a94613570d
At a basic level, remove assumptions about the underlying algorithm (such as output block size and reseeding requirements) from the algorithm-independent logic in randomdev.c. Chacha20 does not have many of the restrictions that AES-ICM does as a PRF (Pseudo-Random Function), because it has a cipher block size of 512 bits. The motivation is that by generalizing the API, Chacha is not penalized by the limitations of AES. In READ_RANDOM_UIO, first attempt to NOWAIT allocate a large enough buffer for the entire user request, or the maximal input we'll accept between signal checking, whichever is smaller. The idea is that the implementation of any randomdev algorithm is then free to divide up large requests in whatever fashion it sees fit. As part of this, two responsibilities from the "algorithm-generic" randomdev code are pushed down into the Fortuna ra_read implementation (and any other future or out-of-tree ra_read implementations): 1. If an algorithm needs to rekey every N bytes, it is responsible for handling that in ra_read(). (I.e., Fortuna's 1MB rekey interval for AES block generation.) 2. If an algorithm uses a block cipher that doesn't tolerate partial-block requests (again, e.g., AES), it is also responsible for handling that in ra_read(). Several APIs are changed from u_int buffer length to the more canonical size_t. Several APIs are changed from taking a blockcount to a bytecount, to permit PRFs like Chacha20 to directly generate quantities of output that are not multiples of RANDOM_BLOCKSIZE (AES block size). The Fortuna algorithm is changed to NOT rekey every 1MiB when in Chacha20 mode (kern.random.use_chacha20_cipher="1"). This is explicitly supported by the math in FS&K §9.4 (Ferguson, Schneier, and Kohno; "Cryptography Engineering"), as well as by their conclusion: "If we had a block cipher with a 256-bit [or greater] block size, then the collisions would not have been an issue at all." For now, continue to break up reads into PAGE_SIZE chunks, as they were before. So, no functional change, mostly. Reviewed by: markm Approved by: secteam(delphij) Differential Revision: https://reviews.freebsd.org/D20312 |
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| bin | ||
| cddl | ||
| contrib | ||
| crypto | ||
| etc | ||
| gnu | ||
| include | ||
| kerberos5 | ||
| lib | ||
| libexec | ||
| release | ||
| rescue | ||
| sbin | ||
| secure | ||
| share | ||
| stand | ||
| sys | ||
| targets | ||
| tests | ||
| tools | ||
| usr.bin | ||
| usr.sbin | ||
| .arcconfig | ||
| .arclint | ||
| .cirrus.yml | ||
| .clang-format | ||
| .gitattributes | ||
| .gitignore | ||
| COPYRIGHT | ||
| LOCKS | ||
| MAINTAINERS | ||
| Makefile | ||
| Makefile.inc1 | ||
| Makefile.libcompat | ||
| Makefile.sys.inc | ||
| ObsoleteFiles.inc | ||
| README | ||
| README.md | ||
| UPDATING | ||
FreeBSD Source:
This is the top level of the FreeBSD source directory. This file
was last revised on:
FreeBSD
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include System include files.
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