s/mime signature not working

[Ch. Tronche]

Given the following code:

#!/usr/bin/python

from M2Crypto import BIO, Rand, SMIME

_text = 'a sign of our times'

def sign(message):
    buf = BIO.MemoryBuffer(message)
    Rand.load_file('randpool.dat', -1)
    s = SMIME.SMIME()
    s.load_key('signer_key.pem', 'signer.pem')
    p7 = s.sign(buf)
    Rand.save_file('randpool.dat')
    out = BIO.MemoryBuffer()
    s.write(out, p7, BIO.MemoryBuffer(message))
    return out.read()

print '2>>', sign(_text)

On Ubuntu 10.04.4 I got the following result (which is what I expect):

2>> MIME-Version: 1.0
Content-Type: multipart/signed; protocol="application/x-pkcs7-signature"; micalg=sha1; boundary="----0B8377C13703649AB80D5DE6996E3D8D"

This is an S/MIME signed message

------0B8377C13703649AB80D5DE6996E3D8D
a sign of our times
------0B8377C13703649AB80D5DE6996E3D8D
Content-Type: application/x-pkcs7-signature; name="smime.p7s"
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename="smime.p7s"
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------0B8377C13703649AB80D5DE6996E3D8D--

However, on 12.04.2, I got this (that is, the signature is missing):

2>> MIME-Version: 1.0
Content-Type: multipart/signed; protocol="application/x-pkcs7-signature"; micalg="sha1"; boundary="----FB1930A6CCBB24D90C563DEBB2C0CBBC"

This is an S/MIME signed message

------FB1930A6CCBB24D90C563DEBB2C0CBBC
a sign of our times

(and that's it)

Version of python-m2crypto is 0.21.1-2ubuntu2.