Sanitize extra blank spaces used when uploading a SSH key

app/models/key.rb

@@ -34,9 +34,8 @@ class Key < ActiveRecord::Base
   after_destroy :refresh_user_cache
 
   def key=(value)
-    value&.delete!("\n\r")
-    value.strip! unless value.blank?
-    write_attribute(:key, value)
+    write_attribute(:key, value.present? ? Gitlab::SSHPublicKey.sanitize(value) : nil)
+
     @public_key = nil
   end
 
@@ -98,7 +97,7 @@ class Key < ActiveRecord::Base
   def generate_fingerprint
     self.fingerprint = nil
 
-    return unless self.key.present?
+    return unless public_key.valid?
 
     self.fingerprint = public_key.fingerprint
   end

changelogs/unreleased/40552-sanitize-extra-blank-spaces-used-when-uploading-a-ssh-key.yml

+---
+title: Sanitize extra blank spaces used when uploading a SSH key
+merge_request: 40552
+author:
+type: fixed

lib/gitlab/ssh_public_key.rb

@@ -21,6 +21,22 @@ module Gitlab
       technology(name)&.supported_sizes
     end
 
+    def self.sanitize(key_content)
+      ssh_type, *parts = key_content.strip.split
+
+      return key_content if parts.empty?
+
+      parts.each_with_object("#{ssh_type} ").with_index do |(part, content), index|
+        content << part
+
+        if Gitlab::SSHPublicKey.new(content).valid?
+          break [content, parts[index + 1]].compact.join(' ') # Add the comment part if present
+        elsif parts.size == index + 1 # return original content if we've reached the last element
+          break key_content
+        end
+      end
+    end
+
     attr_reader :key_text, :key
 
     # Unqualified MD5 fingerprint for compatibility
@@ -37,23 +53,23 @@ module Gitlab
     end
 
     def valid?
-      key.present?
+      key.present? && bits && technology.supported_sizes.include?(bits)
     end
 
     def type
-      technology.name if valid?
+      technology.name if key.present?
     end
 
     def bits
-      return unless valid?
+      return if key.blank?
 
       case type
       when :rsa
-        key.n.num_bits
+        key.n&.num_bits
       when :dsa
-        key.p.num_bits
+        key.p&.num_bits
       when :ecdsa
-        key.group.order.num_bits
+        key.group.order&.num_bits
       when :ed25519
         256
       else

spec/factories/keys.rb

@@ -5,6 +5,10 @@ FactoryBot.define do
     title
     key { Spec::Support::Helpers::KeyGeneratorHelper.new(1024).generate + ' dummy@gitlab.com' }
 
+    factory :key_without_comment do
+      key { Spec::Support::Helpers::KeyGeneratorHelper.new(1024).generate }
+    end
+
     factory :deploy_key, class: 'DeployKey'
 
     factory :personal_key do

spec/lib/gitlab/ssh_public_key_spec.rb

@@ -37,6 +37,41 @@ describe Gitlab::SSHPublicKey, lib: true do
     end
   end
 
+  describe '.sanitize(key_content)' do
+    let(:content) { build(:key).key }
+
+    context 'when key has blank space characters' do
+      it 'removes the extra blank space characters' do
+        unsanitized = content.insert(100, "\n")
+          .insert(40, "\r\n")
+          .insert(30, ' ')
+
+        sanitized = described_class.sanitize(unsanitized)
+        _, body = sanitized.split
+
+        expect(sanitized).not_to eq(unsanitized)
+        expect(body).not_to match(/\s/)
+      end
+    end
+
+    context "when key doesn't have blank space characters" do
+      it "doesn't modify the content" do
+        sanitized = described_class.sanitize(content)
+
+        expect(sanitized).to eq(content)
+      end
+    end
+
+    context "when key is invalid" do
+      it 'returns the original content' do
+        unsanitized = "ssh-foo any content=="
+        sanitized = described_class.sanitize(unsanitized)
+
+        expect(sanitized).to eq(unsanitized)
+      end
+    end
+  end
+
   describe '#valid?' do
     subject { public_key }
 

spec/models/key_spec.rb

@@ -79,15 +79,52 @@ describe Key, :mailer do
       expect(build(:key)).to be_valid
     end
 
-    it 'accepts a key with newline charecters after stripping them' do
-      key = build(:key)
-      key.key = key.key.insert(100, "\n")
-      key.key = key.key.insert(40, "\r\n")
+    it 'rejects the unfingerprintable key (not a key)' do
+      expect(build(:key, key: 'ssh-rsa an-invalid-key==')).not_to be_valid
+    end
+
+    where(:factory, :chars, :expected_sections) do
+      [
+        [:key,                 ["\n", "\r\n"], 3],
+        [:key,                 [' ', ' '],     3],
+        [:key_without_comment, [' ', ' '],     2]
+      ]
+    end
+
+    with_them do
+      let!(:key) { create(factory) }
+      let!(:original_fingerprint) { key.fingerprint }
+
+      it 'accepts a key with blank space characters after stripping them' do
+        modified_key = key.key.insert(100, chars.first).insert(40, chars.last)
+        _, content = modified_key.split
+
+        key.update!(key: modified_key)
+
         expect(key).to be_valid
+        expect(key.key.split.size).to eq(expected_sections)
+
+        expect(content).not_to match(/\s/)
+        expect(original_fingerprint).to eq(key.fingerprint)
+      end
+    end
   end
 
-    it 'rejects the unfingerprintable key (not a key)' do
-      expect(build(:key, key: 'ssh-rsa an-invalid-key==')).not_to be_valid
+  context 'validate size' do
+    where(:key_content, :result) do
+      [
+        [Spec::Support::Helpers::KeyGeneratorHelper.new(512).generate,  false],
+        [Spec::Support::Helpers::KeyGeneratorHelper.new(8192).generate, false],
+        [Spec::Support::Helpers::KeyGeneratorHelper.new(1024).generate, true]
+      ]
+    end
+
+    with_them do
+      it 'validates the size of the key' do
+        key = build(:key, key: key_content)
+
+        expect(key.valid?).to eq(result)
+      end
     end
   end