315 lines
22 KiB
Plaintext
315 lines
22 KiB
Plaintext
---
|
|
layout: docs
|
|
page_title: Vault Lambda Extension
|
|
description: >-
|
|
The Vault Lambda Extension allows a Lambda function to read secrets from a Vault deployment.
|
|
---
|
|
|
|
# Vault Lambda Extension
|
|
|
|
AWS Lambda lets you run code without provisioning and managing servers.
|
|
The [Vault Lambda Extension](https://github.com/hashicorp/vault-lambda-extension) utilizes the AWS Lambda Extensions API to help your Lambda function read secrets from your Vault deployment.
|
|
You can use the [quick-start](https://github.com/hashicorp/vault-lambda-extension/tree/main/quick-start) directory which has an end-to-end example if you would like to try out the extension from scratch.
|
|
|
|
~> **Note**: If you decide to create one from scratch, be aware that this will create real infrastructure with an associated cost as per AWS' pricing.
|
|
|
|
## Usage
|
|
|
|
To use the extension, include one of the following ARNs as a layer in your
|
|
Lambda function, depending on your desired architecture.
|
|
|
|
amd64 (x86_64):
|
|
```text
|
|
arn:aws:lambda:<your-region>:634166935893:layer:vault-lambda-extension:13
|
|
```
|
|
|
|
arm64:
|
|
```text
|
|
arn:aws:lambda:<your-region>:634166935893:layer:vault-lambda-extension-arm64:1
|
|
```
|
|
|
|
Where region may be any of `af-south-1`, `ap-east-1`, `ap-northeast-1`,
|
|
`ap-northeast-2`, `ap-northeast-3`, `ap-south-1`, `ap-southeast-1`,
|
|
`ap-southeast-2`, `ca-central-1`, `eu-central-1`, `eu-north-1`, `eu-south-1`,
|
|
`eu-west-1`, `eu-west-2`, `eu-west-3`, `me-south-1`, `sa-east-1`, `us-east-1`,
|
|
`us-east-2`, `us-west-1`, `us-west-2`.
|
|
|
|
The extension authenticates with Vault using [AWS IAM auth](/vault/docs/auth/aws),
|
|
and all configuration is supplied via environment variables. There are two methods
|
|
to read secrets, which can both be used side-by-side:
|
|
|
|
- **Recommended**: Make unauthenticated requests to the extension's local proxy
|
|
server at `http://127.0.0.1:8200`, which will add an authentication header and
|
|
proxy to the configured `VAULT_ADDR`. Responses from Vault are returned without
|
|
modification.
|
|
- Configure environment variables such as `VAULT_SECRET_PATH` for the extension
|
|
to read a secret and write it to disk.
|
|
|
|
### Adding the extension to your existing Lambda and Vault infrastructure
|
|
|
|
#### Requirements
|
|
|
|
- ARN of the role your Lambda runs as
|
|
- An instance of Vault accessible from AWS Lambda
|
|
- An authenticated `vault` client
|
|
- A secret in Vault that you want your Lambda to access, and a policy giving read access to it
|
|
- Your Lambda function must use one of the [supported runtimes][https://docs.aws.amazon.com/lambda/latest/dg/runtimes-extensions-api.html] for extensions
|
|
|
|
#### Step 1. Configure Vault
|
|
|
|
Enable the aws auth method.
|
|
|
|
```shell-session
|
|
$ vault auth enable aws
|
|
```
|
|
|
|
Configure the AWS client to use the default options.
|
|
|
|
```shell-session
|
|
$ vault write -force auth/aws/config/client
|
|
```
|
|
|
|
Create a role prefixed with the AWS environment name.
