Support for allowing/banning specific username patterns during registration

crates/policy/src/model.rs

@@ -32,6 +32,12 @@ pub enum Code {
     /// The username contains only numeric characters.
     UsernameAllNumeric,
 
+    /// The username is banned.
+    UsernameBanned,
+
+    /// The username is not allowed.
+    UsernameNotAllowed,
+
     /// The email domain is not allowed.
     EmailDomainNotAllowed,
 
@@ -54,6 +60,8 @@ impl Code {
             Self::UsernameTooLong => "username-too-long",
             Self::UsernameInvalidChars => "username-invalid-chars",
             Self::UsernameAllNumeric => "username-all-numeric",
+            Self::UsernameBanned => "username-banned",
+            Self::UsernameNotAllowed => "username-not-allowed",
             Self::EmailDomainNotAllowed => "email-domain-not-allowed",
             Self::EmailDomainBanned => "email-domain-banned",
             Self::EmailNotAllowed => "email-not-allowed",

docs/reference/configuration.md

@@ -382,6 +382,35 @@ policy:
       # don't require clients to provide a client_uri. default: false
       allow_missing_client_uri: false
 
+    # Restrictions on user registration
+    registration:
+      # If specified, the username (localpart) *must* match one of the allowed
+      # usernames. If unspecified, all usernames are allowed.
+      allowed_usernames:
+        # Exact usernames that are allowed
+        literals: ["alice", "bob"]
+        # Substrings that match allowed usernames
+        substrings: ["user"]
+        # Regular expressions that match allowed usernames
+        regexes: ["^[a-z]+$"]
+        # Prefixes that match allowed usernames
+        prefixes: ["user-"]
+        # Suffixes that match allowed usernames
+        suffixes: ["-corp"]
+      # If specified, the username (localpart) *must not* match one of the
+      # banned usernames. If unspecified, all usernames are allowed.
+      banned_usernames:
+        # Exact usernames that are banned
+        literals: ["admin", "root"]
+        # Substrings that match banned usernames
+        substrings: ["admin", "root"]
+        # Regular expressions that match banned usernames
+        regexes: ["^admin$", "^root$"]
+        # Prefixes that match banned usernames
+        prefixes: ["admin-", "root-"]
+        # Suffixes that match banned usernames
+        suffixes: ["-admin", "-root"]
+
     # Restrict what email addresses can be added to a user
     emails:
       # If specified, the email address *must* match one of the allowed addresses.

policies/register/register.rego

@@ -14,6 +14,14 @@ allow if {
 	count(violation) == 0
 }
 
+username_allowed if {
+	not data.registration.allowed_usernames
+}
+
+username_allowed if {
+	common.matches_string_constraints(input.username, data.registration.allowed_usernames)
+}
+
 # METADATA
 # entrypoint: true
 violation contains {"field": "username", "code": "username-too-short", "msg": "username too short"} if {
@@ -39,6 +47,20 @@ violation contains {
 	not regex.match(`^[a-z0-9.=_/-]+$`, input.username)
 }
 
+violation contains {
+	"field": "username", "code": "username-banned",
+	"msg": "username is banned",
+} if {
+	common.matches_string_constraints(input.username, data.registration.banned_usernames)
+}
+
+violation contains {
+	"field": "username", "code": "username-not-allowed",
+	"msg": "username is not allowed",
+} if {
+	not username_allowed
+}
+
 violation contains {"msg": "unspecified registration method"} if {
 	not input.registration_method
 }

policies/register/register_test.rego

@@ -75,6 +75,20 @@ test_numeric_username if {
 	not register.allow with input as {"username": "1234", "registration_method": "upstream-oauth2"}
 }
 
