# Using the AWS Secrets Manager Agent ## How the Secrets Manager Agent works The AWS Secrets Manager Agent is a client-side HTTP service that helps you standardize how you consume secrets from Secrets Manager across your compute environments. You can use it with the following services: + AWS Lambda + Amazon Elastic Container Service + Amazon Elastic Kubernetes Service + Amazon Elastic Compute Cloud The Secrets Manager Agent retrieves and caches secrets in memory, allowing your applications to get secrets from localhost instead of making direct calls to Secrets Manager. The Secrets Manager Agent can only read secrets—it can't modify them. **Important** The Secrets Manager Agent uses the AWS credentials from your environment to call Secrets Manager. It includes protection against Server Side Request Forgery (SSRF) to help improve secret security. The Secrets Manager Agent uses the post-quantum ML-KEM key exchange as the highest-priority key exchange by default. ## Understanding Secrets Manager Agent caching The Secrets Manager Agent uses an in-memory cache that resets when the Secrets Manager Agent restarts. It periodically refreshes cached secret values based on the following: + The default refresh frequency (TTL) is 300 seconds + You can modify the TTL using a configuration file + The refresh occurs when you request a secret after the TTL expires **Note** The Secrets Manager Agent doesn't include cache invalidation. If a secret rotates before the cache entry expires, the Secrets Manager Agent might return a stale secret value. The Secrets Manager Agent returns secret values in the same format as the response of `GetSecretValue`. Secret values aren't encrypted in the cache. **Topics** + [ ## How the Secrets Manager Agent works ](#agent-overview) + [ ## Understanding Secrets Manager Agent caching ](#agent-caching) + [ ## Build the Secrets Manager Agent ](#secrets-manager-agent-build) + [ ## Install the Secrets Manager Agent ](#secrets-manager-agent-install) + [ ## Retrieve secrets with the Secrets Manager Agent ](#secrets-manager-agent-call) + [ ## Understanding the `refreshNow` parameter ](#secrets-manager-agent-refresh) + [ ## Configure the Secrets Manager Agent ](#secrets-manager-agent-config) + [ ## Optional features ](#secrets-manager-agent-features) + [ ## Logging ](#secrets-manager-agent-log) + [ ## Security considerations ](#secrets-manager-agent-security) ## Build the Secrets Manager Agent Before you begin, ensure you have the standard development tools and Rust tools installed for your platform. **Note** Building the agent with the `fips` feature enabled on macOS currently requires the following workaround: Create an environment variable called `SDKROOT` which is set to the result of running `xcrun --show-sdk-path` ------ #### [ RPM-based systems ] **To build on RPM-based systems** 1. Use the `install` script provided in the repository. The script generates a random SSRF token on startup and stores it in the file `/var/run/awssmatoken`. The token is readable by the `awssmatokenreader` group that the install script creates. 1. To allow your application to read the token file, you need to add the user account that your application runs under to the `awssmatokenreader` group. For example, you can grant permissions for your application to read the token file with the following usermod command, where ** is the user ID under which your application runs. ``` sudo usermod -aG awssmatokenreader ``` **Install development tools** On RPM-based systems such as AL2023, install the Development Tools group: ``` sudo yum -y groupinstall "Development Tools" ``` 1. **Install Rust** Follow the instructions at [Install Rust](https://www.rust-lang.org/tools/install) in the *Rust documentation*: ``` curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh # Follow the on-screen instructions . "$HOME/.cargo/env" ``` 1. **Build the agent** Build the Secrets Manager Agent using the cargo build command: ``` cargo build --release ``` You will find the executable under `target/release/aws_secretsmanager_agent`. ------ #### [ Debian-based systems ] **To build on Debian-based systems** 1. **Install development tools** On Debian-based systems such as Ubuntu, install the build-essential package: ``` sudo apt install build-essential ``` 1. **Install Rust** Follow the instructions at [Install Rust](https://www.rust-lang.org/tools/install) in the *Rust documentation*: ``` curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh # Follow the on-screen instructions . "$HOME/.cargo/env" ``` 1. **Build the agent** Build the Secrets Manager Agent using the cargo build command: ``` cargo build --release ``` You will find the executable under `target/release/aws_secretsmanager_agent`. ------ #### [ Windows ] **To build on Windows** 1. **Set up development environment** Follow the instructions at [Set up your dev environment on Windows for Rust](https://learn.microsoft.com/en-us/windows/dev-environment/rust/setup) in the *Microsoft Windows documentation*. 