From 57c0dbcbafaa724313c672830ff0087f56a84c47 Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Thu, 20 Sep 2012 10:40:56 -0400 Subject: [PATCH 01/14] Secure boot: Add new capability Secure boot adds certain policy requirements, including that root must not be able to do anything that could cause the kernel to execute arbitrary code. The simplest way to handle this would seem to be to add a new capability and gate various functionality on that. We'll then strip it from the initial capability set if required. Signed-off-by: Matthew Garrett --- include/linux/capability.h | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/include/linux/capability.h b/include/linux/capability.h index d10b7ed..4345bc8 100644 --- a/include/linux/capability.h +++ b/include/linux/capability.h @@ -364,7 +364,11 @@ struct cpu_vfs_cap_data { #define CAP_BLOCK_SUSPEND 36 -#define CAP_LAST_CAP CAP_BLOCK_SUSPEND +/* Allow things that trivially permit root to modify the running kernel */ + +#define CAP_COMPROMISE_KERNEL 37 + +#define CAP_LAST_CAP CAP_COMPROMISE_KERNEL #define cap_valid(x) ((x) >= 0 && (x) <= CAP_LAST_CAP) -- 1.7.11.4 From 95fd8148be46036e20fc64c480104d2a2b454e27 Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Thu, 20 Sep 2012 10:40:57 -0400 Subject: [PATCH 02/14] PCI: Lock down BAR access in secure boot environments Any hardware that can potentially generate DMA has to be locked down from userspace in order to avoid it being possible for an attacker to cause arbitrary kernel behaviour. Default to paranoid - in future we can potentially relax this for sufficiently IOMMU-isolated devices. Signed-off-by: Matthew Garrett --- drivers/pci/pci-sysfs.c | 9 +++++++++ drivers/pci/proc.c | 8 +++++++- drivers/pci/syscall.c | 2 +- 3 files changed, 17 insertions(+), 2 deletions(-) diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c index 6869009..c03fb85 100644 --- a/drivers/pci/pci-sysfs.c +++ b/drivers/pci/pci-sysfs.c @@ -542,6 +542,9 @@ pci_write_config(struct file* filp, struct kobject *kobj, loff_t init_off = off; u8 *data = (u8*) buf; + if (!capable(CAP_COMPROMISE_KERNEL)) + return -EPERM; + if (off > dev->cfg_size) return 0; if (off + count > dev->cfg_size) { @@ -844,6 +847,9 @@ pci_mmap_resource(struct kobject *kobj, struct bin_attribute *attr, resource_size_t start, end; int i; + if (!capable(CAP_COMPROMISE_KERNEL)) + return -EPERM; + for (i = 0; i < PCI_ROM_RESOURCE; i++) if (res == &pdev->resource[i]) break; @@ -951,6 +957,9 @@ pci_write_resource_io(struct file *filp, struct kobject *kobj, struct bin_attribute *attr, char *buf, loff_t off, size_t count) { + if (!capable(CAP_COMPROMISE_KERNEL)) + return -EPERM; + return pci_resource_io(filp, kobj, attr, buf, off, count, true); } diff --git a/drivers/pci/proc.c b/drivers/pci/proc.c index 27911b5..ac8c9a5 100644 --- a/drivers/pci/proc.c +++ b/drivers/pci/proc.c @@ -135,6 +135,9 @@ proc_bus_pci_write(struct file *file, const char __user *buf, size_t nbytes, lof int size = dp->size; int cnt; + if (!capable(CAP_COMPROMISE_KERNEL)) + return -EPERM; + if (pos >= size) return 0; if (nbytes >= size) @@ -211,6 +214,9 @@ static long proc_bus_pci_ioctl(struct file *file, unsigned int cmd, #endif /* HAVE_PCI_MMAP */ int ret = 0; + if (!capable(CAP_COMPROMISE_KERNEL)) + return -EPERM; + switch (cmd) { case PCIIOC_CONTROLLER: ret = pci_domain_nr(dev->bus); @@ -251,7 +257,7 @@ static int proc_bus_pci_mmap(struct file *file, struct vm_area_struct *vma) struct pci_filp_private *fpriv = file->private_data; int i, ret; - if (!capable(CAP_SYS_RAWIO)) + if (!capable(CAP_SYS_RAWIO) || !capable(CAP_COMPROMISE_KERNEL)) return -EPERM; /* Make sure the caller is mapping a real resource for this device */ diff --git a/drivers/pci/syscall.c b/drivers/pci/syscall.c index e1c1ec5..97e785f 100644 --- a/drivers/pci/syscall.c +++ b/drivers/pci/syscall.c @@ -92,7 +92,7 @@ SYSCALL_DEFINE5(pciconfig_write, unsigned long, bus, unsigned long, dfn, u32 dword; int err = 0; - if (!capable(CAP_SYS_ADMIN)) + if (!capable(CAP_SYS_ADMIN) || !capable(CAP_COMPROMISE_KERNEL)) return -EPERM; dev = pci_get_bus_and_slot(bus, dfn); -- 1.7.11.4 From 2d23d2726583d79062e58abcc32c7dd027d312aa Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Thu, 20 Sep 2012 10:40:58 -0400 Subject: [PATCH 03/14] x86: Lock down IO port access in secure boot environments IO port access would permit users to gain access to PCI configuration registers, which in turn (on a lot of hardware) give