|
|
|
|
```shell-session
|
|
$ vault write auth/aws/role/vault-lambda-role \
|
|
auth_type=iam \
|
|
bound_iam_principal_arn="${YOUR_ARN}" \
|
|
policies="${YOUR_POLICY}" \
|
|
ttl=1h
|
|
```
|
|
|
|
#### Step 2. Option a) Install the extension for Lambda functions packaged in zip archives
|
|
|
|
If you deploy your Lambda function as a zip file, you can add the extension
|
|
to your Lambda layers using the console or [cli](https://docs.aws.amazon.com/lambda/latest/dg/configuration-layers.html#configuration-layers-using):
|
|
|
|
```text
|
|
arn:aws:lambda:<your-region>:634166935893:layer:vault-lambda-extension:11
|
|
```
|
|
|
|
#### Step 2. Option b) Install the extension for Lambda functions packaged in container images
|
|
|
|
Alternatively, if you deploy your Lambda function as a container image, simply
|
|
place the built binary in the `/opt/extensions` directory of your image.
|
|
|
|
Fetch the binary from
|
|
[releases.hashicorp.com](https://releases.hashicorp.com/vault-lambda-extension/).
|
|
The following command requires cURL.
|
|
|
|
```shell-session
|
|
$ curl --silent https://releases.hashicorp.com/vault-lambda-extension/0.5.0/vault-lambda-extension_0.5.0_linux_amd64.zip \
|
|
--output vault-lambda-extension.zip
|
|
```
|
|
|
|
Unzip the donwloaded binary.
|
|
|
|
```shell-session
|
|
$ unzip vault-lambda-extension.zip
|
|
```
|
|
|
|
Optionally, you can verify the integrity of the downloaded zip using the release
|
|
archive checksum verification instructions
|
|
[here](https://www.hashicorp.com/security).
|
|
|
|
Or to build the binary from source. This requires Golang installed. Run from the root of this repository.
|
|
|
|
```shell-session
|
|
$ GOOS=linux GOARCH=amd64 go build -o vault-lambda-extension main.go
|
|
```
|
|
|
|
#### Step 3. Configure vault-lambda-extension
|
|
|
|
Configure the extension using [Lambda environment
|
|
variables](https://docs.aws.amazon.com/lambda/latest/dg/configuration-envvars.html):
|
|
|
|
Set the Vault API address.
|
|
|
|
```shell-session
|
|
$ VAULT_ADDR=http://vault.example.com:8200
|
|
```
|
|
|
|
Set the AWS IAM auth mount point (i.e. the path segment after `auth/` from above).
|
|
|
|
```shell-session
|
|
$ VAULT_AUTH_PROVIDER=aws
|
|
```
|
|
|
|
Set the Vault role to authenticate as. Must be configured for the ARN of your
|
|
Lambda's role.
|
|
|
|
```shell-session
|
|
$ VAULT_AUTH_ROLE=vault-lambda-role
|
|
```
|
|
|
|
The path to a secret in Vault. Can be static or dynamic. Unless
|
|
VAULT_SECRET_FILE is specified, JSON response will be written to
|
|
`/tmp/vault/secret.json`.
|
|
|
|
```shell-session
|
|
$ VAULT_SECRET_PATH=secret/lambda-app/token
|
|
```
|
|
|
|
If everything is correctly set up, your Lambda function can then read secret
|
|
material from `/tmp/vault/secret.json`. The exact contents of the JSON object
|
|
will depend on the secret read, but its schema is the [Secret struct](https://github.com/hashicorp/vault/blob/api/v1.0.4/api/secret.go#L15)
|
|
from the Vault API module.
|
|
|
|
Alternatively, you can send normal Vault API requests over HTTP to the local
|
|
proxy at `http://127.0.0.1:8200`, and the extension will add authentication
|
|
before forwarding the request. Vault responses will be returned unmodified.
|
|
Although local communication is over plain HTTP, the proxy server will use TLS
|
|
to communicate with Vault if configured to do so as detailed below.
|
|
|
|
## Configuration
|
|
|
|
The extension is configured via [Lambda environment variables](https://docs.aws.amazon.com/lambda/latest/dg/configuration-envvars.html).
|
|
Most of the [Vault CLI client's environment variables](/vault/docs/commands#environment-variables) are available,
|
|
as well as some additional variables to configure auth, which secret(s) to read and
|
|
where to write secrets.