1. **Build the agent** Build the Secrets Manager Agent using the cargo build command: ``` cargo build --release ``` You will find the executable under `target/release/aws_secretsmanager_agent.exe`. ------ #### [ Cross-compile natively ] **To cross-compile natively** 1. **Install cross-compile tools** On distributions where the mingw-w64 package is available such as Ubuntu, install the cross-compile toolchain: ``` # Install the cross compile tool chain sudo add-apt-repository universe sudo apt install -y mingw-w64 ``` 1. **Add Rust build targets** Install the Windows GNU build target: ``` rustup target add x86_64-pc-windows-gnu ``` 1. **Build for Windows** Cross-compile the agent for Windows: ``` cargo build --release --target x86_64-pc-windows-gnu ``` You will find the executable at `target/x86_64-pc-windows-gnu/release/aws_secretsmanager_agent.exe`. ------ #### [ Cross compile with Rust cross ] **To cross-compile using Rust cross** If the cross-compile tools are not available natively on the system, you can use the Rust cross project. For more information, see [https://github.com/cross-rs/cross](https://github.com/cross-rs/cross). **Important** We recommend 32GB disk space for the build environment. 1. **Set up Docker** Install and configure Docker: ``` # Install and start docker sudo yum -y install docker sudo systemctl start docker sudo systemctl enable docker # Make docker start after reboot ``` 1. **Configure Docker permissions** Add your user to the docker group: ``` # Give ourselves permission to run the docker images without sudo sudo usermod -aG docker $USER newgrp docker ``` 1. **Build for Windows** Install cross and build the executable: ``` # Install cross and cross compile the executable cargo install cross cross build --release --target x86_64-pc-windows-gnu ``` ------ ## Install the Secrets Manager Agent Choose your compute environment from the following installation options. ------ #### [ Amazon EC2 ] **To install the Secrets Manager Agent on Amazon EC2** 1. **Navigate to configuration directory** Change to the configuration directory: ``` cd aws_secretsmanager_agent/configuration ``` 1. **Run installation script** Run the `install` script provided in the repository. The script generates a random SSRF token on startup and stores it in the file `/var/run/awssmatoken`. The token is readable by the `awssmatokenreader` group that the install script creates. 1. **Configure application permissions** Add the user account that your application runs under to the `awssmatokenreader` group: ``` sudo usermod -aG awssmatokenreader APP_USER ``` Replace *APP\$1USER* with the user ID under which your application runs. ------ #### [ Container Sidecar ] You can run the Secrets Manager Agent as a sidecar container alongside your application by using Docker. Then your application can retrieve secrets from the local HTTP server the Secrets Manager Agent provides. For information about Docker, see the [Docker documentation](https://docs.docker.com). **To create a sidecar container for the Secrets Manager Agent** 1. **Create agent Dockerfile** Create a Dockerfile for the Secrets Manager Agent sidecar container: ``` # Use the latest Debian image as the base FROM debian:latest # Set the working directory inside the container WORKDIR /app # Copy the Secrets Manager Agent binary to the container COPY secrets-manager-agent . # Install any necessary dependencies RUN apt-get update && apt-get install -y ca-certificates # Set the entry point to run the Secrets Manager Agent binary ENTRYPOINT ["./secrets-manager-agent"] ``` 1. **Create application Dockerfile** Create a Dockerfile for your client application. 