aws_config/web_identity_token.rs
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/*
* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
* SPDX-License-Identifier: Apache-2.0
*/
//! Load Credentials from Web Identity Tokens
//!
//! Web identity tokens can be loaded from file. The path may be set in one of three ways:
//! 1. [Environment Variables](#environment-variable-configuration)
//! 2. [AWS profile](#aws-profile-configuration) defined in `~/.aws/config`
//! 3. Static configuration via [`static_configuration`](Builder::static_configuration)
//!
//! _Note: [WebIdentityTokenCredentialsProvider] is part of the [default provider chain](crate::default_provider).
//! Unless you need specific behavior or configuration overrides, it is recommended to use the
//! default chain instead of using this provider directly. This client should be considered a "low level"
//! client as it does not include caching or profile-file resolution when used in isolation._
//!
//! ## Environment Variable Configuration
//! WebIdentityTokenCredentialProvider will load the following environment variables:
//! - `AWS_WEB_IDENTITY_TOKEN_FILE`: **required**, location to find the token file containing a JWT token
//! - `AWS_ROLE_ARN`: **required**, role ARN to assume
//! - `AWS_ROLE_SESSION_NAME`: **optional**: Session name to use when assuming the role
//!
//! ## AWS Profile Configuration
//! _Note: Configuration of the web identity token provider via a shared profile is only supported
//! when using the [`ProfileFileCredentialsProvider`](crate::profile::credentials)._
//!
//! Web identity token credentials can be loaded from `~/.aws/config` in two ways:
//! 1. Directly:
//! ```ini
//! [profile default]
//! role_arn = arn:aws:iam::1234567890123:role/RoleA
//! web_identity_token_file = /token.jwt
//! ```
//!
//! 2. As a source profile for another role:
//!
//! ```ini
//! [profile default]
//! role_arn = arn:aws:iam::123456789:role/RoleA
//! source_profile = base
//!
//! [profile base]
//! role_arn = arn:aws:iam::123456789012:role/s3-reader
//! web_identity_token_file = /token.jwt
//! ```
//!
//! # Examples
//! Web Identity Token providers are part of the [default chain](crate::default_provider::credentials).
//! However, they may be directly constructed if you don't want to use the default provider chain.
//! Unless overridden with [`static_configuration`](Builder::static_configuration), the provider will
//! load configuration from environment variables.
//!
//! ```no_run
//! # async fn test() {
//! use aws_config::web_identity_token::WebIdentityTokenCredentialsProvider;
//! use aws_config::provider_config::ProviderConfig;
//! let provider = WebIdentityTokenCredentialsProvider::builder()
//! .configure(&ProviderConfig::with_default_region().await)
//! .build();
//! # }
//! ```
use crate::provider_config::ProviderConfig;
use crate::sts;
use aws_credential_types::provider::{self, error::CredentialsError, future, ProvideCredentials};
use aws_sdk_sts::{types::PolicyDescriptorType, Client as StsClient};
use aws_smithy_async::time::SharedTimeSource;
use aws_smithy_types::error::display::DisplayErrorContext;
use aws_types::os_shim_internal::{Env, Fs};
use std::borrow::Cow;
use std::path::{Path, PathBuf};
const ENV_VAR_TOKEN_FILE: &str = "AWS_WEB_IDENTITY_TOKEN_FILE";
const ENV_VAR_ROLE_ARN: &str = "AWS_ROLE_ARN";
const ENV_VAR_SESSION_NAME: &str = "AWS_ROLE_SESSION_NAME";
/// Credential provider to load credentials from Web Identity Tokens
///
/// See Module documentation for more details
#[derive(Debug)]
pub struct WebIdentityTokenCredentialsProvider {
source: Source,
time_source: SharedTimeSource,
fs: Fs,
sts_client: StsClient,
policy: Option<String>,
policy_arns: Option<Vec<PolicyDescriptorType>>,
}
impl WebIdentityTokenCredentialsProvider {
/// Builder for this credentials provider
pub fn builder() -> Builder {
Builder::default()
}
}
