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buffer.h uses unsigned values for keeping track of allocated sizes. This means that a call to nettle_buffer_grow could silently truncate a large argument of type size_t (on 64 bit systems), for example.
This issue also applies to nettle_realloc_func
Furthermore, a size computation in nettle_buffer_grow can wrap around, failing to allocate additional buffer space:
if (buffer->size + length > buffer->alloc)
There is another size computation in asn1_der_get_bignum which looks a bit suspicious as well. If 8 * i->length wraps around, then the max_bits restriction is not necessarily enforced:
if (max_bits && (8 * i->length > (16 + max_bits)))
This size computation in pgp_armor needs a guard against wraparound, too:
unsigned text_size = BASE64_ENCODE_LENGTH(length)
+ BASE64_ENCODE_FINAL_LENGTH;
Comment 2Nikos Mavrogiannopoulos
2013-12-11 11:31:17 UTC
This is fixed in nettle's master branch, at the cost of an ABI change. I don't think there is much we can do on that (except maintaining a local version of nettle). Nevertheless, I think the impact is minimal as I don't see the nettle's buffer.h to be used in the projects using nettle.
buffer.h uses unsigned values for keeping track of allocated sizes. This means that a call to nettle_buffer_grow could silently truncate a large argument of type size_t (on 64 bit systems), for example. This issue also applies to nettle_realloc_func Furthermore, a size computation in nettle_buffer_grow can wrap around, failing to allocate additional buffer space: if (buffer->size + length > buffer->alloc) There is another size computation in asn1_der_get_bignum which looks a bit suspicious as well. If 8 * i->length wraps around, then the max_bits restriction is not necessarily enforced: if (max_bits && (8 * i->length > (16 + max_bits))) This size computation in pgp_armor needs a guard against wraparound, too: unsigned text_size = BASE64_ENCODE_LENGTH(length) + BASE64_ENCODE_FINAL_LENGTH;