Re: [Qemu-devel] [PATCH v3 2/4] hw/firmware: Add Edk2Crypto and edk2_add_host_crypto_policy()

[Philippe Mathieu-Daudé]

On Mon, Mar 11, 2019 at 7:27 PM Philippe Mathieu-Daudé
<address@hidden> wrote:
> On 3/11/19 8:26 AM, Markus Armbruster wrote:
> > Philippe Mathieu-Daudé <address@hidden> writes:
> >
> >> The Edk2Crypto object is used to hold configuration values specific
> >> to EDK2.
> >>
> >> The edk2_add_host_crypto_policy() function loads crypto policies
> >> from the host, and register them as fw_cfg named file items.
> >> So far only the 'https' policy is supported.
> >>
> >> A usercase example is the 'HTTPS Boof' feature of OVMF [*].
> >>
> >> Usage example:
> >>
> >>   $ qemu-system-x86_64 \
> >>       --object edk2_crypto,id=https,\
> >>               ciphers=/etc/crypto-policies/back-ends/openssl.config,\
> >>               cacerts=/etc/pki/ca-trust/extracted/edk2/cacerts.bin
> >>
> >> (On Fedora these files are provided by the ca-certificates and
> >> crypto-policies packages).
> >>
> >> [*]: https://github.com/tianocore/edk2/blob/master/OvmfPkg/README
> >>
> >> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
> >> ---
> >> v3:
> >> - '-object' -> '--object' in commit description (Eric)
> >> - reworded the 'TODO: g_free' comment
> >> ---
> >>  MAINTAINERS                             |   8 ++
> >>  hw/Makefile.objs                        |   1 +
> >>  hw/firmware/Makefile.objs               |   1 +
> >>  hw/firmware/uefi_edk2_crypto_policies.c | 177 ++++++++++++++++++++++++
> >>  include/hw/firmware/uefi_edk2.h         |  28 ++++
> >>  5 files changed, 215 insertions(+)
> >>  create mode 100644 hw/firmware/Makefile.objs
> >>  create mode 100644 hw/firmware/uefi_edk2_crypto_policies.c
> >>  create mode 100644 include/hw/firmware/uefi_edk2.h
> >>
> >> diff --git a/MAINTAINERS b/MAINTAINERS
> >> index cf09a4c127..70122b3d0d 100644
> >> --- a/MAINTAINERS
> >> +++ b/MAINTAINERS
> >> @@ -2206,6 +2206,14 @@ F: include/hw/i2c/smbus_master.h
> >>  F: include/hw/i2c/smbus_slave.h
> >>  F: include/hw/i2c/smbus_eeprom.h
> >>
> >> +EDK2 Firmware
> >> +M: Laszlo Ersek <address@hidden>
> >> +M: Philippe Mathieu-Daudé <address@hidden>
> >> +S: Maintained
> >> +F: docs/interop/firmware.json
> >> +F: hw/firmware/uefi_edk2_crypto_policies.c
> >> +F: include/hw/firmware/uefi_edk2.h
> >> +
> >>  Usermode Emulation
> >>  ------------------
> >>  Overall
> >> diff --git a/hw/Makefile.objs b/hw/Makefile.objs
> >> index 82aa7fab8e..2b075aa1e0 100644
> >> --- a/hw/Makefile.objs
> >> +++ b/hw/Makefile.objs
> >> @@ -8,6 +8,7 @@ devices-dirs-$(CONFIG_SOFTMMU) += char/
> >>  devices-dirs-$(CONFIG_SOFTMMU) += cpu/
> >>  devices-dirs-$(CONFIG_SOFTMMU) += display/
> >>  devices-dirs-$(CONFIG_SOFTMMU) += dma/
> >> +devices-dirs-$(CONFIG_SOFTMMU) += firmware/
> >>  devices-dirs-$(CONFIG_SOFTMMU) += gpio/
> >>  devices-dirs-$(CONFIG_HYPERV) += hyperv/
> >>  devices-dirs-$(CONFIG_I2C) += i2c/
> >> diff --git a/hw/firmware/Makefile.objs b/hw/firmware/Makefile.objs
> >> new file mode 100644
> >> index 0000000000..ea1f6d44df
> >> --- /dev/null
> >> +++ b/hw/firmware/Makefile.objs
> >> @@ -0,0 +1 @@
> >> +common-obj-y += uefi_edk2_crypto_policies.o
> >> diff --git a/hw/firmware/uefi_edk2_crypto_policies.c 
> >> b/hw/firmware/uefi_edk2_crypto_policies.c
> >> new file mode 100644
> >> index 0000000000..5f88819a50
> >> --- /dev/null
> >> +++ b/hw/firmware/uefi_edk2_crypto_policies.c
> >> @@ -0,0 +1,177 @@
> >> +/*
> >> + * UEFI EDK2 Support
> >> + *
> >> + * Copyright (c) 2019 Red Hat Inc.
