cryptsetup: Out-of-bounds write when validating segments (CVE-2020-14382)

There's a bug in LUKS2 format validation code, that is effectively invoked on every device/image presenting itself as LUKS2 container. The bug is in segments validation code in file 'lib/luks2/luks2_json_metadata.c' in function hdr_validate_segments(struct crypt_device *cd, json_object *hdr_jobj) where the code does not check for possible overflow on memory allocation used for intervals array (see statement "intervals = malloc(first_backup * sizeof(*intervals));"). Due to the bug, library can be tricked to expect such allocation was successful but for far less memory then originally expected. Later it may read data FROM image crafted by an attacker and actually write such data BEYOND allocated memory. The bug was introduced in cryptsetup 2.2.0.

Fixed In Version:

cryptsetup 2.3.4

References:

Patch:

https://gitlab.com/cryptsetup/cryptsetup/-/commit/52f5cb8cedf22fb3e14c744814ec8af7614146c7

Affected branches:

master (a9196112)
3.12-stable
3.11-stable

Edited Sep 22, 2020 by Leo

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