[Bug 60497] New: crypt32: PFXImportCertStore() fails for a PFX with an empty password created by BouncyCastle (MAC verification failed)

[WineHQ Bugzilla]

http://bugs.winehq.org/show_bug.cgi?id=60497

            Bug ID: 60497
           Summary: crypt32: PFXImportCertStore() fails for a PFX with an
                    empty password created by BouncyCastle (MAC
                    verification failed)
           Product: Wine
           Version: 11.19
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: crypt32
          Assignee: [e-mail]
          Reporter: [e-mail]
  Target Milestone: ---
      Distribution: ---

PFXImportCertStore() with an empty password fails for PKCS#12 files written by
BouncyCastle
(C#, Pkcs12Store.Save() with an empty password; seen with BouncyCastle.Crypto
1.8):

  GnuTLS error: The Message Authentication Code verification failed.

The same files import on Windows. In my case, SALTO ProAccess Space 6.14 stores
such PFX files
(per-device certificates, EC keys) and loads them with X509Certificate2 in .NET
Framework 4.8.
That works on Windows and fails under Wine.

Cause: for an empty password BouncyCastle computes the MAC over a zero-length
password, instead
of a single BMPString null character (00 00). open_cert_store() always passes
"" to
gnutls_pkcs12_verify_mac(), which GnuTLS turns into 00 00, so the MAC check
fails.
gnutls_pkcs12_verify_mac(p12, NULL) succeeds. Windows accepts both encodings of
an empty password,
and OpenSSL also accepts these files with an empty password.

Reproducer (attached): pfxcheck.c (plain C, mingw-w64: x86_64-w64-mingw32-gcc
pfxcheck.c -lcrypt32)
and bc-empty.pfx (throwaway RSA test certificate, CN=test, empty password,
written with
pfxgen.cs/BouncyCastle):

  wine pfxcheck.exe bc-empty.pfx
  Wine 11.19:      PFXImportCertStore(""): FAILED
  with the patch:  PFXImportCertStore(""): OK, cert 1, private key: yes

The same file re-saved with the password "test" imports fine on unpatched Wine,
so this concerns
only the empty-password case. (Unpatched Wine also leaves the last error unset
on this failure;
that is bug 60234.)

A suggested patch is attached (tested on Wine 11.19, applies to master too): if
the MAC check
fails and the password is empty, retry gnutls_pkcs12_verify_mac() with NULL,
and if that
succeeds use NULL for the bag decryption too. 32- and 64-bit tested; crypt32
conformance
tests unchanged. For builds with the old WoW64 layout, the i386-unix crypt32.so
needs it as well.

Not done yet: a conformance test (a small BouncyCastle-style PFX with a
zero-length-password MAC
embedded in tests/store.c or tests/main.c would do it).

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