diff --git a/.rubocop.yml b/.rubocop.yml
index c5aa833..be9600f 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -17,6 +17,9 @@
   Exclude:
     - 'spec/**/*'
 
+Metrics/ParameterLists:
+  MaxOptionalParameters: 4
+
 Style/Documentation:
   Enabled: false
 
diff --git a/lib/gitlab/client/groups.rb b/lib/gitlab/client/groups.rb
index 4c08b30..63afb1a 100644
--- a/lib/gitlab/client/groups.rb
+++ b/lib/gitlab/client/groups.rb
@@ -270,5 +270,55 @@
     def delete_ldap_group_links(id, commonname, provider)
       delete("/groups/#{url_encode id}/ldap_group_links/#{url_encode provider}/#{url_encode commonname}")
     end
+
+    # Gets group custom_attributes.
+    #
+    # @example
+    #   Gitlab.group_custom_attributes(2)
+    #
+    # @param  [Integer] group_id The ID of a group.
+    # @return [Gitlab::ObjectifiedHash]
+    def group_custom_attributes(group_id)
+      get("/groups/#{group_id}/custom_attributes")
+    end
+
+    # Gets single group custom_attribute.
+    #
+    # @example
+    #   Gitlab.group_custom_attribute('key', 2)
+    #
+    # @param  [String] key The custom_attributes key
+    # @param  [Integer] group_id The ID of a group.
+    # @return [Gitlab::ObjectifiedHash]
+    def group_custom_attribute(key, group_id)
+      get("/groups/#{group_id}/custom_attributes/#{key}")
+    end
+
+    # Creates a new custom_attribute
+    #
+    # @example
+    #   Gitlab.add_custom_attribute('some_new_key', 'some_new_value', 2)
+    #
+    # @param  [String] key The custom_attributes key
+    # @param  [String] value The custom_attributes value
+    # @param  [Integer] group_id The ID of a group.
+    # @return [Gitlab::ObjectifiedHash]
+    def add_group_custom_attribute(key, value, group_id)
+      url = "/groups/#{group_id}/custom_attributes/#{key}"
+      put(url, body: { value: value })
+    end
+
+    # Delete custom_attribute
+    # Will delete a custom_attribute
+    #
+    # @example
+    #   Gitlab.delete_group_custom_attribute('somekey', 2)
+    #
+    # @param  [String] key The custom_attribute key to delete
+    # @param  [Integer] group_id The ID of a group.
+    # @return [Boolean]
+    def delete_group_custom_attribute(key, group_id = nil)
+      delete("/groups/#{group_id}/custom_attributes/#{key}")
+    end
   end
 end
diff --git a/lib/gitlab/client/keys.rb b/lib/gitlab/client/keys.rb
index cbba34f..e3384d8 100644
--- a/lib/gitlab/client/keys.rb
+++ b/lib/gitlab/client/keys.rb
@@ -14,5 +14,16 @@
     def key(id)
       get("/keys/#{id}")
     end
+
+    # Gets information about a key by key fingerprint.
+    #
+    # @example
+    #   Gitlab.key_by_fingerprint("9f:70:33:b3:50:4d:9a:a3:ef:ea:13:9b:87:0f:7f:7e")
+    #
+    # @param  [String] fingerprint The Fingerprint of a key.
+    # @return [Gitlab::ObjectifiedHash]
+    def key_by_fingerprint(fingerprint)
+      get('/keys', query: { fingerprint: fingerprint })
+    end
   end
 end
diff --git a/lib/gitlab/client/projects.rb b/lib/gitlab/client/projects.rb
index 400f75e..b51f59d 100644
--- a/lib/gitlab/client/projects.rb
+++ b/lib/gitlab/client/projects.rb
@@ -640,5 +640,55 @@
     def unarchive_project(id)
       post("/projects/#{url_encode id}/unarchive")
     end
+
+    # Gets project custom_attributes.
+    #
+    # @example
+    #   Gitlab.project_custom_attributes(2)
+    #
+    # @param  [Integer] project_id The ID of a project.
