3des-cfb failing to decrypt

[Andrew Stevenson]

Hi,

I am trying to use libgcrypt to decrypt some data encoded using 
3des-cfb. Unfortunately I only ever manage to decrypt the first 
character. I'm guessing its user error on my behalf though I've been 
through the documentation several times and can't see what I'm doing wrong.

I have some example code posted here: 
https://gist.github.com/andrew-stevenson-sociomantic/7b28d0bd9f8f34bcef00

It has hard coded key, iv, cipher text and plain text. It then tries to 
decrypt the cipher text with OpenSSL/libcrypto, libmcrypt and libgcrypt, 
asserting after each that the decrypted test matches the plaintext. The 
libcrypto and libmcrypt methods work OK but decrypt_3des_gcrypt doesn't 
so the assert on line 148 fails.

Can someone see what I'm doing wrong?

Thanks,

Andrew