access to MMIO register space. This would potentially permit root to trigger arbitrary DMA, so lock it down by default. Signed-off-by: Matthew Garrett --- arch/x86/kernel/ioport.c | 4 ++-- drivers/char/mem.c | 3 +++ 2 files changed, 5 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/ioport.c b/arch/x86/kernel/ioport.c index 8c96897..a2578c4 100644 --- a/arch/x86/kernel/ioport.c +++ b/arch/x86/kernel/ioport.c @@ -28,7 +28,7 @@ asmlinkage long sys_ioperm(unsigned long from, unsigned long num, int turn_on) if ((from + num <= from) || (from + num > IO_BITMAP_BITS)) return -EINVAL; - if (turn_on && !capable(CAP_SYS_RAWIO)) + if (turn_on && (!capable(CAP_SYS_RAWIO) || !capable(CAP_COMPROMISE_KERNEL))) return -EPERM; /* @@ -102,7 +102,7 @@ long sys_iopl(unsigned int level, struct pt_regs *regs) return -EINVAL; /* Trying to gain more privileges? */ if (level > old) { - if (!capable(CAP_SYS_RAWIO)) + if (!capable(CAP_SYS_RAWIO) || !capable(CAP_COMPROMISE_KERNEL)) return -EPERM; } regs->flags = (regs->flags & ~X86_EFLAGS_IOPL) | (level << 12); diff --git a/drivers/char/mem.c b/drivers/char/mem.c index e5eedfa..1e0a660 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -597,6 +597,9 @@ static ssize_t write_port(struct file *file, const char __user *buf, unsigned long i = *ppos; const char __user * tmp = buf; + if (!capable(CAP_COMPROMISE_KERNEL)) + return -EPERM; + if (!access_ok(VERIFY_READ, buf, count)) return -EFAULT; while (count-- > 0 && i < 65536) { -- 1.7.11.4 From e063cb2f3a667d2540682d4bdbef91fdb23b1a84 Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Thu, 20 Sep 2012 10:40:59 -0400 Subject: [PATCH 04/14] ACPI: Limit access to custom_method It must be impossible for even root to get code executed in kernel context under a secure boot environment. custom_method effectively allows arbitrary access to system memory, so it needs to have a capability check here. Signed-off-by: Matthew Garrett --- drivers/acpi/custom_method.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c index 5d42c24..247d58b 100644 --- a/drivers/acpi/custom_method.c +++ b/drivers/acpi/custom_method.c @@ -29,6 +29,9 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf, struct acpi_table_header table; acpi_status status; + if (!capable(CAP_COMPROMISE_KERNEL)) + return -EPERM; + if (!(*ppos)) { /* parse the table header to get the table length */ if (count <= sizeof(struct acpi_table_header)) -- 1.7.11.4 From a1cccbd084c7355dcb2be7ae2934f168ce9ba9d5 Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Thu, 20 Sep 2012 10:41:00 -0400 Subject: [PATCH 05/14] asus-wmi: Restrict debugfs interface We have no way of validating what all of the Asus WMI methods do on a given machine, and there's a risk that some will allow hardware state to be manipulated in such a way that arbitrary code can be executed in the kernel. Add a capability check to prevent that. Signed-off-by: Matthew Garrett --- drivers/platform/x86/asus-wmi.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c index 2eb9fe8..61e055d 100644 --- a/drivers/platform/x86/asus-wmi.c +++ b/drivers/platform/x86/asus-wmi.c @@ -1523,6 +1523,9 @@ static int show_dsts(struct seq_file *m, void *data) int err; u32 retval = -1; + if (!capable(CAP_COMPROMISE_KERNEL)) + return -EPERM; + err = asus_wmi_get_devstate(asus, asus->debug.dev_id, &retval); if (err < 0) @@ -1539,6 +1542,9 @@ static int show_devs(struct seq_file *m, void *data) int err; u32 retval = -1; + if (!capable(CAP_COMPROMISE_KERNEL)) + return -EPERM; + err = asus_wmi_set_devstate(asus->debug.dev_id, asus->debug.ctrl_param, &retval); @@ -1563,6 +1569,9 @@ static int show_call(struct seq_file *m, void *data) union acpi_object *obj; acpi_status status; + if (!capable(CAP_COMPROMISE_KERNEL)) + return -EPERM; + status = wmi_evaluate_method(ASUS_WMI_MGMT_GUID, 1, asus->debug.method_id, &input, &output); -- 1.7.11.4 From 1c9e53b626268f82509062751eda14e8572717cf Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Thu, 20 Sep 2012 10:41:01 -0400 Subject: [PATCH 06/14] Restrict /dev/mem and /dev/kmem in secure boot setups Allowing users to write to address space makes it possible for the kernel to be subverted. Restrict this when we need to protect the kernel. Signed-off-by: Matthew Garrett --- drivers/char/mem.