+    # @return [Gitlab::ObjectifiedHash]
+    def project_custom_attributes(project_id)
+      get("/projects/#{project_id}/custom_attributes")
+    end
+
+    # Gets single project custom_attribute.
+    #
+    # @example
+    #   Gitlab.project_custom_attribute(key, 2)
+    #
+    # @param  [String] key The custom_attributes key
+    # @param  [Integer] project_id The ID of a project.
+    # @return [Gitlab::ObjectifiedHash]
+    def project_custom_attribute(key, project_id)
+      get("/projects/#{project_id}/custom_attributes/#{key}")
+    end
+
+    # Creates a new custom_attribute
+    #
+    # @example
+    #   Gitlab.add_custom_attribute('some_new_key', 'some_new_value', 2)
+    #
+    # @param  [String] key The custom_attributes key
+    # @param  [String] value The custom_attributes value
+    # @param  [Integer] project_id The ID of a project.
+    # @return [Gitlab::ObjectifiedHash]
+    def add_project_custom_attribute(key, value, project_id)
+      url = "/projects/#{project_id}/custom_attributes/#{key}"
+      put(url, body: { value: value })
+    end
+
+    # Delete custom_attribute
+    # Will delete a custom_attribute
+    #
+    # @example
+    #   Gitlab.delete_project_custom_attribute('somekey', 2)
+    #
+    # @param  [String] key The custom_attribute key to delete
+    # @param  [Integer] project_id The ID of a project.
+    # @return [Boolean]
+    def delete_project_custom_attribute(key, project_id = nil)
+      delete("/projects/#{project_id}/custom_attributes/#{key}")
+    end
   end
 end
diff --git a/lib/gitlab/client/users.rb b/lib/gitlab/client/users.rb
index 696aaa9..500a014 100644
--- a/lib/gitlab/client/users.rb
+++ b/lib/gitlab/client/users.rb
@@ -279,5 +279,55 @@
       options[:search] = search
       get('/users', query: options)
     end
+
+    # Gets user custom_attributes.
+    #
+    # @example
+    #   Gitlab.user_custom_attributes(2)
+    #
+    # @param  [Integer] user_id The ID of a user.
+    # @return [Gitlab::ObjectifiedHash]
+    def user_custom_attributes(user_id)
+      get("/users/#{user_id}/custom_attributes")
+    end
+
+    # Gets single user custom_attribute.
+    #
+    # @example
+    #   Gitlab.user_custom_attribute(key, 2)
+    #
+    # @param  [String] key The custom_attributes key
+    # @param  [Integer] user_id The ID of a user.
+    # @return [Gitlab::ObjectifiedHash]
+    def user_custom_attribute(key, user_id)
+      get("/users/#{user_id}/custom_attributes/#{key}")
+    end
+
+    # Creates a new custom_attribute
+    #
+    # @example
+    #   Gitlab.add_custom_attribute('some_new_key', 'some_new_value', 2)
+    #
+    # @param  [String] key The custom_attributes key
+    # @param  [String] value The custom_attributes value
+    # @param  [Integer] user_id The ID of a user.
+    # @return [Gitlab::ObjectifiedHash]
+    def add_user_custom_attribute(key, value, user_id)
+      url = "/users/#{user_id}/custom_attributes/#{key}"
+      put(url, body: { value: value })
+    end
+
+    # Delete custom_attribute
+    # Will delete a custom_attribute
+    #
+    # @example
+    #   Gitlab.delete_user_custom_attribute('somekey', 2)
+    #
+    # @param  [String] key The custom_attribute key to delete
+    # @param  [Integer] user_id The ID of a user.
