Add support for ecdsa ssh keys

lib/vagrant.rb

@@ -5,6 +5,7 @@
 
 # Add patches to log4r to support trace level
 require "vagrant/patches/log4r"
+require "vagrant/patches/net-ssh"
 # Set our log levels and include trace
 require 'log4r/configurator'
 Log4r::Configurator.custom_levels(*(["TRACE"] + Log4r::Log4rConfig::LogLevels))

lib/vagrant/errors.rb

@@ -863,6 +863,10 @@ class SSHKeyTypeNotSupported < VagrantError
       error_key(:ssh_key_type_not_supported)
     end
 
+    class SSHKeyTypeNotSupportedByServer < VagrantError
+      error_key(:ssh_key_type_not_supported_by_server)
+    end
+
     class SSHNoExitStatus < VagrantError
       error_key(:ssh_no_exit_status)
     end

lib/vagrant/patches/net-ssh.rb

@@ -0,0 +1,76 @@
+# Copyright (c) HashiCorp, Inc.
+# SPDX-License-Identifier: BUSL-1.1
+
+require "net/ssh"
+require "net/ssh/buffer"
+
+# Set the version requirement for when net-ssh should be patched
+NET_SSH_PATCH_REQUIREMENT = Gem::Requirement.new(">= 7.0.0", "< 7.2.2")
+
+# This patch provides support for properly loading ECDSA private keys
+if NET_SSH_PATCH_REQUIREMENT.satisfied_by?(Gem::Version.new(Net::SSH::Version::STRING))
+  Net::SSH::Buffer.class_eval do
+    def vagrant_read_private_keyblob(type)
+      case type
+      when /^ecdsa\-sha2\-(\w*)$/
+        curve_name_in_type = $1
+        curve_name_in_key = read_string
+
+        unless curve_name_in_type == curve_name_in_key
+          raise Net::SSH::Exception, "curve name mismatched (`#{curve_name_in_key}' with `#{curve_name_in_type}')"
+        end
+
+        public_key_oct = read_string
+        priv_key_bignum = read_bignum
+        begin
+          curvename = OpenSSL::PKey::EC::CurveNameAlias[curve_name_in_key]
+          group = OpenSSL::PKey::EC::Group.new(curvename)
+          point = OpenSSL::PKey::EC::Point.new(group, OpenSSL::BN.new(public_key_oct, 2))
+          priv_bn = OpenSSL::BN.new(priv_key_bignum, 2)
+          asn1 = OpenSSL::ASN1::Sequence(
+            [
+              OpenSSL::ASN1::Integer.new(OpenSSL::BN.new(0)),
+              OpenSSL::ASN1::Sequence.new(
+                [
+                  OpenSSL::ASN1::ObjectId("id-ecPublicKey"),
+                  OpenSSL::ASN1::ObjectId(curvename)
+                ]
+              ),
+              OpenSSL::ASN1::OctetString.new(
+                OpenSSL::ASN1::Sequence.new(
+                  [
+                    OpenSSL::ASN1::Integer.new(OpenSSL::BN.new(1)),
+                    OpenSSL::ASN1::OctetString.new(priv_bn.to_s(2)),
+                    OpenSSL::ASN1::ASN1Data.new(
+                      [
+                        OpenSSL::ASN1::BitString.new(point.to_octet_string(:uncompressed)),
+                      ], 1, :CONTEXT_SPECIFIC,
+                    )
+                  ]
+                ).to_der
+              )
+            ]
+          )
+
+          key = OpenSSL::PKey::EC.new(asn1.to_der)
+
+          return key
+        rescue OpenSSL::PKey::ECError
+          raise NotImplementedError, "unsupported key type `#{type}'"
+        end
+      else
+        netssh_read_private_keyblob(type)
+      end
+    end
+
+    alias_method :netssh_read_private_keyblob, :read_private_keyblob
+    alias_method :read_private_keyblob, :vagrant_read_private_keyblob
+  end
+
+  OpenSSL::PKey::EC::Point.class_eval do
+    include Net::SSH::Authentication::PubKeyFingerprint
+    def to_pem
+      "#{ssh_type} #{self.to_bn.to_s(2)}"
+    end
+  end
+end

