1 files changed, 352 insertions, 212 deletions

diff --git a/src/api/signature/payload.rs b/src/api/signature/payload.rs
index 423aad93..e2334ce7 100644
--- a/src/api/signature/payload.rs
+++ b/src/api/signature/payload.rs
@@ -1,7 +1,9 @@
 use std::collections::HashMap;
+use std::convert::{TryFrom, TryInto};
 
 use chrono::{DateTime, Duration, NaiveDateTime, TimeZone, Utc};
 use hmac::Mac;
+use hyper::header::{HeaderMap, HeaderName, HeaderValue, AUTHORIZATION, CONTENT_TYPE, HOST};
 use hyper::{body::Incoming as IncomingBody, Method, Request};
 use sha2::{Digest, Sha256};
 
@@ -17,64 +19,82 @@ use super::{compute_scope, signing_hmac};
 use crate::encoding::uri_encode;
 use crate::signature::error::*;
 
+pub const X_AMZ_ALGORITHM: HeaderName = HeaderName::from_static("x-amz-algorithm");
+pub const X_AMZ_CREDENTIAL: HeaderName = HeaderName::from_static("x-amz-credential");
+pub const X_AMZ_DATE: HeaderName = HeaderName::from_static("x-amz-date");
+pub const X_AMZ_EXPIRES: HeaderName = HeaderName::from_static("x-amz-expires");
+pub const X_AMZ_SIGNEDHEADERS: HeaderName = HeaderName::from_static("x-amz-signedheaders");
+pub const X_AMZ_SIGNATURE: HeaderName = HeaderName::from_static("x-amz-signature");
+pub const X_AMZ_CONTENT_SH256: HeaderName = HeaderName::from_static("x-amz-content-sha256");
+
+pub const AWS4_HMAC_SHA256: &str = "AWS4-HMAC-SHA256";
+pub const UNSIGNED_PAYLOAD: &str = "UNSIGNED-PAYLOAD";
+
 pub async fn check_payload_signature(
 	garage: &Garage,
 	service: &'static str,
 	request: &Request<IncomingBody>,
 ) -> Result<(Option<Key>, Option<Hash>), Error> {
-	let mut headers = HashMap::new();
-	for (key, val) in request.headers() {
-		headers.insert(key.to_string(), val.to_str()?.to_string());
-	}
-	if let Some(query) = request.uri().query() {
-		let query_pairs = url::form_urlencoded::parse(query.as_bytes());
-		for (key, val) in query_pairs {
-			headers.insert(key.to_lowercase(), val.to_string());
-		}
-	}
+	let query = parse_query_map(request.uri())?;
 
-	let authorization = if let Some(authorization) = headers.get("authorization") {
-		parse_authorization(authorization, &headers)?
-	} else if let Some(algorithm) = headers.get("x-amz-algorithm") {
-		parse_query_authorization(algorithm, &headers)?
+	let res = if query.contains_key(X_AMZ_ALGORITHM) {
+		check_presigned_signature(garage, service, request, query).await
 	} else {
-		let content_sha256 = headers.get("x-amz-content-sha256");
-		if let Some(content_sha256) = content_sha256.filter(|c| "UNSIGNED-PAYLOAD" != c.as_str()) {
-			let sha256 = hex::decode(content_sha256)
-				.ok()
-				.and_then(|bytes| Hash::try_from(&bytes))
-				.ok_or_bad_request("Invalid content sha256 hash")?;
-			return Ok((None, Some(sha256)));
-		} else {
-			return Ok((None, None));
-		}
+		check_standard_signature(garage, service, request, query).await
 	};
 
