…mentation (aws#2227)

- Fix instruction that caused out-of-bound read in the input reading of
the 16x loop (which processes a batch of 16 blocks of AES, 1 block = 16
bytes). This was triggered on lengths that are in the range 
[16*k * (16 bytes), (16*k +3)* (16 bytes)-1], k = 1, 2, ... 
The instruction was reading up to 3*16 bytes beyond the input length bound.

- The fix was inspired by the 8x loop in
https://github.com/aws/aws-lc/blob/becf5785c131012bb5a64f3da6cdb117ddc0f431/crypto/fipsmodule/aes/asm/aesni-xts-avx512.pl#L2544

- The existing unit tests cover those cases but there were no explicit
memory protections and ASAN doesn't instrument assembly code to check
for out-of-bound reads even when the subsequent memory is explicitly
poisoned.
 
### Call-outs:
N/A

### Testing:
On c6i, without the fix, the unit test segfaults
```
./crypto/crypto_test "--gtest_filter=XTSTest.*"
Note: Google Test filter = XTSTest.*
[==========] Running 4 tests from 1 test suite.
[----------] Global test environment set-up.
[----------] 4 tests from XTSTest
[ RUN      ] XTSTest.TestVectors
Segmentation fault (core dumped)
```
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.

…ts. (#2286)

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](https://github.com/aws/aws-lc/blob/v1.48.5/crypto/fipsmodule/aes/asm/aesni-xts-avx512.pl#L1809-L1810)
and decrypt

[crypto/fipsmodule/aes/asm/aesni-xts-avx512.pl#2572-L2573](https://github.com/aws/aws-lc/blob/v1.48.5/crypto/fipsmodule/aes/asm/aesni-xts-avx512.pl#L2572-L2573).

### Testing:
The efficacy of the added test was shown by changing the decrypt
cipher-stealing code for example to:
```diff
--- 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](https://github.com/aws/aws-lc/blob/v1.48.5/crypto/fipsmodule/aes/asm/aesni-xts-avx512.pl#L2429)
- 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
```@@ -2607,7 +2607,7 @@ ___
 
   .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.

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.

…ts. (aws#2286)

This change hardens the tests introduced in aws#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](https://github.com/aws/aws-lc/blob/v1.48.5/crypto/fipsmodule/aes/asm/aesni-xts-avx512.pl#L1809-L1810)
and decrypt

[crypto/fipsmodule/aes/asm/aesni-xts-avx512.pl#2572-L2573](https://github.com/aws/aws-lc/blob/v1.48.5/crypto/fipsmodule/aes/asm/aesni-xts-avx512.pl#L2572-L2573).

The efficacy of the added test was shown by changing the decrypt
cipher-stealing code for example to:
```diff
--- 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](https://github.com/aws/aws-lc/blob/v1.48.5/crypto/fipsmodule/aes/asm/aesni-xts-avx512.pl#L2429)
- 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
```@@ -2607,7 +2607,7 @@ ___

   .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.

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.

…ts. (aws#2286)

This change hardens the tests introduced in aws#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](https://github.com/aws/aws-lc/blob/v1.48.5/crypto/fipsmodule/aes/asm/aesni-xts-avx512.pl#L1809-L1810)
and decrypt

[crypto/fipsmodule/aes/asm/aesni-xts-avx512.pl#2572-L2573](https://github.com/aws/aws-lc/blob/v1.48.5/crypto/fipsmodule/aes/asm/aesni-xts-avx512.pl#L2572-L2573).

The efficacy of the added test was shown by changing the decrypt
cipher-stealing code for example to:
```diff
--- 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](https://github.com/aws/aws-lc/blob/v1.48.5/crypto/fipsmodule/aes/asm/aesni-xts-avx512.pl#L2429)
- 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
```@@ -2607,7 +2607,7 @@ ___

   .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.

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.

(cherry picked from commit a39439b)