|
|
|
|
| Environment variable | Description | Required | Example value |
|
|
| --------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------- | --------------------------- |
|
|
| `VLE_VAULT_ADDR` | Vault address to connect to. Takes precedence over `VAULT_ADDR` so that clients of the proxy server can be configured using the standard `VAULT_ADDR` | No | `https://x.x.x.x:8200` |
|
|
| `VAULT_ADDR` | Vault address to connect to if `VLE_VAULT_ADDR` is not set. Required if `VLE_VAULT_ADDR` is not set | No | `https://x.x.x.x:8200` |
|
|
| `VAULT_AUTH_PROVIDER` | Name of the configured AWS IAM auth route on Vault | Yes | `aws` |
|
|
| `VAULT_AUTH_ROLE` | Vault role to authenticate as | Yes | `lambda-app` |
|
|
| `VAULT_IAM_SERVER_ID` | Value to pass to the Vault server via the [`X-Vault-AWS-IAM-Server-ID` HTTP Header for AWS Authentication](/vault/api-docs/auth/aws#iam_server_id_header_value) | No | `vault.example.com` |
|
|
| `VAULT_SECRET_PATH` | Secret path to read, written to `/tmp/vault/secret.json` unless `VAULT_SECRET_FILE` is specified | No | `database/creds/lambda-app` |
|
|
| `VAULT_SECRET_FILE` | Path to write the JSON response for `VAULT_SECRET_PATH` | No | `/tmp/db.json` |
|
|
| `VAULT_SECRET_PATH_FOO` | Additional secret path to read, where FOO can be any name, as long as a matching `VAULT_SECRET_FILE_FOO` is specified | No | `secret/lambda-app/token` |
|
|
| `VAULT_SECRET_FILE_FOO` | Must exist for any correspondingly named `VAULT_SECRET_PATH_FOO`. Name has no further effect beyond matching to the correct path variable | No | `/tmp/token` |
|
|
| `VAULT_TOKEN_EXPIRY_GRACE_PERIOD` | Period at the end of the proxy server's auth token TTL where it will consider the token expired and attempt to re-authenticate to Vault. Must have a unit and be parseable by `time.Duration`. Defaults to 10s. | No | `1m` |
|
|
| `VAULT_STS_ENDPOINT_REGION` | The region of the STS regional endpoint to authenticate with. If the AWS IAM auth mount specified uses a regional STS endpoint, then this needs to match the region of that endpoint. Defaults to using the global endpoint, or the region the Lambda resides in if `AWS_STS_REGIONAL_ENDPOINTS` is set to `regional` | No | `eu-west-1` |
|
|
|
|
The remaining environment variables are not required, and function exactly as
|
|
described in the [Vault Commands (CLI)](/vault/docs/commands#environment-variables) documentation. However,
|
|
note that `VAULT_CLIENT_TIMEOUT` cannot extend the timeout beyond the 10s
|
|
initialization timeout imposed by the Extensions API when writing files to disk.