+	if let Err(e) = &res {
+		error!("ERROR IN SIGNATURE\n{:?}\n{}", request, e);
+	}
+
+	res
+}
+
+async fn check_standard_signature(
+	garage: &Garage,
+	service: &'static str,
+	request: &Request<IncomingBody>,
+	query: HeaderMap,
+) -> Result<(Option<Key>, Option<Hash>), Error> {
+	let authorization = Authorization::parse(request.headers())?;
+
+	// Verify that all necessary request headers are signed
+	let signed_headers = split_signed_headers(&authorization)?;
+	for (name, _) in request.headers().iter() {
+		if name.as_str().starts_with("x-amz-") || name == CONTENT_TYPE {
+			if !signed_headers.contains(name) {
+				return Err(Error::bad_request(format!(
+					"Header `{}` should be signed",
+					name
+				)));
+			}
+		}
+	}
+	if !signed_headers.contains(&HOST) {
+		return Err(Error::bad_request("Header `Host` should be signed"));
+	}
+
 	let canonical_request = canonical_request(
 		service,
 		request.method(),
-		request.uri(),
-		&headers,
-		&authorization.signed_headers,
+		request.uri().path(),
+		&query,
+		request.headers(),
+		signed_headers,
 		&authorization.content_sha256,
+	)?;
+	let string_to_sign = string_to_sign(
+		&authorization.date,
+		&authorization.scope,
+		&canonical_request,
 	);
-	let (_, scope) = parse_credential(&authorization.credential)?;
-	let string_to_sign = string_to_sign(&authorization.date, &scope, &canonical_request);
 
 	trace!("canonical request:\n{}", canonical_request);
 	trace!("string to sign:\n{}", string_to_sign);
 
-	let key = verify_v4(
-		garage,
-		service,
-		&authorization.credential,
-		&authorization.date,
-		&authorization.signature,
-		string_to_sign.as_bytes(),
-	)
-	.await?;
+	let key = verify_v4(garage, service, &authorization, string_to_sign.as_bytes()).await?;
 
-	let content_sha256 = if authorization.content_sha256 == "UNSIGNED-PAYLOAD" {
+	let content_sha256 = if authorization.content_sha256 == UNSIGNED_PAYLOAD {
 		None
 	} else if authorization.content_sha256 == "STREAMING-AWS4-HMAC-SHA256-PAYLOAD" {
 		let bytes = hex::decode(authorization.signature).ok_or_bad_request("Invalid signature")?;
@@ -88,142 +108,92 @@ pub async fn check_payload_signature(
 	Ok((Some(key), content_sha256))
 }
 
-struct Authorization {
-	credential: String,
-	signed_headers: String,
-	signature: String,
-	content_sha256: String,
-	date: DateTime<Utc>,
-}
-
-fn parse_authorization(
-	authorization: &str,
-	headers: &HashMap<String, String>,
-) -> Result<Authorization, Error> {
-	let first_space = authorization
-		.find(' ')
-		.ok_or_bad_request("Authorization field to short")?;
-	let (auth_kind, rest) = authorization.split_at(first_space);
-
-	if auth_kind != "AWS4-HMAC-SHA256" {
-		return Err(Error::bad_request("Unsupported authorization method"));
+async fn check_presigned_signature(
+	garage: &Garage,
+	service: &'static str,
+	request: &Request<IncomingBody>,
+	mut query: HeaderMap,
+) -> Result<(Option<Key>, Option<Hash>), Error> {
+	let algorithm = query.get(X_AMZ_ALGORITHM).unwrap().to_str()?;
+	let authorization = Authorization::parse_presigned(algorithm, &query)?;
+
+	// Check that all mandatory signed headers are included
+	let signed_headers = split_signed_headers(&authorization)?;
+	for (name, _) in request.headers().iter() {
+		if name.as_str().starts_with("x-amz-") {
+			if !signed_headers.contains(name) {
+				return Err(Error::bad_request(format!(
+					"Header `{}` should be signed",
+					name
+				)));
+			}
+		}
 	}
-
-	let mut auth_params = HashMap::new();
-	for auth_part in rest.split(',') {
-		let auth_part = auth_part.trim();
-		let eq = auth_part
-			.find('=')
-			.ok_or_bad_request("Field without value in authorization header")?;
-		let (key, value) = auth_part.split_at(eq);
-		auth_params.insert(key.to_string(), value.trim_start_matches('=').to_string());
+	if !signed_headers.contains(&HOST) {
+		return Err(Error::bad_request("Header `Host` should be signed"));
 	}
 
