Add support for POSIX LDAP schema

In the POSIX LDAP schema, there is no 'memberOf' attribute returned
in relation to which groups a person is a member of. Rather, it is
necessary to query the group objects which have the people as members.
This commit adds an additional filter, which if specified explicitly
searches for groups, rather than relying on the 'memberOf' attribute.
This enables Grafana to work with LDAP POSIX schema (e.g. OpenLDAP
etc.)

Signed-off-by: Alex Bligh <alex@alex.org.uk>

conf/ldap.toml

@@ -18,11 +18,32 @@ bind_dn = "cn=admin,dc=grafana,dc=org"
 # Search user bind password
 bind_password = 'grafana'
 
+# Schema's supporting memberOf
+
 # Search filter, for example "(cn=%s)" or "(sAMAccountName=%s)"
 search_filter = "(cn=%s)"
 # An array of base dns to search through
 search_base_dns = ["dc=grafana,dc=org"]
 
+# Uncomment this section (and comment out the previous 2 entries) to use POSIX schema.
+# In POSIX LDAP schemas, querying the people 'ou' gives you entries that do not have a
+# memberOf attribute, so a secondary query must be made for groups. This is done by
+# enabling group_search_filter below. You must also set
+#    member_of = "cn"
+# in [servers.attributes] below.
+#
+# Search filter, used to retrieve the user
+# search_filter = "(uid=%s)"
+#
+# An array of the base DNs to search through for users. Typically uses ou=people.
+# search_base_dns = ["ou=people,dc=grafana,dc=org"]
+#
+# Group search filter, to retrieve the groups of which the user is a member
+# group_search_filter = "(&(objectClass=posixGroup)(memberUid=%s))"
+#
+# An array of the base DNs to search through for groups. Typically uses ou=groups
+# group_search_base_dns = ["ou=groups,dc=grafana,dc=org"]
+
 # Specify names of the ldap attributes your ldap uses
 [servers.attributes]
 name = "givenName"

pkg/login/ldap.go

@@ -311,18 +311,51 @@ func (a *ldapAuther) searchForUser(username string) (*ldapUserInfo, error) {
 		return nil, errors.New("Ldap search matched more than one entry, please review your filter setting")
 	}
 
+	var memberOf []string
+	if a.server.GroupSearchFilter == "" {
+		memberOf = getLdapAttrArray(a.server.Attr.MemberOf, searchResult)
+	} else {
+		// If we are using a POSIX LDAP schema it won't support memberOf, so we manually search the groups
+		var groupSearchResult *ldap.SearchResult
+		for _, groupSearchBase := range a.server.GroupSearchBaseDNs {
+			filter := strings.Replace(a.server.GroupSearchFilter, "%s", username, -1)
+			groupSearchReq := ldap.SearchRequest{
+				BaseDN:       groupSearchBase,
+				Scope:        ldap.ScopeWholeSubtree,
+				DerefAliases: ldap.NeverDerefAliases,
+				Attributes: []string{
+					// Here MemberOf would be the thing that identifies the group, which is normally 'cn'
+					a.server.Attr.MemberOf,
+				},
+				Filter: filter,
+			}
+
+			groupSearchResult, err = a.conn.Search(&groupSearchReq)
+			if err != nil {
+				return nil, err
+			}
+
+			if len(groupSearchResult.Entries) > 0 {
+				for i := range groupSearchResult.Entries {
+					memberOf = append(memberOf, getLdapAttrN(a.server.Attr.MemberOf, groupSearchResult, i))
+				}
+				break
+			}
+		}
+	}
+
 	return &ldapUserInfo{
 		DN:        searchResult.Entries[0].DN,
 		LastName:  getLdapAttr(a.server.Attr.Surname, searchResult),
 		FirstName: getLdapAttr(a.server.Attr.Name, searchResult),
 		Username:  getLdapAttr(a.server.Attr.Username, searchResult),
 		Email:     getLdapAttr(a.server.Attr.Email, searchResult),
-		MemberOf:  getLdapAttrArray(a.server.Attr.MemberOf, searchResult),
+		MemberOf:  memberOf,
 	}, nil
 }
 
-func getLdapAttr(name string, result *ldap.SearchResult) string {
-	for _, attr := range result.Entries[0].Attributes {
+func getLdapAttrN(name string, result *ldap.SearchResult, n int) string {
+	for _, attr := range result.Entries[n].Attributes {
 		if attr.Name == name {
 			if len(attr.Values) > 0 {
 				return attr.Values[0]
@@ -332,6 +365,10 @@ func getLdapAttr(name string, result *ldap.SearchResult) string {
 	return ""
 }
 
+func getLdapAttr(name string, result *ldap.SearchResult) string {
+	return getLdapAttrN(name, result, 0)
+}
+
 func getLdapAttrArray(name string, result *ldap.SearchResult) []string {
 	for _, attr := range result.Entries[0].Attributes {
 		if attr.Name == name {

pkg/login/settings.go

@@ -27,6 +27,9 @@ type LdapServerConf struct {
 	SearchFilter  string   `toml:"search_filter"`
 	SearchBaseDNs []string `toml:"search_base_dns"`
 
+	GroupSearchFilter  string   `toml:"group_search_filter"`
+	GroupSearchBaseDNs []string `toml:"group_search_base_dns"`
+
 	LdapGroups []*LdapGroupToOrgRole `toml:"group_mappings"`
 }