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k2v signature verification: double urlencoding (see comment in source code)

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This commit is contained in:
Alex Auvolat 2023-05-18 00:06:03 +02:00
parent c26a4308b4
commit 746b0090e4
2 changed files with 39 additions and 2 deletions
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40
src/api/signature/payload.rs
View file

@ -19,7 +19,7 @@ use crate::signature::error::*;
pub async fn check_payload_signature(
garage: &Garage,
service: &str,
service: &'static str,
request: &Request<Body>,
) -> Result<(Option<Key>, Option<Hash>), Error> {
let mut headers = HashMap::new();
@ -51,6 +51,7 @@ pub async fn check_payload_signature(
};
let canonical_request = canonical_request(
service,
request.method(),
request.uri(),
&headers,
@ -231,15 +232,50 @@ pub fn string_to_sign(datetime: &DateTime<Utc>, scope_string: &str, canonical_re
}
pub fn canonical_request(
service: &'static str,
method: &Method,
uri: &hyper::Uri,
headers: &HashMap<String, String>,
signed_headers: &str,
content_sha256: &str,
) -> String {
// There seems to be evidence that in AWSv4 signatures, the path component is url-encoded
// a second time when building the canonical request, as specified in this documentation page:
// -> https://docs.aws.amazon.com/rolesanywhere/latest/userguide/authentication-sign-process.html
// However this documentation page is for a specific service ("roles anywhere"), and
// in the S3 service we know for a fact that there is no double-urlencoding, because all of
// the tests we made with external software work without it.
//
// The theory is that double-urlencoding occurs for all services except S3,
// which is what is implemented in rusoto_signature:
// -> https://docs.rs/rusoto_signature/latest/src/rusoto_signature/signature.rs.html#464
//
// Digging into the code of the official AWS Rust SDK, we learn that double-URI-encoding can
// be set or unset on a per-request basis (the signature crates, aws-sigv4 and aws-sig-auth,
// are agnostic to this). Grepping the codebase confirms that S3 is the only API for which
// double_uri_encode is set to false, meaning it is true (its default value) for all other
// AWS services. We will therefore implement this behavior in Garage as well.
//
// Note that this documentation page, which is touted as the "authoritative reference" on
// AWSv4 signatures, makes no mention of either single- or double-urlencoding:
// -> https://docs.aws.amazon.com/IAM/latest/UserGuide/create-signed-request.html
// This page of the S3 documentation does also not mention anything specific:
// -> https://docs.aws.amazon.com/AmazonS3/latest/API/sig-v4-header-based-auth.html
//
// Note that there is also the issue of path normalization, which I hope is unrelated to the
// one of URI-encoding. At least in aws-sigv4 both parameters can be set independently,
// and rusoto_signature does not seem to do any effective path normalization, even though
// it mentions it in the comments (same link to the souce code as above).
// We make the explicit choice of NOT normalizing paths in the K2V API because doing so
// would make non-normalized paths invalid K2V partition keys, and we don't want that.
let path: std::borrow::Cow<str> = if service != "s3" {
uri_encode(uri.path(), false).into()
} else {
uri.path().into()
};
[
method.as_str(),
uri.path(),
&path,
&canonical_query_string(uri),
&canonical_header_string(headers, signed_headers),
"",

1
src/garage/tests/common/custom_requester.rs
View file

@ -209,6 +209,7 @@ impl<'a> RequestBuilder<'a> {
all_headers.extend(self.unsigned_headers.clone());
let canonical_request = signature::payload::canonical_request(
self.service,
&self.method,
&Uri::try_from(&uri).unwrap(),
&all_headers,