Module migration 

Migrating from 0.10 to 0.11

Version 0.11 brings significant changes to the scratchstack-aws-signature crate. These changes are intended to make the crate more ergonomic (easier for consumers to use) and more efficient (less copying of data).

Unfortunately, this means that the 0.11 version is not backwards compatible with the 0.10 version.

Changes

Elimination of Request type.

The main change is the elimination of the scratchstack_aws_signature::Request type. Instead, http::Request is used directly and there is no longer a need to copy data from one Request type to the other.

With this, there is also no need to use the GetSigningKeyRequest type in the validation code. (This type is used to pass get signing key requests.)

This sample code from 0.10:

let http_req = http::Request::get("https://example.com").body(())?;
let sig_req = scratchstack_aws_signature::Request::from_http_request_parts(
    &http_req.into_parts().0, None);
let gsk_req = sig_req.to_get_signing_request(SigningKeyKind::KSigning, REGION, SERVICE)?;
let (principal, signing_key) = get_signing_key_service.call(gsk_req).await?;
sig4_verify(&sig_req, &signing_key, None, REGION, SERVICE)?;

Would be written in 0.11:

let http_req = http::Request::get("https://example.com").body(())?;
let (parts, body, auth) = sigv4_validate_request(
    req, &REGION, &SERVICE, &mut get_signing_key_service, Utc::now(),
    NO_ADDITIONAL_SIGNED_HEADERS, SignatureOptions::default())?;

Compile-time key type checking

In 0.10, keys of different types were all stored as the SigningKey type with a discriminator, SigningKeyKind, indicating the underlying key type at runtime. This made it impossible to use compile-time checks to ensure that the correct key type was used.

In 0.11, the SigningKey type has been replaced with a distinct key type for each key type:

• KSecretKey: The raw secret key prefixed with "AWS4".
• KDateKey: Key derived KSecretKey and the current UTC date.
• KRegionKey: Key derived from KDateKey and the region.
• KServiceKey: Key derived from KRegionKey and the service.
• KSigningKey: Key derived from KServiceKey and the string “aws4_request”.

These types have fixed sizes. KSecretKey has a const parameter that specifies the maximum secret key size (including the "AWS4" prefix), which defaults to 44 (the size of AWS-issued secret keys).

Signing key functions changed

Previously, get_signing_key_fn() was used to convert a function into a Tower Service that could be used to get signing keys. This is now called service_for_signing_key_fn().

In addition, the signature of the function passed in has changed. Previously, parameters to the function were broken out separately:

async fn get_signing_key(
   kind: SigningKeyKind,
   access_key: String,
   session_token: Option<String>,
   request_date: DateTime<Utc>,
   region: String,
   service: String)
-> Result<(PrincipalActor, SigningKey), SignatureError>

These parameters are now encapsulated in the (non-exhaustive) GetSigningKeyRequest type, and the tuple of (PrincipalActor, SigningKey) is now encapsulated in the GetSigningKeyResponse type. The function signature is now:

use tower::BoxError;
 
async fn get_signing_key(req: GetSigningKeyRequest) -> Result<GetSigningKeyResponse, BoxError>

Both of these types have builder APIs to construct them.

Principal types updated

This crate uses the Principal type from scratchstack_aws_principal v0.4. Previously, the PrincipalActor from v0.3 of that crate was used. In v0.4, only actor principals are supported; v0.3 attempted to support both actor and policy principals, but this was riddled with implementation errors.

Type-dependencies from other crates exposed

This crate now uses types two other crates in its APIs: scratchstack_aws_principal and scratchstack_errors. To reduce the possibility of accidentally using a different version of these crates, they are re-exported here under principal and errors modules, respectively.