|
|
|
|
| Environment variable | Description | Required | Example value |
|
|
| ----------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------- | ------------------- |
|
|
| `VAULT_CACERT` | Path to a PEM-encoded CA certificate _file_ on the local disk | No | `/tmp/ca.crt` |
|
|
| `VAULT_CAPATH` | Path to a _directory_ of PEM-encoded CA certificate files on the local disk | No | `/tmp/certs` |
|
|
| `VAULT_CLIENT_CERT` | Path to a PEM-encoded client certificate on the local disk | No | `/tmp/client.crt` |
|
|
| `VAULT_CLIENT_KEY` | Path to an unencrypted, PEM-encoded private key on disk which corresponds to the matching client certificate | No | `/tmp/client.key` |
|
|
| `VAULT_CLIENT_TIMEOUT` | Timeout for Vault requests. Default value is 60s. Ignored by proxy server. **Any value over 10s will exceed the Extensions API timeout and therefore have no effect** | No | `5s` |
|
|
| `VAULT_MAX_RETRIES` | Maximum number of retries on `5xx` error codes. Defaults to 2. Ignored by proxy server | No | `2` |
|
|
| `VAULT_SKIP_VERIFY` | Do not verify Vault's presented certificate before communicating with it. Setting this variable is not recommended and voids Vault's [security model](/vault/docs/internals/security) | No | `true` |
|
|
| `VAULT_TLS_SERVER_NAME` | Name to use as the SNI host when connecting via TLS | No | `vault.example.com` |
|
|
| `VAULT_RATE_LIMIT` | Only applies to a single invocation of the extension. See [Vault Commands (CLI)](/vault/docs/commands#environment-variables) documentation for details. Ignored by proxy server | No | `10` |
|
|
| `VAULT_NAMESPACE` | The namespace to use for pre-configured secrets. Ignored by proxy server | No | `education` |
|
|
| `VAULT_DEFAULT_CACHE_TTL` | The time to live configuration (aka, TTL) of the cache used by proxy server. Must have a unit and be parsable as a time.Duration. Required for caching to be enabled. | No | `15m` |
|
|
| `VAULT_DEFAULT_CACHE_ENABLED` | Enable caching for all requests, without needing to set the X-Vault-Cache-Control header for each request. Must be set to a boolean value. | No | `true` |
|
|
| `VAULT_ASSUMED_ROLE_ARN` | Valid ARN of an IAM role that can be assumed by the execution role assigned to your Lambda function. | No | `arn:aws:iam::123456789012:role/xaccounts3access`
|
|
| `VAULT_LOG_LEVEL` | Log verbosity level, one of TRACE, DEBUG, INFO, WARN, ERROR, OFF. Defaults to INFO. | No | `DEBUG`
|
|
|
|
### AWS STS client configuration
|
|
|
|
In addition to Vault configuration, you can configure certain aspects of the STS
|
|
client the extension uses through the usual AWS environment variables. For example,
|
|
if your Vault instance's IAM auth is configured to use regional STS endpoints:
|
|
|
|
```shell-session
|
|
$ vault write auth/aws/config/client \
|
|
sts_endpoint="https://sts.eu-west-1.amazonaws.com" \
|
|
sts_region="eu-west-1"
|
|
```
|
|
|
|
Then you may need to configure the extension's STS client to also use the regional
|
|
STS endpoint by setting `AWS_STS_REGIONAL_ENDPOINTS=regional`, because both the AWS Golang
|
|
SDK and Vault IAM auth method default to using the global endpoint in many regions.
|
|
See documentation on [`sts_regional_endpoints`](https://docs.aws.amazon.com/credref/latest/refdocs/setting-global-sts_regional_endpoints.html) for more information.
|
|
|
|
### Caching
|
|
|
|
Caching can be configured for the extension's local proxy server so that it does
|
|
not forward every HTTP request to Vault. The main consideration behind caching
|
|
design is to make caching an explicit opt-in at the request level, so that it is
|
|
only enabled for scenarios where caching makes sense without negative impact in
|
|
others. To turn on caching, set the environment variable
|
|
`VAULT_DEFAULT_CACHE_TTL` to a valid value that is parsable as a time.Duration
|
|
in Go, for example, "15m", "1h", "2m3s" or "1h2m3s", depending on application
|
|
needs. An invalid or negative value will be treated the same as a missing value,
|
|
in which case, caching will not be set up and enabled.
|
|
|
|
Then requests with HTTP method of "GET", and the HTTP header
|
|
`X-Vault-Cache-Control: cache` will be returned directly from the cache if
|
|
there's a cache hit. On a cache miss the request will be forwarded to Vault and
|
|
the response returned and cached. If the header is set to
|
|
`X-Vault-Cache-Control: recache`, the cache lookup will be skipped, and the
|
|
request will be forwarded to Vault and the response returned and cached.
|
|
Currently, the cache key is a hash of the request URL path, headers, body, and
|
|
token.
