Secrets Access Guide

The Doppler CLI is supremely flexible when it comes to accessing your secrets. In this guide, we'll show you the most common usage patterns:

Mounting

For applications that read secrets from a file, you can mount an ephemeral .env or JSON file. You can also mount a custom file format using a secrets template.

Your secrets are mounted as a Linux named pipe that can be read like a file and is automatically cleaned up when the Doppler process exits, making it the only secure method for supplying secrets via the file system.

Simply specify the --mount flag and pass the name of the file to mount. The format will automatically be detected for .env and .json files.

To mount an .env file:

doppler run --mount .env -- php artisan serve
doppler run --mount .env -- npm start

To mount a JSON file:

doppler run --mount env.json -- npm start

Specify the format using --mount-format if the extension doesn't automatically map to a known format:

doppler run --mount app.config --mount-format json -- npm start

You can also use a custom template. For example, lets configure Firebase's Cloud Functions emulator using a .runtimeconfig.json file:

doppler run \
  --mount .runtimeconfig.json \
  --mount-template .runtimeconfig.tmpl -- \
  firebase emulators:start --only functions
{ "doppler": {{tojson .}} }

To further increase security, you can restrict the number reads using the --mount-max-reads flag. For example, PHP configuration caching that only needs to read the .env file once:

doppler run --mount .env --mount-max-reads 1 \
    --command="php artisan config:cache && php artisan serve"

If using Python and the dotenv package, you'll need to slightly adjust your usage of load_dotenv:

with open ('.env') as env_file:
     load_dotenv(stream=env_file)

Secrets mounting is perfect for dynamic kubectl config files:

KUBECONFIG=./kube-config doppler run \
  --mount kube-config \
  --mount-template ./kube-config.tmpl \
  -- kubectl get secrets
{{.KUBE_CONFIG}}

Dynamic SSH Key Management

Setting a max number of reads is also great for dynamic SSH private keys, ensuring the private key is deleted once the connection is established:

# Nested doppler run so the ssh command can use the SSH_USER and SSH_HOST env vars
# NOTE: The ssh command needs to read the private key twice
doppler run -- \
  doppler run \
    --mount ssh.key \
    --mount-template ssh.key.tmpl \
    --mount-max-reads 2 \ 
    --command 'ssh [email protected]$SSH_HOST -i ssh.key'
{{.SSH_KEY}}

Injection

You can also injects secrets into your application via environment variables, using the doppler run command.

doppler run -- npm start

Potential danger when injecting secrets

🚧

Caution

There exists environment variable names that can have unintended consequences when used. In the worst case, they can lead to Remote Code Execution. We advise against using these variables names unless you know what you are doing.

Operating System Variables

Linux

  • PROMPT_COMMAND
  • LD_PRELOAD
  • LD_LIBRARY_PATH

Windows

  • WINDIR
  • USERPROFILE

MacOS

  • DYLD_INSERT_LIBRARIES

Language Interpreter Variables

Perl

  • PERL5OPT

Python

  • PERL5OPT
  • PYTHONWARNINGS
  • BROWSER

PHP

  • HOSTNAME
  • PHPRC

NodeJS

  • NODE_VERSION
  • NODE_OPTIONS

Remediation

This danger only exists when injecting secrets as environment variables. We strongly recommend mounting secrets to an ephemeral file.

Getting Values

Fetch the plain value of a single secret, e.g. JSON credentials used by a CLI:

doppler secrets get GCP_SERVICE_ACCOUNT_JSON --plain > gcp_credentials.json

You can also use a secret value in a shell command by using the --command flag, e.g. performing a curl request using Basic Authentication:

doppler run --command='curl -u $USER:$TOKEN https://example.com'

You can download secrets to a file when environment variables aren't sufficient, e.g. supplying a TLS certificate and key to a webserver:

doppler secrets get TLS_CERT --plain > /etc/tls/cert.pem
doppler secrets get TLS_KEY --plain > /etc/tls/key.pem

Get the values of multiple secrets at once in either plain or JSON format:

# Plain
doppler secrets get DOPPLER_PROJECT DOPPLER_CONFIG --plain

# JSON
doppler secrets get DOPPLER_PROJECT DOPPLER_CONFIG --json

You can also get a nice dashboard-style view with the option to exclude the values:

# Names and values
doppler secrets

# Just names
doppler secrets --only-names

# Names as a JSON array
doppler secrets --only-names --json | jq keys

Filtering

You can use the doppler secrets download command in conjunction with tools such as grep and jq to get a filtered list of secrets.

