(MODULES-9578) Create authorized_key in root path

Previously, when the `target` property was set, the ssh_authorized_key
resource could not create directories/files within root-owned paths.
This behavior is due to the module switching context to the user, then
attempting to create the directory/file as the specified user,
ultimately failing because of insufficient permissions.

This commit adds a new parameter, `drop_privileges` which when set to
false allows the module to write a ssh_authorized_key file in a
privileged path. Due to the possible security implications of this,
the parameter must be manually specified in order to activate this
functionality.

A path is considered to be privileged/trusted if all of its ancestors:
- do not contain any symlinks
- have the same owner as the user who runs Puppet
- are not world/group writable

3 files changed, 87 insertions, 17 deletions

diff --git a/spec/acceptance/tests/resource/ssh_authorized_key/create_spec.rb b/spec/acceptance/tests/resource/ssh_authorized_key/create_spec.rb
index 34154ee..bfc75a7 100644
--- a/spec/acceptance/tests/resource/ssh_authorized_key/create_spec.rb
+++ b/spec/acceptance/tests/resource/ssh_authorized_key/create_spec.rb
@@ -7,13 +7,11 @@ RSpec.context 'ssh_authorized_key: Create' do
   let(:name) { "pl#{rand(999_999).to_i}" }
   let(:custom_key_directory) { "/etc/ssh_authorized_keys_#{name}" }
   let(:custom_key) { "#{custom_key_directory}/authorized_keys_#{name}" }
-  let(:custom_name) { "custom_#{name}" }
 
   before(:each) do
     posix_agents.each do |agent|
-      on(agent, "cp #{auth_keys} /tmp/auth_keys", acceptable_exit_codes: [0, 1])
+      on(agent, "cp -a #{auth_keys} /tmp/auth_keys", acceptable_exit_codes: [0, 1])
       on(agent, "rm -f #{auth_keys}")
-      on(agent, "mkdir #{custom_key_directory}")
     end
   end
 
@@ -21,7 +19,6 @@ RSpec.context 'ssh_authorized_key: Create' do
     posix_agents.each do |agent|
       # (teardown) restore the #{auth_keys} file
       on(agent, "mv /tmp/auth_keys #{auth_keys}", acceptable_exit_codes: [0, 1])
-      on(agent, "rm -rf #{custom_key_directory}")
     end
   end
 
@@ -37,17 +34,54 @@ RSpec.context 'ssh_authorized_key: Create' do
         fail_test "didn't find the ssh_authorized_key for #{name}" unless stdout.include? name.to_s
       end
     end
-    it "#{agent} should create an entry for an SSH authorized key in a custom location" do
-      custom_args = ['ensure=present',
-                     'user=$LOGNAME',
-                     "type='rsa'",
-                     "key='mykey'",
-                     "target='#{custom_key}'"]
 
-      on(agent, puppet_resource('ssh_authorized_key', custom_name.to_s, custom_args))
+    it "#{agent} should create an entry for an SSH authorized key in a custom location" do
+      on(agent, "mkdir #{custom_key_directory}")
+      args = ['ensure=present',
+              'user=$LOGNAME',
+              "type='rsa'",
+              "key='mykey'",
+              "target='#{custom_key}'"]
+      on(agent, puppet_resource('ssh_authorized_key', name.to_s, args))
 
       on(agent, "cat #{custom_key}") do |_res|
-        fail_test "didn't find the ssh_authorized_key for #{custom_name}" unless stdout.include? name.to_s
+        fail_test "didn't find the ssh_authorized_key for #{name}" unless stdout.include? name.to_s
+      end
+      on(agent, "rm -rf #{custom_key_directory}")
+    end
+
+    it "#{agent} should fail if target user doesn't have permissions for symlinked path" do
+      # create a dummy user
+      on(agent, puppet_resource('user', 'testuser', 'ensure=present', 'managehome=true'))
+
+      on(agent, "mkdir #{custom_key_directory}")
+
+      # as the user, symlink an owned directory to something inside /root
+      on(agent, puppet_resource('file', '/home/testuser/tmp', ['ensure=/etc', 'owner=testuser']))
+      args = ['ensure=present',
+              'user=testuser',
+              "type='rsa'",
+              "key='mykey'",
+              'drop_privileges=false',
+              "target=/home/testuser/tmp/ssh_authorized_keys_#{name}/authorized_keys_#{name}"]
+      on(agent, puppet_resource('ssh_authorized_key', name.to_s, args)) do |_res|
+        fail_test unless stderr =~ %r{the target path is not trusted}
+      end
+      on(agent, "rm -rf #{custom_key_directory}")
+
+      # purge the user
+      on(agent, puppet_resource('user', 'testuser', 'ensure=absent'))
+    end
+
+    it "#{agent} should not create directories for SSH authorized key in a custom location" do
+      args = ['ensure=present',
+              'user=$LOGNAME',
+              "type='rsa'",
+              "key='mykey'",
+              'drop_privileges=false',
+              "target='#{custom_key}'"]
+      on(agent, puppet_resource('ssh_authorized_key', name.to_s, args), acceptable_exit_codes: [0, 1]) do |_res|
+        fail_test unless stderr =~ %r{the target path is not trusted}
       end
     end
   end
diff --git a/spec/acceptance/tests/resource/ssh_authorized_key/destroy_spec.rb b/spec/acceptance/tests/resource/ssh_authorized_key/destroy_spec.rb
index af160ce..a491eb6 100644
--- a/spec/acceptance/tests/resource/ssh_authorized_key/destroy_spec.rb
+++ b/spec/acceptance/tests/resource/ssh_authorized_key/destroy_spec.rb
@@ -5,13 +5,14 @@ RSpec.context 'sshkeys: Destroy' do
 
