Support STREAMING-AWS4-HMAC-SHA256-PAYLOAD (#64) (#156)

Closes #64.

Reviewed-on: https://git.deuxfleurs.fr/Deuxfleurs/garage/pulls/156
Co-authored-by: Jill <kokakiwi@deuxfleurs.fr>
Co-committed-by: Jill <kokakiwi@deuxfleurs.fr>

src/api/signature/mod.rs

@@ -0,0 +1,47 @@
+use chrono::{DateTime, Utc};
+use hmac::{Hmac, Mac, NewMac};
+use sha2::Sha256;
+
+use garage_util::data::{sha256sum, Hash};
+
+use crate::error::*;
+
+pub mod payload;
+pub mod streaming;
+
+pub const SHORT_DATE: &str = "%Y%m%d";
+pub const LONG_DATETIME: &str = "%Y%m%dT%H%M%SZ";
+
+type HmacSha256 = Hmac<Sha256>;
+
+pub fn verify_signed_content(expected_sha256: Hash, body: &[u8]) -> Result<(), Error> {
+	if expected_sha256 != sha256sum(body) {
+		return Err(Error::BadRequest(
+			"Request content hash does not match signed hash".to_string(),
+		));
+	}
+	Ok(())
+}
+
+pub fn signing_hmac(
+	datetime: &DateTime<Utc>,
+	secret_key: &str,
+	region: &str,
+	service: &str,
+) -> Result<HmacSha256, crypto_mac::InvalidKeyLength> {
+	let secret = String::from("AWS4") + secret_key;
+	let mut date_hmac = HmacSha256::new_varkey(secret.as_bytes())?;
+	date_hmac.update(datetime.format(SHORT_DATE).to_string().as_bytes());
+	let mut region_hmac = HmacSha256::new_varkey(&date_hmac.finalize().into_bytes())?;
+	region_hmac.update(region.as_bytes());
+	let mut service_hmac = HmacSha256::new_varkey(&region_hmac.finalize().into_bytes())?;
+	service_hmac.update(service.as_bytes());
+	let mut signing_hmac = HmacSha256::new_varkey(&service_hmac.finalize().into_bytes())?;
+	signing_hmac.update(b"aws4_request");
+	let hmac = HmacSha256::new_varkey(&signing_hmac.finalize().into_bytes())?;
+	Ok(hmac)
+}
+
+pub fn compute_scope(datetime: &DateTime<Utc>, region: &str) -> String {
+	format!("{}/{}/s3/aws4_request", datetime.format(SHORT_DATE), region,)
+}