add an aes test

This combines some test vectors from the implementation & a NIST
standards document, plus the code from the docstring.

The test vectors were eyeball-verified.

tests/circuitpython/aes.py

@@ -0,0 +1,99 @@
+import aesio
+from binascii import hexlify, unhexlify
+
+# doc example
+key = b"Sixteen byte key"
+inp = b"CircuitPython!!!"  # Note: 16-bytes long
+outp = bytearray(len(inp))
+cipher = aesio.AES(key, aesio.MODE_ECB)
+cipher.encrypt_into(inp, outp)
+print(str(hexlify(outp), ""))
+
+cipher = aesio.AES(key, aesio.MODE_ECB)
+cipher.decrypt_into(outp, outp)
+print(str(outp, ""))
+print()
+
+print("ECB")
+# ECB mode test vector, from the aes.c source
+plaintext = unhexlify(
+    "6bc1bee22e409f96e93d7e117393172a"
+    "ae2d8a571e03ac9c9eb76fac45af8e51"
+    "30c81c46a35ce411e5fbc1191a0a52ef"
+    "f69f2445df4f9b17ad2b417be66c3710"
+)
+
+key = unhexlify("2b7e151628aed2a6abf7158809cf4f3c")
+
+cyphertext = bytearray(len(plaintext))
+cipher = aesio.AES(key, aesio.MODE_ECB)
+for i in range(0, len(plaintext), 16):
+    output = memoryview(cyphertext)[i : i + 16]
+    cipher.encrypt_into(plaintext[i : i + 16], output)
+    print(str(hexlify(output), ""))
+print()
+
+plaintext = bytearray(len(plaintext))
+cipher = aesio.AES(key, aesio.MODE_ECB)
+for i in range(0, len(plaintext), 16):
+    output = memoryview(plaintext)[i : i + 16]
+    cipher.decrypt_into(cyphertext[i : i + 16], output)
+    print(str(hexlify(output), ""))
+print()
+
+print("CBC")
+# CBC128-AES128 test vector from NIST Special Publication 800-38A, 2001 edition, p50
+
+plaintext = unhexlify(
+    "6bc1bee22e409f96e93d7e117393172a"
+    "ae2d8a571e03ac9c9eb76fac45af8e51"
+    "30c81c46a35ce411e5fbc1191a0a52ef"
+    "f69f2445df4f9b17ad2b417be66c3710"
+)
+
+key = unhexlify("2b7e151628aed2a6abf7158809cf4f3c")
+iv = unhexlify("000102030405060708090a0b0c0d0e0f")
+cyphertext = bytearray(len(plaintext))
+cipher = aesio.AES(key, aesio.MODE_CBC, IV=iv)
+for i in range(0, len(plaintext), 16):
+    output = memoryview(cyphertext)[i : i + 16]
+    cipher.encrypt_into(plaintext[i : i + 16], output)
+    print(str(hexlify(output), ""))
+print()
+
+plaintext = bytearray(len(plaintext))
+cipher = aesio.AES(key, aesio.MODE_CBC, IV=iv)
+for i in range(0, len(plaintext), 16):
+    output = memoryview(plaintext)[i : i + 16]
+    cipher.decrypt_into(cyphertext[i : i + 16], output)
+    print(str(hexlify(output), ""))
+print()
+
+
+print("CTR")
+# CTR128-AES128 test vector from NIST Special Publication 800-38A, 2001 edition, p55
+
+plaintext = unhexlify(
+    "6bc1bee22e409f96e93d7e117393172a"
+    "ae2d8a571e03ac9c9eb76fac45af8e51"
+    "30c81c46a35ce411e5fbc1191a0a52ef"
+    "f69f2445df4f9b17ad2b417be66c3710"
+)
+
+key = unhexlify("2b7e151628aed2a6abf7158809cf4f3c")
+counter = unhexlify("f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff")
+cyphertext = bytearray(len(plaintext))
+cipher = aesio.AES(key, aesio.MODE_CTR, IV=counter)
+for i in range(0, len(plaintext), 16):
+    output = memoryview(cyphertext)[i : i + 16]
+    cipher.encrypt_into(plaintext[i : i + 16], output)
+    print(str(hexlify(output), ""))
+print()
+
+plaintext = bytearray(len(plaintext))
+cipher = aesio.AES(key, aesio.MODE_CTR, IV=counter)
+for i in range(0, len(plaintext), 16):
+    output = memoryview(plaintext)[i : i + 16]
+    cipher.decrypt_into(cyphertext[i : i + 16], output)
+    print(str(hexlify(output), ""))
+print()

tests/circuitpython/aes.py.exp

@@ -0,0 +1,36 @@
+abb1a1f98f57409e455ac06e71535ffe
+CircuitPython!!!
+
+ECB
+3ad77bb40d7a3660a89ecaf32466ef97
+f5d3d58503b9699de785895a96fdbaaf
+43b1cd7f598ece23881b00e3ed030688
+7b0c785e27e8ad3f8223207104725dd4
+
+6bc1bee22e409f96e93d7e117393172a
+ae2d8a571e03ac9c9eb76fac45af8e51
+30c81c46a35ce411e5fbc1191a0a52ef
+f69f2445df4f9b17ad2b417be66c3710
+
+CBC
+7649abac8119b246cee98e9b12e9197d
+5086cb9b507219ee95db113a917678b2
+73bed6b8e3c1743b7116e69e22229516
+3ff1caa1681fac09120eca307586e1a7
+
+6bc1bee22e409f96e93d7e117393172a
+ae2d8a571e03ac9c9eb76fac45af8e51
+30c81c46a35ce411e5fbc1191a0a52ef
+f69f2445df4f9b17ad2b417be66c3710
+
+CTR
+874d6191b620e3261bef6864990db6ce
+9806f66b7970fdff8617187bb9fffdff
+5ae4df3edbd5d35e5b4f09020db03eab
+1e031dda2fbe03d1792170a0f3009cee
+
+6bc1bee22e409f96e93d7e117393172a
+ae2d8a571e03ac9c9eb76fac45af8e51
+30c81c46a35ce411e5fbc1191a0a52ef
+f69f2445df4f9b17ad2b417be66c3710
+