add regex for oidc group matching

connector/oidc/oidc.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"net/http"
 	"net/url"
+	"regexp"
 	"strings"
 	"time"
 
@@ -93,6 +94,7 @@ type Config struct {
 	// ClaimMutations holds all claim mutations options
 	ClaimMutations struct {
 		NewGroupFromClaims []NewGroupFromClaims `json:"newGroupFromClaims"`
+		FilterGroupClaims  FilterGroupClaims    `json:"filterGroupClaims"`
 	} `json:"claimModifications"`
 }
 
@@ -112,6 +114,12 @@ type NewGroupFromClaims struct {
 	Prefix string `json:"prefix"`
 }
 
+// FilterGroupClaims is a regex filter for to keep only the matching groups.
+// This is useful when the groups list is too large to fit within an HTTP header.
+type FilterGroupClaims struct {
+	GroupsFilter string `json:"groupsFilter"`
+}
+
 // Domains that don't support basic auth. golang.org/x/oauth2 has an internal
 // list, but it only matches specific URLs, not top level domains.
 var brokenAuthHeaderDomains = []string{
@@ -184,6 +192,14 @@ func (c *Config) Open(id string, logger log.Logger) (conn connector.Connector, e
 		c.PromptType = "consent"
 	}
 
+	var groupsFilter *regexp.Regexp
+	if c.ClaimMutations.FilterGroupClaims.GroupsFilter != "" {
+		groupsFilter, err = regexp.Compile(c.ClaimMutations.FilterGroupClaims.GroupsFilter)
+		if err != nil {
+			logger.Warnf("ignoring invalid regex `%s`", c.ClaimMutations.FilterGroupClaims.GroupsFilter)
+		}
+	}
+
 	clientID := c.ClientID
 	return &oidcConnector{
 		provider:    provider,
@@ -214,6 +230,7 @@ func (c *Config) Open(id string, logger log.Logger) (conn connector.Connector, e
 		emailKey:                  c.ClaimMapping.EmailKey,
 		groupsKey:                 c.ClaimMapping.GroupsKey,
 		newGroupFromClaims:        c.ClaimMutations.NewGroupFromClaims,
+		groupsFilter:              groupsFilter,
 	}, nil
 }
 
@@ -243,6 +260,7 @@ type oidcConnector struct {
 	emailKey                  string
 	groupsKey                 string
 	newGroupFromClaims        []NewGroupFromClaims
+	groupsFilter              *regexp.Regexp
 }
 
 func (c *oidcConnector) Close() error {
@@ -446,6 +464,9 @@ func (c *oidcConnector) createIdentity(ctx context.Context, identity connector.I
 		if found {
 			for _, v := range vs {
 				if s, ok := v.(string); ok {
+					if c.groupsFilter != nil && !c.groupsFilter.MatchString(s) {
+						continue
+					}
 					groups = append(groups, s)
 				} else {
 					return identity, fmt.Errorf("malformed \"%v\" claim", groupsKey)

connector/oidc/oidc_test.go

@@ -62,6 +62,7 @@ func TestHandleCallback(t *testing.T) {
 		expectPreferredUsername   string
 		expectedEmailField        string
 		token                     map[string]interface{}
+		groupsRegex               string
 		newGroupFromClaims        []NewGroupFromClaims
 	}{
 		{
@@ -362,6 +363,23 @@ func TestHandleCallback(t *testing.T) {
 				"non-string-claim2": 666,
 			},
 		},
+		{
+			name:               "filterGroupClaims",
+			userIDKey:          "", // not configured
+			userNameKey:        "", // not configured
+			groupsRegex:        `^.*\d$`,
+			expectUserID:       "subvalue",
+			expectUserName:     "namevalue",
+			expectGroups:       []string{"group1", "group2"},
+			expectedEmailField: "emailvalue",
+			token: map[string]interface{}{
+				"sub":            "subvalue",
+				"name":           "namevalue",
+				"groups":         []string{"group1", "group2", "groupA", "groupB"},
+				"email":          "emailvalue",
+				"email_verified": true,
+			},
+		},
 	}
 
 	for _, tc := range tests {
@@ -398,6 +416,7 @@ func TestHandleCallback(t *testing.T) {
 			config.ClaimMapping.EmailKey = tc.emailKey
 			config.ClaimMapping.GroupsKey = tc.groupsKey
 			config.ClaimMutations.NewGroupFromClaims = tc.newGroupFromClaims
+			config.ClaimMutations.FilterGroupClaims.GroupsFilter = tc.groupsRegex
 
 			conn, err := newConnector(config)
 			if err != nil {