webrick: Support bcrypt password hashing

This adds a password_hash keyword argument to
WEBrick::HTTPAuth::Htpasswd#initialize.  If set to :bcrypt, it
will create bcrypt hashes instead of crypt hashes, and will
raise an exception if the .htpasswd file uses crypt hashes.

If :bcrypt is used, then instead of calling
BasicAuth.make_passwd (which uses crypt),
WEBrick::HTTPAuth::Htpasswd#set_passwd will set the bcrypt
password directly.  It isn't possible to change the
make_passwd API to accept the password hash format, as that
would break configurations who use Htpasswd#auth_type= to set
a custom auth_type.

This modifies WEBrick::HTTPAuth::BasicAuth to handle checking
both crypt and bcrypt hashes.

There are commented out requires for 'string/crypt', to handle
when String#crypt is deprecated and the undeprecated version is
moved to a gem.

There is also a commented out warning for the case when
the password_hash keyword is not specified and 'string/crypt'
cannot be required.  I think the warning makes sense to nudge
users to using bcrypt.

I've updated the tests to test nil, :crypt, and :bcrypt values
for the password_hash keyword, skipping the bcrypt tests if the
bcrypt library cannot be required.

[ruby-core:88111] [Feature #14940]

From: Jeremy Evans <code@jeremyevans.net>

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64060 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

2 files changed, 45 insertions, 4 deletions

diff --git a/lib/webrick/httpauth/basicauth.rb b/lib/webrick/httpauth/basicauth.rb
index e23420fdfa..751885bc3e 100644
--- a/lib/webrick/httpauth/basicauth.rb
+++ b/lib/webrick/httpauth/basicauth.rb
@@ -24,7 +24,7 @@ module WEBrick
     #
     #   config = { :Realm => 'BasicAuth example realm' }
     #
-    #   htpasswd = WEBrick::HTTPAuth::Htpasswd.new 'my_password_file'
+    #   htpasswd = WEBrick::HTTPAuth::Htpasswd.new 'my_password_file', password_hash: :bcrypt
     #   htpasswd.set_passwd config[:Realm], 'username', 'password'
     #   htpasswd.flush
     #
@@ -81,7 +81,15 @@ module WEBrick
           error("%s: the user is not allowed.", userid)
           challenge(req, res)
         end
-        if password.crypt(encpass) != encpass
+
+        case encpass
+        when /\A\$2[aby]\$/
+          password_matches = BCrypt::Password.new(encpass.sub(/\A\$2[aby]\$/, '$2a$')) == password
+        else
+          password_matches = password.crypt(encpass) == encpass
+        end
+
+        unless password_matches
           error("%s: password unmatch.", userid)
           challenge(req, res)
         end
diff --git a/lib/webrick/httpauth/htpasswd.rb b/lib/webrick/httpauth/htpasswd.rb
index 976eeeb13e..cff18a8012 100644
--- a/lib/webrick/httpauth/htpasswd.rb
+++ b/lib/webrick/httpauth/htpasswd.rb
@@ -35,11 +35,29 @@ module WEBrick
       ##
       # Open a password database at +path+
 
-      def initialize(path)
+      def initialize(path, password_hash: nil)
         @path = path
         @mtime = Time.at(0)
         @passwd = Hash.new
         @auth_type = BasicAuth
+        @password_hash = password_hash
+
+        case @password_hash
+        when nil
+          # begin
+          #   require "string/crypt"
+          # rescue LoadError
+          #   warn("Unable to load string/crypt, proceeding with deprecated use of String#crypt, consider using password_hash: :bcrypt")
+          # end
+          @password_hash = :crypt
+        when :crypt
+          # require "string/crypt"
+        when :bcrypt
+          require "bcrypt"
+        else
+          raise ArgumentError, "only :crypt and :bcrypt are supported for password_hash keyword argument"
+        end
+
         File.open(@path,"a").close unless File.exist?(@path)
         reload
       end
@@ -56,6 +74,14 @@ module WEBrick
               line.chomp!
               case line
               when %r!\A[^:]+:[a-zA-Z0-9./]{13}\z!
+                if @password_hash == :bcrypt
+                  raise StandardError, ".htpasswd file contains crypt password, only bcrypt passwords supported"
+                end
+                user, pass = line.split(":")
+              when %r!\A[^:]+:\$2[aby]\$\d{2}\$.{53}\z!
+                if @password_hash == :crypt
+                  raise StandardError, ".htpasswd file contains bcrypt password, only crypt passwords supported"
+                end
                 user, pass = line.split(":")
               when /:\$/, /:{SHA}/
                 raise NotImplementedError,
@@ -102,7 +128,14 @@ module WEBrick
       # Sets a password in the database for +user+ in +realm+ to +pass+.
 
       def set_passwd(realm, user, pass)
-        @passwd[user] = make_passwd(realm, user, pass)
+        if @password_hash == :bcrypt
+          # Cost of 5 to match Apache default, and because the
+          # bcrypt default of 10 will introduce significant delays
+          # for every request.
+          @passwd[user] = BCrypt::Password.create(pass, :cost=>5)
+        else
+          @passwd[user] = make_passwd(realm, user, pass)
+        end
       end
 
       ##