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Read length after args in String#setbyte
Prevents RCE
Reported by https://hackerone.com/raydot
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Craig Lehmann authored and bouk committed Nov 24, 2016
1 parent a630c4f commit 83005d83d8ba95524436409d5d73fd82b63bc115
Showing 2 changed files with 14 additions and 1 deletion.
@@ -23,10 +23,11 @@ static mrb_value
mrb_str_setbyte(mrb_state *mrb, mrb_value str)
{
mrb_int pos, byte;
long len = RSTRING_LEN(str);
long len;

mrb_get_args(mrb, "ii", &pos, &byte);

len = RSTRING_LEN(str);
if (pos < -len || len <= pos)
mrb_raisef(mrb, E_INDEX_ERROR, "index %S is out of array", mrb_fixnum_value(pos));
if (pos < 0)
@@ -30,6 +30,18 @@
assert_equal("Hello", str1)
end

assert("String#setbyte raises IndexError if arg conversion resizes String") do
$s = "01234\n"
class Tmp
def to_i
$s.chomp! ''
95
end
end
tmp = Tmp.new
assert_raise(IndexError) { $s.setbyte(5, tmp) }
end

assert('String#byteslice') do
str1 = "hello"
assert_equal("e", str1.byteslice(1))

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