+test_allowed_username if {
+	register.allow with input as {"username": "hello", "registration_method": "upstream-oauth2"}
+		with data.registration.allowed_usernames.literals as ["hello"]
+	not register.allow with input as {"username": "hello", "registration_method": "upstream-oauth2"}
+		with data.registration.allowed_usernames.literals as ["world"]
+}
+
+test_banned_username if {
+	not register.allow with input as {"username": "hello", "registration_method": "upstream-oauth2"}
+		with data.registration.banned_usernames.literals as ["hello"]
+	register.allow with input as {"username": "hello", "registration_method": "upstream-oauth2"}
+		with data.registration.banned_usernames.literals as ["world"]
+}
+
 test_ip_ban if {
 	not register.allow with input as {
 		"username": "hello",

templates/components/field.html

@@ -69,6 +69,10 @@
                 {{ _("mas.errors.username_invalid_chars") }}
               {% elif error.code == "username-all-numeric" %}
                 {{ _("mas.errors.username_all_numeric") }}
+              {% elif error.code == "username-banned" %}
+                {{ _("mas.errors.username_banned") }}
+              {% elif error.code == "username-not-allowed" %}
+                {{ _("mas.errors.username_not_allowed") }}
               {% elif error.code == "email-domain-not-allowed" %}
                 {{ _("mas.errors.email_domain_not_allowed") }}
               {% elif error.code == "email-domain-banned" %}

translations/en.json

@@ -299,23 +299,23 @@
       },
       "denied_policy": "Denied by policy: %(policy)s",
       "@denied_policy": {
-        "context": "components/errors.html:17:7-58, components/field.html:81:19-70"
+        "context": "components/errors.html:17:7-58, components/field.html:85:19-70"
       },
       "email_banned": "Email is banned by the server policy",
       "@email_banned": {
-        "context": "components/field.html:79:19-47"
+        "context": "components/field.html:83:19-47"
       },
       "email_domain_banned": "Email domain is banned by the server policy",
       "@email_domain_banned": {
-        "context": "components/field.html:75:19-54"
+        "context": "components/field.html:79:19-54"
       },
       "email_domain_not_allowed": "Email domain is not allowed by the server policy",
       "@email_domain_not_allowed": {
-        "context": "components/field.html:73:19-59"
+        "context": "components/field.html:77:19-59"
       },
       "email_not_allowed": "Email is not allowed by the server policy",
       "@email_not_allowed": {
-        "context": "components/field.html:77:19-52"
+        "context": "components/field.html:81:19-52"
       },
       "field_required": "This field is required",
       "@field_required": {
@@ -327,7 +327,7 @@
       },
       "password_mismatch": "Password fields don't match",
       "@password_mismatch": {
-        "context": "components/errors.html:13:7-40, components/field.html:84:17-50"
+        "context": "components/errors.html:13:7-40, components/field.html:88:17-50"
       },
       "rate_limit_exceeded": "You've made too many requests in a short period. Please wait a few minutes and try again.",
       "@rate_limit_exceeded": {
@@ -337,10 +337,20 @@
       "@username_all_numeric": {
         "context": "components/field.html:71:19-55"
       },
+      "username_banned": "Username is banned by the server policy",
+      "@username_banned": {
+        "context": "components/field.html:73:19-50",
+        "description": "Error message shown on registration, when the username matches a pattern that is banned by the server policy."
+      },
       "username_invalid_chars": "Username contains invalid characters. Use lowercase letters, numbers, dashes and underscores only.",
       "@username_invalid_chars": {
         "context": "components/field.html:69:19-57"
       },
+      "username_not_allowed": "Username is not allowed by the server policy",
+      "@username_not_allowed": {
+        "context": "components/field.html:75:19-55",
+        "description": "Error message shown on registration, when the username *does not match* any of the patterns that are allowed by the server policy."
+      },
       "username_taken": "This username is already taken",
       "@username_taken": {
         "context": "components/field.html:62:17-47"
@@ -424,7 +434,7 @@
     },
     "or_separator": "Or",
     "@or_separator": {
-      "context": "components/field.html:103:10-31",
+      "context": "components/field.html:107:10-31",
       "description": "Separator between the login methods"
     },
     "policy_violation": {