+    # @return [Boolean]
+    def delete_user_custom_attribute(key, user_id)
+      delete("/users/#{user_id}/custom_attributes/#{key}")
+    end
   end
 end
diff --git a/spec/fixtures/group_custom_attribute.json b/spec/fixtures/group_custom_attribute.json
new file mode 100644
index 0000000..71f3d98
--- /dev/null
+++ b/spec/fixtures/group_custom_attribute.json
@@ -0,0 +1 @@
+{"key":"some_new_key","value":"some_new_value"}
diff --git a/spec/fixtures/group_custom_attributes.json b/spec/fixtures/group_custom_attributes.json
new file mode 100644
index 0000000..c26f1c7
--- /dev/null
+++ b/spec/fixtures/group_custom_attributes.json
@@ -0,0 +1 @@
+[{"key":"somekey","value":"somevalue"},{"key":"somekey2","value":"somevalue2"}]
diff --git a/spec/fixtures/project_custom_attribute.json b/spec/fixtures/project_custom_attribute.json
new file mode 100644
index 0000000..71f3d98
--- /dev/null
+++ b/spec/fixtures/project_custom_attribute.json
@@ -0,0 +1 @@
+{"key":"some_new_key","value":"some_new_value"}
diff --git a/spec/fixtures/project_custom_attributes.json b/spec/fixtures/project_custom_attributes.json
new file mode 100644
index 0000000..c26f1c7
--- /dev/null
+++ b/spec/fixtures/project_custom_attributes.json
@@ -0,0 +1 @@
+[{"key":"somekey","value":"somevalue"},{"key":"somekey2","value":"somevalue2"}]
diff --git a/spec/fixtures/user_custom_attribute.json b/spec/fixtures/user_custom_attribute.json
new file mode 100644
index 0000000..71f3d98
--- /dev/null
+++ b/spec/fixtures/user_custom_attribute.json
@@ -0,0 +1 @@
+{"key":"some_new_key","value":"some_new_value"}
diff --git a/spec/fixtures/user_custom_attributes.json b/spec/fixtures/user_custom_attributes.json
new file mode 100644
index 0000000..c26f1c7
--- /dev/null
+++ b/spec/fixtures/user_custom_attributes.json
@@ -0,0 +1 @@
+[{"key":"somekey","value":"somevalue"},{"key":"somekey2","value":"somevalue2"}]
diff --git a/spec/gitlab/client/groups_spec.rb b/spec/gitlab/client/groups_spec.rb
index 69a7e9b..95c2fde 100644
--- a/spec/gitlab/client/groups_spec.rb
+++ b/spec/gitlab/client/groups_spec.rb
@@ -345,4 +345,73 @@
       expect(a_delete('/groups/1/ldap_group_links/ldap/all')).to have_been_made
     end
   end
+
+  describe '.group_custom_attributes' do
+    before do
+      stub_get('/groups/2/custom_attributes', 'group_custom_attributes')
+      @custom_attributes = Gitlab.group_custom_attributes(2)
+    end
+
+    it 'gets the correct resource' do
+      expect(a_get('/groups/2/custom_attributes')).to have_been_made
+    end
+
+    it 'returns a information about a custom_attribute of group' do
+      expect(@custom_attributes.first.key).to eq 'somekey'
+      expect(@custom_attributes.last.value).to eq('somevalue2')
+    end
+  end
+
+  describe '.group_custom_attribute' do
+    before do
+      stub_get('/groups/2/custom_attributes/some_new_key', 'group_custom_attribute')
+      @custom_attribute = Gitlab.group_custom_attribute('some_new_key', 2)
+    end
+
+    it 'gets the correct resource' do
+      expect(a_get('/groups/2/custom_attributes/some_new_key')).to have_been_made
+    end
+
+    it 'returns a information about the single custom_attribute of group' do
+      expect(@custom_attribute.key).to eq 'some_new_key'
+      expect(@custom_attribute.value).to eq('some_new_value')
+    end
+  end
+
+  describe '.add_custom_attribute' do
+    describe 'with group ID' do
+      before do
+        stub_put('/groups/2/custom_attributes/some_new_key', 'group_custom_attribute')
+        @custom_attribute = Gitlab.add_group_custom_attribute('some_new_key', 'some_new_value', 2)
+      end
+
+      it 'gets the correct resource' do
+        body = { value: 'some_new_value' }
