[Bug 2086515] Re: Cryptographically unsafe RNG used for FIT images

[Heinrich Schuchardt]

Upstream asked me to send the patch to the public mailing list:
https://lists.denx.de/pipermail/u-boot/2024-November/570344.html


** Information type changed from Private Security to Public Security

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Title:
  Cryptographically unsafe RNG used for FIT images

Status in u-boot package in Ubuntu:
  New

Bug description:
  The mkimage tool uses the random() function for generating the
  initialization vector used for AES encryption inside FIT images. As
  the PRNG used for the random() function has only 2^31 states this is
  cryptographically unsafe. See appended patch.

  "The ideal IV is a random or pseudorandom number. It must also be
  nonrepeating. Both randomness and nonrepetitiveness are crucial to
  prevent attackers from finding patterns in similar parts of the
  encrypted message and then using this information to decrypt the
  message. The IV need not be secret." [1]

  [1] https://www.techtarget.com/whatis/definition/initialization-
  vector-IV

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