#[derive(Debug)]
enum Source {
Env(Env),
Static(StaticConfiguration),
}
/// Statically configured WebIdentityToken configuration
#[derive(Debug, Clone)]
pub struct StaticConfiguration {
/// Location of the file containing the web identity token
pub web_identity_token_file: PathBuf,
/// RoleArn to assume
pub role_arn: String,
/// Session name to use when assuming the role
pub session_name: String,
}
impl ProvideCredentials for WebIdentityTokenCredentialsProvider {
fn provide_credentials<'a>(&'a self) -> future::ProvideCredentials<'a>
where
Self: 'a,
{
future::ProvideCredentials::new(self.credentials())
}
}
impl WebIdentityTokenCredentialsProvider {
fn source(&self) -> Result<Cow<'_, StaticConfiguration>, CredentialsError> {
match &self.source {
Source::Env(env) => {
let token_file = env.get(ENV_VAR_TOKEN_FILE).map_err(|_| {
CredentialsError::not_loaded(format!("${} was not set", ENV_VAR_TOKEN_FILE))
})?;
let role_arn = env.get(ENV_VAR_ROLE_ARN).map_err(|_| {
CredentialsError::invalid_configuration(
"AWS_ROLE_ARN environment variable must be set",
)
})?;
let session_name = env.get(ENV_VAR_SESSION_NAME).unwrap_or_else(|_| {
sts::util::default_session_name("web-identity-token", self.time_source.now())
});
Ok(Cow::Owned(StaticConfiguration {
web_identity_token_file: token_file.into(),
role_arn,
session_name,
}))
}
Source::Static(conf) => Ok(Cow::Borrowed(conf)),
}
}
async fn credentials(&self) -> provider::Result {
let conf = self.source()?;
load_credentials(
&self.fs,
&self.sts_client,
self.policy.clone(),
self.policy_arns.clone(),
&conf.web_identity_token_file,
&conf.role_arn,
&conf.session_name,
)
.await
}
}
/// Builder for [`WebIdentityTokenCredentialsProvider`].
#[derive(Debug, Default)]
pub struct Builder {
source: Option<Source>,
config: Option<ProviderConfig>,
policy: Option<String>,
policy_arns: Option<Vec<PolicyDescriptorType>>,
}
impl Builder {
/// Configure generic options of the [WebIdentityTokenCredentialsProvider]
///
/// # Examples
/// ```no_run
/// # async fn test() {
/// use aws_config::web_identity_token::WebIdentityTokenCredentialsProvider;
/// use aws_config::provider_config::ProviderConfig;
/// let provider = WebIdentityTokenCredentialsProvider::builder()
/// .configure(&ProviderConfig::with_default_region().await)
/// .build();
/// # }
/// ```
pub fn configure(mut self, provider_config: &ProviderConfig) -> Self {
self.config = Some(provider_config.clone());
self
}
/// Configure this builder to use [`StaticConfiguration`].
///
/// WebIdentityToken providers load credentials from the file system. The file system path used
/// may either determine be loaded from environment variables (default), or via a statically
/// configured path.
pub fn static_configuration(mut self, config: StaticConfiguration) -> Self {
self.source = Some(Source::Static(config));
self
}
/// Set an IAM policy in JSON format that you want to use as an inline session policy.
///
/// This parameter is optional
/// For more information, see
/// [policy](aws_sdk_sts::operation::assume_role::builders::AssumeRoleInputBuilder::policy_arns)
pub fn policy(mut self, policy: impl Into<String>) -> Self {
self.policy = Some(policy.into());
self
}
/// Set the Amazon Resource Names (ARNs) of the IAM managed policies that you want to use as managed session policies.
///
/// This parameter is optional.
/// For more information, see
/// [policy_arns](aws_sdk_sts::operation::assume_role::builders::AssumeRoleInputBuilder::policy_arns)
pub fn policy_arns(mut self, policy_arns: Vec<String>) -> Self {
self.policy_arns = Some(
policy_arns
.into_iter()
.map(|arn| PolicyDescriptorType::builder().arn(arn).build())
.collect::<Vec<_>>(),
);
self
}
/// Build a [`WebIdentityTokenCredentialsProvider`]
///
/// ## Panics
/// If no connector has been enabled via crate features and no connector has been provided via the
/// builder, this function will panic.
