Adding detection of out-of-bound pre-bound memory read to AES-XTS tests.

[nebeid]

Issues:

Addresses #V1681992550

Description of changes:

This change hardens the tests introduced in #2227 Fix out-of-bound (OOB) input read in AES-XTS Decrypt in AVX-512 implementation.
It adds a memory page preceding the input and output buffer that is protected against read and write in order to detect any under-read, in which case a segfault occurs.

The suspected code that can potentially cause a "pre-bound" OOB is the cipher-stealing section in Encrypt
crypto/fipsmodule/aes/asm/aesni-xts-avx512.pl#L1809-L1810
and decrypt
crypto/fipsmodule/aes/asm/aesni-xts-avx512.pl#2572-L2573.

Testing:

The efficacy of the added test was shown by changing the decrypt cipher-stealing code for example to:

--- a/crypto/fipsmodule/aes/asm/aesni-xts-avx512.pl
+++ b/crypto/fipsmodule/aes/asm/aesni-xts-avx512.pl
@@ -2569,7 +2569,7 @@ ___
   vpshufb       %xmm10,%xmm8,%xmm8
 
 
-  vmovdqu       -0x10($input,$length,1),%xmm3
+  vmovdqu       -0x12($input,$length,1),%xmm3
   vmovdqu       %xmm8,-0x10($output,$length,1)

With this change, a segmentation fault occurs in the test vector of input length 17 bytes (1 AES block + 1 byte); which is the smallest test vector that requires cipher stealing. At the changed line:

• $input points at byte 16, i.e. past the first block
• $length = 1, after l.2429
• the read index with the diff change is $input + $length - 18 = $input -17, which points at byte "-1", i.e. the byte right before byte 0 of the input, i.e. an underread, this causes a segfault at this vector.
• Other larger changes, e.g. -0x20, will have the same result.

Another test changes the location of the written output

 
   .L_done_${rndsuffix}:
   # store last ciphertext value
-  vmovdqu       %xmm8,-0x10($output)
+  vmovdqu       %xmm8,-0x11($output)
 ___
   }

• This test caused a segfault with the smallest input of 1 block = 16 bytes

Similar tests in the encrypt path gave the same result of segfaulting when trying to read before the input beginning.

Call-outs:

N/A

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license and the ISC license.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.04%. Comparing base (652f7a9) to head (bae956c).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2286      +/-   ##
==========================================
+ Coverage   79.02%   79.04%   +0.01%     
==========================================
  Files         614      614              
  Lines      106934   106953      +19     
  Branches    15145    15146       +1     
==========================================
+ Hits        84504    84537      +33     
+ Misses      21777    21762      -15     
- Partials      653      654       +1     

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