Tests: read known data from the test volumes without mounting (#1907)

The Linux workflow checks the content of the Tests/*.hc volumes by
mounting them, which needs root, FUSE and the installed package, and so
only runs on x86_64. Add a test that recovers the same data through the
volume layer instead, so it also runs on other architectures, e.g. on the
big-endian cross build under qemu-user.

Tests/volume_read_test.cpp opens a volume read-only and reads its data
area with Volume::ReadSectors: in one call, as multi-sector ranges at
nonzero offsets with odd sector counts, again with the encryption thread
pool running, and one sector at a time; every read must match the first.
CPU features are detected as in the application, and the character set
is taken from the environment (LC_CTYPE) so that paths with non-ASCII
characters work; if that locale is unavailable, the test continues in the
C locale and says so.

Tests/test_volume_read.py builds it against Volume.a and Platform.a of a
finished standard Linux build (CXX and NM can be set for a cross build)
and checks the plaintext of every Tests/test.*.hc volume: the FAT boot
sector, DUMMY.TXT with the content "Dummy" at the cluster given by the
root directory, and a known SHA-256 digest of the whole data area. A
volume without a digest, or a digest without a volume, is an error.

It runs in the Linux workflow after the .deb build and in the build job
of the big-endian workflow (test.sha512.hc only in the automatic check,
all volumes in the full run), and requires the thread pool there.

Signed-off-by: Ville Takio <ville+git@takio.fi>

.github/workflows/build-linux.yml

@@ -22,6 +22,9 @@ on:
       - 'src/Volume/**'
       - 'src/Makefile'
       - 'Tests/test_linux_privilege_helpers.py'
+      - 'Tests/test.*.hc'
+      - 'Tests/test_volume_read.py'
+      - 'Tests/volume_read_test.cpp'
       - '.github/workflows/build-linux.yml'
   pull_request:
     branches: [ "master" ]
@@ -44,6 +47,9 @@ on:
       - 'src/Volume/**'
       - 'src/Makefile'
       - 'Tests/test_linux_privilege_helpers.py'
+      - 'Tests/test.*.hc'
+      - 'Tests/test_volume_read.py'
+      - 'Tests/volume_read_test.cpp'
       - '.github/workflows/build-linux.yml'
 
 concurrency:
@@ -129,6 +135,12 @@ jobs:
         name: veracrypt-console-debs-${{ matrix.os }}
         path: /tmp/VeraCrypt_Packaging/Console/Packaging/veracrypt-console-*.*
 
+    # Decrypts the Tests/*.hc volumes through Volume::ReadSectors, without
+    # mounting, using the archives that the last build above (the console
+    # version) left in src, and checks known data.
+    - name: Read known data from the test volumes
+      run: python3 Tests/test_volume_read.py --build-dir src --require-thread-pool
+
     - name: Install and test VeraCrypt GUI .deb packages
       run: |
         sudo apt install -y /tmp/VeraCrypt_Packaging/GUI/Packaging/veracrypt-*.deb