Linzer

Linzer is a Ruby library for HTTP Message Signatures (RFC 9421).

Install

Add the following line to your Gemfile:

gem "linzer"

Or just gem install linzer.

Usage

To sign a HTTP message:

key = Linzer.generate_ed25519_key
# => #<Linzer::Ed25519::Key:0x00000fe13e9bd208

headers = {
  "date" => "Fri, 23 Feb 2024 17:57:23 GMT",
  "x-custom-header" => "foo"
}

request = Linzer.new_request(:post, "/some_uri", {}, headers)
# => #<Rack::Request:0x0000000104c1c8c0
#       @env={"HTTP_DATE"=>"Fri, 23 Feb 2024 17:57:23 GMT", "HTTP_X_CUSTOM..."
#       @params=nil>

message = Linzer::Message.new(request)
# => #<Linzer::Message:0x0000000104afa960
#       @operation=#<Rack::Request:0x00000001049754a0
#       @env={"HTTP_DATE"=>"Fri, 23 Feb 2024 17:57:23 GMT", "HTTP_X_CUSTOM..."
#       @params=nil>>

fields = %w[date x-custom-header @method @path]

signature = Linzer.sign(key, message, fields)
# => #<Linzer::Signature:0x0000000111f77ad0 ...

pp signature.to_h
# => {"signature"=>"sig1=:Cv1TUCxUpX+5SVa7pH0Xh...",
#  "signature-input"=>"sig1=(\"date\" \"x-custom-header\" ..."}

Use the message signature with any HTTP client:

require "net/http"

http = Net::HTTP.new("localhost", 9292)
http.set_debug_output($stderr)
response = http.post("/some_uri", "data", headers.merge(signature.to_h))
# opening connection to localhost:9292...
# opened
# <- "POST /some_uri HTTP/1.1\r\n
# <- Date: Fri, 23 Feb 2024 17:57:23 GMT\r\n
# <- X-Custom-Header: foo\r\n
# <- Signature: sig1=:Cv1TUCxUpX+5SVa7pH0X...
# <- Signature-Input: sig1=(\"date\" \"x-custom-header\" \"@method\"...
# <- Accept-Encoding: gzip;q=1.0,deflate;q=0.6,identity;q=0.3\r\n
# <- Accept: */*\r\n
# <- User-Agent: Ruby\r\n
# <- Connection: close\r\n
# <- Host: localhost:9292
# <- Content-Length: 4\r\n
# <- Content-Type: application/x-www-form-urlencoded\r\n\r\n"
# <- "data"
#
# -> "HTTP/1.1 200 OK\r\n"
# -> "Content-Type: text/html;charset=utf-8\r\n"
# -> "Content-Length: 0\r\n"
# -> "X-Xss-Protection: 1; mode=block\r\n"
# -> "X-Content-Type-Options: nosniff\r\n"
# -> "X-Frame-Options: SAMEORIGIN\r\n"
# -> "Server: WEBrick/1.8.1 (Ruby/3.2.0/2022-12-25)\r\n"
# -> "Date: Thu, 28 Mar 2024 17:19:21 GMT\r\n"
# -> "Connection: close\r\n"
# -> "\r\n"
# reading 0 bytes...
# -> ""
# read 0 bytes
# Conn close
# => #<Net::HTTPOK 200 OK readbody=true>

To verify a valid signature:

test_ed25519_key_pub = key.material.public_to_pem
# => "-----BEGIN PUBLIC KEY-----\nMCowBQYDK2VwAyEAK1ZrC4JqC356pRsUiLVJdFZ3dAjo909VfWs1li33MCQ=\n-----END PUBLIC KEY-----\n"

pubkey = Linzer.new_ed25519_public_key(test_ed25519_key_pub, "some-key-ed25519")
# => #<Linzer::Ed25519::Key:0x00000fe19b9384b0

# if you have to, there is a helper method to build a request object on the server side
# although any standard Ruby web server or framework (Sinatra, Rails, etc) should expose
# a request object and this should not be required for most cases.
#
# request = Linzer.new_request(:post, "/some_uri", {}, headers)

message = Linzer::Message.new(request)

signature = Linzer::Signature.build(message.headers)

Linzer.verify(pubkey, message, signature)
# => true

What if an invalid signature if verified?

result = Linzer.verify(pubkey, message, signature)
lib/linzer/verifier.rb:38:in `verify_or_fail': Failed to verify message: Invalid signature. (Linzer::Error)

HTTP responses are also supported

HTTP responses can also be signed and verified in the same way as requests.

headers = {
  "date" => "Sat, 30 Mar 2024 21:40:13 GMT",
  "x-response-custom" => "bar"
}

response = Linzer.new_response("request body", 200, headers)
# or just use the response object exposed by your HTTP framework

message = Linzer::Message.new(response)
fields  = %w[@status date x-response-custom]

signature = Linzer.sign(key, message, fields)

pp signature.to_h
# => {"signature"=>
#   "sig1=:tCldwXqbISktyABrmbhszo...",
#  "signature-input"=>"sig1=(\"@status\" \"date\" ..."}

For now, to consult additional details just take a look at source code and/or the unit tests.

Please note that is still early days and extensive testing is still ongoing. For now only the following algorithms are supported: RSASSA-PSS using SHA-512, HMAC-SHA256, Ed25519 and ECDSA (P-256 and P-384 curves).

I'll be expanding the library to cover more functionality specified in the RFC in subsequent releases.

Ruby version compatibility

linzer is built in Continuous Integration on Ruby 3.0+.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/nomadium/linzer. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the Linzer project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.