-	let cred = auth_params
-		.get("Credential")
-		.ok_or_bad_request("Could not find Credential in Authorization field")?;
-
-	let content_sha256 = headers
-		.get("x-amz-content-sha256")
-		.ok_or_bad_request("Missing X-Amz-Content-Sha256 field")?;
+	query.remove(X_AMZ_SIGNATURE);
+	let canonical_request = canonical_request(
+		service,
+		request.method(),
+		request.uri().path(),
+		&query,
+		request.headers(),
+		signed_headers,
+		&authorization.content_sha256,
+	)?;
+	let string_to_sign = string_to_sign(
+		&authorization.date,
+		&authorization.scope,
+		&canonical_request,
+	);
 
-	let date = headers
-		.get("x-amz-date")
-		.ok_or_bad_request("Missing X-Amz-Date field")
-		.map_err(Error::from)
-		.and_then(|d| parse_date(d))?;
+	trace!("canonical request:\n{}", canonical_request);
+	trace!("string to sign:\n{}", string_to_sign);
 
-	if Utc::now() - date > Duration::hours(24) {
-		return Err(Error::bad_request("Date is too old".to_string()));
-	}
+	let key = verify_v4(garage, service, &authorization, string_to_sign.as_bytes()).await?;
 
-	let auth = Authorization {
-		credential: cred.to_string(),
-		signed_headers: auth_params
-			.get("SignedHeaders")
-			.ok_or_bad_request("Could not find SignedHeaders in Authorization field")?
-			.to_string(),
-		signature: auth_params
-			.get("Signature")
-			.ok_or_bad_request("Could not find Signature in Authorization field")?
-			.to_string(),
-		content_sha256: content_sha256.to_string(),
-		date,
-	};
-	Ok(auth)
+	Ok((Some(key), None))
 }
 
-fn parse_query_authorization(
-	algorithm: &str,
-	headers: &HashMap<String, String>,
-) -> Result<Authorization, Error> {
-	if algorithm != "AWS4-HMAC-SHA256" {
-		return Err(Error::bad_request(
-			"Unsupported authorization method".to_string(),
-		));
-	}
-
-	let cred = headers
-		.get("x-amz-credential")
-		.ok_or_bad_request("X-Amz-Credential not found in query parameters")?;
-	let signed_headers = headers
-		.get("x-amz-signedheaders")
-		.ok_or_bad_request("X-Amz-SignedHeaders not found in query parameters")?;
-	let signature = headers
-		.get("x-amz-signature")
-		.ok_or_bad_request("X-Amz-Signature not found in query parameters")?;
-	let content_sha256 = headers
-		.get("x-amz-content-sha256")
-		.map(|x| x.as_str())
-		.unwrap_or("UNSIGNED-PAYLOAD");
-
-	let duration = headers
-		.get("x-amz-expires")
-		.ok_or_bad_request("X-Amz-Expires not found in query parameters")?
-		.parse()
-		.map_err(|_| Error::bad_request("X-Amz-Expires is not a number".to_string()))?;
-
-	if duration > 7 * 24 * 3600 {
-		return Err(Error::bad_request(
-			"X-Amz-Expires may not exceed a week".to_string(),
-		));
-	}
-
-	let date = headers
-		.get("x-amz-date")
-		.ok_or_bad_request("Missing X-Amz-Date field")
-		.map_err(Error::from)
-		.and_then(|d| parse_date(d))?;
-
-	if Utc::now() - date > Duration::seconds(duration) {
-		return Err(Error::bad_request("Date is too old".to_string()));
+pub fn parse_query_map(uri: &http::uri::Uri) -> Result<HeaderMap, Error> {
+	let mut query = HeaderMap::new();
+	if let Some(query_str) = uri.query() {
+		let query_pairs = url::form_urlencoded::parse(query_str.as_bytes());
+		for (key, val) in query_pairs {
+			let name: HeaderName = key
+				.to_lowercase()
+				.try_into()
+				.ok_or_bad_request("invalid query parameter name")?;
+			let value = HeaderValue::from_bytes(val.as_bytes())
+				.ok_or_bad_request("invalid query parameter value")?;
+			if query.insert(name.clone(), value).is_some() {
+				return Err(Error::bad_request(format!(
+					"duplicate query parameter: `{}`",
+					name
+				)));
+			}
+		}
 	}
-
-	Ok(Authorization {
-		credential: cred.to_string(),
-		signed_headers: signed_headers.to_string(),
-		signature: signature.to_string(),
-		content_sha256: content_sha256.to_string(),
-		date,
-	})
+	Ok(query)
 }
 