> >> + *
> >> + * Author:
> >> + *  Philippe Mathieu-Daudé <address@hidden>
> >> + *
> >> + * This work is licensed under the terms of the GNU GPL, version 2 or 
> >> later.
> >> + * See the COPYING file in the top-level directory.
> >> + */
> >> +
> >> +#include "qemu/osdep.h"
> >> +#include "qapi/error.h"
> >> +#include "qom/object_interfaces.h"
> >> +#include "hw/firmware/uefi_edk2.h"
> >> +
> >> +
> >> +#define TYPE_EDK2_CRYPTO "edk2_crypto"
> >> +
> >> +#define EDK2_CRYPTO_CLASS(klass) \
> >> +     OBJECT_CLASS_CHECK(Edk2CryptoClass, (klass), \
> >> +                        TYPE_EDK2_CRYPTO)
> >> +#define EDK2_CRYPTO_GET_CLASS(obj) \
> >> +     OBJECT_GET_CLASS(Edk2CryptoClass, (obj), \
> >> +                      TYPE_EDK2_CRYPTO)
> >> +#define EDK2_CRYPTO(obj) \
> >> +     INTERFACE_CHECK(Edk2Crypto, (obj), \
> >> +                     TYPE_EDK2_CRYPTO)
> >
> > Uh, should this be OBJECT_CLASS_CHECK()?  TYPE_EDK2_CRYPTO is a
> > TYPE_OBJECT, not a TYPE_INTERFACE...

OBJECT_CHECK() actually.

> Good catch!
>
> >> +
> >> +typedef struct Edk2Crypto {
> >> +    Object parent_obj;
> >> +
> >> +    /*
> >> +     * Path to the acceptable ciphersuites and the preferred order from
> >> +     * the host-side crypto policy.
> >> +     */
> >> +    char *ciphers_path;
> >> +
> >> +    /* Path to the trusted CA certificates configured on the host side. */
> >> +    char *cacerts_path;
> >> +} Edk2Crypto;
> >
> > Bike-shedding: I prefer to call file names file names, and reserve
> > "path" for search paths.  But it's your shed, not mine.
>
> OK.
>
> >> +
> >> +typedef struct Edk2CryptoClass {
> >> +    ObjectClass parent_class;
> >> +} Edk2CryptoClass;
> >> +
> >> +
> >> +static void edk2_crypto_prop_set_ciphers(Object *obj, const char *value,
> >> +                                         Error **errp G_GNUC_UNUSED)
> >> +{
> >> +    Edk2Crypto *s = EDK2_CRYPTO(obj);
> >> +
> >> +    g_free(s->ciphers_path);
> >> +    s->ciphers_path = g_strdup(value);
> >> +}
> >> +
> >> +static char *edk2_crypto_prop_get_ciphers(Object *obj,
> >> +                                          Error **errp G_GNUC_UNUSED)
> >> +{
> >> +    Edk2Crypto *s = EDK2_CRYPTO(obj);
> >> +
> >> +    return g_strdup(s->ciphers_path);
> >> +}
> >> +
> >> +static void edk2_crypto_prop_set_cacerts(Object *obj, const char *value,
> >> +                                         Error **errp G_GNUC_UNUSED)
> >> +{
> >> +    Edk2Crypto *s = EDK2_CRYPTO(obj);
> >> +
> >> +    g_free(s->cacerts_path);
> >> +    s->cacerts_path = g_strdup(value);
> >> +}
> >> +
> >> +static char *edk2_crypto_prop_get_cacerts(Object *obj,
> >> +                                          Error **errp G_GNUC_UNUSED)
> >> +{
> >> +    Edk2Crypto *s = EDK2_CRYPTO(obj);
> >> +
> >> +    return g_strdup(s->cacerts_path);
> >> +}
> >> +
> >> +static void edk2_crypto_finalize(Object *obj)
> >> +{
> >> +    Edk2Crypto *s = EDK2_CRYPTO(obj);
> >> +
> >> +    g_free(s->ciphers_path);
> >> +    g_free(s->cacerts_path);
> >> +}
> >> +
> >> +static void edk2_crypto_class_init(ObjectClass *oc, void *data)
> >> +{
> >> +    object_class_property_add_str(oc, "ciphers",
> >> +                                  edk2_crypto_prop_get_ciphers,
> >> +                                  edk2_crypto_prop_set_ciphers,
> >> +                                  NULL);
> >> +    object_class_property_add_str(oc, "cacerts",
> >> +                                  edk2_crypto_prop_get_cacerts,
> >> +                                  edk2_crypto_prop_set_cacerts,
> >> +                                  NULL);
> >> +}
> >> +
> >> +static const TypeInfo edk2_crypto_info = {
> >> +    .parent = TYPE_OBJECT,
> >> +    .name = TYPE_EDK2_CRYPTO,
> >> +    .instance_size = sizeof(Edk2Crypto),
> >> +    .instance_finalize = edk2_crypto_finalize,
> >> +    .class_size = sizeof(Edk2CryptoClass),
