Backport of Fix handling of username_as_alias during LDAP authentication into release/1.10.x

builtin/credential/ldap/backend.go

@@ -60,7 +60,7 @@ type backend struct {
 	*framework.Backend
 }
 
-func (b *backend) Login(ctx context.Context, req *logical.Request, username string, password string) (string, []string, *logical.Response, []string, error) {
+func (b *backend) Login(ctx context.Context, req *logical.Request, username string, password string, usernameAsAlias bool) (string, []string, *logical.Response, []string, error) {
 	cfg, err := b.Config(ctx, req)
 	if err != nil {
 		return "", nil, nil, nil, err
@@ -199,6 +199,10 @@ func (b *backend) Login(ctx context.Context, req *logical.Request, username stri
 	// Policies from each group may overlap
 	policies = strutil.RemoveDuplicates(policies, true)
 
+	if usernameAsAlias {
+		return username, policies, ldapResponse, allGroups, nil
+	}
+
 	entityAliasAttribute, err := ldapClient.GetUserAliasAttributeValue(cfg.ConfigEntry, c, username)
 	if err != nil {
 		return "", nil, logical.ErrorResponse(err.Error()), nil, nil

builtin/credential/ldap/backend_test.go

@@ -618,6 +618,30 @@ func TestBackend_basic_authbind_userfilter(t *testing.T) {
 			testAccStepLoginFailure(t, "hermes conrad", "hermes"),
 		},
 	})
+
+	// If UserAttr returns multiple attributes that can be used as alias then
+	// we return an error...
+	cfg.UserAttr = "employeeType"
+	cfg.UserFilter = "(cn={{.Username}})"
+	cfg.UsernameAsAlias = false
+	logicaltest.Test(t, logicaltest.TestCase{
+		CredentialBackend: b,
+		Steps: []logicaltest.TestStep{
+			testAccStepConfigUrl(t, cfg),
+			testAccStepLoginFailure(t, "hermes conrad", "hermes"),
+		},
+	})
+
+	// ...unless username_as_alias has been set in which case we don't care
+	// about the alias returned by the LDAP server and always use the username
+	cfg.UsernameAsAlias = true
+	logicaltest.Test(t, logicaltest.TestCase{
+		CredentialBackend: b,
+		Steps: []logicaltest.TestStep{
+			testAccStepConfigUrl(t, cfg),
+			testAccStepLoginNoAttachedPolicies(t, "hermes conrad", "hermes"),
+		},
+	})
 }
 
 func TestBackend_basic_authbind_metadata_name(t *testing.T) {
@@ -805,6 +829,7 @@ func testAccStepConfigUrl(t *testing.T, cfg *ldaputil.ConfigEntry) logicaltest.T
 			"case_sensitive_names": true,
 			"token_policies":       "abc,xyz",
 			"request_timeout":      cfg.RequestTimeout,
+			"username_as_alias":    cfg.UsernameAsAlias,
 		},
 	}
 }

builtin/credential/ldap/path_login.go

@@ -73,7 +73,7 @@ func (b *backend) pathLogin(ctx context.Context, req *logical.Request, d *framew
 	username := d.Get("username").(string)
 	password := d.Get("password").(string)
 
-	effectiveUsername, policies, resp, groupNames, err := b.Login(ctx, req, username, password)
+	effectiveUsername, policies, resp, groupNames, err := b.Login(ctx, req, username, password, cfg.UsernameAsAlias)
 	// Handle an internal error
 	if err != nil {
 		return nil, err
@@ -103,10 +103,6 @@ func (b *backend) pathLogin(ctx context.Context, req *logical.Request, d *framew
 		},
 	}
 
-	if cfg.UsernameAsAlias {
-		auth.Alias.Name = username
-	}
-
 	cfg.PopulateTokenAuth(auth)
 
 	// Add in configured policies from mappings
@@ -139,7 +135,7 @@ func (b *backend) pathLoginRenew(ctx context.Context, req *logical.Request, d *f
 	username := req.Auth.Metadata["username"]
 	password := req.Auth.InternalData["password"].(string)
 
-	_, loginPolicies, resp, groupNames, err := b.Login(ctx, req, username, password)
+	_, loginPolicies, resp, groupNames, err := b.Login(ctx, req, username, password, cfg.UsernameAsAlias)
 	if err != nil || (resp != nil && resp.IsError()) {
 		return resp, err
 	}

changelog/15525.txt

@@ -0,0 +1,8 @@
+```release-note:bug
+auth/ldap: The logic for setting the entity alias when `username_as_alias` is set
+has been fixed. The previous behavior would make a request to the LDAP server to
+get `user_attr` before discarding it and using the username instead. This would
+make it impossible for a user to connect if this attribute was missing or had
+multiple values, even though it would not be used anyway. This has been fixed
+and the username is now used without making superfluous LDAP searches.
+```

sdk/helper/ldaputil/client.go

@@ -244,7 +244,7 @@ func (c *Client) GetUserAliasAttributeValue(cfg *ConfigEntry, conn Connection, u
 		}
 
 		if len(result.Entries[0].Attributes) != 1 {
-			return aliasAttributeValue, errwrap.Wrapf("LDAP attribute missing for entity alias mapping{{err}}", err)
+			return aliasAttributeValue, fmt.Errorf("LDAP attribute missing for entity alias mapping")
 		}
 
 		if len(result.Entries[0].Attributes[0].Values) != 1 {