djsundog/circuitpython
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Add overflow checks for int to bytes conversions

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For both small and long integers, raise an exception if calling
struct.pack, adding an element to an array.array, or formatting an int
with int.to_bytes would overflow the requested size.
This commit is contained in:
Matt Wozniski 2019-05-08 23:50:35 -04:00
parent e041df73bb
commit 095c844004
3 changed files with 60 additions and 4 deletions
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18
py/binary.c
View File

@ -304,15 +304,18 @@ void mp_binary_set_val(char struct_type, char val_type, mp_obj_t val_in, byte **
break;
}
#endif
default:
default: {
bool signed_type = is_signed(val_type);
#if MICROPY_LONGINT_IMPL != MICROPY_LONGINT_IMPL_NONE
if (MP_OBJ_IS_TYPE(val_in, &mp_type_int)) {
mp_obj_int_buffer_overflow_check(val_in, size, signed_type);
mp_obj_int_to_bytes_impl(val_in, struct_type == '>', size, p);
return;
} else
#endif
{
val = mp_obj_get_int(val_in);
mp_obj_int_buffer_overflow_check(val_in, size, signed_type);
// zero/sign extend if needed
if (BYTES_PER_WORD < 8 && size > sizeof(val)) {
int c = (is_signed(val_type) && (mp_int_t)val < 0) ? 0xff : 0x00;
@ -322,6 +325,7 @@ void mp_binary_set_val(char struct_type, char val_type, mp_obj_t val_in, byte **
}
}
}
}
}
mp_binary_set_int(MIN((size_t)size, sizeof(val)), struct_type == '>', p, val);
@ -343,16 +347,22 @@ void mp_binary_set_val_array(char typecode, void *p, mp_uint_t index, mp_obj_t v
((mp_obj_t*)p)[index] = val_in;
break;
#endif
default:
default: {
size_t size = mp_binary_get_size('@', typecode, NULL);
bool signed_type = is_signed(typecode);
#if MICROPY_LONGINT_IMPL != MICROPY_LONGINT_IMPL_NONE
if (MP_OBJ_IS_TYPE(val_in, &mp_type_int)) {
size_t size = mp_binary_get_size('@', typecode, NULL);
mp_obj_int_buffer_overflow_check(val_in, size, signed_type);
mp_obj_int_to_bytes_impl(val_in, MP_ENDIANNESS_BIG,
size, (uint8_t*)p + index * size);
return;
}
#endif
mp_binary_set_val_array_from_int(typecode, p, index, mp_obj_get_int(val_in));
mp_int_t val = mp_obj_get_int(val_in);
mp_obj_int_buffer_overflow_check(val_in, size, signed_type);
mp_binary_set_val_array_from_int(typecode, p, index, val);
}
}
}

45
py/objint.c
View File

@ -300,6 +300,49 @@ char *mp_obj_int_formatted(char **buf, size_t *buf_size, size_t *fmt_size, mp_co
return b;
}
void mp_obj_int_buffer_overflow_check(mp_obj_t self_in, size_t nbytes, bool is_signed)
{
if (is_signed) {
// edge = 1 << (nbytes * 8 - 1)
mp_obj_t edge = mp_binary_op(MP_BINARY_OP_INPLACE_LSHIFT,
mp_obj_new_int(1),
mp_obj_new_int(nbytes * 8 - 1));
// if self >= edge, we don't fit
if (mp_binary_op(MP_BINARY_OP_MORE_EQUAL, self_in, edge) == mp_const_true) {
goto raise;
}
// edge = -edge
edge = mp_unary_op(MP_UNARY_OP_NEGATIVE, edge);
// if self < edge, we don't fit
if (mp_binary_op(MP_BINARY_OP_LESS, self_in, edge) == mp_const_true) {
goto raise;
}
} else {
if (mp_obj_int_sign(self_in) < 0) {
// Negative numbers never fit in an unsigned value
goto raise;
}
// edge = 1 << (nbytes * 8)
mp_obj_t edge = mp_binary_op(MP_BINARY_OP_INPLACE_LSHIFT,
mp_obj_new_int(1),
mp_obj_new_int(nbytes * 8));
// if self >= edge, we don't fit
if (mp_binary_op(MP_BINARY_OP_MORE_EQUAL, self_in, edge) == mp_const_true) {
goto raise;
}
}
return;
raise:
mp_raise_ValueError_varg(translate("value would overflow a %d byte buffer"), nbytes);
}
#if MICROPY_LONGINT_IMPL == MICROPY_LONGINT_IMPL_NONE
int mp_obj_int_sign(mp_obj_t self_in) {
@ -435,6 +478,8 @@ STATIC mp_obj_t int_to_bytes(size_t n_args, const mp_obj_t *args) {
byte *data = (byte*)vstr.buf;
memset(data, 0, len);
mp_obj_int_buffer_overflow_check(args[0], len, false);
#if MICROPY_LONGINT_IMPL != MICROPY_LONGINT_IMPL_NONE
if (!MP_OBJ_IS_SMALL_INT(args[0])) {
mp_obj_int_to_bytes_impl(args[0], big_endian, len, data);

1
py/objint.h
View File

@ -53,6 +53,7 @@ char *mp_obj_int_formatted(char **buf, size_t *buf_size, size_t *fmt_size, mp_co
int base, const char *prefix, char base_char, char comma);
char *mp_obj_int_formatted_impl(char **buf, size_t *buf_size, size_t *fmt_size, mp_const_obj_t self_in,
int base, const char *prefix, char base_char, char comma);
void mp_obj_int_buffer_overflow_check(mp_obj_t self_in, size_t nbytes, bool is_signed);
mp_int_t mp_obj_int_hash(mp_obj_t self_in);
mp_obj_t mp_obj_int_from_bytes_impl(bool big_endian, size_t len, const byte *buf);
void mp_obj_int_to_bytes_impl(mp_obj_t self_in, bool big_endian, size_t len, byte *buf);