+        expect(a_put('/groups/2/custom_attributes/some_new_key').with(body: body)).to have_been_made
+        expect(a_put('/groups/2/custom_attributes/some_new_key')).to have_been_made
+      end
+
+      it 'returns information about a new custom attribute' do
+        expect(@custom_attribute.key).to eq 'some_new_key'
+        expect(@custom_attribute.value).to eq 'some_new_value'
+      end
+    end
+  end
+
+  describe '.delete_custom_attribute' do
+    describe 'with group ID' do
+      before do
+        stub_delete('/groups/2/custom_attributes/some_new_key', 'group_custom_attribute')
+        @custom_attribute = Gitlab.delete_group_custom_attribute('some_new_key', 2)
+      end
+
+      it 'gets the correct resource' do
+        expect(a_delete('/groups/2/custom_attributes/some_new_key')).to have_been_made
+      end
+
+      it 'returns information about a deleted custom_attribute' do
+        expect(@custom_attribute).to be_truthy
+      end
+    end
+  end
 end
diff --git a/spec/gitlab/client/keys_spec.rb b/spec/gitlab/client/keys_spec.rb
index aa639e1..673c71d 100644
--- a/spec/gitlab/client/keys_spec.rb
+++ b/spec/gitlab/client/keys_spec.rb
@@ -18,4 +18,20 @@
       expect(@key.title).to eq('narkoz@helium')
     end
   end
+
+  describe '.key_by_fingerprint' do
+    before do
+      stub_get('/keys?fingerprint=9f:70:33:b3:50:4d:9a:a3:ef:ea:13:9b:87:0f:7f:7e', 'key')
+      @key = Gitlab.key_by_fingerprint('9f:70:33:b3:50:4d:9a:a3:ef:ea:13:9b:87:0f:7f:7e')
+    end
+
+    it 'gets the correct resource' do
+      expect(a_get('/keys?fingerprint=9f:70:33:b3:50:4d:9a:a3:ef:ea:13:9b:87:0f:7f:7e')).to have_been_made
+    end
+
+    it 'returns information about a key' do
+      expect(@key.id).to eq(1)
+      expect(@key.title).to eq('narkoz@helium')
+    end
+  end
 end
diff --git a/spec/gitlab/client/projects_spec.rb b/spec/gitlab/client/projects_spec.rb
index 3f8bd07..f1d15cf 100644
--- a/spec/gitlab/client/projects_spec.rb
+++ b/spec/gitlab/client/projects_spec.rb
@@ -840,4 +840,73 @@
       expect(@unarchived_project.archived).to eq(false)
     end
   end
+
+  describe '.project_custom_attributes' do
+    before do
+      stub_get('/projects/2/custom_attributes', 'project_custom_attributes')
+      @custom_attributes = Gitlab.project_custom_attributes(2)
+    end
+
+    it 'gets the correct resource' do
+      expect(a_get('/projects/2/custom_attributes')).to have_been_made
+    end
+
+    it 'returns a information about a custom_attribute of project' do
+      expect(@custom_attributes.first.key).to eq 'somekey'
+      expect(@custom_attributes.last.value).to eq('somevalue2')
+    end
+  end
+
+  describe '.project_custom_attribute' do
+    before do
+      stub_get('/projects/2/custom_attributes/some_new_key', 'project_custom_attribute')
+      @custom_attribute = Gitlab.project_custom_attribute('some_new_key', 2)
+    end
+
+    it 'gets the correct resource' do
+      expect(a_get('/projects/2/custom_attributes/some_new_key')).to have_been_made
+    end
+
+    it 'returns a information about the single custom_attribute of project' do
+      expect(@custom_attribute.key).to eq 'some_new_key'
+      expect(@custom_attribute.value).to eq('some_new_value')
+    end
+  end
+
+  describe '.add_custom_attribute' do
+    describe 'with project ID' do
+      before do
+        stub_put('/projects/2/custom_attributes/some_new_key', 'project_custom_attribute')
+        @custom_attribute = Gitlab.add_project_custom_attribute('some_new_key', 'some_new_value', 2)
+      end
+
+      it 'gets the correct resource' do
+        body = { value: 'some_new_value' }
