Padding issue on input strings that are a len multiple of 32

[fairbairn]

Here’s the issue..

iex(1)> secret = "fJXYWeIEcXMO3tLDheFVezM5QWBVFvkymG80n0Rluqs="
"fJXYWeIEcXMO3tLDheFVezM5QWBVFvkymG80n0Rluqs="
iex(2)> s = "abc"
"abc"
iex(3)> {:ok, _iv, t} = Fernet.generate(s, key: secret)
{:ok,
 <<171, 20, 174, 159, 83, 157, 204, 91, 237, 149, 121, 205, 255, 101, 152, 241>>,
 "gAAAAABbMo1mqxSun1OdzFvtlXnN_2WY8TlATVJvCKC6oPuO_kzHnLSC3YN6uj0b-a0DBzBQYfWmaxdUb28p3-RyFOLV8gBwPQ=="}
iex(4)> t
"gAAAAABbMo1mqxSun1OdzFvtlXnN_2WY8TlATVJvCKC6oPuO_kzHnLSC3YN6uj0b-a0DBzBQYfWmaxdUb28p3-RyFOLV8gBwPQ=="
iex(5)> Fernet.verify(t, key: secret)
{:ok, "abc"}
iex(6)> s = String.pad_trailing("hello", 32)
"hello                           "
iex(7)> {:ok, _iv, t} = Fernet.generate(s, key: secret)
{:ok,
 <<4, 195, 63, 250, 139, 163, 64, 222, 249, 190, 47, 118, 19, 79, 199, 13>>,
 "gAAAAABbMo2BBMM_-oujQN75vi92E0_HDf-TWTLLZYX6S3sqDyJh4QL9Qqi4oPP47mEcc5OBQ2qUmqJfJVmt1UBuRBK096V8Rp5M-f-sjS79HKJedlg9Ay4="}
iex(8)> Fernet.verify(t, key: secret)
{:error, "padding error"}

[kennyp]

@fairbairn I think I have this fixed with PR #9. It also gave me a chance to a property based test that we always can verify what we generate.

[kennyp]

@fairbairn v0.3.1 has been released. Let me know if you have any more issues.