-fn parse_credential(cred: &str) -> Result<(String, String), Error> {
-	let first_slash = cred
-		.find('/')
-		.ok_or_bad_request("Credentials does not contain '/' in authorization field")?;
-	let (key_id, scope) = cred.split_at(first_slash);
-	Ok((
-		key_id.to_string(),
-		scope.trim_start_matches('/').to_string(),
-	))
+fn split_signed_headers(authorization: &Authorization) -> Result<Vec<HeaderName>, Error> {
+	let signed_headers = authorization
+		.signed_headers
+		.split(';')
+		.map(HeaderName::try_from)
+		.collect::<Result<Vec<HeaderName>, _>>()
+		.ok_or_bad_request("invalid header name")?;
+	Ok(signed_headers)
 }
 
 pub fn string_to_sign(datetime: &DateTime<Utc>, scope_string: &str, canonical_req: &str) -> String {
 	let mut hasher = Sha256::default();
 	hasher.update(canonical_req.as_bytes());
 	[
-		"AWS4-HMAC-SHA256",
+		AWS4_HMAC_SHA256,
 		&datetime.format(LONG_DATETIME).to_string(),
 		scope_string,
 		&hex::encode(hasher.finalize().as_slice()),
@@ -234,11 +204,12 @@ 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,
+	canonical_uri: &str,
+	query: &HeaderMap,
+	headers: &HeaderMap,
+	mut signed_headers: Vec<HeaderName>,
 	content_sha256: &str,
-) -> String {
+) -> Result<String, Error> {
 	// 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
@@ -268,49 +239,52 @@ pub fn canonical_request(
 	// 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()
+	let canonical_uri: std::borrow::Cow<str> = if service != "s3" {
+		uri_encode(canonical_uri, false).into()
 	} else {
-		uri.path().into()
+		canonical_uri.into()
 	};
-	[
-		method.as_str(),
-		&path,
-		&canonical_query_string(uri),
-		&canonical_header_string(headers, signed_headers),
-		"",
-		signed_headers,
-		content_sha256,
-	]
-	.join("\n")
-}
-
-fn canonical_header_string(headers: &HashMap<String, String>, signed_headers: &str) -> String {
-	let signed_headers_vec = signed_headers.split(';').collect::<Vec<_>>();
-	let mut items = headers
-		.iter()
-		.filter(|(key, _)| signed_headers_vec.contains(&key.as_str()))
-		.collect::<Vec<_>>();
-	items.sort_by(|(k1, _), (k2, _)| k1.cmp(k2));
-	items
-		.iter()
-		.map(|(key, value)| key.to_lowercase() + ":" + value.trim())
-		.collect::<Vec<_>>()
-		.join("\n")
-}
 
-fn canonical_query_string(uri: &hyper::Uri) -> String {
-	if let Some(query) = uri.query() {
-		let query_pairs = url::form_urlencoded::parse(query.as_bytes());
-		let mut items = query_pairs
-			.filter(|(key, _)| key != "X-Amz-Signature")
-			.map(|(key, value)| uri_encode(&key, true) + "=" + &uri_encode(&value, true))
-			.collect::<Vec<_>>();
+	// Canonical query string from passed HeaderMap
+	let canonical_query_string = {
+		let mut items = Vec::with_capacity(query.len());
+		for (key, value) in query.iter() {
+			let value = std::str::from_utf8(value.as_bytes())?;
+			items.push(uri_encode(key.as_str(), true) + "=" + &uri_encode(value, true));
+		}
 		items.sort();
 		items.join("&")
-	} else {
-		"".to_string()
-	}
+	};
+
+	// Canonical header string calculated from signed headers
+	signed_headers.sort_by(|h1, h2| h1.as_str().cmp(h2.as_str()));
+	let canonical_header_string = {
+		let mut items = Vec::with_capacity(signed_headers.len());
+		for name in signed_headers.iter() {
+			let value = headers
+				.get(name)
+				.ok_or_bad_request(format!("signed header `{}` is not present", name))?
+				.to_str()?;
+			items.push((name, value));
+		}
+		items
+			.iter()
+			.map(|(key, value)| format!("{}:{}", key.as_str(), value.trim()))
+			.collect::<Vec<_>>()
+			.join("\n")
+	};
+	let signed_headers = signed_headers.join(";");
+
+	let list = [
+		method.as_str(),
+		&canonical_uri,
+		&canonical_query_string,
+		&canonical_header_string,
+		"",
+		&signed_headers,
+		content_sha256,
+	];
+	Ok(list.join("\n"))
 }
 