   let(:auth_keys) { '~/.ssh/authorized_keys' }
   let(:name) { "pl#{rand(999_999).to_i}" }
+  let(:custom_key_directory) { "/etc/ssh_authorized_keys_#{name}" }
+  let(:custom_key) { "#{custom_key_directory}/authorized_keys_#{name}" }
 
   before(:each) do
     posix_agents.each do |agent|
-      on(agent, "cp #{auth_keys} /tmp/auth_keys", acceptable_exit_codes: [0, 1])
-
+      on(agent, "cp -a #{auth_keys} /tmp/auth_keys", acceptable_exit_codes: [0, 1])
+      on(agent, "rm -f #{auth_keys}")
       on(agent, "echo '' >> #{auth_keys} && echo 'ssh-rsa mykey #{name}' >> #{auth_keys}")
-      on(agent, "chown $LOGNAME #{auth_keys}")
     end
   end
 
@@ -34,5 +35,21 @@ RSpec.context 'sshkeys: Destroy' do
         expect(stdout).not_to include(name.to_s)
       end
     end
+
+    it "#{agent} should delete an entry for an SSH authorized key in a custom location" do
+      on(agent, "mkdir #{custom_key_directory}")
+      on(agent, "echo '' >> #{custom_key} && echo 'ssh-rsa mykey #{name}' >> #{custom_key}")
+      args = ['ensure=absent',
+              'user=$LOGNAME',
+              "type='rsa'",
+              "key='mykey'",
+              "target='#{custom_key}'"]
+      on(agent, puppet_resource('ssh_authorized_key', name.to_s, args))
+
+      on(agent, "cat #{custom_key}") do |_res|
+        expect(stdout).not_to include(name.to_s)
+      end
+      on(agent, "rm -rf #{custom_key_directory}")
+    end
   end
 end
diff --git a/spec/acceptance/tests/resource/ssh_authorized_key/modify_spec.rb b/spec/acceptance/tests/resource/ssh_authorized_key/modify_spec.rb
index 3a46374..711d2fc 100644
--- a/spec/acceptance/tests/resource/ssh_authorized_key/modify_spec.rb
+++ b/spec/acceptance/tests/resource/ssh_authorized_key/modify_spec.rb
@@ -3,12 +3,14 @@ require 'spec_helper_acceptance'
 RSpec.context 'sshkeys: Modify' do
   let(:auth_keys) { '~/.ssh/authorized_keys' }
   let(:name) { "pl#{rand(999_999).to_i}" }
+  let(:custom_key_directory) { "/etc/ssh_authorized_keys_#{name}" }
+  let(:custom_key) { "#{custom_key_directory}/authorized_keys_#{name}" }
 
   before(:each) do
     posix_agents.each do |agent|
-      on(agent, "cp #{auth_keys} /tmp/auth_keys", acceptable_exit_codes: [0, 1])
+      on(agent, "cp -a #{auth_keys} /tmp/auth_keys", acceptable_exit_codes: [0, 1])
+      on(agent, "rm -f #{auth_keys}")
       on(agent, "echo '' >> #{auth_keys} && echo 'ssh-rsa mykey #{name}' >> #{auth_keys}")
-      on(agent, "chown $LOGNAME #{auth_keys}")
     end
   end
 
@@ -32,5 +34,22 @@ RSpec.context 'sshkeys: Modify' do
         expect(stdout).not_to include("mykey #{name}")
       end
     end
+
+    it "#{agent} should update an entry for an SSH authorized key in a custom location" do
+      on(agent, "mkdir #{custom_key_directory}")
+      on(agent, "echo '' >> #{custom_key} && echo 'ssh-rsa mykey #{name}' >> #{custom_key}")
+      args = ['ensure=present',
+              'user=$LOGNAME',
+              "type='rsa'",
+              "key='mynewshinykey'",
+              "target='#{custom_key}'"]
+      on(agent, puppet_resource('ssh_authorized_key', name.to_s, args))
+
+      on(agent, "cat #{custom_key}") do |_res|
+        expect(stdout).to include("mynewshinykey #{name}")
+        expect(stdout).not_to include("mykey #{name}")
+      end
+      on(agent, "rm -rf #{custom_key_directory}")
+    end
   end
 end