1. **Create Docker Compose file** Create a Docker Compose file to run both containers with a shared network interface: **Important** You must load AWS credentials and the SSRF token for the application to be able to use the Secrets Manager Agent. For Amazon EKS and Amazon ECS, see the following: [Manage access](https://docs.aws.amazon.com/eks/latest/userguide/cluster-auth.html) in the *Amazon EKS User Guide* [Amazon ECS task IAM role](https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task-iam-roles.html) in the *Amazon ECS Developer Guide* ``` version: '3' services: client-application: container_name: client-application build: context: . dockerfile: Dockerfile.client command: tail -f /dev/null # Keep the container running secrets-manager-agent: container_name: secrets-manager-agent build: context: . dockerfile: Dockerfile.agent network_mode: "container:client-application" # Attach to the client-application container's network depends_on: - client-application ``` 1. **Copy agent binary** Copy the `secrets-manager-agent` binary to the same directory that contains your Dockerfiles and Docker Compose file. 1. **Build and run containers** Build and run the containers using Docker Compose: ``` docker-compose up --build ``` 1. **Next steps** You can now use the Secrets Manager Agent to retrieve secrets from your client container. For more information, see [Retrieve secrets with the Secrets Manager Agent](#secrets-manager-agent-call). ------ #### [ Lambda ] You can [package the Secrets Manager Agent as a Lambda extension](https://docs.aws.amazon.com/lambda/latest/dg/packaging-layers.html). Then you can [add it to your Lambda function as a layer](https://docs.aws.amazon.com/lambda/latest/dg/adding-layers.html) and call the Secrets Manager Agent from your Lambda function to get secrets. The following instructions show how to get a secret named *MyTest* by using the example script `secrets-manager-agent-extension.sh` in [https://github.com/aws/aws-secretsmanager-agent](https://github.com/aws/aws-secretsmanager-agent) to install the Secrets Manager Agent as a Lambda extension. **To create a Lambda extension for the Secrets Manager Agent** 1. **Package the agent layer** From the root of the Secrets Manager Agent code package, run the following commands: ``` AWS_ACCOUNT_ID=AWS_ACCOUNT_ID LAMBDA_ARN=LAMBDA_ARN # Build the release binary cargo build --release --target=x86_64-unknown-linux-gnu # Copy the release binary into the `bin` folder mkdir -p ./bin cp ./target/x86_64-unknown-linux-gnu/release/aws_secretsmanager_agent ./bin/secrets-manager-agent # Copy the `secrets-manager-agent-extension.sh` example script into the `extensions` folder. mkdir -p ./extensions cp aws_secretsmanager_agent/examples/example-lambda-extension/secrets-manager-agent-extension.sh ./extensions # Zip the extension shell script and the binary zip secrets-manager-agent-extension.zip bin/* extensions/* # Publish the layer version LAYER_VERSION_ARN=$(aws lambda publish-layer-version \ --layer-name secrets-manager-agent-extension \ --zip-file "fileb://secrets-manager-agent-extension.zip" | jq -r '.LayerVersionArn') ``` 1. **Configure SSRF token** The default configuration of the agent will automatically set the SSRF token to the value set in the pre-set `AWS_SESSION_TOKEN` or `AWS_CONTAINER_AUTHORIZATION_TOKEN` environment variables (the latter variable for Lambda functions with SnapStart enabled). Alternatively, you can define the `AWS_TOKEN` environment variable with an arbitrary value for your Lambda function instead as this variable takes precedence over the other two. If you choose to use the `AWS_TOKEN` environment variable, you must set that environment variable with a `lambda:UpdateFunctionConfiguration` call. 1. **Attach layer to function** Attach the layer version to your Lambda function: ``` # Attach the layer version to the Lambda function aws lambda update-function-configuration \ --function-name $LAMBDA_ARN \ --layers "$LAYER_VERSION_ARN" ``` 1. **Update function code** Update your Lambda function to query `http://localhost:2773/secretsmanager/get?secretId=MyTest` with the `X-Aws-codes-Secrets-Token` header value set to the value of the SSRF token sourced from one the environment variables mentioned above to retrieve the secret. Be sure to implement retry logic in your application code to accommodate delays in initialization and registration of the Lambda extension. 1. **Test the function** Invoke the Lambda function to verify that the secret is being correctly fetched. ------ ## Retrieve secrets with the Secrets Manager Agent To retrieve a secret, call the local Secrets Manager Agent endpoint with the secret name or ARN as a query parameter. By default, the Secrets Manager Agent retrieves the `AWSCURRENT` version of the secret. To retrieve a different version, use either the versionStage or versionId parameter. **Important** To help protect the Secrets Manager Agent, you must include a SSRF token header as part of each request: `X-Aws-Parameters-Secrets-Token`. The Secrets Manager Agent denies requests that don't have this header or that have an invalid SSRF token. You can customize the SSRF header name in the [Configure the Secrets Manager Agent](#secrets-manager-agent-config). ### Required permissions The Secrets Manager Agent uses the AWS SDK for Rust, which uses the [AWS