Filter secrets in env format using grep:

# Get secrets containing the string "CLOUDWATCH"
doppler secrets download --no-file --format env | grep CLOUDWATCH

# Get secrets starting with "CLOUDWATCH"
doppler secrets download --no-file --format env | grep ^CLOUDWATCH

Filter objects in JSON format using jq:

# Get secrets containing the string "CLOUDWATCH"
doppler secrets download --no-file --format json | \
    jq -r '. | to_entries[] | select(.key | contains("CLOUDWATCH)")) | { (.key): (.value)}' | \
    jq -s add

# Get secrets starting with "CLOUDWATCH"
doppler secrets download --no-file --format json | \
    jq -r '. | to_entries[] | select(.key | startswith("CLOUDWATCH")) | { (.key): (.value)}' | \
    jq -s add

You can also combine filtering with formatting. For example, create an SSH authorized_keys file with the value from secrets with an SSH_PUB_KEY_ prefix.

# If secrets in Doppler were
# SSH_PUB_KEY_SERVER_A="ssh-ed25519 AAA..."
# SSH_PUB_KEY_SERVER_B="ssh-ed25519 BBB..."

doppler secrets download --no-file --format env-no-quotes | grep ^SSH_PUB_KEY_ | cut -d"=" -f2 > authorized_keys && chmod 600 authorized_keys

Downloading

πŸ“˜

We strongly recommend against downloading secrets in plain text to the file system. Instead, use Doppler's mount feature to mount secrets as an ephemeral file.

Formats

Using the dopper secrets download command, you can download your secrets in a variety of formats:

  • json (default)
  • yaml
  • env
  • env-no-quotes
  • docker
  • dotnet-json

For example, to download secrets as a .env file:

# Avoid storing secrets unencrypted whenever possible
doppler secrets download --no-file --format env > .env

Custom formats can be achieved by piping secrets in JSON format to jq and transforming the keys and values:

# Apache environment variable syntax
doppler secrets download --no-file | jq -r '. | to_entries[] | "SetEnv \(.key) \"\(.value)\""' > apache/env-vars.conf

Downloading secrets in plain text is only recommended when used with bash process substitution to supply secrets to a command expecting a file, but without it ever touching the file system.

Works great with Docker:

docker run \
   --env-file <(doppler secrets download --no-file --format docker) \
    your/image

And Kubernetes:

kubectl create secret generic \
    doppler-env-vars --from-env-file <(doppler secrets download --no-file --format docker)

You can even embed the secrets as part of a larger output, such as syncing Doppler secrets to AWS Lambda using JSON:

aws lambda update-function-configuration \
    --function-name doppler-test \
    --environment $(echo "{\"Variables\":$(doppler secrets download --no-file)}")

Name Transformers

Name Transformers alter the default UPPER_SNAKE_CASE format using the --name-transformer option:

# ASP.NET Core
doppler run --nane-transformer dotnet-env -- dotnet run

# Terraform
doppler run --name-transformer tf-var -- terraform apply

The following naming conventions are supported:

TypeDefaultTransform
camelAPI_KEYapiKey
upper-camelAPI_KEYApiKey
lower-snakeAPI_KEYapi_key
tf-varAPI_KEYTF_VAR_api_key
dotnet-envSMTP__USER_NAMESmtp__UserName

FAQs

How do I export Doppler secrets into the current shell?

A situation may arise when you need to populate a shell with environment variables from Doppler.

sdfds

🚧

Exercise caution with this functionality as every process executed in your shell will now have access to your secrets.

You could create a child shell spawned by the Doppler CLI:

doppler run -- sh -c 'bash'
doppler run -- sh -c 'zsh'
doppler run -- sh -c 'sh'

Or use doppler secrets download in conjunction with process substitution to promote Doppler local variables to environment variables.

set -a
source <(doppler secrets download --no-file --format env)
set +a