I came across a situation recently where secrets were being leaked via SaltStack deployments, run from a CI job. I’ll explain how this can happen, and give some suggestions to reduce the risk.

A common workflow in SaltStack is to store secrets in a pillar on the salt master, which allows data to be encrypted until compilation. The file.managed module can then be used to templatize configuration files and inject secrets from the encrypted pillars.

The problem appears when the file templates are changed within the salt state; by default, file.managed will display a diff of the file changes, and any secrets that would be injected into the file will be shown in cleartext in the diff.

Example

Suppose we have a salt pillar that contains an encrypted password (the plaintext is my57r0nkP455w0rd!):

app: password: | -----BEGIN PGP MESSAGE----- Version: GnuPG v1 hQEMA/yXXF3hJbt6AQf+JCGag2mOyVmIi7QNRF2eagUtktot8sujCDVTCOTJe6tM 5+bxlJUaqK2iZA7sO6arMu8myZTor9A0gDf+s+ij/S4LAURR4CT2OX/wI3gpnQw0 oJt2bztbcl7ZqsRM1DP943Rx5XPOksCFvFR1ftzfF9zoohkpS9axx2WyQWnQqCs0 x3QOr9RpBoMZU153N2YnG8ys5tskFQMHMaGGhXJSln8vDw9hodWTzO0OxS67Wp5L 3fty7ruPZiJ/jeoKjC5BLPl0IFOJ0/ctRUF70OgEy72UozX7TD6sGghUwF16aDcc EZf9CUZHed8GMVOGAU5ZoDCFwSrF3ZGK6L8Ens6269JMARp2jf/+nI7/qCtVP+qy XGFur7xY/XkmMIhXcqeaBT6ZZojCMBgFOv0A2P7zFdl1uIFLeA+Uk/DfZhQLNxa/ 7y96iQXPL4CZVXUuAw== =bIm3 -----END PGP MESSAGE-----

We want our state to copy a simple, YAML config file onto the root of our target systems; the file template looks like this:

password: {{ pillar['app']['password'] }}

And the corresponding salt state, config-example that looks like:

copy yaml config: file.managed: - name: /config.yml - source: salt://config-example/config.yml - template: jinja

When we apply the salt state, we get output like this:

$ sudo salt 'test-machine' state.apply config-example test-machine: ---------- ID: copy yaml config Function: file.managed Name: /config.yml Result: True Comment: File /config.yml updated Started: 00:57:23.942488 Duration: 43.845 ms Changes: ---------- diff: New file mode: 0644 Summary for test-machine ------------------------ Succeeded: 1 (changed=1) Failed: 0 ------------ Total states run: 1 Total run time: 43.845 ms

Now suppose we add another parameter to the config template:

password: {{ pillar['app']['password'] }} new_parameter: true

When we reapply the state, we see a diff (and our password!):

$ sudo salt 'test-machine' state.apply config-example test-machine: ---------- ID: copy yaml config Function: file.managed Name: /config.yml Result: True Comment: File /config.yml updated Started: 01:09:38.271871 Duration: 35.597 ms Changes: ---------- diff: --- +++ @@ -1 +1,2 @@ password: my57r0nkP455w0rd! +new_parameter: true Summary for test-machine ------------------------ Succeeded: 1 (changed=1) Failed: 0 ------------ Total states run: 1 Total run time: 35.597 ms

Depending on how the salt state is applied, this output can end up any number of places; for example, when run from a Jenkins job the output above will land on filesystem of the build master, with the password in plain text. Depending on how the retention policies for build logs are set, these credentials can accumulate over time.

Solutions

There are a couple of ways to address this issue–locally in file module itself, and globally in the salt configuration files.

Local Settings

The file.managed function has a boolean parameter called show_changes; by default its value is True, but setting it to False prevents the diff from being displayed:

$ sudo salt 'test-machine' state.apply config-example test-machine: ---------- ID: copy yaml config Function: file.managed Name: /config.yml Result: True Comment: File /config.yml updated Started: 01:09:38.271871 Duration: 35.597 ms Changes: ---------- diff: Summary for test-machine ------------------------ Succeeded: 1 (changed=1) Failed: 0 ------------ Total states run: 1 Total run time: 35.597 ms

Global Settings

While it may be possible to enforce the use of the show_changes flag via git hooks or similar, it’s not always the best solution, and there may be many file.managed calls within a typical machine configuration. Another way to control the output is via the configuration of the salt master itself There are a few settings that govern output verbosity, but state_output is the one we’re interested in.

If we set the state_output config value to terse, we’ll get a simple success or failure message for our states, regardless of whether the show_changes flag is set on our state:

$ sudo salt 'test-machine' state.apply config-example test-machine: Name: /config.yml - Function: file.managed - Result: Changed Started: - 01:41:00.549403 Duration: 35.582 ms Summary for test-machine ------------------------ Succeeded: 1 (changed=1) Failed: 0 ------------ Total states run: 1 Total run time: 35.582 ms

If you need more verbose output while troubleshooting a salt state, you can always adjust the level at the command line, using --state_output=full.

Conclusion

Even with gpg encryption, it’s possible for plaintext secrets to wind up in the output of salt commands. Pay attention to your output, and adjust your salt configuration to minimize exposure.

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