[PATCH 20/21] crypto: support upto 5 parallel certificate identities

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

The default (required) identity is stored in server-cert.pem /
client-cert.pem and server-key.pem / client-key.pem.

The 4 extra (optional) identities are stored in server-cert-$N.pem /
client-cert-$N.pem and server-key-$N.pem / client-key-$N.pem. The
numbering starts at 0 and the first missing cert/key pair will
terminate the loading process.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 crypto/tlscreds.c             | 10 +++++-
 crypto/tlscredspriv.h         |  3 ++
 crypto/tlscredsx509.c         | 68 ++++++++++++++++++++++++++++-------
 crypto/tlssession.c           |  1 +
 crypto/trace-events           |  1 +
 docs/system/tls.rst           | 54 ++++++++++++++++++++++++++--
 include/crypto/tlscredsx509.h |  6 ++++
 7 files changed, 127 insertions(+), 16 deletions(-)

diff --git a/crypto/tlscreds.c b/crypto/tlscreds.c
index 85268f3b57..b7e77f6285 100644
--- a/crypto/tlscreds.c
+++ b/crypto/tlscreds.c
@@ -85,6 +85,14 @@ qcrypto_tls_creds_get_dh_params_file(QCryptoTLSCreds *creds,
 }
 
 
+char *
+qcrypto_tls_creds_build_path(QCryptoTLSCreds *creds,
+                             const char *filename)
+{
+    return g_strdup_printf("%s/%s", creds->dir, filename);
+}
+
+
 int
 qcrypto_tls_creds_get_path(QCryptoTLSCreds *creds,
                            const char *filename,
@@ -94,7 +102,7 @@ qcrypto_tls_creds_get_path(QCryptoTLSCreds *creds,
 {
     int ret = -1;
 
-    *cred = g_strdup_printf("%s/%s", creds->dir, filename);
+    *cred = qcrypto_tls_creds_build_path(creds, filename);
 
     if (access(*cred, R_OK) < 0) {
         if (errno == ENOENT && !required) {
diff --git a/crypto/tlscredspriv.h b/crypto/tlscredspriv.h
index 69dac02437..8f2d096c7f 100644
--- a/crypto/tlscredspriv.h
+++ b/crypto/tlscredspriv.h
@@ -39,6 +39,9 @@ struct QCryptoTLSCreds {
 
 #ifdef CONFIG_GNUTLS
 
+char *qcrypto_tls_creds_build_path(QCryptoTLSCreds *creds,
+                                   const char *filename);
+
 int qcrypto_tls_creds_get_path(QCryptoTLSCreds *creds,
                                const char *filename,
                                bool required,
diff --git a/crypto/tlscredsx509.c b/crypto/tlscredsx509.c
index d7d1f594c0..fa92431906 100644
--- a/crypto/tlscredsx509.c
+++ b/crypto/tlscredsx509.c
@@ -686,7 +686,6 @@ qcrypto_tls_creds_x509_load_identity(QCryptoTLSCredsX509 *creds,
                                      QCryptoTLSCredsBox *box,
                                      const char *certbase,
                                      const char *keybase,
-                                     bool isOptional,
                                      Error **errp)
 {
     g_autoptr(QCryptoTLSCredsX509IdentFiles) files =
@@ -694,9 +693,9 @@ qcrypto_tls_creds_x509_load_identity(QCryptoTLSCredsX509 *creds,
     int ret;
 
     if (qcrypto_tls_creds_get_path(&creds->parent_obj, certbase,
-                                   !isOptional, &files->certpath, errp) < 0 ||
+                                   false, &files->certpath, errp) < 0 ||
         qcrypto_tls_creds_get_path(&creds->parent_obj, keybase,
-                                   !isOptional, &files->keypath, errp) < 0) {
+                                   false, &files->keypath, errp) < 0) {
         return NULL;
     }
 
@@ -705,13 +704,17 @@ qcrypto_tls_creds_x509_load_identity(QCryptoTLSCredsX509 *creds,
         return NULL;
     }
     if (files->certpath && !files->keypath) {
-        error_setg(errp, "Cert '%s' without corresponding key",
-                   files->certpath);
+        g_autofree char *keypath =
+            qcrypto_tls_creds_build_path(&creds->parent_obj, keybase);
+        error_setg(errp, "Cert '%s' without corresponding key '%s'",
+                   files->certpath, keypath);
         return NULL;
     }
     if (!files->certpath && files->keypath) {
-        error_setg(errp, "Key '%s' without corresponding cert",
-                   files->keypath);
+        g_autofree char *certpath =
+            qcrypto_tls_creds_build_path(&creds->parent_obj, certbase);
+        error_setg(errp, "Key '%s' without corresponding cert '%s'",
+                   files->keypath, certpath);
         return NULL;
     }
 