 pub fn parse_date(date: &str) -> Result<DateTime<Utc>, Error> {
@@ -322,28 +296,24 @@ pub fn parse_date(date: &str) -> Result<DateTime<Utc>, Error> {
 pub async fn verify_v4(
 	garage: &Garage,
 	service: &str,
-	credential: &str,
-	date: &DateTime<Utc>,
-	signature: &str,
+	auth: &Authorization,
 	payload: &[u8],
 ) -> Result<Key, Error> {
-	let (key_id, scope) = parse_credential(credential)?;
-
-	let scope_expected = compute_scope(date, &garage.config.s3_api.s3_region, service);
-	if scope != scope_expected {
-		return Err(Error::AuthorizationHeaderMalformed(scope.to_string()));
+	let scope_expected = compute_scope(&auth.date, &garage.config.s3_api.s3_region, service);
+	if auth.scope != scope_expected {
+		return Err(Error::AuthorizationHeaderMalformed(auth.scope.to_string()));
 	}
 
 	let key = garage
 		.key_table
-		.get(&EmptyKey, &key_id)
+		.get(&EmptyKey, &auth.key_id)
 		.await?
 		.filter(|k| !k.state.is_deleted())
-		.ok_or_else(|| Error::forbidden(format!("No such key: {}", &key_id)))?;
+		.ok_or_else(|| Error::forbidden(format!("No such key: {}", &auth.key_id)))?;
 	let key_p = key.params().unwrap();
 
 	let mut hmac = signing_hmac(
-		date,
+		&auth.date,
 		&key_p.secret_key,
 		&garage.config.s3_api.s3_region,
 		service,
@@ -351,9 +321,179 @@ pub async fn verify_v4(
 	.ok_or_internal_error("Unable to build signing HMAC")?;
 	hmac.update(payload);
 	let our_signature = hex::encode(hmac.finalize().into_bytes());
-	if signature != our_signature {
+	if auth.signature != our_signature {
 		return Err(Error::forbidden("Invalid signature".to_string()));
 	}
 
