Implement HMAC SHA256 function in nushell

Author: samoylovfp

modules/crypto/hmac.nu

@@ -0,0 +1,21 @@
+export def "hmac sha256" [--key: oneof<binary, string>]: oneof<string, binary> -> binary {
+    let message = $in | into binary
+    let key = $key | into binary
+
+    const block_size = 64
+
+    let key_len = ($key | length)
+    let key = match $key_len {
+        64 => $key,
+        65.. => ($key | hash sha256 --binary),
+        _ => {bytes build $key (1..($block_size - $key_len) | each {0x[00]} | bytes collect)} 
+    }
+
+    let i_key = $key | bits xor ((1..$block_size) | each {0x[36]} | bytes collect)
+    let o_key = $key | bits xor ((1..$block_size) | each {0x[5c]} | bytes collect)
+    
+    bytes build $i_key $message 
+    | hash sha256 --binary
+    | bytes build $o_key $in
+    | hash sha256 --binary
+}