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py/binary: Change internal bytearray typecode from 0 to 1.
The value of 0 can't be used because otherwise mp_binary_get_size will let a null byte through as the type code (intepreted as byterray). This can lead to invalid type-specifier strings being let through without an error in the struct module, and even buffer overruns.
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Lines changed: 30 additions & 2 deletions

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‎py/binary.h‎

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -29,8 +29,9 @@
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#include "py/obj.h"
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// Use special typecode to differentiate repr() of bytearray vs array.array('B')
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// (underlyingly they're same).
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#define BYTEARRAY_TYPECODE 0
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// (underlyingly they're same). Can't use 0 here because that's used to detect
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// type-specification errors due to end-of-string.
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#define BYTEARRAY_TYPECODE 1
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size_t mp_binary_get_size(char struct_type, char val_type, mp_uint_t *palign);
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mp_obj_t mp_binary_get_val_array(char typecode, void *p, mp_uint_t index);

‎tests/basics/struct2.py‎

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Original file line numberDiff line numberDiff line change
@@ -40,3 +40,30 @@
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struct.calcsize('0z')
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except:
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print('Exception')
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# check that a count without a type specifier raises an exception
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try:
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struct.calcsize('1')
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except:
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print('Exception')
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try:
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struct.pack('1')
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except:
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print('Exception')
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try:
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struct.pack_into('1', bytearray(4), 0, 'xx')
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except:
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print('Exception')
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try:
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struct.unpack('1', 'xx')
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except:
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print('Exception')
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try:
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struct.unpack_from('1', 'xx')
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except:
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print('Exception')

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