == "" is an
error validated by validateRule.

[Vadim Sh., 2017/08/04 23:37:52]

Done.

+
+		// There should be no overlap between service account sets covered by each
+		// rule.
+		for _, account := range rule.ServiceAccount {
+			if name, ok := accounts[account]; ok {
+				ctx.Error("service account %q is mentioned by more than one rule (%q and %q)", account, name, rule.Name)
+			} else {
+				accounts[account] = rule.Name
+			}
+		}
+
+		validateRule(fmt.Sprintf("rule #%d: %q", i+1, rule.Name), rule, ctx)
+	}
+}
+
+// validateRule checks single ServiceAccountRule proto.
+func validateRule(title string, r *admin.ServiceAccountRule, ctx *validation.Context) {
+	ctx.Enter(title)
+	defer ctx.Exit()
+
+	if r.Name == "" {
+		ctx.Error(`"name" is required`)
+	}
+
+	// Note: we allow any of the sets to be empty. The rule will just not match
+	// anything in this case, this is fine.
+	validateEmails("service_account", r.ServiceAccount, ctx)
+	validateScopes("allowed_scope", r.AllowedScope, ctx)
+	validateIdSet("end_user", r.EndUser, ctx)
+	validateIdSet("proxy", r.Proxy, ctx)
+
+	if r.MaxGrantValidityDuration != 0 {
+		switch {
+		case r.MaxGrantValidityDuration < 0:
+			ctx.Error(`"max_grant_validity_duration" must be positive`)
+		case r.MaxGrantValidityDuration > 7*24*3600:

[smut, 2017/08/04 23:07:37]

Can this be defined somewhere as maximum allowable grant validity duration?
Local to validateRule is fine, I just want it reused in the ctx.Error.

[Vadim Sh., 2017/08/04 23:37:52]

Done.

Though I have a nagging suspicion that in reality 1 week is probably not going
to work anyway because GAE rotates signing keys faster than that. We'll see.

+			ctx.Error(`"max_grant_validity_duration" must be smaller than 604801`)

[smut, 2017/08/04 23:07:37]

Once maxixmum allowable grant validity duration is defined, change to say
"max_grant_validity_duration" must not exceed %d.

As it is 7*24*3600 and 604801 have to be manually kept in sync.

[Vadim Sh., 2017/08/04 23:37:52]

Done.

+		}
+	}
+}
+
+func validateEmails(field string, emails []string, ctx *validation.Context) {
+	ctx.Enter("%q", field)
+	defer ctx.Exit()
+	for _, email := range emails {
+		// We reuse 'user:' identity validator, user identities are emails too.
+		if _, err := identity.MakeIdentity("user:" + email); err != nil {
+			ctx.Error("bad email %q - %s", email, err)
+		}
+	}
+}
+
+func validateScopes(field string, scopes []string, ctx *validation.Context) {
+	ctx.Enter("%q", field)
+	defer ctx.Exit()
+	for _, scope := range scopes {
+		if !strings.HasPrefix(scope, "https://www.googleapis.com/") {
+			ctx.Error("bad scope %q", scope)
+		}
+	}
+}
+
+func validateIdSet(field string, ids []string, ctx *validation.Context) {
+	ctx.Enter("%q", field)
+	defer ctx.Exit()
+	for _, entry := range ids {
+		if strings.HasPrefix(entry, "group:") {
+			if entry[len("group:"):] == "" {
+				ctx.Error("bad group entry - no group name")
+			}
+		} else if _, err := identity.MakeIdentity(entry); err != nil {
+			ctx.Error("bad identity %q - %s", entry, err)
+		}
+	}
 }