Implement HMAC SHA256 function in nushell

modules/README.md

@@ -26,6 +26,7 @@
   - [virtual\_environments](#virtual_environments)
   - [weather](#weather)
   - [webscraping](#webscraping)
+  - [crypto](#crypto)
 
 
 ## [after](./after)
@@ -269,3 +270,6 @@ Simple scripts to demonstrate how to scrape websites in nushell. Requires `query
 ## [result](./result/)
 A module to include in the config which enables storing and convenient access of previously output
 results.
+
+## [crypto](./crypto/)
+Tools for cryptography

modules/crypto/README.md

@@ -0,0 +1,3 @@
+# Cryptography
+
+Tools for cryptography.

modules/crypto/hmac.nu

@@ -0,0 +1,32 @@
+
+# HMAC-SHA256 implementation
+#
+# This is a message authentication algorithm,
+# using a shared secret key this allows two peers to validate that the message wasn't tampered with.
+# Used for example for issuing JWT tokens.
+@example "generate a message authentication code" {
+    "The quick brown fox jumps over the lazy dog" 
+    | hmac sha256 --key "key" 
+    | encode hex
+} --result "F7BC83F430538424B13298E6AA6FB143EF4D59A14946175997479DBC2D1A3CD8"
+export def "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
+}