pub fn build(self) -> WebIdentityTokenCredentialsProvider {
let conf = self.config.unwrap_or_default();
let source = self.source.unwrap_or_else(|| Source::Env(conf.env()));
WebIdentityTokenCredentialsProvider {
source,
fs: conf.fs(),
sts_client: StsClient::new(&conf.client_config()),
time_source: conf.time_source(),
policy: self.policy,
policy_arns: self.policy_arns,
}
}
}
async fn load_credentials(
fs: &Fs,
sts_client: &StsClient,
policy: Option<String>,
policy_arns: Option<Vec<PolicyDescriptorType>>,
token_file: impl AsRef<Path>,
role_arn: &str,
session_name: &str,
) -> provider::Result {
let token = fs
.read_to_end(token_file)
.await
.map_err(CredentialsError::provider_error)?;
let token = String::from_utf8(token).map_err(|_utf_8_error| {
CredentialsError::unhandled("WebIdentityToken was not valid UTF-8")
})?;
let resp = sts_client.assume_role_with_web_identity()
.role_arn(role_arn)
.role_session_name(session_name)
.set_policy(policy)
.set_policy_arns(policy_arns)
.web_identity_token(token)
.send()
.await
.map_err(|sdk_error| {
tracing::warn!(error = %DisplayErrorContext(&sdk_error), "STS returned an error assuming web identity role");
CredentialsError::provider_error(sdk_error)
})?;
sts::util::into_credentials(resp.credentials, "WebIdentityToken")
}
#[cfg(test)]
mod test {
use crate::provider_config::ProviderConfig;
use crate::test_case::no_traffic_client;
use crate::web_identity_token::{
Builder, ENV_VAR_ROLE_ARN, ENV_VAR_SESSION_NAME, ENV_VAR_TOKEN_FILE,
};
use aws_credential_types::provider::error::CredentialsError;
use aws_smithy_async::rt::sleep::TokioSleep;
use aws_smithy_types::error::display::DisplayErrorContext;
use aws_types::os_shim_internal::{Env, Fs};
use aws_types::region::Region;
use std::collections::HashMap;
#[tokio::test]
async fn unloaded_provider() {
// empty environment
let conf = ProviderConfig::empty()
.with_sleep_impl(TokioSleep::new())
.with_env(Env::from_slice(&[]))
.with_http_client(no_traffic_client())
.with_region(Some(Region::from_static("us-east-1")));
let provider = Builder::default().configure(&conf).build();
let err = provider
.credentials()
.await
.expect_err("should fail, provider not loaded");
match err {
CredentialsError::CredentialsNotLoaded { .. } => { /* ok */ }
_ => panic!("incorrect error variant"),
}
}
#[tokio::test]
async fn missing_env_var() {
let env = Env::from_slice(&[(ENV_VAR_TOKEN_FILE, "/token.jwt")]);
let region = Some(Region::new("us-east-1"));
let provider = Builder::default()
.configure(
&ProviderConfig::empty()
.with_sleep_impl(TokioSleep::new())
.with_region(region)
.with_env(env)
.with_http_client(no_traffic_client()),
)
.build();
let err = provider
.credentials()
.await
.expect_err("should fail, provider not loaded");
assert!(
format!("{}", DisplayErrorContext(&err)).contains("AWS_ROLE_ARN"),
"`{}` did not contain expected string",
err
);
match err {
CredentialsError::InvalidConfiguration { .. } => { /* ok */ }
_ => panic!("incorrect error variant"),
}
}
#[tokio::test]
async fn fs_missing_file() {
let env = Env::from_slice(&[
(ENV_VAR_TOKEN_FILE, "/token.jwt"),
(ENV_VAR_ROLE_ARN, "arn:aws:iam::123456789123:role/test-role"),
(ENV_VAR_SESSION_NAME, "test-session"),
]);
let fs = Fs::from_raw_map(HashMap::new());
let provider = Builder::default()
.configure(
&ProviderConfig::empty()
.with_sleep_impl(TokioSleep::new())
.with_http_client(no_traffic_client())
.with_region(Some(Region::new("us-east-1")))
.with_env(env)
.with_fs(fs),
)
.build();
let err = provider.credentials().await.expect_err("no JWT token");
match err {
CredentialsError::ProviderError { .. } => { /* ok */ }
_ => panic!("incorrect error variant"),
}
}
}