crypto: add sanity checking of TLS x509 credentials

If the administrator incorrectly sets up their x509 certificates,
the errors seen at runtime during connection attempts are very
obscure and difficult to diagnose. This has been a particular
problem for people using openssl to generate their certificates
instead of the gnutls certtool, because the openssl tools don't
turn on the various x509 extensions that gnutls expects to be
present by default.

This change thus adds support in the TLS credentials object to
sanity check the certificates when QEMU first loads them. This
gives the administrator immediate feedback for the majority of
common configuration mistakes, reducing the pain involved in
setting up TLS. The code is derived from equivalent code that
has been part of libvirt's TLS support and has been seen to be
valuable in assisting admins.

It is possible to disable the sanity checking, however, via
the new 'sanity-check' property on the tls-creds object type,
with a value of 'no'.

Unit tests are included in this change to verify the correctness
of the sanity checking code in all the key scenarios it is
intended to cope with. As part of the test suite, the pkix_asn1_tab.c
from gnutls is imported. This file is intentionally copied from the
(long since obsolete) gnutls 1.6.3 source tree, since that version
was still under GPLv2+, rather than the GPLv3+ of gnutls >= 2.0.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/trace-events b/trace-events
index b1de160..207821d 100644
--- a/trace-events
+++ b/trace-events
@@ -1676,3 +1676,8 @@ qcrypto_tls_creds_anon_load(void *creds, const char *dir) "TLS creds anon load c
 
 # crypto/tlscredsx509.c
 qcrypto_tls_creds_x509_load(void *creds, const char *dir) "TLS creds x509 load creds=%p dir=%s"
+qcrypto_tls_creds_x509_check_basic_constraints(void *creds, const char *file, int status) "TLS creds x509 check basic constraints creds=%p file=%s status=%d"
+qcrypto_tls_creds_x509_check_key_usage(void *creds, const char *file, int status, int usage, int critical) "TLS creds x509 check key usage creds=%p file=%s status=%d usage=%d critical=%d"
+qcrypto_tls_creds_x509_check_key_purpose(void *creds, const char *file, int status, const char *usage, int critical) "TLS creds x509 check key usage creds=%p file=%s status=%d usage=%s critical=%d"
+qcrypto_tls_creds_x509_load_cert(void *creds, int isServer, const char *file) "TLS creds x509 load cert creds=%p isServer=%d file=%s"
+qcrypto_tls_creds_x509_load_cert_list(void *creds, const char *file) "TLS creds x509 load cert list creds=%p file=%s"