Rename to jwt_full to avoid collision with existing nim-jwt.

src/main/jwt_full/private/crypto/hmac.nim

@@ -0,0 +1,47 @@
+import std/logging
+
+import bearssl
+
+import ../../jwa
+import ../../jwk
+
+import ../encoding
+
+proc bearHMAC(message: string, alg: JwtAlgorithm, key: string): string =
+
+  var vtable: ptr HashClass
+  var hashSize: int
+
+  case alg:
+    of HS256: vtable = addr sha256Vtable; hashSize = sha256Size
+    of HS384: vtable = addr sha384Vtable; hashSize = sha384Size
+    of HS512: vtable = addr sha512Vtable; hashSize = sha512Size
+    else: raise newException(ValueError,
+      "Unsupported HMAC algorithm '" & $alg & "'")
+
+  if key.len < hashSize:
+    warn( "Computing an HMAC with a small key (" & $key.len & " bytes). It " &
+      "is recommended to use keys of at least " & $hashSize & " bytes for " &
+      $alg)
+
+  var keyCtx: HmacKeyContext
+  var hmacCtx: HmacContext
+
+  hmacKeyInit(addr keyCtx, vtable, key.cstring, key.len)
+  hmacInit(addr hmacCtx, addr keyCtx, 0)
+  hmacUpdate(addr hmacCtx, message.cstring, message.len)
+
+  let resLen = hmacSize(addr hmacCtx)
+  result = newString(resLen)
+  discard hmacOut(addr hmacCtx, addr result[0])
+
+proc hmac*(message: string, alg: JwtAlgorithm, key: string): string =
+  return bearHMAC(message, alg, key)
+
+proc hmac*(message: string, alg: JwtAlgorithm, key: JWK): string =
+  if key.keyKind != Octet:
+    raise newException(ValueError,
+      $alg & " requires an octet key (\"typ\"=\"oct\"), not a \"typ\"=\"" &
+      $(key.keyKind) & "\" key.")
+
+  return bearHMAC(message, alg, b64UrlDecode(key.octKey.k))