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

[Markus Armbruster <armbru@redhat.com>]

Philippe Mathieu-Daudé <philmd@redhat.com> 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 <philmd@redhat.com>
> ---
> 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 <lersek@redhat.com>
> +M: Philippe Mathieu-Daudé <philmd@redhat.com>
> +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 <philmd@redhat.com>
> + *
> + * 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...

> +
> +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.

> +
> +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?

> +        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 <philmd@redhat.com>
> + *
> + * 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?

> +
> +#endif /* HW_FIRMWARE_UEFI_EDK2_H */