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Peter Anvin" , Vincenzo Frascino , Mark Rutland , Sami Tolvanen , Masahiro Yamada , Linux ARM , Linux Kernel Mailing List , X86 ML , linux-integrity , linux-efi , "Lee, Chun-Yi" Date: Wed, 14 Oct 2020 07:56:17 -0400 In-Reply-To: References: <20201014104032.9776-1-clin@suse.com> <20201014104032.9776-2-clin@suse.com> Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.28.5 (3.28.5-12.el8) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.235,18.0.687 definitions=2020-10-14_07:2020-10-14,2020-10-14 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 bulkscore=0 lowpriorityscore=0 adultscore=0 priorityscore=1501 clxscore=1011 malwarescore=0 suspectscore=3 mlxlogscore=999 spamscore=0 impostorscore=0 mlxscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2010140085 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2020-10-14 at 13:00 +0200, Ard Biesheuvel wrote: > Hello Chester, > > Thanks for looking into this. > > Some comments below. > > On Wed, 14 Oct 2020 at 12:41, Chester Lin wrote: > > > > Separate the get_sb_mode() from arch/x86 and treat it as a common function > > [rename to efi_get_secureboot_mode] so all EFI-based architectures can > > reuse the same logic. > > > > Signed-off-by: Chester Lin > > --- > > arch/x86/kernel/ima_arch.c | 47 ++------------------------------------ > > drivers/firmware/efi/efi.c | 43 ++++++++++++++++++++++++++++++++++ > > include/linux/efi.h | 5 ++++ > > 3 files changed, 50 insertions(+), 45 deletions(-) > > > > diff --git a/arch/x86/kernel/ima_arch.c b/arch/x86/kernel/ima_arch.c > > index 7dfb1e808928..ed4623ecda6e 100644 > > --- a/arch/x86/kernel/ima_arch.c > > +++ b/arch/x86/kernel/ima_arch.c > > @@ -8,49 +8,6 @@ > > > > extern struct boot_params boot_params; > > > > -static enum efi_secureboot_mode get_sb_mode(void) > > -{ > > - efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID; > > - efi_status_t status; > > - unsigned long size; > > - u8 secboot, setupmode; > > - > > - size = sizeof(secboot); > > - > > - if (!efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE)) { > > - pr_info("ima: secureboot mode unknown, no efi\n"); > > - return efi_secureboot_mode_unknown; > > - } > > - > > - /* Get variable contents into buffer */ > > - status = efi.get_variable(L"SecureBoot", &efi_variable_guid, > > - NULL, &size, &secboot); > > - if (status == EFI_NOT_FOUND) { > > - pr_info("ima: secureboot mode disabled\n"); > > - return efi_secureboot_mode_disabled; > > - } > > - > > - if (status != EFI_SUCCESS) { > > - pr_info("ima: secureboot mode unknown\n"); > > - return efi_secureboot_mode_unknown; > > - } > > - > > - size = sizeof(setupmode); > > - status = efi.get_variable(L"SetupMode", &efi_variable_guid, > > - NULL, &size, &setupmode); > > - > > - if (status != EFI_SUCCESS) /* ignore unknown SetupMode */ > > - setupmode = 0; > > - > > - if (secboot == 0 || setupmode == 1) { > > - pr_info("ima: secureboot mode disabled\n"); > > - return efi_secureboot_mode_disabled; > > - } > > - > > - pr_info("ima: secureboot mode enabled\n"); > > - return efi_secureboot_mode_enabled; > > -} > > - > > bool arch_ima_get_secureboot(void) > > { > > static enum efi_secureboot_mode sb_mode; > > @@ -60,7 +17,7 @@ bool arch_ima_get_secureboot(void) > > sb_mode = boot_params.secure_boot; > > > > if (sb_mode == efi_secureboot_mode_unset) > > - sb_mode = get_sb_mode(); > > + sb_mode = efi_get_secureboot_mode(); > > initialized = true; > > } > > > > @@ -70,7 +27,7 @@ bool arch_ima_get_secureboot(void) > > return false; > > } > > > > -/* secureboot arch rules */ > > +/* secure and trusted boot arch rules */ > > static const char * const sb_arch_rules[] = { > > #if !IS_ENABLED(CONFIG_KEXEC_SIG) > > "appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig", > > diff --git a/drivers/firmware/efi/efi.c b/drivers/firmware/efi/efi.c > > index 5e5480a0a32d..68ffa6a069c0 100644 > > --- a/drivers/firmware/efi/efi.c > > +++ b/drivers/firmware/efi/efi.c > > @@ -1022,3 +1022,46 @@ static int __init register_update_efi_random_seed(void) > > } > > late_initcall(register_update_efi_random_seed); > > #endif > > + > > +enum efi_secureboot_mode efi_get_secureboot_mode(void) > > +{ > > + efi_guid_t efi_variable_guid = EFI_GLOBAL_VARIABLE_GUID; > > + efi_status_t status; > > + unsigned long size; > > + u8 secboot, setupmode; > > + > > + size = sizeof(secboot); > > + > > + if (!efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE)) { > > + pr_info("ima: secureboot mode unknown, no efi\n"); > > These prints don't belong here anymore. > > Also, it would be useful if we could reuse this logic in the EFI stub > as well, which is built as a separate executable, and does not provide > efi.get_variable(). > > So, you could you please break this up into > > static inline > enum efi_secureboot_mode efi_get_secureboot_mode(efi_get_variable_t *get_var) > { > } > > placed into include/linux/efi.h, which encapsulates the core logic, > but using get_var(), and without the prints. > > Then, we could put something like > > bool efi_ima_get_secureboot(void) > { > } > > in drivers/firmware/efi/efi.c (guarded by #ifdef CONFIG_IMA_xxx), > which performs the > efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE)) check, calls > efi_get_secureboot_mode(efi.get_variable), and implements the logic. > > And actually, if the logic is identical between x86 and arm64, I > wonder if it wouldn't be better to put the whole thing into > > drivers/firmware/efi/efi-ima.c > > or > > security/integrity/ima/ima-efi.c > > with the only difference being the boot_params->secure_boot access for > x86, which we can factor out to a static inline helper. > > Mimi, any thoughts here? Sounds good. Keeping as much IMA code in the IMA directory makes sense. The IMA Makefile would then include ima-efi.c based on an EFI Kconfig option. thanks, Mimi > > > > > + return efi_secureboot_mode_unknown; > > + } > > + > > + /* Get variable contents into buffer */ > > + status = efi.get_variable(L"SecureBoot", &efi_variable_guid, > > + NULL, &size, &secboot); > > + if (status == EFI_NOT_FOUND) { > > + pr_info("ima: secureboot mode disabled\n"); > > + return efi_secureboot_mode_disabled; > > + } > > + > > + if (status != EFI_SUCCESS) { > > + pr_info("ima: secureboot mode unknown\n"); > > + return efi_secureboot_mode_unknown; > > + } > > + > > + size = sizeof(setupmode); > > + status = efi.get_variable(L"SetupMode", &efi_variable_guid, > > + NULL, &size, &setupmode); > > + > > + if (status != EFI_SUCCESS) /* ignore unknown SetupMode */ > > + setupmode = 0; > > + > > + if (secboot == 0 || setupmode == 1) { > > + pr_info("ima: secureboot mode disabled\n"); > > + return efi_secureboot_mode_disabled; > > + } > > + > > + pr_info("ima: secureboot mode enabled\n"); > > + return efi_secureboot_mode_enabled; > > +} > > diff --git a/include/linux/efi.h b/include/linux/efi.h > > index d7c0e73af2b9..a73e5ae04672 100644 > > --- a/include/linux/efi.h > > +++ b/include/linux/efi.h > > @@ -1076,8 +1076,13 @@ static inline int efi_runtime_map_copy(void *buf, size_t bufsz) > > > > #ifdef CONFIG_EFI > > extern bool efi_runtime_disabled(void); > > +extern enum efi_secureboot_mode efi_get_secureboot_mode(void); > > #else > > static inline bool efi_runtime_disabled(void) { return true; } > > +static inline enum efi_secureboot_mode efi_get_secureboot_mode(void) > > +{ > > + return efi_secureboot_mode_disabled; > > +} > > #endif > > > > extern void efi_call_virt_check_flags(unsigned long flags, const char *call); > > -- > > 2.26.1 > >