Show why personal OIDC logins are refused

Personal Google and Microsoft accounts were rejected with a raw
JSON unauthorized response after the OIDC callback. Redirect to a
dedicated auth page that explains the enterprise-account
requirement, and check enterprise eligibility before xms_edov so
Microsoft consumer accounts get the same clear error.

Signed-off-by: Cursor Agent <cursoragent@cursor.com>

Co-authored-by: Bryan FRIMIN <bryan@frimin.fr>

pkg/iam/oidc/service.go

@@ -165,6 +165,30 @@ func (c *idTokenClaims) isEmailDomainOwnerVerified() bool {
 	return false
 }
 
+// validateIDTokenClaims enforces provider-specific account requirements.
+// Enterprise eligibility is checked before email-verification claims so
+// personal Google/Microsoft accounts surface ErrPersonalAccountNotAllowed
+// rather than a generic email-verification failure (e.g. missing xms_edov).
+func validateIDTokenClaims(info *providerInfo, claims *idTokenClaims) error {
+	if claims.Email == "" {
+		return NewMissingEmailClaimError()
+	}
+
+	if !info.enterpriseChecker(claims) {
+		return NewPersonalAccountNotAllowedError()
+	}
+
+	if !info.trustProviderEmail && !claims.isEmailVerified() {
+		return NewEmailNotVerifiedError()
+	}
+
+	if info.requireEmailDomainOwnerVerified && !claims.isEmailDomainOwnerVerified() {
+		return NewEmailNotVerifiedError()
+	}
+
+	return nil
+}
+
 var (
 	googleEndpoint = oauth2.Endpoint{
 		AuthURL:  "https://accounts.google.com/o/oauth2/v2/auth",
@@ -423,20 +447,8 @@ func (s *Service) HandleCallback(
 		return nil, "", nil, fmt.Errorf("cannot verify id token: %w", err)
 	}
 
-	if claims.Email == "" {
-		return nil, "", nil, NewMissingEmailClaimError()
-	}
-
-	if !info.trustProviderEmail && !claims.isEmailVerified() {
-		return nil, "", nil, NewEmailNotVerifiedError()
-	}
-
-	if info.requireEmailDomainOwnerVerified && !claims.isEmailDomainOwnerVerified() {
-		return nil, "", nil, NewEmailNotVerifiedError()
-	}
-
-	if !info.enterpriseChecker(claims) {
-		return nil, "", nil, NewPersonalAccountNotAllowedError()
+	if err := validateIDTokenClaims(info, claims); err != nil {
+		return nil, "", nil, err
 	}
 
 	email, err := mail.ParseAddr(claims.Email)

pkg/iam/oidc/service_test.go

@@ -21,6 +21,7 @@
 package oidc
 
 import (
+	"errors"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -89,3 +90,65 @@ func TestIsEmailDomainOwnerVerified(t *testing.T) {
 		)
 	}
 }
+
+func TestValidateIDTokenClaims_PersonalAccounts(t *testing.T) {
+	t.Parallel()
+
+	s := newTestService(t)
+
+	t.Run("rejects Google personal account without hosted domain", func(t *testing.T) {
+		t.Parallel()
+
+		err := validateIDTokenClaims(
+			s.providers[coredata.OIDCProviderGoogle],
+			&idTokenClaims{
+				Email:         "user@gmail.com",
+				EmailVerified: true,
+			},
+		)
+		_, ok := errors.AsType[*ErrPersonalAccountNotAllowed](err)
+		assert.True(t, ok, "got %T: %v", err, err)
+	})
+
+	t.Run("rejects Microsoft personal account before xms_edov check", func(t *testing.T) {
+		t.Parallel()
+
+		err := validateIDTokenClaims(
+			s.providers[coredata.OIDCProviderMicrosoft],
+			&idTokenClaims{
+				Issuer: "https://login.microsoftonline.com/" + microsoftConsumerTenantID + "/v2.0",
+				Email:  "user@outlook.com",
+			},
+		)
+		_, ok := errors.AsType[*ErrPersonalAccountNotAllowed](err)
+		assert.True(t, ok, "got %T: %v", err, err)
+	})
+
+	t.Run("accepts Google Workspace account with hosted domain", func(t *testing.T) {
+		t.Parallel()
+
+		err := validateIDTokenClaims(
+			s.providers[coredata.OIDCProviderGoogle],
+			&idTokenClaims{
+				Email:         "user@acme.com",
+				EmailVerified: true,
+				HostedDomain:  "acme.com",
+			},
+		)
+		assert.NoError(t, err)
+	})
+
+	t.Run("rejects Microsoft enterprise account missing xms_edov", func(t *testing.T) {
+		t.Parallel()
+
+		err := validateIDTokenClaims(
+			s.providers[coredata.OIDCProviderMicrosoft],
+			&idTokenClaims{
+				Issuer: "https://login.microsoftonline.com/tenant-id/v2.0",
+				Email:  "user@acme.com",
+			},
+		)
+		_, ok := errors.AsType[*ErrEmailNotVerified](err)
+		assert.True(t, ok, "got %T: %v", err, err)
+	})
+}

pkg/server/api/connect/v1/oidc_handler.go

@@ -32,6 +32,7 @@ import (
 	"go.probo.inc/probo/pkg/coredata"
 	"go.probo.inc/probo/pkg/gid"
 	"go.probo.inc/probo/pkg/iam"
+	"go.probo.inc/probo/pkg/iam/oidc"
 	"go.probo.inc/probo/pkg/mail"
 	"go.probo.inc/probo/pkg/saferedirect"
 	"go.probo.inc/probo/pkg/securecookie"
@@ -130,6 +131,13 @@ func (h *OIDCHandler) CallbackHandler(w http.ResponseWriter, r *http.Request) {
 
 	identity, continueURL, organizationID, err := h.iam.OIDCService.HandleCallback(ctx, provider, stateParam, code)
 	if err != nil {
+		if _, ok := errors.AsType[*oidc.ErrPersonalAccountNotAllowed](err); ok {
+			h.logger.WarnCtx(ctx, "OIDC login rejected: personal account not allowed")
+			http.Redirect(w, r, "/auth/personal-account-not-allowed", http.StatusFound)
+
+			return
+		}
+
 		h.logger.ErrorCtx(ctx, "cannot handle OIDC callback", log.Error(err))
 		httpserver.RenderError(w, http.StatusUnauthorized, errors.New("authentication failed"))