#!/usr/bin/env python3
"""Back up one MTD partition of the GPON stick over telnet, md5-verified.
Usage: gpon_backup.py <mtd_index> <outfile> [idle_timeout] [hard_cap]
Streams `cat /dev/mtdN | uuencode` over the telnet session and uudecodes locally
(Python's uu module was removed in 3.13, so we decode by hand)."""
import socket, sys, time, re, hashlib
from gpon_env import HOST, PORT, USER, PASS

idx = sys.argv[1]
outfile = sys.argv[2]
idle_to = float(sys.argv[3]) if len(sys.argv)>3 else 12.0
hard_cap = float(sys.argv[4]) if len(sys.argv)>4 else 300.0

def strip_iac(data, outbuf):
    res=bytearray(); i=0
    while i<len(data):
        b=data[i]
        if b==0xFF and i+1<len(data):
            c=data[i+1]
            if c in (251,252,253,254) and i+2<len(data):
                o=data[i+2]
                if c==253: outbuf.append(bytes([255,252,o]))
                elif c==251: outbuf.append(bytes([255,254,o]))
                i+=3; continue
            elif c==250:
                j=data.find(b'\xff\xf0', i+2); i=len(data) if j<0 else j+2; continue
            else: i+=2; continue
        res.append(b); i+=1
    return bytes(res)

s=socket.create_connection((HOST,PORT),timeout=8)
def rx(idle, cap, stop=None):
    s.settimeout(0.5); buf=bytearray(); last=time.time(); start=time.time()
    while True:
        try:
            d=s.recv(16384)
            if not d: break
            ob=[]; buf.extend(strip_iac(d,ob))
            for o in ob: s.sendall(o)
            last=time.time()
            if stop and stop(buf): break
        except socket.timeout:
            if time.time()-last>idle: break
        if time.time()-start>cap: break
    return buf.decode('latin-1','replace')

def send(x): s.sendall(x.encode()+b'\r\n')

out=rx(2,8)
if re.search(r'(ogin|sername)',out): send(USER); out+=rx(2,6)
if re.search(r'assword',out,re.I): send(PASS); out+=rx(2,6)
send('system'); rx(1.5,5)
send('shell'); rx(1.5,5)

send('md5sum /dev/mtd%s'%idx)
m=rx(90,150, stop=lambda b: re.search(rb'[0-9a-f]{32}\s+/dev/mtd',b))
mm=re.search(r'([0-9a-f]{32})\s+/dev/mtd%s'%re.escape(idx), m)
expected=mm.group(1) if mm else None

t0=time.time()
send('cat /dev/mtd%s | uuencode p'%idx)
def done(b):
    bi=b.find(b'begin ')
    return bi>=0 and (b'\nend\r' in b[bi:] or b'\nend\n' in b[bi:])
d=rx(idle_to, hard_cap, stop=done)
dt=time.time()-t0
try: s.close()
except Exception: pass

def uudecode(text):
    out=bytearray(); started=False
    for ln in text.split('\n'):
        ln=ln.rstrip('\r')
        if not started:
            if ln.startswith('begin '): started=True
            continue
        if ln=='end': break
        if ln=='' or ln=='`': continue
        n=(ord(ln[0])-0x20)&0x3f
        if n<=0: continue
        data=ln[1:]; dec=bytearray()
        for i in range(0,len(data),4):
            g=data[i:i+4]; v=[(ord(c)-0x20)&0x3f for c in g]
            while len(v)<4: v.append(0)
            dec.append(((v[0]<<2)|(v[1]>>4))&0xff)
            dec.append(((v[1]<<4)|(v[2]>>2))&0xff)
            dec.append(((v[2]<<6)|v[3])&0xff)
        out.extend(dec[:n])
    return bytes(out)

raw=uudecode(d)
with open(outfile,'wb') as f: f.write(raw)
actual=hashlib.md5(raw).hexdigest()
print("mtd%s -> %s : %d bytes in %.1fs"%(idx,outfile,len(raw),dt))
print("  expected md5 (stick): %s"%expected)
print("  actual   md5 (local): %s"%actual)
print("  VERIFY: %s"%("OK" if (expected and actual==expected) else "*** MISMATCH / INCOMPLETE ***"))