void give_out (header *hd)
/***** give_out
print a value.
*****/
{ switch(hd->type)
{ case s_real : double_out(*realof(hd)); output("\n"); break;
case s_complex : complex_out(*realof(hd),*imagof(hd));
output("\n"); break;
case s_matrix : out_matrix(hd); break;
case s_cmatrix : out_cmatrix(hd); break;
case s_imatrix : out_imatrix(hd); break;
case s_string : output(stringof(hd)); output("\n"); break;
case s_interval : interval_out(*aof(hd),*bof(hd));
output("\n"); break;
default : output("?\n");
}
}
void string_instrumentationt::do_format_string_write(
goto_programt &dest,
goto_programt::const_targett target,
const code_function_callt::argumentst &arguments,
unsigned format_string_inx,
unsigned argument_start_inx,
const std::string &function_name)
{
const exprt &format_arg = arguments[format_string_inx];
if(format_arg.id()=="address_of" &&
format_arg.op0().id()=="index" &&
format_arg.op0().op0().id()==ID_string_constant) // constant format
{
format_token_listt token_list;
parse_format_string(format_arg.op0().op0(), token_list);
unsigned args=0;
for(format_token_listt::const_iterator it=token_list.begin();
it!=token_list.end();
it++)
{
if(find(it->flags.begin(), it->flags.end(), format_tokent::ASTERISK)!=
it->flags.end())
continue; // asterisk means `ignore this'
switch(it->type)
{
case format_tokent::STRING:
{
const exprt &argument=arguments[argument_start_inx+args];
const typet &arg_type=ns.follow(argument.type());
goto_programt::targett assertion=dest.add_instruction();
assertion->location=target->location;
assertion->location.set("property", "string");
std::string comment("format string buffer overflow in ");
comment += function_name;
assertion->location.set("comment", comment);
if(it->field_width!=0)
{
exprt fwidth = from_integer(it->field_width, uint_type());
exprt fw_1("+", uint_type());
exprt one = gen_one(uint_type());
fw_1.move_to_operands(fwidth);
fw_1.move_to_operands(one); // +1 for 0-char
exprt fw_lt_bs;
if(arg_type.id()=="pointer")
fw_lt_bs=binary_relation_exprt(fw_1, "<=", buffer_size(argument));
else
{
index_exprt index;
index.array()=argument;
index.index()=gen_zero(uint_type());
address_of_exprt aof(index);
fw_lt_bs=binary_relation_exprt(fw_1, "<=", buffer_size(aof));
}
assertion->make_assertion(fw_lt_bs);
}
else
{
// this is a possible overflow.
assertion->make_assertion(false_exprt());
}
// now kill the contents
invalidate_buffer(dest, target, argument, arg_type, it->field_width);
args++;
break;
}
case format_tokent::TEXT:
case format_tokent::UNKNOWN:
{
// nothing
break;
}
default: // everything else
{
const exprt &argument=arguments[argument_start_inx+args];
const typet &arg_type=ns.follow(argument.type());
goto_programt::targett assignment=dest.add_instruction(ASSIGN);
assignment->location=target->location;
exprt lhs("dereference", arg_type.subtype());
lhs.copy_to_operands(argument);
exprt rhs=side_effect_expr_nondett(lhs.type());
rhs.location()=target->location;
assignment->code=code_assignt(lhs, rhs);
args++;
break;
}
}
}
}
else // non-const format string
{
for(unsigned i=argument_start_inx; i<arguments.size(); i++)
{
const typet &arg_type=ns.follow(arguments[i].type());
// Note: is_string_type() is a `good guess' here. Actually
// any of the pointers could point into an array. But it
// would suck if we had to invalidate all variables.
// Luckily this case isn't needed too often.
if(is_string_type(arg_type))
{
goto_programt::targett assertion=dest.add_instruction();
assertion->location=target->location;
assertion->location.set("property", "string");
std::string comment("format string buffer overflow in ");
comment += function_name;
assertion->location.set("comment", comment);
// as we don't know any field width for the %s that
// should be here during runtime, we just report a
// possibly false positive
assertion->make_assertion(false_exprt());
invalidate_buffer(dest, target, arguments[i], arg_type, 0);
}
else
{
goto_programt::targett assignment = dest.add_instruction(ASSIGN);
assignment->location=target->location;
exprt lhs("dereference", arg_type.subtype());
lhs.copy_to_operands(arguments[i]);
exprt rhs=side_effect_expr_nondett(lhs.type());
rhs.location()=target->location;
assignment->code=code_assignt(lhs, rhs);
}
}
}
}
