✨ Add trace stringprep profile for ANONYMOUS SASL

Author: nevans

lib/net/imap/stringprep.rb

@@ -11,6 +11,7 @@ class IMAP < Protocol
     module StringPrep
       autoload :SASLprep, File.expand_path("stringprep/saslprep", __dir__)
       autoload :Tables,   File.expand_path("stringprep/tables",   __dir__)
+      autoload :Trace,    File.expand_path("stringprep/trace",    __dir__)
 
       # ArgumentError raised when +string+ is invalid for the stringprep
       # +profile+.

lib/net/imap/stringprep/trace.rb

@@ -0,0 +1,85 @@
+# frozen_string_literal: true
+
+module Net
+  class IMAP
+    module StringPrep
+
+      # Defined in RFC-4505[https://tools.ietf.org/html/rfc4505] §3, The +trace+
+      # profile of \StringPrep is used by the +ANONYMOUS+ \SASL mechanism.
+      module Trace
+
+        # Defined in RFC-4505[https://tools.ietf.org/html/rfc4505] §3.
+        STRINGPREP_PROFILE = "trace"
+
+        # >>>
+        #   The character repertoire of this profile is Unicode 3.2 [Unicode].
+        UNASSIGNED_TABLE = "A.1"
+
+        # >>>
+        #   No mapping is required by this profile.
+        MAPPING_TABLES = nil
+
+        # >>>
+        #   No Unicode normalization is required by this profile.
+        NORMALIZATION = nil
+
+        # From RFC-4505[https://tools.ietf.org/html/rfc4505] §3, The "trace"
+        # Profile of "Stringprep":
+        # >>>
+        #   Characters from the following tables of [StringPrep] are prohibited:
+        #
+        #   - C.2.1 (ASCII control characters)
+        #   - C.2.2 (Non-ASCII control characters)
+        #   - C.3 (Private use characters)
+        #   - C.4 (Non-character code points)
+        #   - C.5 (Surrogate codes)
+        #   - C.6 (Inappropriate for plain text)
+        #   - C.8 (Change display properties are deprecated)
+        #   - C.9 (Tagging characters)
+        #
+        #   No additional characters are prohibited.
+        PROHIBITED_TABLES = %w[C.2.1 C.2.2 C.3 C.4 C.5 C.6 C.8 C.9].freeze
+
+        # >>>
+        #   This profile requires bidirectional character checking per Section 6
+        #   of [StringPrep].
+        CHECK_BIDI = true
+
+        module_function
+
+        # From RFC-4505[https://tools.ietf.org/html/rfc4505] §3, The "trace"
+        # Profile of "Stringprep":
+        # >>>
+        #   The character repertoire of this profile is Unicode 3.2 [Unicode].
+        #
+        #   No mapping is required by this profile.
+        #
+        #   No Unicode normalization is required by this profile.
+        #
+        #   The list of unassigned code points for this profile is that provided
+        #   in Appendix A of [StringPrep].  Unassigned code points are not
+        #   prohibited.
+        #
+        #   Characters from the following tables of [StringPrep] are prohibited:
+        #   (documented on PROHIBITED_TABLES)
+        #
+        #   This profile requires bidirectional character checking per Section 6
+        #   of [StringPrep].
+        def stringprep_trace(string, **opts)
+          StringPrep.stringprep(
+            string,
+            unassigned:    UNASSIGNED_TABLE,
+            maps:          MAPPING_TABLES,
+            prohibited:    PROHIBITED_TABLES,
+            normalization: NORMALIZATION,
+            bidi:          CHECK_BIDI,
+            profile:       STRINGPREP_PROFILE,
+            **opts,
+          )
+        end
+
+      end
+
+    end
+  end
+end

test/net/imap/test_stringprep_profiles.rb

@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+require "net/imap"
+require "net/imap/sasl/stringprep"
+require "test/unit"
+
+class StringPrepProfilesTest < Test::Unit::TestCase
+  include Net::IMAP::StringPrep
+  include Net::IMAP::StringPrep::Trace
+
+  def test_trace_profile_prohibit_ctrl_chars
+    assert_raise(ProhibitedCodepoint) {
+      stringprep_trace("no\ncontrol\rchars")
+    }
+  end
+
+  def test_trace_profile_prohibit_tagging_chars
+    assert_raise(ProhibitedCodepoint) {
+      stringprep_trace("regional flags use tagging chars: e.g." \
+                       "🏴󠁧󠁢󠁥󠁮󠁧󠁿 England, " \
+                       "🏴󠁧󠁢󠁳󠁣󠁴󠁿 Scotland, " \
+                       "🏴󠁧󠁢󠁷󠁬󠁳󠁿 Wales.")
+    }
+  end
+
+end