Commit 993aec27 authored by Philippe Mathieu-Daudé's avatar Philippe Mathieu-Daudé
Browse files

crypto: Add tls-cipher-suites object 



On the host OS, various aspects of TLS operation are configurable.
In particular it is possible for the sysadmin to control the TLS
cipher/protocol algorithms that applications are permitted to use.

* Any given crypto library has a built-in default priority list
  defined by the distro maintainer of the library package (or by
  upstream).

* The "crypto-policies" RPM (or equivalent host OS package)
  provides a config file such as "/etc/crypto-policies/config",
  where the sysadmin can set a high level (library-independent)
  policy.

  The "update-crypto-policies --set" command (or equivalent) is
  used to translate the global policy to individual library
  representations, producing files such as
  "/etc/crypto-policies/back-ends/*.config". The generated files,
  if present, are loaded by the various crypto libraries to
  override their own built-in defaults.

  For example, the GNUTLS library may read
  "/etc/crypto-policies/back-ends/gnutls.config".

* A management application (or the QEMU user) may overide the
  system-wide crypto-policies config via their own config, if
  they need to diverge from the former.

Thus the priority order is "QEMU user config" > "crypto-policies
system config" > "library built-in config".

Introduce the "tls-cipher-suites" object for exposing the ordered
list of permitted TLS cipher suites from the host side to the
guest firmware, via fw_cfg. The list is represented as an array
of bytes.

The priority at which the host-side policy is retrieved is given
by the "priority" property of the new object type. For example,
"priority=@SYSTEM" may be used to refer to
"/etc/crypto-policies/back-ends/gnutls.config" (given that QEMU
uses GNUTLS).

The firmware uses the IANA_TLS_CIPHER array for configuring
guest-side TLS, for example in UEFI HTTPS Boot.

[Description from Daniel P. Berrangé, edited by Laszlo Ersek.]

Signed-off-by: default avatarPhilippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: default avatarDaniel P. Berrangé <berrange@redhat.com>
Acked-by: default avatarLaszlo Ersek <lersek@redhat.com>
Message-Id: <20200623172726.21040-2-philmd@redhat.com>
parent 4abf70a6

crypto/Makefile.objs

+1 −0
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ crypto-obj-y += cipher.o 
crypto-obj-$(CONFIG_AF_ALG) += afalg.o

crypto-obj-$(CONFIG_AF_ALG) += cipher-afalg.o

crypto-obj-$(CONFIG_AF_ALG) += hash-afalg.o

crypto-obj-$(CONFIG_GNUTLS) += tls-cipher-suites.o

crypto-obj-y += tlscreds.o

crypto-obj-y += tlscredsanon.o

crypto-obj-y += tlscredspsk.o

crypto/tls-cipher-suites.c

0 → 100644
+115 −0
Original line number Diff line number Diff line 
/*

 * QEMU TLS Cipher Suites

 *

 * Copyright (c) 2018-2020 Red Hat, Inc.

 *

 * Author: Philippe Mathieu-Daudé <philmd@redhat.com>

 *

 * SPDX-License-Identifier: GPL-2.0-or-later

 */



#include "qemu/osdep.h"

#include "qapi/error.h"

#include "qom/object_interfaces.h"

#include "crypto/tlscreds.h"

#include "crypto/tls-cipher-suites.h"

#include "trace.h"



/*

 * IANA registered TLS ciphers:

 * https://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml#tls-parameters-4

 */

typedef struct {

    uint8_t data[2];

} QEMU_PACKED IANA_TLS_CIPHER;



GByteArray *qcrypto_tls_cipher_suites_get_data(QCryptoTLSCipherSuites *obj,

                                               Error **errp)

{

    QCryptoTLSCreds *creds = QCRYPTO_TLS_CREDS(obj);

    gnutls_priority_t pcache;

    GByteArray *byte_array;

    const char *err;

    size_t i;

    int ret;



    trace_qcrypto_tls_cipher_suite_priority(creds->priority);

    ret = gnutls_priority_init(&pcache, creds->priority, &err);

    if (ret < 0) {

        error_setg(errp, "Syntax error using priority '%s': %s",

                   creds->priority, gnutls_strerror(ret));

        return NULL;

    }



    byte_array = g_byte_array_new();



    for (i = 0;; i++) {

        int ret;

        unsigned idx;

        const char *name;

        IANA_TLS_CIPHER cipher;

        gnutls_protocol_t protocol;

        const char *version;



        ret = gnutls_priority_get_cipher_suite_index(pcache, i, &idx);

        if (ret == GNUTLS_E_REQUESTED_DATA_NOT_AVAILABLE) {

            break;

        }

        if (ret == GNUTLS_E_UNKNOWN_CIPHER_SUITE) {

            continue;

        }



        name = gnutls_cipher_suite_info(idx, (unsigned char *)&cipher,

                                        NULL, NULL, NULL, &protocol);

        if (name == NULL) {

            continue;

