embed.py

import base64
import struct
import sys

def chunk(data):
    return struct.pack('>L', len(data)) + data

data = chunk(b'ssh-rsa') + chunk(b'\x23') + chunk(b'\x00' + open(sys.argv[1]).read())
sys.stdout.write('ssh-rsa %s' % base64.b64encode(data))

retrieval.py

# curl https://github.com/{user}.keys | python retrieval.py
import re
import sys
import base64
import struct

def get_chunk(s, i):
    l, = struct.unpack('>L', s[i:i + 4])
    i += 4
    n = i + l
    data = s[i:n]
    if len(data) != l:
        raise Exception('Unexpected EOS')
    return data, n

def generate_chunk(s):
    i = 0
    while i < len(s):
        data, i = get_chunk(s, i)
        yield data

for lineno, key in enumerate(sys.stdin, 1):
    key = key.rstrip()
    g = re.match(r'^(?:ssh-rsa|ssh-dsa)\s+(.*)$', key)
    if g:
        chunks = base64.b64decode(g.group(1))
        try:
            gen = generate_chunk(chunks)
            sig = gen.next()
            if sig in (b'ssh-rsa', b'ssh-dsa'):
                gen.next()
                pix = gen.next()[1:]
                format = None
                if pix[0:2] == b'\xff\xd8':
                    format = 'jpg'
                elif pix[0:4] == b'\x89PNG':
                    format = 'png'
                elif pix[0:6] == b'GIF89a':
                    format = 'gif'
                if format is not None:
                    filename = '%08d.%s' % (lineno, format)
                    print("got a picture! gonna save it as %s" % filename)
                    open(filename, 'w').write(pix)
                continue
        except Exception:
            pass
    print("invalid key at line %d" % lineno)