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#!/usr/bin/env python3
"""Malformed TA images: does the pre-authentication header parser hold up?
Every LOAD_TA in this audit used a well-formed signed image. The header parse runs before
authentication can complete, so a malformed image exercises code reachable by any host
without needing a valid signature -- the classic pre-auth surface.
Mutations of a real signed image (signature will fail; the question is HOW it fails):
truncations at several points, header length fields set to 0 / huge / negative, and a
header byte flipped. Benign = a clean error status. A stall or a crash is a finding.
Control: the unmodified image must load with 0x0; if it does not the rig is wrong.
"""
import glob, struct, sys, time
sys.path.insert(0,'/root/psp/hw')
from tinygrad import Device
import tinygrad.runtime.autogen.am.am as am
from ring_wrap import install
adev=Device["AMD"].iface.dev_impl; psp=adev.psp
submit=install(psp,adev)
def alloc(n):
pa=adev.mm.palloc(n,align=0x1000,zero=True,boot=False); return pa,adev.paddr2mc(pa)
base=open(glob.glob('/root/psp/contall/ta_42-0-0-6_1c874c3c*')[0],'rb').read()
def load(blob, applen=None, tag=''):
ap_,amc=alloc(0x80000); cp,cmc=alloc(0x8000)
n=(len(blob)+3)&~3
adev.vram.view(ap_,max(n,4))[:] = (blob+b'\x00'*(n-len(blob)))[:max(n,4)]
adev.gmc.flush_hdp()
c=am.struct_psp_gfx_cmd_resp(cmd_id=am.GFX_CMD_ID_LOAD_TA); t=c.cmd.cmd_load_ta
t.app_phy_addr_lo,t.app_phy_addr_hi=amc&0xFFFFFFFF,amc>>32
t.app_len=len(blob) if applen is None else applen
t.cmd_buf_phy_addr_lo,t.cmd_buf_phy_addr_hi=cmc&0xFFFFFFFF,cmc>>32; t.cmd_buf_len=0x4000
t0=time.time()
try: r=submit(c); st=r.resp.status&0xFFFFFFFF
except Exception as e:
try: st=int(str(e).strip().split()[-1])&0xFFFFFFFF
except Exception: st=-1
dt=time.time()-t0
print(' %-40s -> %#-12x %.1fs%s'%(tag,st,dt,' <<< STALL' if dt>5 else ''), flush=True)
return dt>5
if load(base, None, 'CONTROL unmodified image'): sys.exit(3)
cases=[]
for frac,nm in ((0.99,'99%'),(0.75,'75%'),(0.5,'50%'),(0.1,'10%')):
cases.append((base[:int(len(base)*frac)], None, 'truncated to '+nm))
for off in (0x10,0x14,0x18,0x1c,0x20,0x24):
for val,vn in ((0,'0'),(0xFFFFFFFF,'ones'),(0x7FFFFFFF,'maxint')):
b=bytearray(base); struct.pack_into('<I',b,off,val)
cases.append((bytes(b), None, 'hdr[%#x]=%s'%(off,vn)))
cases.append((base, 0x7FFFFFFF, 'app_len = 0x7fffffff'))
cases.append((base, len(base)*4, 'app_len = 4x real'))
for blob,al,tag in cases:
if load(blob, al, tag): print(' (stalled, aborting)', flush=True); break
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