Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 806C1C6FD1C for ; Tue, 14 Mar 2023 11:25:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231185AbjCNLZH (ORCPT ); Tue, 14 Mar 2023 07:25:07 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45428 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231382AbjCNLZA (ORCPT ); Tue, 14 Mar 2023 07:25:00 -0400 Received: from mail-wm1-x32b.google.com (mail-wm1-x32b.google.com [IPv6:2a00:1450:4864:20::32b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 28C7B5D74D for ; Tue, 14 Mar 2023 04:24:58 -0700 (PDT) Received: by mail-wm1-x32b.google.com with SMTP id fm20-20020a05600c0c1400b003ead37e6588so12888242wmb.5 for ; Tue, 14 Mar 2023 04:24:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; t=1678793096; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=bYSl+4VaNhyfbrRBiFejg1i2ozlbsnIGA6bpYEVONug=; b=n3q3geUE4XDBFLqPpKurOdnjyisVsUirbwmImkHFR3uyTFE8Dm9hrO4/ciepIjG0th BQaeJg8Qh02uXsdRmILcJlx4snzCgqhMeQm8aMstAAninEKjP/2LCR/VgEZNWg1Y5jjj lJJq+LwzbsaDg44Q341SK05M8KgtmKaNc72bdFFboIgUGtqjy5T5xyf6CeA8t+uIMXF8 kFsP8gCIK+Jg+KbghIlC9JQTQAbL8KsPexFnuAntAt7H64snSqwvVrhBvYPQTB8pjBNQ iVWuEAtiGVxRm/mjt+p6iYf1dHjIy9k8LZa/OpQMCeQe0VzqnTRHa1ooYDgKe4JRLxR1 vp7Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1678793096; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=bYSl+4VaNhyfbrRBiFejg1i2ozlbsnIGA6bpYEVONug=; b=tdzvn8ZQqIEuI5+2qz3IZTgaJK8m7tYCJFuvp5k1SaEK0wRVdrJLyeSFXI36j+rbKy oqgYLTuVxtH2qxPOODgV+E3TXRJD3ghM7Ymsp9vggCTIgHlR9gRvJdTGuDvcGv1nBm6b bkLXMhaaxBFVBiNq+A1obgVbo8khjhDna1qRHASas/Gu7uTXrGl9og9VrnL8RohtMpam Uz7PNZtkSL9WOOsbGuKKDnnwt+0exbThKowLus4VGPyOaPdZgdG4NTwKqrD2YJ7pa5tg Sm4eOr7tMXZ5sxjRZLYYrLRs7w/N+TLUGldXytnddjzsw8oKRmcgMhdAz5JBQiRfPGCx df0g== X-Gm-Message-State: AO0yUKVm+pAR2l8CNGJYx4qTFTd2E7Rly+gP1wNSCgp2TPh9NtYu0yL7 eWh+Q122TmC8QlAxeUQaAapviNDStWB2/b/C3HhLtQ== X-Google-Smtp-Source: AK7set8Kz7/dD8LnpPwyze+Kz24D01g89gLghl6zu6I+yzxHvIVm9Ra8XlTG/uDtFsWMTdFu6ThdQYB8ueTQzc0P3OQ= X-Received: by 2002:a05:600c:512a:b0:3ed:26fa:6ee5 with SMTP id o42-20020a05600c512a00b003ed26fa6ee5mr1570767wms.4.1678793096442; Tue, 14 Mar 2023 04:24:56 -0700 (PDT) MIME-Version: 1.0 References: <20230313100414.v7.1.I8e7f9b01d9ac940507d78e15368e200a6a69bedb@changeid> In-Reply-To: <20230313100414.v7.1.I8e7f9b01d9ac940507d78e15368e200a6a69bedb@changeid> From: Jens Wiklander Date: Tue, 14 Mar 2023 12:24:45 +0100 Message-ID: Subject: Re: [PATCH v7] tee: optee: Add SMC for loading OP-TEE image To: Jeffrey Kardatzke Cc: op-tee@lists.trustedfirmware.org, Jeffrey Kardatzke , Jonathan Corbet , Sumit Garg , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 13, 2023 at 6:16=E2=80=AFPM Jeffrey Kardatzke wrote: > > Adds an SMC call that will pass an OP-TEE binary image to EL3 and > instruct it to load it as the BL32 payload. This works in conjunction > with a feature added to Trusted Firmware for ARMv8 and above > architectures that supports this. > > The main purpose of this change is to facilitate updating the OP-TEE > component on devices via a rootfs change rather than having to do a > firmware update. Further details are linked to in the Kconfig file. > > Signed-off-by: Jeffrey Kardatzke > Signed-off-by: Jeffrey Kardatzke > --- > > Changes in v7: > - Added documentation to Documentation/staging/tee.rst > > Changes in v6: > - Expanded Kconfig documentation > > Changes in v5: > - Renamed config option > - Added runtime warning when config is used > > Changes in v4: > - Update commit message > - Added more documentation > - Renamed config option, added ARM64 dependency > > Changes in v3: > - Removed state tracking for driver