|
|
|
|
Caching may also be enabled for all requests by setting the environment variable
|
|
`VAULT_DEFAULT_CACHE_ENABLED` to `true`. Then all requests will be fetched and/or
|
|
cached as though the header `X-Vault-Cache-Control: cache` was present. Setting
|
|
the header to `nocache` on a request will opt-out of caching entirely in this
|
|
configuration. Setting the header to `recache` will skip the cache lookup and
|
|
return and cache the response from Vault as described previously.
|
|
|
|
## Limitations
|
|
|
|
Secrets written to disk or returned from the proxy server will not be automatically
|
|
refreshed when they expire. This is particularly important if you configure the
|
|
extension to write secrets to disk, because the extension will only write to disk
|
|
once per execution environment, rather than once per function invocation. If you
|
|
use [provisioned concurrency](https://docs.aws.amazon.com/lambda/latest/dg/configuration-concurrency.html#configuration-concurrency-provisioned) or if your Lambda
|
|
is invoked often enough that execution contexts live beyond the lifetime of the
|
|
secret, then secrets on disk are likely to become invalid.
|
|
|
|
In line with [Lambda best practices](https://docs.aws.amazon.com/lambda/latest/dg/best-practices.html), we recommend avoiding
|
|
writing secrets to disk where possible, and exclusively consuming secrets via
|
|
the proxy server. However, the proxy server will still not perform any additional
|
|
processing with returned secrets such as automatic lease renewal. The proxy server's
|
|
own Vault auth token is the only thing that gets automatically refreshed. It will
|
|
synchronously refresh its own token before proxying requests if the token is
|
|
expired (including a grace window), and it will attempt to renew its token if the
|
|
token is nearly expired but renewable.
|
|
|
|
## Performance impact
|
|
|
|
AWS Lambda pricing is based on [number of invocations, time of execution and memory
|
|
used](https://aws.amazon.com/lambda/pricing/). The following table details some approximate performance
|
|
related statistics to help assess the cost impact of this extension. Note that AWS
|
|
Lambda allocates [CPU power in proportion to memory](https://docs.aws.amazon.com/lambda/latest/dg/configuration-memory.html) so results
|
|
will vary widely. These benchmarks were run with the minimum 128MB of memory allocated
|
|
so aim to give an approximate baseline.
|
|
|
|
| Metric | Value | Description | Derivation |
|
|
| -------------- | ---------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------- |
|
|
| Layer size | 8.5MB | The size of the unpacked extension binary | `ls -la` |
|
|
| Init latency | 8.5ms (standard deviation 2.4ms) + one network round trip to authenticate to Vault | Extension initialization time in a new execution environment. Authentication round trip time will be highly deployment-dependent | Instrumented in code |
|
|
| Invoke latency | <1ms | The base processing time for each function invocation, assuming no calls to the proxy server | Instrumented in code |
|
|
| Memory impact | 12MB | The marginal impact on "Max Memory Used" when running the extension | As reported by Lambda when running Hello World function with and without extension |
|
|
|
|
## Uploading to your own AWS account and region
|
|
|
|
If you would like to upload the extension as a Lambda layer in your own AWS
|
|
account and region, you can do the following:
|
|
|
|
```shell-session
|
|
$ curl --silent https://releases.hashicorp.com/vault-lambda-extension/0.5.0/vault-lambda-extension_0.5.0_linux_amd64.zip \
|
|
--output vault-lambda-extension.zip
|
|
```
|
|
|
|
Set your target AWS region.
|
|
|
|
```shell-session
|
|
$ export REGION="YOUR REGION HERE"
|
|
```
|
|
|
|
Upload the extension as a Lambda layer.
|
|
|
|
```shell-session
|
|
$ aws lambda publish-layer-version \
|
|
--layer-name vault-lambda-extension \
|
|
--zip-file "fileb://vault-lambda-extension.zip" \
|
|
--region "${REGION}"
|
|
```
|
|
|
|
## Tutorial
|
|
|
|
For step-by-step instructions, refer to the [Vault AWS Lambda Extension](/vault/tutorials/app-integration/aws-lambda) tutorial for details on how to create an AWS Lambda function and use the Vault Lambda Extension to authenticate with Vault.
|