        }



        version = gnutls_protocol_get_name(protocol);

        g_byte_array_append(byte_array, cipher.data, 2);

        trace_qcrypto_tls_cipher_suite_info(cipher.data[0],

                                            cipher.data[1],

                                            version, name);

    }

    trace_qcrypto_tls_cipher_suite_count(byte_array->len);

    gnutls_priority_deinit(pcache);



    return byte_array;

}



static void qcrypto_tls_cipher_suites_complete(UserCreatable *uc,

                                               Error **errp)

{

    QCryptoTLSCreds *creds = QCRYPTO_TLS_CREDS(uc);



    if (!creds->priority) {

        error_setg(errp, "'priority' property is not set");

        return;

    }

}



static void qcrypto_tls_cipher_suites_class_init(ObjectClass *oc, void *data)

{

    UserCreatableClass *ucc = USER_CREATABLE_CLASS(oc);



    ucc->complete = qcrypto_tls_cipher_suites_complete;

}



static const TypeInfo qcrypto_tls_cipher_suites_info = {

    .parent = TYPE_QCRYPTO_TLS_CREDS,

    .name = TYPE_QCRYPTO_TLS_CIPHER_SUITES,

    .instance_size = sizeof(QCryptoTLSCreds),

    .class_size = sizeof(QCryptoTLSCredsClass),

    .class_init = qcrypto_tls_cipher_suites_class_init,

    .interfaces = (InterfaceInfo[]) {

        { TYPE_USER_CREATABLE },

        { }

    }

};



static void qcrypto_tls_cipher_suites_register_types(void)

{

    type_register_static(&qcrypto_tls_cipher_suites_info);

}



type_init(qcrypto_tls_cipher_suites_register_types);

crypto/trace-events

+5 −0
Original line number Diff line number Diff line
@@ -21,3 +21,8 @@ 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"



# tls-cipher-suites.c

qcrypto_tls_cipher_suite_priority(const char *name) "priority: %s"

qcrypto_tls_cipher_suite_info(uint8_t data0, uint8_t data1, const char *version, const char *name) "data=[0x%02x,0x%02x] version=%s name=%s"

qcrypto_tls_cipher_suite_count(unsigned count) "count: %u"

include/crypto/tls-cipher-suites.h

0 → 100644
+39 −0
Original line number Diff line number Diff line 
/*

 * QEMU TLS Cipher Suites Registry (RFC8447)

 *

 * Copyright (c) 2018-2020 Red Hat, Inc.

 *

 * Author: Philippe Mathieu-Daudé <philmd@redhat.com>

 *

 * SPDX-License-Identifier: GPL-2.0-or-later

 */



#ifndef QCRYPTO_TLSCIPHERSUITES_H

#define QCRYPTO_TLSCIPHERSUITES_H



#include "qom/object.h"

#include "crypto/tlscreds.h"



#define TYPE_QCRYPTO_TLS_CIPHER_SUITES "tls-cipher-suites"

#define QCRYPTO_TLS_CIPHER_SUITES(obj) \

    OBJECT_CHECK(QCryptoTLSCipherSuites, (obj), TYPE_QCRYPTO_TLS_CIPHER_SUITES)



typedef struct QCryptoTLSCipherSuites {

    /* <private> */

    QCryptoTLSCreds parent_obj;

    /* <public> */

} QCryptoTLSCipherSuites;



/**

  * qcrypto_tls_cipher_suites_get_data:

  * @obj: pointer to a TLS cipher suites object

  * @errp: pointer to a NULL-initialized error object

  *

  * Returns: reference to a byte array containing the data.

  * The caller should release the reference when no longer

  * required.

  */

GByteArray *qcrypto_tls_cipher_suites_get_data(QCryptoTLSCipherSuites *obj,

                                               Error **errp);



#endif /* QCRYPTO_TLSCIPHERSUITES_H */

qemu-options.hx

+19 −0
Original line number Diff line number Diff line
@@ -4567,6 +4567,25 @@ SRST 
        string as described at

        https://gnutls.org/manual/html_node/Priority-Strings.html.



    ``-object tls-cipher-suites,id=id,priority=priority``

        Creates a TLS cipher suites object, which can be used to control

        the TLS cipher/protocol algorithms that applications are permitted

        to use.



        The ``id`` parameter is a unique ID which frontends will use to

        access the ordered list of permitted TLS cipher suites from the

        host.



        The ``priority`` parameter allows to override the global default

        priority used by gnutls. This can be useful if the system

        administrator needs to use a weaker set of crypto priorities for

        QEMU without potentially forcing the weakness onto all

        applications. Or conversely if one wants wants a stronger

        default for QEMU than for all other applications, they can do

        this through this parameter. Its format is a gnutls priority

        string as described at

        https://gnutls.org/manual/html_node/Priority-Strings.html.



    ``-object filter-buffer,id=id,netdev=netdevid,interval=t[,queue=all|rx|tx][,status=on|off][,position=head|tail|id=<id>][,insert=behind|before]``

        Interval t can't be 0, this filter batches the packet delivery:

        all packets arriving in a given interval on netdev netdevid are