credential provider chain](https://docs.aws.amazon.com/sdk-for-rust/latest/dg/credentials.html). The identity of these IAM credentials determines the permissions the Secrets Manager Agent has to retrieve secrets. + `secretsmanager:DescribeSecret` + `secretsmanager:GetSecretValue` For more information about permissions, see [Permissions reference for AWS Secrets Manager](auth-and-access.md#reference_iam-permissions). **Important** After the secret value is pulled into the Secrets Manager Agent, any user with access to the compute environment and SSRF token can access the secret from the Secrets Manager Agent cache. For more information, see [Security considerations](#secrets-manager-agent-security). ### Example requests ------ #### [ curl ] **Example – Get a secret using curl** The following curl example shows how to get a secret from the Secrets Manager Agent. The example relies on the SSRF being present in a file, which is where it is stored by the install script. ``` curl -v -H \\ "X-Aws-Parameters-Secrets-Token: $(/var/run/awssmatoken)" \\ 'http://localhost:2773/secretsmanager/get?secretId=YOUR_SECRET_ID' \\ echo ``` ------ #### [ Python ] **Example – Get a secret using Python** The following Python example shows how to get a secret from the Secrets Manager Agent. The example relies on the SSRF being present in a file, which is where it is stored by the install script. ``` import requests import json # Function that fetches the secret from Secrets Manager Agent for the provided secret id. def get_secret(): # Construct the URL for the GET request url = f"http://localhost:2773/secretsmanager/get?secretId=YOUR_SECRET_ID" # Get the SSRF token from the token file with open('/var/run/awssmatoken') as fp: token = fp.read() headers = { "X-Aws-Parameters-Secrets-Token": token.strip() } try: # Send the GET request with headers response = requests.get(url, headers=headers) # Check if the request was successful if response.status_code == 200: # Return the secret value return response.text else: # Handle error cases raise Exception(f"Status code {response.status_code} - {response.text}") except Exception as e: # Handle network errors raise Exception(f"Error: {e}") ``` ------ ## Understanding the `refreshNow` parameter The Secrets Manager Agent uses an in-memory cache to store secret values, which it refreshes periodically. By default, this refresh occurs when you request a secret after the Time to Live (TTL) has expired, typically every 300 seconds. However, this approach can sometimes result in stale secret values, especially if a secret rotates before the cache entry expires. To address this limitation, the Secrets Manager Agent supports a parameter called `refreshNow` in the URL. You can use this parameter to force an immediate refresh of a secret's value, bypassing the cache and ensuring you have the most up-to-date information. **Default behavior (without `refreshNow`)** + Uses cached values until TTL expires + Refreshes secrets only after TTL (default 300 seconds) + May return stale values if secrets rotate before the cache expires **Behavior with `refreshNow=true`** + Bypasses the cache entirely + Retrieves the latest secret value directly from Secrets Manager + Updates the cache with the fresh value and resets the TTL + Ensures you always get the most current secret value ### Force-refresh a secret value **Important** The default value of `refreshNow` is `false`. When set to `true`, it overrides the TTL specified in the Secrets Manager Agent configuration file and makes an API call to Secrets Manager. ------ #### [ curl ] **Example – Force-refresh a secret using curl** The following curl example shows how to force the Secrets Manager Agent to refresh the secret. The example relies on the SSRF being present in a file, which is where it is stored by the install script. ``` curl -v -H \\ "X-Aws-Parameters-Secrets-Token: $(/var/run/awssmatoken)" \\ 'http://localhost:2773/secretsmanager/get?secretId=YOUR_SECRET_ID&refreshNow=true' \\ echo ``` ------ #### [ Python ] **Example – Force-refresh a secret using Python** The following Python example shows how to get a secret from the Secrets Manager Agent. The example relies on the SSRF being present in a file, which is where it is stored by the install script. ``` import requests import json # Function that fetches the secret from Secrets Manager Agent for the provided secret id. def get_secret(): # Construct the URL for the GET request url = f"http://localhost:2773/secretsmanager/get?secretId=YOUR_SECRET_ID&refreshNow=true" # Get the SSRF token from the token file with open('/var/run/awssmatoken') as fp: token = fp.read() headers = { "X-Aws-Parameters-Secrets-Token": token.strip() } try: # Send the GET request with headers response = requests.get(url, headers=headers) # Check if the request was successful if response.status_code == 200: # Return the secret value return response.text else: # Handle error cases raise Exception(f"Status code {response.status_code} - {response.text}") except Exception as e: # Handle network errors raise Exception(f"Error: {e}") ``` ------ ## Configure the Secrets Manager Agent To change the configuration of the Secrets Manager Agent, create a [TOML](https://toml.io/en/) config file, and then call `./aws_secretsmanager_agent --config config.toml`.Configuration options **`log_level`** The level of detail reported in logs for the Secrets Manager Agent: DEBUG, INFO, WARN, ERROR, or NONE. The default is INFO. **`log_to_file`** Whether to log to a file or stdout/stderr: `true` or `false`. The default is `true`. **`http_port`** The port for the local HTTP server, in the range 1024 to 65535. The default is 2773. **`region`** The AWS Region to use for requests. If no Region is specified, the Secrets Manager Agent determines the Region from the SDK. For more information, see [Specify your credentials and default Region](https://docs.aws.amazon.com/sdk-for-rust/latest/dg/credentials.html) in the *AWS SDK for Rust Developer Guide*. **`ttl_seconds`** The TTL in seconds for the cached items, in the range 0 to 3600. The default is 300. 0 indicates that there is no caching. **`cache_size`** The maximum number of secrets that can be stored in the cache, in the range 1 to 1000. The default is 1000. **`ssrf_headers`** A list of header names the Secrets Manager Agent checks for the SSRF token. The default is "X-Aws-Parameters-Secrets-Token, X-Vault-Token". **`ssrf_env_variables`** A list of environment variable names the Secrets Manager Agent checks in sequential order for the SSRF token. The environment variable can contain the token or a reference to the token file as in: `AWS_TOKEN=file:///var/run/awssmatoken`. The default is "AWS\$1TOKEN, AWS\$1SESSION\$1TOKEN, AWS\$1CONTAINER\$1AUTHORIZATION\$1TOKEN". **`path_prefix`** The URI prefix used to determine if the request is a path based request. The default is "/v1/". **`max_conn`** The maximum number of connections from HTTP clients that the Secrets Manager Agent allows, in the range 1 to 1000. The default is 800. ## Optional features The Secrets Manager Agent can be built with optional features by passing the `--features` flag to `cargo build`. The available features are:Build features **`prefer-post-quantum`** Makes `X25519MLKEM768` the highest-priority key exchange algorithm. Otherwise, it is available but not highest-priority. `X25519MLKEM768` is a hybrid, post-quantum-secure key exchange algorithm. **`fips`** Restricts the cipher suites used by the agent to only FIPS-approved ciphers. ## Logging **Local logging** The Secrets Manager Agent logs errors locally to the file `logs/secrets_manager_agent.log` or to stdout/stderr depending on the `log_to_file` config variable. When your application calls the Secrets Manager Agent to get a secret, those calls appear in the local log. They do not appear in the CloudTrail logs. **Log rotation** The Secrets Manager Agent creates a new log file when the file reaches 10 MB, and it stores up to five log files total. **AWS service logging** The log does not go to Secrets Manager, CloudTrail, or CloudWatch. Requests to get secrets from the Secrets Manager Agent do not appear in those logs. When the Secrets Manager Agent makes a call to Secrets Manager to get a secret, that call is recorded in CloudTrail with a user agent string containing `aws-secrets-manager-agent`. You can configure logging options in the [Configure the Secrets Manager Agent](#secrets-manager-agent-config). ## Security considerations **Domain of trust** For an agent architecture, the domain of trust is where the agent endpoint and SSRF token are accessible, which is usually the entire host. The domain of trust for the Secrets Manager Agent should match the domain where the Secrets Manager credentials are available in order to maintain the same security posture. For example, on Amazon EC2 the domain of trust for the Secrets Manager Agent would be the same as the domain of the credentials when using roles for Amazon EC2. **Important** Security conscious applications that are not already using an agent solution with the Secrets Manager credentials locked down to the application should consider using the language-specific AWS SDKs or caching solutions. For more information, see [Get secrets](https://docs.aws.amazon.com/secretsmanager/latest/userguide/retrieving-secrets.html).