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Find file Copy path
66 lines (53 sloc) 2.17 KB
import angr
import claripy
def main():
p = angr.Project("license", load_options={'auto_load_libs': False})
# Create a blank state
state = p.factory.blank_state()
# Build the file whose name is weird
license_name = "_a\nb\tc_"
# This is the license file
# From analyzing the binary, we know that the license file should have five
# lines in total, and each line has 6 characters. Not setting file content
# may also work, but in that case, angr will produce many more paths, and we
# will spent much more time in path trimming.
bytestring = None
for i in range(5):
line = [ ]
for j in range(6):
line.append(state.solver.BVS('license_file_byte_%d_%d' % (i, j), 8))
state.add_constraints(line[-1] != b'\n')
if bytestring is None:
bytestring = claripy.Concat(*line)
else:
bytestring = bytestring.concat(state.solver.BVV(b'\n'), *line)
license_file = angr.storage.file.SimFile(license_name, bytestring)
state.fs.insert(license_name, license_file)
simgr = p.factory.simulation_manager(state)
simgr.explore(
find=(0x400e93, ),
avoid=(0x400bb1, 0x400b8f, 0x400b6d, 0x400a85,
0x400ebf, 0x400a59)
)
# One path will be found
found = simgr.found[0]
rsp = found.regs.rsp
flag_addr = rsp + 0x278 - 0xd8 # Ripped from IDA
# Perform an inline call to strlen() in order to determine the length of the
# flag
FAKE_ADDR = 0x100000
strlen = lambda state, arguments: \
angr.SIM_PROCEDURES['libc']['strlen'](p, FAKE_ADDR, p.arch).execute(
state, arguments=arguments
)
flag_length = strlen(found, arguments=[flag_addr]).ret_expr
# In case it's not null-terminated, we get the least number as the length
flag_length_int = min(found.solver.eval_upto(flag_length, 3))
# Read out the flag!
flag_int = found.solver.eval(found.memory.load(flag_addr, flag_length_int))
flag = bytes.fromhex(hex(flag_int)[2:])
return flag
def test():
assert main() == b'ASIS{8d2cc30143831881f94cb05dcf0b83e0}'
if __name__ == '__main__':
print(main())