password-hash: add Encoding::ShaCrypt (#1352)

Adds support for a Base64 variant used by `sha1_crypt`, `sha256_crypt`,
`sha512_crypt`, and `md5_crypt`.

Uses `base64ct::Base64ShaCrypt` as the backing implementation.

Also marks the `Encoding` enum as `#[non_exhaustive]` to allow future additions
in a non-breaking manner.

---------

Co-authored-by: Tony Arcieri <[email protected]>

password-hash/Cargo.toml

@@ -17,7 +17,7 @@ edition = "2021"
 rust-version = "1.60"
 
 [dependencies]
-base64ct = "1"
+base64ct = "1.6"
 subtle = { version = "2", default-features = false }
 
 # optional dependencies

password-hash/src/encoding.rs

@@ -1,11 +1,13 @@
 //! Base64 encoding variants.
 
 use base64ct::{
-    Base64Bcrypt, Base64Crypt, Base64Unpadded as B64, Encoding as _, Error as B64Error,
+    Base64Bcrypt, Base64Crypt, Base64ShaCrypt, Base64Unpadded as B64, Encoding as _,
+    Error as B64Error,
 };
 
 /// Base64 encoding variants.
 #[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord)]
+#[non_exhaustive]
 pub enum Encoding {
     /// "B64" encoding: standard Base64 without padding.
     ///
@@ -31,6 +33,15 @@ pub enum Encoding {
     /// 0x2e-0x39, 0x41-0x5a, 0x61-0x7a
     /// ```
     Crypt,
+
+    /// `crypt(3)` Base64 encoding for the following schemes.
+    /// - sha1_crypt,
+    /// - sha256_crypt,
+    /// - sha512_crypt,
+    /// - md5_crypt
+    /// [.-9]      [A-Z]      [a-z]
+    /// 0x2e-0x39, 0x41-0x5a, 0x61-0x7a
+    ShaCrypt,
 }
 
 impl Default for Encoding {
@@ -46,6 +57,7 @@ impl Encoding {
             Self::B64 => B64::decode(src, dst),
             Self::Bcrypt => Base64Bcrypt::decode(src, dst),
             Self::Crypt => Base64Crypt::decode(src, dst),
+            Self::ShaCrypt => Base64ShaCrypt::decode(src, dst),
         }
     }
 
@@ -58,6 +70,7 @@ impl Encoding {
             Self::B64 => B64::encode(src, dst),
             Self::Bcrypt => Base64Bcrypt::encode(src, dst),
             Self::Crypt => Base64Crypt::encode(src, dst),
+            Self::ShaCrypt => Base64ShaCrypt::encode(src, dst),
         }
         .map_err(Into::into)
     }
@@ -68,6 +81,7 @@ impl Encoding {
             Self::B64 => B64::encoded_len(bytes),
             Self::Bcrypt => Base64Bcrypt::encoded_len(bytes),
             Self::Crypt => Base64Crypt::encoded_len(bytes),
+            Self::ShaCrypt => Base64ShaCrypt::encoded_len(bytes),
         }
     }
 }