hmac: Calculate correct digest when non-trivial key is used.

This incorrect behavior was a result of the function that performs
table-driven byte translation. The function first used the chr(...)
function to convert each resulting byte, represented as an integer,
to a string of length one. Then, the <str>.encode(...) function was
used to convert the string to a byte string with an intended length
of one. That didn't work well for bytes with high bit set, as they
were trated as UTF-8 chars. Instead, perform operations directly on
bytes.

This was an artifact of porting this to MicroPython, as the original
CPython module uses bytes.translate(...) method (not available in
uPy).

Author: ccooper21

hmac/hmac.py

@@ -13,7 +13,7 @@
 trans_36 = bytes((x ^ 0x36) for x in range(256))
 
 def translate(d, t):
-    return b''.join([ chr(t[x]).encode('ascii') for x in d ])
+    return bytes(t[x] for x in d)
 
 # The size of the digests returned by HMAC depends on the underlying
 # hashing module used.  Use digest_size from the instance of HMAC instead.

hmac/metadata.txt

@@ -1,4 +1,4 @@
 srctype = cpython
 type = module
-version = 3.4.2-2
+version = 3.4.2-3
 depends = warnings, hashlib

hmac/setup.py

@@ -7,7 +7,7 @@
 import optimize_upip
 
 setup(name='micropython-hmac',
-      version='3.4.2-2',
+      version='3.4.2-3',
       description='CPython hmac module ported to MicroPython',
       long_description='This is a module ported from CPython standard library to be compatible with\nMicroPython interpreter. Usually, this means applying small patches for\nfeatures not supported (yet, or at all) in MicroPython. Sometimes, heavier\nchanges are required. Note that CPython modules are written with availability\nof vast resources in mind, and may not work for MicroPython ports with\nlimited heap. If you are affected by such a case, please help reimplement\nthe module from scratch.',
       url='https://github.com/micropython/micropython-lib',

hmac/test_hmac.py

@@ -20,3 +20,29 @@
 if dig != '59942f31b6f5473fb4eb630fabf5358a49bc11d24ebc83b114b4af30d6ef47ea14b673f478586f520a0b9c53b27c8f8dd618c165ef586195bd4e98293d34df1a':
     raise Exception("Error")
 
+key = b'\x06\x1au\x90|Xz;o\x1b<\xafGL\xbfn\x8a\xc94YPfC^\xb9\xdd)\x7f\xaf\x85\xa1\xed\x82\xbexp\xaf\x13\x1a\x9d'
+
+dig = hmac.new(key[:20], msg=msg, digestmod=sha256).hexdigest()
+
+print('59e332b881df09fdecf569c8b142b27fc989638720aeda2813f82442b6e3d91b')
+print(dig)
+
+if dig != '59e332b881df09fdecf569c8b142b27fc989638720aeda2813f82442b6e3d91b':
+    raise Exception("Error")
+
+dig = hmac.new(key[:32], msg=msg, digestmod=sha256).hexdigest()
+
+print('b72fed815cd71acfa3a2f5cf2343679565fa18e7cd92226ab443aabd1fd7b7b0')
+print(dig)
+
+if dig != 'b72fed815cd71acfa3a2f5cf2343679565fa18e7cd92226ab443aabd1fd7b7b0':
+    raise Exception("Error")
+
+dig = hmac.new(key, msg=msg, digestmod=sha256).hexdigest()
+
+print('4e51beae6c2b0f90bb3e99d8e93a32d168b6c1e9b7d2130e2d668a3b3e10358d')
+print(dig)
+
+if dig != '4e51beae6c2b0f90bb3e99d8e93a32d168b6c1e9b7d2130e2d668a3b3e10358d':
+    raise Exception("Error")
+