reload > - Check UID of service to verify it needs image load > > Changes in v2: > - Fixed compile issue when feature is disabled > - Addressed minor comments > - Added state tracking for driver reload > > Documentation/staging/tee.rst | 41 +++++++++++++++ > drivers/tee/optee/Kconfig | 17 ++++++ > drivers/tee/optee/optee_msg.h | 12 +++++ > drivers/tee/optee/optee_smc.h | 24 +++++++++ > drivers/tee/optee/smc_abi.c | 97 +++++++++++++++++++++++++++++++++++ > 5 files changed, 191 insertions(+) > > diff --git a/Documentation/staging/tee.rst b/Documentation/staging/tee.rs= t > index 498343c7ab08..315aa8e35e6b 100644 > --- a/Documentation/staging/tee.rst > +++ b/Documentation/staging/tee.rst > @@ -214,6 +214,47 @@ call is done from the thread assisting the interrupt= handler. This is a > building block for OP-TEE OS in secure world to implement the top half a= nd > bottom half style of device drivers. > > +OPTEE_INSECURE_LOAD_IMAGE Kconfig option > +---------------------------------------- > + > +The OPTEE_INSECURE_LOAD_IMAGE Kconfig option enables the ability to load= the > +BL32 OP-TEE image from the kernel after the kernel boots, rather than lo= ading > +it from the firmware before the kernel boots. This also requires enablin= g the > +corresponding option in Trusted Firmware for Arm. The documentation ther= e > +explains the security threat associated with enabling this as well as > +mitigations at the firmware and platform level. > +https://trustedfirmware-a.readthedocs.io/en/latest/threat_model/threat_m= odel.html > + > +There are additional attack vectors/mitigations for the kernel that shou= ld be > +addressed when using this option. > + > +1. Boot chain security. > + Attack vector: Replace the OP-TEE OS image in the rootfs to gain cont= rol of > + the system. > + Migitation: There must be boot chain security that verifies the kerne= l and > + rootfs, otherwise an attacker can modify the loaded OP-TE= E > + binary by modifying it in the rootfs. > +3. Alternate boot modes. > + Attack vector: Using an alternate boot mode (i.e. recovery mode), the= OP-TEE > + driver isn't loaded, leaving the SMC hole open. > + Mitigation: If there are alternate methods of booting the device, suc= h as a > + recovery mode, it should be ensured that the same mitigat= ions are > + applied in that mode. > +3. Attacks prior to SMC invocation. > + Attack vector: Code that is executed prior to issuing the SMC call to= load > + OP-TEE can be exploited to then load an alternate OS i= mage. > + Mitigation: The OP-TEE driver must be loaded before any potential att= ack > + vectors are opened up. This should include mounting of an= y > + modifiable filesystems, opening of network ports or commu= nicating > + with external devices (e.g. USB). > +4. Blocking SMC call to load OP-TEE. > + Attack vector: Prevent the driver from being probed, so the SMC call = to load > + OP-TEE isn't executed when desired, leaving it open to= being > + executed later and loading a modified OS. > + Mitigation: It is recommended to build the OP-TEE driver as an includ= ed > + driver rather than a module to prevent exploits that may = cause > + the module to not be loaded. > + > AMD-TEE driver > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > diff --git a/drivers/tee/optee/Kconfig b/drivers/tee/optee/Kconfig > index f121c224e682..70898bbd5809 100644 > --- a/drivers/tee/optee/Kconfig > +++ b/drivers/tee/optee/Kconfig > @@ -7,3 +7,20 @@ config OPTEE > help > This implements the OP-TEE Trusted Execution Environment (TEE) > driver. > + > +config OPTEE_INSECURE_LOAD_IMAGE > + bool "Load OP-TEE image as