From 6550b3f3547735dffb3e8d437c5d622e97cfdf75 Mon Sep 17 00:00:00 2001
From: Philippe Pittoli <karchnu@karchnu.fr>
Date: Sun, 27 Apr 2025 17:41:11 +0200
Subject: [PATCH] Enable domain wildcards.

---
 src/GenericParser/DomainParser.purs        | 13 ++++++++++++-
 src/GenericParser/DomainParserRFC1035.purs | 13 ++++++++++++-
 test/TestValues.purs                       |  1 +
 3 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/src/GenericParser/DomainParser.purs b/src/GenericParser/DomainParser.purs
index 9333bae..3b17f47 100644
--- a/src/GenericParser/DomainParser.purs
+++ b/src/GenericParser/DomainParser.purs
@@ -73,10 +73,21 @@ sub_eof = do
 
 -- | From RFC 1035: <domain> ::= <subdomain> | " "
 -- |
+-- | Since RFC 1034 requires to accept '*' as leftmost domain label, the rule should be:
+-- | <domain> ::= <subdomain> | "*." <subdomain> | " "
+-- |
 -- | Accepting an optional '.' at the end of the subdomain doesn't conform
 -- | to the (prefered) syntax of a domain as described in RFC 1035.
 -- | However, this last '.' character should be acceptable in most applications.
 -- | In some cases, a fully qualified domain name (FQDN) such as `example.com.`
 -- | has to be differenciated from a "relative" name (www).
+-- |
+-- | For documentation about wildcards, see RFC 4592.
 domain :: Parser DomainError String
-domain = (string " " *> eof) <|> sub_eof
+domain = (string " " *> eof) <|> wildcard <|> sub_eof
+  where
+    wildcard :: Parser DomainError String
+    wildcard = do
+      _ <- string "*."
+      rest <- sub_eof
+      pure $ "*." <> rest
diff --git a/src/GenericParser/DomainParserRFC1035.purs b/src/GenericParser/DomainParserRFC1035.purs
index f3f29a0..5556902 100644
--- a/src/GenericParser/DomainParserRFC1035.purs
+++ b/src/GenericParser/DomainParserRFC1035.purs
@@ -79,10 +79,21 @@ sub_eof = do
 
 -- | From RFC 1035: <domain> ::= <subdomain> | " "
 -- |
+-- | Since RFC 1034 requires to accept '*' as leftmost domain label, the rule should be:
+-- | <domain> ::= <subdomain> | "*." <subdomain> | " "
+-- |
 -- | Accepting an optional '.' at the end of the subdomain doesn't conform
 -- | to the (prefered) syntax of a domain as described in RFC 1035.
 -- | However, this last '.' character should be acceptable in most applications.
 -- | In some cases, a fully qualified domain name (FQDN) such as `example.com.`
 -- | has to be differenciated from a "relative" name (www).
+-- |
+-- | For documentation about wildcards, see RFC 4592.
 domain :: Parser DomainError String
-domain = (string " " *> eof) <|> sub_eof
+domain = (string " " *> eof) <|> wildcard <|> sub_eof
+  where
+    wildcard :: Parser DomainError String
+    wildcard = do
+      _ <- string "*."
+      rest <- sub_eof
+      pure $ "*." <> rest
diff --git a/test/TestValues.purs b/test/TestValues.purs
index 029d397..87a26da 100644
--- a/test/TestValues.purs
+++ b/test/TestValues.purs
@@ -15,6 +15,7 @@ domains
     , "xblah.a2.org"
     , "xblah.a33.org"
     , "_dmarc.example.com"
+    , "*.example.com"
     ]
 
 ipv4_addresses :: Array String