lib/vagrant/util.rb

@@ -36,7 +36,7 @@ module Remote
     autoload :IO,                        'vagrant/util/io'
     autoload :IPV4Interfaces,            'vagrant/util/ipv4_interfaces'
     autoload :IsPortOpen,                'vagrant/util/is_port_open'
-    autoload :KeyPair,                   'vagrant/util/key_pair'
+    autoload :Keypair,                   'vagrant/util/keypair'
     autoload :LineBuffer,                'vagrant/util/line_buffer'
     autoload :LineEndingHelpers,         'vagrant/util/line_ending_helpers'
     autoload :LoggingFormatter,          'vagrant/util/logging_formatter'

lib/vagrant/util/keypair.rb

@@ -10,15 +10,43 @@
 module Vagrant
   module Util
     class Keypair
+      # Magic string header
+      AUTH_MAGIC = "openssh-key-v1".freeze
+      # Header of private key file content
+      PRIVATE_KEY_START = "-----BEGIN OPENSSH PRIVATE KEY-----\n".freeze
+      # Footer of private key file content
+      PRIVATE_KEY_END = "-----END OPENSSH PRIVATE KEY-----\n".freeze
+
+      # Check if provided key is a supported key type
+      #
+      # @param [Symbol] key Key type to check
+      # @return [Boolean] key type is supported
+      def self.valid_type?(key)
+        VALID_TYPES.keys.include?(key)
+      end
+
+      # @return [Array<Symbol>] list of supported key types
+      def self.available_types
+        PREFER_KEY_TYPES.values
+      end
+
+      # Create a new keypair
+      #
+      # @param [String] password Password for the key or nil for no password (only supported for rsa type)
+      # @param [Symbol] type Key type to generate
+      # @return [Array<String, String, String>] Public key, openssh private key, openssh public key with comment
+      def self.create(password=nil, type: :rsa)
+        if !VALID_TYPES.key?(type)
+          raise ArgumentError,
+                "Invalid key type requested (supported types: #{available_types.map(&:inspect).join(", ")})"
+        end
+
+        VALID_TYPES[type].create(password)
+      end
+
       class Ed25519
-        # Magic string header
-        AUTH_MAGIC = "openssh-key-v1".freeze
         # Key type identifier
         KEY_TYPE = "ssh-ed25519".freeze
-        # Header of private key file content
-        PRIVATE_KEY_START = "-----BEGIN OPENSSH PRIVATE KEY-----\n".freeze
-        # Footer of private key file content
-        PRIVATE_KEY_END = "-----END OPENSSH PRIVATE KEY-----\n".freeze
 
         # Encodes given string
         #
@@ -95,6 +123,9 @@ def self.create(password=nil)
       class Rsa
         extend Retryable
 
+        # Key type identifier
+        KEY_TYPE = "ssh-rsa"
+
         # Creates an SSH keypair and returns it.
         #
         # @param [String] password Password for the key, or nil for no password.
@@ -140,19 +171,123 @@ def self.create(password=nil)
         end
       end
 
-      # Supported key types.
-      VALID_TYPES = {ed25519: Ed25519, rsa: Rsa}.freeze
-      # Ordered mapping of openssh key type name to lookup name
-      PREFER_KEY_TYPES = {"ssh-ed25519".freeze => :ed25519, "ssh-rsa".freeze => :rsa}.freeze
+      # Base class for Ecdsa type keys to subclass
+      class Ecdsa
+        # Encodes given string
+        #
+        # @param [String] s String to encode
+        # @return [String]
+        def self.string(s)
+          [s.length].pack("N") + s
+        end
 
-      def self.create(password=nil, type: :rsa)
-        if !VALID_TYPES.key?(type)
-          raise ArgumentError,
-                "Invalid key type requested (supported types: #{VALID_TYPES.keys.map(&:inspect)})"
+        # Encodes given string with padding to block size
+        #
+        # @param [String] s String to encode
+        # @param [Integer] blocksize Defined block size
+        # @return [String]
+        def self.padded_string(s, blocksize)
+          pad = blocksize - (s.length % blocksize)
+          string(s + Array(1..pad).pack("c*"))
         end
 