firmware" > + default n > + depends on OPTEE && ARM64 > + help > + This loads the BL32 image for OP-TEE as firmware when the drive= r is > + probed. This returns -EPROBE_DEFER until the firmware is loadab= le from > + the filesystem which is determined by checking the system_state= until > + it is in SYSTEM_RUNNING. This also requires enabling the corres= ponding > + option in Trusted Firmware for Arm. The documentation there exp= lains > + the security threat associated with enabling this as well as > + mitigations at the firmware and platform level. > + https://trustedfirmware-a.readthedocs.io/en/latest/threat_model= /threat_model.html > + > + Additional documentation on kernel security risks are at > + Documentation/staging/tee.rst. > diff --git a/drivers/tee/optee/optee_msg.h b/drivers/tee/optee/optee_msg.= h > index 70e9cc2ee96b..e8840a82b983 100644 > --- a/drivers/tee/optee/optee_msg.h > +++ b/drivers/tee/optee/optee_msg.h > @@ -241,11 +241,23 @@ struct optee_msg_arg { > * 384fb3e0-e7f8-11e3-af63-0002a5d5c51b. > * Represented in 4 32-bit words in OPTEE_MSG_UID_0, OPTEE_MSG_UID_1, > * OPTEE_MSG_UID_2, OPTEE_MSG_UID_3. > + * > + * In the case where the OP-TEE image is loaded by the kernel, this will > + * initially return an alternate UID to reflect that we are communicatin= g with > + * the TF-A image loading service at that time instead of OP-TEE. That U= ID is: > + * a3fbeab1-1246-315d-c7c4-06b9c03cbea4. > + * Represented in 4 32-bit words in OPTEE_MSG_IMAGE_LOAD_UID_0, > + * OPTEE_MSG_IMAGE_LOAD_UID_1, OPTEE_MSG_IMAGE_LOAD_UID_2, > + * OPTEE_MSG_IMAGE_LOAD_UID_3. > */ > #define OPTEE_MSG_UID_0 0x384fb3e0 > #define OPTEE_MSG_UID_1 0xe7f811e3 > #define OPTEE_MSG_UID_2 0xaf630002 > #define OPTEE_MSG_UID_3 0xa5d5c51b > +#define OPTEE_MSG_IMAGE_LOAD_UID_0 0xa3fbeab1 > +#define OPTEE_MSG_IMAGE_LOAD_UID_1 0x1246315d > +#define OPTEE_MSG_IMAGE_LOAD_UID_2 0xc7c406b9 > +#define OPTEE_MSG_IMAGE_LOAD_UID_3 0xc03cbea4 > #define OPTEE_MSG_FUNCID_CALLS_UID 0xFF01 > > /* > diff --git a/drivers/tee/optee/optee_smc.h b/drivers/tee/optee/optee_smc.= h > index 73b5e7760d10..7d9fa426505b 100644 > --- a/drivers/tee/optee/optee_smc.h > +++ b/drivers/tee/optee/optee_smc.h > @@ -104,6 +104,30 @@ struct optee_smc_call_get_os_revision_result { > unsigned long reserved1; > }; > > +/* > + * Load Trusted OS from optee/tee.bin in the Linux firmware. > + * > + * WARNING: Use this cautiously as it could lead to insecure loading of = the > + * Trusted OS. > + * This SMC instructs EL3 to load a binary and execute it as the Trusted= OS. > + * > + * Call register usage: > + * a0 SMC Function ID, OPTEE_SMC_CALL_LOAD_IMAGE > + * a1 Upper 32bit of a 64bit size for the payload > + * a2 Lower 32bit of a 64bit size for the payload > + * a3 Upper 32bit of the physical address for the payload > + * a4 Lower 32bit of the physical address for the payload > + * > + * The payload is in the OP-TEE image format. > + * > + * Returns result in a0, 0 on success and an error code otherwise. > + */ > +#define OPTEE_SMC_FUNCID_LOAD_IMAGE 2 > +#define OPTEE_SMC_CALL_LOAD_IMAGE \ > + ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_32, \ > + ARM_SMCCC_OWNER_TRUSTED_OS_END, \ > + OPTEE_SMC_FUNCID_LOAD_IMAGE) > + > /* > * Call with struct optee_msg_arg as argument > * > diff --git a/drivers/tee/optee/smc_abi.c b/drivers/tee/optee/smc_abi.c > index a1c1fa1a9c28..00b6b69b6f79 100644 > --- a/drivers/tee/optee/smc_abi.c > +++ b/drivers/tee/optee/smc_abi.c > @@ -8,9 +8,11 @@ > > #include > #include > +#include > #include > #include > #include > +#include > #include > #include > #include > @@ -1149,6 +1151,22 @@ static bool optee_msg_api_uid_is_optee_api(optee_i= nvoke_fn *invoke_fn) > return false; > } > > +#ifdef CONFIG_OPTEE_INSECURE_LOAD_IMAGE > +static bool optee_msg_api_uid_is_optee_image_load(optee_invoke_fn *invok= e_fn) > +{ > + struct arm_smccc_res res; > + > + invoke_fn(OPTEE_SMC_CALLS_UID, 0, 0, 0, 0, 0, 0, 0, &res); > + > + if (res.a0 =3D=3D OPTEE_MSG_IMAGE_LOAD_UID_0 && > + res.a1 =3D=3D OPTEE_MSG_IMAGE_LOAD_UID_1 && > + res.a2 =3D=3D OPTEE_MSG_IMAGE_LOAD_UID_2 && > + res.a3 =3D=3D OPTEE_MSG_IMAGE_LOAD_UID_3) > + return true; > + return false; > +} > +#endif > + > static void optee_msg_get_os_revision(optee_invoke_fn *invoke_fn) > { > union { > @@ -1354,6 +1372,81 @@ static void optee_shutdown(struct platform_device = *pdev) > optee_disable_shm_cache(optee); > } > > +#ifdef CONFIG_OPTEE_INSECURE_LOAD_IMAGE > + > +#define OPTEE_FW_IMAGE "optee/tee.bin" > + > +static int optee_load_fw(struct platform_device *pdev, > + optee_invoke_fn *invoke_fn) Please align with the '(' on the line above. > +{ > + const struct firmware *fw =3D NULL; > + struct arm_smccc_res res; > + phys_addr_t data_pa; > + u8 *data_buf =3D NULL; > + u64 data_size; > + u32 data_pa_high, data_pa_low; > + u32 data_size_high, data_size_low; > + int rc; > + > + if (!optee_msg_api_uid_is_optee_image_load(invoke_fn)) > + return 0; > + > + rc =3D request_firmware(&fw, OPTEE_FW_IMAGE, &pdev->dev); > + if (rc) { > + /* > + * The firmware in the rootfs will not be accessible unti= l we > + * are in the SYSTEM_RUNNING state, so return EPROBE_DEFE= R until > + * that point. > + */ > + if (system_state < SYSTEM_RUNNING) > + return -EPROBE_DEFER; > + goto fw_err; > + } > + > + data_size =3D fw->size; > + /* > + * This uses the GFP_DMA flag to ensure we are allocated memory i= n the > + * 32-bit space since TF-A cannot map memory beyond the 32-bit bo= undary. > + */ > + data_buf =3D kmalloc(fw->size, GFP_KERNEL | GFP_DMA); > + if (!data_buf) { > + rc =3D -ENOMEM; > + goto fw_err; > + } > + memcpy(data_buf, fw->data, fw->size); > + data_pa =3D virt_to_phys(data_buf); > + reg_pair_from_64(&data_pa_high, &data_pa_low, data_pa); > + reg_pair_from_64(&data_size_high, &data_size_low, data_size); > + goto fw_load; > + > +fw_err: > + pr_warn("image loading failed\n"); > + data_pa_high =3D data_pa_low =3D data_size_high =3D data_size_low= =3D 0; > + > +fw_load: > + /* > + * Always invoke the SMC, even if loading the image fails, to ind= icate > + * to EL3 that we have passed the point where it should allow inv= oking > + * this SMC. > + */ > + pr_warn("OP-TEE image loaded from kernel, this can be insecure"); > + invoke_fn(OPTEE_SMC_CALL_LOAD_IMAGE, data_size_high, data_size_lo= w, > + data_pa_high, data_pa_low, 0, 0, 0, &res); > + if (!rc) > + rc =3D res.a0; > + if (fw) > + release_firmware(fw); > + kfree(data_buf); > + > + return rc; > +} > +#else > +static inline int optee_load_fw(struct platform_device *__unused1, > + optee_invoke_fn *__unused2) { Please align with the '(' on the line above. The `{` should be at the start of the next line. I'd prefer the normal names of the parameters instead even if they are unus= ed. Cheers, Jens > + return 0; > +} > +#endif > + > static int optee_probe(struct platform_device *pdev) > { > optee_invoke_fn *invoke_fn; > @@ -1372,6 +1465,10 @@ static int optee_probe(struct platform_device *pde= v) > if (IS_ERR(invoke_fn)) > return PTR_ERR(invoke_fn); > > + rc =3D optee_load_fw(pdev, invoke_fn); > + if (rc) > + return rc; > + > if (!optee_msg_api_uid_is_optee_api(invoke_fn)) { > pr_warn("api uid mismatch\n"); > return -EINVAL; > -- > 2.40.0.rc1.284.g88254d51c5-goog >