> >> +    .class_init = edk2_crypto_class_init,
> >> +    .interfaces = (InterfaceInfo[]) {
> >> +        { TYPE_USER_CREATABLE },
> >> +        { }
> >> +    }
> >> +};
> >> +
> >> +static void edk2_crypto_register_types(void)
> >> +{
> >> +    type_register_static(&edk2_crypto_info);
> >> +}
> >> +
> >> +type_init(edk2_crypto_register_types);
> >> +
> >> +static Edk2Crypto *edk2_crypto_by_id(const char *edk_crypto_id, Error 
> >> **errp)
> >> +{
> >> +    Object *obj;
> >> +    Object *container;
> >> +
> >> +    container = object_get_objects_root();
> >> +    obj = object_resolve_path_component(container,
> >> +                                        edk_crypto_id);
> >> +    if (!obj) {
> >> +        error_setg(errp, "Cannot find EDK2 crypto object ID %s",
> >> +                   edk_crypto_id);
> >> +        return NULL;
> >> +    }
> >> +
> >> +    if (!object_dynamic_cast(obj, TYPE_EDK2_CRYPTO)) {
> >> +        error_setg(errp, "Object '%s' is not a EDK2 crypto subclass",
> >> +                   edk_crypto_id);
> >> +        return NULL;
> >> +    }
> >> +
> >> +    return EDK2_CRYPTO(obj);
> >> +}
> >> +
> >> +void edk2_add_host_crypto_policy(FWCfgState *fw_cfg)
> >> +{
> >> +    Edk2Crypto *s;
> >> +
> >> +    s = edk2_crypto_by_id("https", NULL);
> >> +    if (!s) {
> >> +        return;
> >> +    }
> >> +
> >> +    if (s->ciphers_path) {
> >> +        /*
> >> +         * Note:
> >> +         * Unlike with fw_cfg_add_file() where the allocated data has
> >> +         * to be valid for the lifetime of the FwCfg object, there is
> >> +         * no such contract interface with fw_cfg_add_file_from_host().
> >
> > In my review of PATCH 1, I argue there should be.
> >
> >> +         * It would be easier that the FwCfg object keeps reference of
> >> +         * its allocated memory and releases it when destroy, but it
> >> +         * currently doesn't. Meanwhile we simply add this TODO comment.
> >> +         */
> >> +        fw_cfg_add_file_from_host(fw_cfg, "etc/edk2/https/ciphers",
> >> +                                  s->ciphers_path, NULL);
> >> +    }
> >> +
> >> +    if (s->cacerts_path) {
> >> +        /*
> >> +         * TODO: g_free the returned pointer
> >> +         * (see previous comment for ciphers_path in this function).
> >> +         */
> >
> > Is it even possible to reolve this TODO?  Is there any point in time
> > where we can free the returned pointer without leaving a dangling
> > pointer in @fw_cfg?
>
> I understood Laszlo suggested the fw_cfg devices do the garbage collection.
>
> >> +        fw_cfg_add_file_from_host(fw_cfg, "etc/edk2/https/cacerts",
> >> +                                  s->cacerts_path, NULL);
> >> +    }
> >> +}
> >> diff --git a/include/hw/firmware/uefi_edk2.h 
> >> b/include/hw/firmware/uefi_edk2.h
> >> new file mode 100644
> >> index 0000000000..e0b2fb160a
> >> --- /dev/null
> >> +++ b/include/hw/firmware/uefi_edk2.h
> >> @@ -0,0 +1,28 @@
> >> +/*
> >> + * UEFI EDK2 Support
> >> + *
> >> + * Copyright (c) 2019 Red Hat Inc.
> >> + *
> >> + * Author:
> >> + *  Philippe Mathieu-Daudé <address@hidden>
> >> + *
> >> + * This work is licensed under the terms of the GNU GPL, version 2 or 
> >> later.
> >> + * See the COPYING file in the top-level directory.
> >> + */
> >> +
> >> +#ifndef HW_FIRMWARE_UEFI_EDK2_H
> >> +#define HW_FIRMWARE_UEFI_EDK2_H
> >> +
> >> +#include "hw/nvram/fw_cfg.h"
> >> +
> >> +/**
> >> + * edk2_add_host_crypto_policy:
> >> + * @s: fw_cfg device being modified
> >> + *
> >> + * Add a new named file containing the host crypto policy.
> >> + *
> >> + * Currently only the 'https' policy is supported.
> >> + */
> >> +void edk2_add_host_crypto_policy(FWCfgState *s);
> >
> > Out of curiosity, what happens if you call this more than once?
>
> Such curiosity is useful, thanks :)
>
> >> +
> >> +#endif /* HW_FIRMWARE_UEFI_EDK2_H */