@@ -750,7 +753,9 @@ qcrypto_tls_creds_x509_load_identities(QCryptoTLSCredsX509 *creds,
                                        bool isServer,
                                        Error **errp)
 {
+    ERRP_GUARD();
     QCryptoTLSCredsX509IdentFiles *ifiles;
+    size_t i;
 
     ifiles = qcrypto_tls_creds_x509_load_identity(
         creds, box,
@@ -760,15 +765,52 @@ qcrypto_tls_creds_x509_load_identities(QCryptoTLSCredsX509 *creds,
         isServer ?
         QCRYPTO_TLS_CREDS_X509_SERVER_KEY :
         QCRYPTO_TLS_CREDS_X509_CLIENT_KEY,
-        !isServer, errp);
-    if (!ifiles) {
+        errp);
+    if (!ifiles && *errp) {
         return -1;
     }
 
-    files->identities = g_renew(QCryptoTLSCredsX509IdentFiles *,
-                                files->identities,
-                                files->nidentities + 1);
-    files->identities[files->nidentities++] = ifiles;
+    if (ifiles) {
+        files->identities = g_renew(QCryptoTLSCredsX509IdentFiles *,
+                                    files->identities,
+                                    files->nidentities + 1);
+        files->identities[files->nidentities++] = ifiles;
+    }
+
+    for (i = 0; i < QCRYPTO_TLS_CREDS_X509_IDENTITY_MAX; i++) {
+        g_autofree char *cert = g_strdup_printf(
+            isServer ?
+            QCRYPTO_TLS_CREDS_X509_SERVER_CERT_N :
+            QCRYPTO_TLS_CREDS_X509_CLIENT_CERT_N, i);
+        g_autofree char *key = g_strdup_printf(
+            isServer ?
+            QCRYPTO_TLS_CREDS_X509_SERVER_KEY_N :
+            QCRYPTO_TLS_CREDS_X509_CLIENT_KEY_N, i);
+
+        ifiles = qcrypto_tls_creds_x509_load_identity(creds, box,
+                                                      cert, key, errp);
+        if (!ifiles && *errp) {
+            return -1;
+        }
+        if (!ifiles) {
+            break;
+        }
+
+        files->identities = g_renew(QCryptoTLSCredsX509IdentFiles *,
+                                    files->identities,
+                                    files->nidentities + 1);
+        files->identities[files->nidentities++] = ifiles;
+    }
+
+    if (files->nidentities == 0 && isServer) {
+        g_autofree char *certpath = qcrypto_tls_creds_build_path(
+            &creds->parent_obj, QCRYPTO_TLS_CREDS_X509_SERVER_CERT);
+        g_autofree char *keypath = qcrypto_tls_creds_build_path(
+            &creds->parent_obj, QCRYPTO_TLS_CREDS_X509_SERVER_KEY);
+        error_setg(errp, "Missing server cert '%s' & key '%s'",
+                   certpath, keypath);
+        return -1;
+    }
 
     return 0;
 }
diff --git a/crypto/tlssession.c b/crypto/tlssession.c
index a1dc3b3ce0..314e3e96ba 100644
--- a/crypto/tlssession.c
+++ b/crypto/tlssession.c
@@ -345,6 +345,7 @@ qcrypto_tls_session_check_certificate(QCryptoTLSSession *session,
                 goto error;
             }
             session->peername = (char *)g_steal_pointer(&dname.data);
+            trace_qcrypto_tls_session_check_x509_dn(session, session->peername);
             if (session->authzid) {
                 bool allow;
 
diff --git a/crypto/trace-events b/crypto/trace-events
index d0e33427fa..771f9b8a6e 100644
--- a/crypto/trace-events
+++ b/crypto/trace-events
@@ -21,6 +21,7 @@ qcrypto_tls_creds_x509_load_cert_list(void *creds, const char *file) "TLS creds
 # tlssession.c
 qcrypto_tls_session_new(void *session, void *creds, const char *hostname, const char *authzid, int endpoint) "TLS session new session=%p creds=%p hostname=%s authzid=%s endpoint=%d"
 qcrypto_tls_session_check_creds(void *session, const char *status) "TLS session check creds session=%p status=%s"
+qcrypto_tls_session_check_x509_dn(void *session, const char *dname) "TLS session check x509 distinguished name session=%p dname=%s"
 qcrypto_tls_session_parameters(void *session, int threadSafety, int protocol, int cipher) "TLS session parameters session=%p threadSafety=%d protocol=%d cipher=%d"
 qcrypto_tls_session_bug1717_workaround(void *session) "TLS session bug1717 workaround session=%p"
 
diff --git a/docs/system/tls.rst b/docs/system/tls.rst
index 44c4bf04e9..7cec4ac3df 100644
--- a/docs/system/tls.rst
+++ b/docs/system/tls.rst
@@ -36,8 +36,58 @@ server and exposing it directly to remote browser clients. In such a
 case it might be useful to use a commercial CA to avoid needing to
 install custom CA certs in the web browsers.
 