-        VALID_TYPES[type].create(password)
+        # Creates an ed25519 SSH key pair
+        # @return [Array<String, String, String>] Public key, openssh private key, openssh public key with comment
+        # @note Password support was not included as it's not actively used anywhere. If it ends up being
+        # something that's needed, it can be revisited
+        def self.create(password=nil)
+          if password
+            raise NotImplementedError,
+                  "Ecdsa key pair generation does not support passwords"
+          end
+
+          # Generate the key
+          base_key = OpenSSL::PKey::EC.generate(self.const_get(:OPENSSL_CURVE))
+          # Define the comment used for the key
+          comment = "vagrant"
+
+          # Grab the raw public key
+          public_key = base_key.public_key.to_bn.to_s(2)
+          # Encode the public key for use building the openssh private key
+          encoded_public_key = string(self.const_get(:KEY_TYPE)) + string(self.const_get(:OPENSSH_CURVE)) + string(public_key)
+          # Format the public key into the openssh public key format for writing
+          openssh_public_key = "#{self.const_get(:KEY_TYPE)} #{Base64.encode64(encoded_public_key).gsub("\n", "")} #{comment}"
+
+          pk_value = base_key.private_key.to_s(2)
+          # Pad the start of the key if required
+          if pk_value.length % 8 == 0
+            pk_value = "\0#{pk_value}"
+          end
+
+          # Agent encoded private key is used when building the openssh private key
+          # (https://datatracker.ietf.org/doc/html/draft-miller-ssh-agent#section-4.2.3)
+          # (https://dnaeon.github.io/openssh-private-key-binary-format/)
+          agent_private_key = [
+            ([SecureRandom.random_number((2**32)-1)] * 2).pack("NN"), # checkint, random uint32 value, twice (used for encryption verification)
+            encoded_public_key, # includes the key type and public key
+            string(pk_value), # private key
+            string(comment), # comment for the key
+          ].join
+
+          # Build openssh private key data (https://github.com/openssh/openssh-portable/blob/master/PROTOCOL.key)
+          private_key = [
+            AUTH_MAGIC + "\0", # Magic string
+            string("none"), # cipher name, no encryption, so none
+            string("none"), # kdf name, no encryption, so none
+            string(""), # kdf options/data, no encryption, so empty string
+            [1].pack("N"), # Number of keys (just one)
+            string(encoded_public_key), # The public key
+            padded_string(agent_private_key, 8) # Private key encoded with agent rules, padded for 8 byte block size
+          ].join
+
+          # Create the openssh private key content
+          openssh_private_key = [
+            PRIVATE_KEY_START,
+            Base64.encode64(private_key),
+            PRIVATE_KEY_END,
+          ].join
+
+          return [public_key, openssh_private_key, openssh_public_key]
+        end
+      end
+
+      class Ecdsa256 < Ecdsa
+        KEY_TYPE = "ecdsa-sha2-nistp256".freeze
+        OPENSSH_CURVE = "nistp256".freeze
+        OPENSSL_CURVE = "prime256v1".freeze
+      end
+
+      class Ecdsa384 < Ecdsa
+        KEY_TYPE = "ecdsa-sha2-nistp384".freeze
+        OPENSSH_CURVE = "nistp384".freeze
+        OPENSSL_CURVE = "secp384r1".freeze
       end
+
+      class Ecdsa521 < Ecdsa
+        KEY_TYPE = "ecdsa-sha2-nistp521".freeze
+        OPENSSH_CURVE = "nistp521".freeze
+        OPENSSL_CURVE = "secp521r1".freeze
+      end
+
+      # Supported key types.
+      VALID_TYPES = {
+        ecdsa256: Ecdsa256,
+        ecdsa384: Ecdsa384,
+        ecdsa521: Ecdsa521,
+        ed25519: Ed25519,
+        rsa: Rsa
+      }.freeze
+
+      # Ordered mapping of openssh key type name to lookup name. The
+      # order defined here is based on preference. Note that ecdsa
+      # ordering is based on performance
+      PREFER_KEY_TYPES = {
+        Ed25519::KEY_TYPE => :ed25519,
+        Ecdsa256::KEY_TYPE => :ecdsa256,
+        Ecdsa521::KEY_TYPE => :ecdsa521,
+        Ecdsa384::KEY_TYPE => :ecdsa384,
+        Rsa::KEY_TYPE => :rsa,
+      }.freeze
     end
   end
 end