 	Ok(key)
 }
+
+// ============ Authorization header, or X-Amz-* query params =========
+
+pub struct Authorization {
+	key_id: String,
+	scope: String,
+	signed_headers: String,
+	signature: String,
+	content_sha256: String,
+	date: DateTime<Utc>,
+}
+
+impl Authorization {
+	fn parse(headers: &HeaderMap) -> Result<Self, Error> {
+		let authorization = headers
+			.get(AUTHORIZATION)
+			.ok_or_bad_request("Missing authorization header")?
+			.to_str()?;
+
+		let (auth_kind, rest) = authorization
+			.split_once(' ')
+			.ok_or_bad_request("Authorization field to short")?;
+
+		if auth_kind != AWS4_HMAC_SHA256 {
+			return Err(Error::bad_request("Unsupported authorization method"));
+		}
+
+		let mut auth_params = HashMap::new();
+		for auth_part in rest.split(',') {
+			let auth_part = auth_part.trim();
+			let eq = auth_part
+				.find('=')
+				.ok_or_bad_request("Field without value in authorization header")?;
+			let (key, value) = auth_part.split_at(eq);
+			auth_params.insert(key.to_string(), value.trim_start_matches('=').to_string());
+		}
+
+		let cred = auth_params
+			.get("Credential")
+			.ok_or_bad_request("Could not find Credential in Authorization field")?;
+		let signed_headers = auth_params
+			.get("SignedHeaders")
+			.ok_or_bad_request("Could not find SignedHeaders in Authorization field")?
+			.to_string();
+		let signature = auth_params
+			.get("Signature")
+			.ok_or_bad_request("Could not find Signature in Authorization field")?
+			.to_string();
+
+		let content_sha256 = headers
+			.get(X_AMZ_CONTENT_SH256)
+			.ok_or_bad_request("Missing X-Amz-Content-Sha256 field")?;
+
+		let date = headers
+			.get(X_AMZ_DATE)
+			.ok_or_bad_request("Missing X-Amz-Date field")
+			.map_err(Error::from)?
+			.to_str()?;
+		let date = parse_date(date)?;
+
+		if Utc::now() - date > Duration::hours(24) {
+			return Err(Error::bad_request("Date is too old".to_string()));
+		}
+
+		let (key_id, scope) = parse_credential(cred)?;
+		let auth = Authorization {
+			key_id,
+			scope,
+			signed_headers,
+			signature,
+			content_sha256: content_sha256.to_str()?.to_string(),
+			date,
+		};
+		Ok(auth)
+	}
+
+	fn parse_presigned(algorithm: &str, query: &HeaderMap) -> Result<Self, Error> {
+		if algorithm != AWS4_HMAC_SHA256 {
+			return Err(Error::bad_request(
+				"Unsupported authorization method".to_string(),
+			));
+		}
+
+		let cred = query
+			.get(X_AMZ_CREDENTIAL)
+			.ok_or_bad_request("X-Amz-Credential not found in query parameters")?;
+		let signed_headers = query
+			.get(X_AMZ_SIGNEDHEADERS)
+			.ok_or_bad_request("X-Amz-SignedHeaders not found in query parameters")?;
+		let signature = query
+			.get(X_AMZ_SIGNATURE)
+			.ok_or_bad_request("X-Amz-Signature not found in query parameters")?;
+
+		let duration = query
+			.get(X_AMZ_EXPIRES)
+			.ok_or_bad_request("X-Amz-Expires not found in query parameters")?
+			.to_str()?
+			.parse()
+			.map_err(|_| Error::bad_request("X-Amz-Expires is not a number".to_string()))?;
+
+		if duration > 7 * 24 * 3600 {
+			return Err(Error::bad_request(
+				"X-Amz-Expires may not exceed a week".to_string(),
+			));
+		}
+
+		let date = query
+			.get(X_AMZ_DATE)
+			.ok_or_bad_request("Missing X-Amz-Date field")?
+			.to_str()?;
+		let date = parse_date(date)?;
+
+		if Utc::now() - date > Duration::seconds(duration) {
+			return Err(Error::bad_request("Date is too old".to_string()));
+		}
+
+		let (key_id, scope) = parse_credential(cred.to_str()?)?;
+		Ok(Authorization {
+			key_id,
+			scope,
+			signed_headers: signed_headers.to_str()?.to_string(),
+			signature: signature.to_str()?.to_string(),
+			content_sha256: UNSIGNED_PAYLOAD.to_string(),
+			date,
+		})
+	}
+
+	pub(crate) fn parse_form(params: &HeaderMap) -> Result<Self, Error> {
+		let credential = params
+			.get(X_AMZ_CREDENTIAL)
+			.ok_or_else(|| Error::forbidden("Garage does not support anonymous access yet"))?
+			.to_str()?;
+		let signature = params
+			.get(X_AMZ_SIGNATURE)
+			.ok_or_bad_request("No signature was provided")?
+			.to_str()?
+			.to_string();
+		let date = params
+			.get(X_AMZ_DATE)
+			.ok_or_bad_request("No date was provided")?
+			.to_str()?;
+		let date = parse_date(date)?;
+
+		if Utc::now() - date > Duration::hours(24) {
+			return Err(Error::bad_request("Date is too old".to_string()));
+		}
+
+		let (key_id, scope) = parse_credential(credential)?;
+		let auth = Authorization {
+			key_id,
+			scope,
+			signed_headers: "".to_string(),
+			signature,
+			content_sha256: UNSIGNED_PAYLOAD.to_string(),
+			date,
+		};
+		Ok(auth)
+	}
+}
+
+fn parse_credential(cred: &str) -> Result<(String, String), Error> {
+	let first_slash = cred
+		.find('/')
+		.ok_or_bad_request("Credentials does not contain '/' in authorization field")?;
+	let (key_id, scope) = cred.split_at(first_slash);
+	Ok((
+		key_id.to_string(),
+		scope.trim_start_matches('/').to_string(),
+	))
+}