[PATCH v2 6/6] crypto: fix error reporting in cert chain checks

["Daniel P. Berrangé" <berrange@redhat.com>]

The loop that checks the CA certificate chain can fail to report
an error message if one of the certs in the chain has an issuer
than is not present in the chain. In this case, the outer loop
'while (checking_issuer)' will terminate after failing to find
the issuer, and no error message will be reported.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 crypto/tlscredsx509.c | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/crypto/tlscredsx509.c b/crypto/tlscredsx509.c
index 89a8e261d5..d42f2afaea 100644
--- a/crypto/tlscredsx509.c
+++ b/crypto/tlscredsx509.c
@@ -319,7 +319,6 @@ qcrypto_tls_creds_check_authority_chain(QCryptoTLSCredsX509 *creds,
                                         Error **errp)
 {
     gnutls_x509_crt_t cert_to_check = certs[ncerts - 1];
-    int checking_issuer = 1;
     int retval = 0;
     gnutls_datum_t dn = {}, dnissuer = {};
 
@@ -346,8 +345,8 @@ qcrypto_tls_creds_check_authority_chain(QCryptoTLSCredsX509 *creds,
         }
     }
 
-    while (checking_issuer) {
-        checking_issuer = 0;
+    for (;;) {
+        gnutls_x509_crt_t cert_issuer = NULL;
 
         if (gnutls_x509_crt_check_issuer(cert_to_check,
                                          cert_to_check)) {
@@ -362,19 +361,30 @@ qcrypto_tls_creds_check_authority_chain(QCryptoTLSCredsX509 *creds,
         for (int i = 0; i < ncacerts; i++) {
             if (gnutls_x509_crt_check_issuer(cert_to_check,
                                              cacerts[i])) {
-                retval = qcrypto_tls_creds_check_cert(
-                    creds, cacerts[i], cacertFile,
-                    isServer, isCA, errp);
-                if (retval < 0) {
-                    return retval;
-                }
-                cert_to_check = cacerts[i];
-                checking_issuer = 1;
+                cert_issuer = cacerts[i];
                 break;
             }
         }
+        if (!cert_issuer) {
+            break;
+        }
+
+        if (qcrypto_tls_creds_check_cert(creds, cert_issuer, cacertFile,
+                                         isServer, isCA, errp) < 0) {
+            return -1;
+        }
+
+        cert_to_check = cert_issuer;
     }
 
+    retval = gnutls_x509_crt_get_dn2(cert_to_check, &dn);
+    if (retval < 0) {
+        error_setg(errp, "Unable to fetch cert DN: %s",
+                   gnutls_strerror(retval));
+        return -1;
+    }
+    error_setg(errp, "Cert '%s' has no issuer in CA chain", dn.data);
+    gnutls_free(dn.data);
     return -1;
 }
 
-- 
2.50.1