+        expect(a_put('/projects/2/custom_attributes/some_new_key').with(body: body)).to have_been_made
+        expect(a_put('/projects/2/custom_attributes/some_new_key')).to have_been_made
+      end
+
+      it 'returns information about a new custom attribute' do
+        expect(@custom_attribute.key).to eq 'some_new_key'
+        expect(@custom_attribute.value).to eq 'some_new_value'
+      end
+    end
+  end
+
+  describe '.delete_custom_attribute' do
+    describe 'with project ID' do
+      before do
+        stub_delete('/projects/2/custom_attributes/some_new_key', 'project_custom_attribute')
+        @custom_attribute = Gitlab.delete_project_custom_attribute('some_new_key', 2)
+      end
+
+      it 'gets the correct resource' do
+        expect(a_delete('/projects/2/custom_attributes/some_new_key')).to have_been_made
+      end
+
+      it 'returns information about a deleted custom_attribute' do
+        expect(@custom_attribute).to be_truthy
+      end
+    end
+  end
 end
diff --git a/spec/gitlab/client/users_spec.rb b/spec/gitlab/client/users_spec.rb
index 893bad5..9ea60c4 100644
--- a/spec/gitlab/client/users_spec.rb
+++ b/spec/gitlab/client/users_spec.rb
@@ -478,4 +478,73 @@
       expect(@users.last.id).to eq(2)
     end
   end
+
+  describe '.user_custom_attributes' do
+    before do
+      stub_get('/users/2/custom_attributes', 'user_custom_attributes')
+      @custom_attributes = Gitlab.user_custom_attributes(2)
+    end
+
+    it 'gets the correct resource' do
+      expect(a_get('/users/2/custom_attributes')).to have_been_made
+    end
+
+    it 'returns a information about a custom_attribute of user' do
+      expect(@custom_attributes.first.key).to eq 'somekey'
+      expect(@custom_attributes.last.value).to eq('somevalue2')
+    end
+  end
+
+  describe '.user_custom_attribute' do
+    before do
+      stub_get('/users/2/custom_attributes/some_new_key', 'user_custom_attribute')
+      @custom_attribute = Gitlab.user_custom_attribute('some_new_key', 2)
+    end
+
+    it 'gets the correct resource' do
+      expect(a_get('/users/2/custom_attributes/some_new_key')).to have_been_made
+    end
+
+    it 'returns a information about the single custom_attribute of user' do
+      expect(@custom_attribute.key).to eq 'some_new_key'
+      expect(@custom_attribute.value).to eq('some_new_value')
+    end
+  end
+
+  describe '.add_custom_attribute' do
+    describe 'with user ID' do
+      before do
+        stub_put('/users/2/custom_attributes/some_new_key', 'user_custom_attribute')
+        @custom_attribute = Gitlab.add_user_custom_attribute('some_new_key', 'some_new_value', 2)
+      end
+
+      it 'gets the correct resource' do
+        body = { value: 'some_new_value' }
+        expect(a_put('/users/2/custom_attributes/some_new_key').with(body: body)).to have_been_made
+        expect(a_put('/users/2/custom_attributes/some_new_key')).to have_been_made
+      end
+
+      it 'returns information about a new custom attribute' do
+        expect(@custom_attribute.key).to eq 'some_new_key'
+        expect(@custom_attribute.value).to eq 'some_new_value'
+      end
+    end
+  end
+
+  describe '.delete_custom_attribute' do
+    describe 'with user ID' do
+      before do
+        stub_delete('/users/2/custom_attributes/some_new_key', 'user_custom_attribute')
+        @custom_attribute = Gitlab.delete_user_custom_attribute('some_new_key', 2)
+      end
+
+      it 'gets the correct resource' do
+        expect(a_delete('/users/2/custom_attributes/some_new_key')).to have_been_made
+      end
+
+      it 'returns information about a deleted custom_attribute' do
+        expect(@custom_attribute).to be_truthy
+      end
+    end
+  end
 end