ext/dba: bound CDB record lengths against the file size#22778
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The cdb handler passed 32-bit key and data lengths read from the file straight to zend_string_alloc(). On 32-bit a length near UINT32_MAX wraps the struct-size computation to a few bytes while the following read copies the trailing file data past it, overflowing the heap. Capture the file size at open and reject any record length that exceeds it before allocating, in the firstkey, nextkey and fetch handlers. Closes phpGH-22778
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The cdb handler read the 32-bit key and data length fields from the file and passed them directly to zend_string_alloc(). On 32-bit a length near UINT32_MAX wraps the struct size to a few bytes while the following read copies the trailing file bytes past that allocation, a heap overflow reachable by opening a crafted .cdb (64-bit only OOMs). Capture the file size at open and reject any record length that exceeds it, in firstkey, nextkey and fetch. Reproducer: a 2048-byte header with a first-record key length of 0xFFFFFFFF plus trailing bytes segfaults dba_firstkey() on 32-bit.