-The recommendation is for the server to keep its certificates in either
-``/etc/pki/qemu`` or for unprivileged users in ``$HOME/.pki/qemu``.
+.. _tls_cert_file_naming:
+
+Certificate file naming
+~~~~~~~~~~~~~~~~~~~~~~~
+
+In a simple setup, where all QEMU instances on a machine share the
+same TLS configuration, it is suggested that QEMU certificates be
+kept in either ``/etc/pki/qemu`` or, for unprivileged users, in
+``$HOME/.pki/qemu``. Where different QEMU subsystems require
+different certificate configurations, sub-dirs of these locations
+may be chosen.
+
+The default file names that QEMU will traditionally load are:
+
+* ``ca-cert.pem`` - mandatory; for both client and server configurations
+* ``ca-crl.pem`` - optional; for server configurations only
+* ``server-cert.pem`` - mandatory; for server configurations only
+* ``server-key.pem`` - mandatory; for server configurations only
+* ``client-cert.pem`` - optional; for client configurations only
+* ``client-key.pem`` - optional; for client configurations only
+* ``dh-params.pem`` - optional; for server configurations only
+
+Since QEMU 10.2.0, there is support for loading upto four additional
+identities:
+
+* ``server-cert-[IDX].pem`` - optional; for server configurations only
+* ``server-key-[IDX].pem`` - optional; for server configurations only
+* ``client-cert-[IDX].pem`` - optional; for client configurations only
+* ``client-key-[IDX].pem`` - optional; for client configurations only
+
+where ``-[IDX]`` is one of the digits 0-3. Loading will terminate at
+the first absent index. The index based certificate files may be used
+as a replacement for, or in addition to, the traditional non-index
+based certificate files. The traditional certificate files will be
+loaded first, if present, then the index based certificates. Where
+multiple certificates are compatible with a TLS session, the first
+loaded certificate will preferred. IOW file naming can influence
+which certificates are used for a session.
+
+The use of multiple sets of certificates is intended to allow an
+incremental transition to certificates using different crytographic
+algorithms. This allows a newly deployed QEMU to introduce use of
+stronger cryptographic algorithms that will be preferred when talking
+to other newly deployed QEMU instances, while retaining compatbility
+with certificates issued to a historically deployed QEMU. This is
+notably useful to support live migration from an old QEMU deployed
+on older operating system releases, which may support fewer crypto
+algorithm choices than the current OS.
+
+The certificate creation commands below will be illustrated using
+the traditional naming scheme, but their args can be substituted
+to use the indexed naming in the obvious manner.
 
 .. _tls_005fgenerate_005fca:
 
diff --git a/include/crypto/tlscredsx509.h b/include/crypto/tlscredsx509.h
index c4daba21a6..61b7f73573 100644
--- a/include/crypto/tlscredsx509.h
+++ b/include/crypto/tlscredsx509.h
@@ -37,7 +37,13 @@ typedef struct QCryptoTLSCredsX509Class QCryptoTLSCredsX509Class;
 #define QCRYPTO_TLS_CREDS_X509_SERVER_CERT "server-cert.pem"
 #define QCRYPTO_TLS_CREDS_X509_CLIENT_KEY "client-key.pem"
 #define QCRYPTO_TLS_CREDS_X509_CLIENT_CERT "client-cert.pem"
+#define QCRYPTO_TLS_CREDS_X509_SERVER_KEY_N "server-key-%zu.pem"
+#define QCRYPTO_TLS_CREDS_X509_SERVER_CERT_N "server-cert-%zu.pem"
+#define QCRYPTO_TLS_CREDS_X509_CLIENT_KEY_N "client-key-%zu.pem"
+#define QCRYPTO_TLS_CREDS_X509_CLIENT_CERT_N "client-cert-%zu.pem"
 
+/* Max number of additional cert/key pairs (ie _N constants) */
+#define QCRYPTO_TLS_CREDS_X509_IDENTITY_MAX 4
 
 /**
  * QCryptoTLSCredsX509:
-- 
2.51.1