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 1e0a660..33eb947 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -158,6 +158,9 @@ static ssize_t write_mem(struct file *file, const char __user *buf, unsigned long copied; void *ptr; + if (!capable(CAP_COMPROMISE_KERNEL)) + return -EPERM; + if (!valid_phys_addr_range(p, count)) return -EFAULT; @@ -530,6 +533,9 @@ static ssize_t write_kmem(struct file *file, const char __user *buf, char * kbuf; /* k-addr because vwrite() takes vmlist_lock rwlock */ int err = 0; + if (!capable(CAP_COMPROMISE_KERNEL)) + return -EPERM; + if (p < (unsigned long) high_memory) { unsigned long to_write = min_t(unsigned long, count, (unsigned long)high_memory - p); -- 1.7.11.4 From fbf919bf372b9a7a08bdacac8129d47ced1b1f19 Mon Sep 17 00:00:00 2001 From: Josh Boyer Date: Thu, 20 Sep 2012 10:41:02 -0400 Subject: [PATCH 07/14] Secure boot: Add a dummy kernel parameter that will switch on Secure Boot mode This forcibly drops CAP_COMPROMISE_KERNEL from both cap_permitted and cap_bset in the init_cred struct, which everything else inherits from. This works on any machine and can be used to develop even if the box doesn't have UEFI. Signed-off-by: Josh Boyer --- Documentation/kernel-parameters.txt | 7 +++++++ kernel/cred.c | 17 +++++++++++++++++ 2 files changed, 24 insertions(+) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 9b2b8d3..93978d5 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -2562,6 +2562,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted. Note: increases power consumption, thus should only be enabled if running jitter sensitive (HPC/RT) workloads. + secureboot_enable= + [KNL] Enables an emulated UEFI Secure Boot mode. This + locks down various aspects of the kernel guarded by the + CAP_COMPROMISE_KERNEL capability. This includes things + like /dev/mem, IO port access, and other areas. It can + be used on non-UEFI machines for testing purposes. + security= [SECURITY] Choose a security module to enable at boot. If this boot parameter is not specified, only the first security module asking for security registration will be diff --git a/kernel/cred.c b/kernel/cred.c index de728ac..7e6e83f 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -623,6 +623,23 @@ void __init cred_init(void) 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); } +void __init secureboot_enable() +{ + pr_info("Secure boot enabled\n"); + cap_lower((&init_cred)->cap_bset, CAP_COMPROMISE_KERNEL); + cap_lower((&init_cred)->cap_permitted, CAP_COMPROMISE_KERNEL); +} + +/* Dummy Secure Boot enable option to fake out UEFI SB=1 */ +static int __init secureboot_enable_opt(char *str) +{ + int sb_enable = !!simple_strtol(str, NULL, 0); + if (sb_enable) + secureboot_enable(); + return 1; +} +__setup("secureboot_enable=", secureboot_enable_opt); + /** * prepare_kernel_cred - Prepare a set of credentials for a kernel service * @daemon: A userspace daemon to be used as a reference -- 1.7.11.4 From 43ed7865d867ae692e30227d66fa58cdecbd9269 Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Thu, 20 Sep 2012 10:41:03 -0400 Subject: [PATCH 08/14] efi: Enable secure boot lockdown automatically when enabled in firmware The firmware has a set of flags that indicate whether secure boot is enabled and enforcing. Use them to indicate whether the kernel should lock itself down. Signed-off-by: Matthew Garrett --- Documentation/x86/zero-page.txt | 2 ++ arch/x86/boot/compressed/eboot.c | 32 ++++++++++++++++++++++++++++++++ arch/x86/include/asm/bootparam.h | 3 ++- arch/x86/kernel/setup.c | 3 +++ include/linux/cred.h | 2 ++ 5 files changed, 41 insertions(+), 1 deletion(-) diff --git a/Documentation/x86/zero-page.txt b/Documentation/x86/zero-page.txt index cf5437d..7f9ed48 100644 --- a/Documentation/x86/zero-page.txt +++ b/Documentation/x86/zero-page.txt @@ -27,6 +27,8 @@ Offset Proto Name Meaning 1E9/001 ALL eddbuf_entries Number of entries in eddbuf (below) 1EA/001 ALL edd_mbr_sig_buf_entries Number of entries in edd_mbr_sig_buffer (below) +1EB/001 ALL kbd_status Numlock is enabled +1EC/001 ALL secure_boot Kernel should enable secure boot lockdowns 290/040 ALL edd_mbr_sig_buffer EDD MBR signatures 2D0/A00 ALL e820_map E820 memory map table (array of struct e820entry) diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c index b3e0227..3789356 100644 --- a/arch/x86/boot/compressed/eboot.c +++ b/arch/x86/boot/compressed/eboot.c @@ -724,6 +724,36 @@ fail: return status; } +static int get_secure_boot(efi_system_table_t *_table) +{ + u8 sb, setup; + unsigned long datasize = sizeof(sb); + efi_guid_t var_guid = EFI_GLOBAL_VARIABLE_GUID; + efi_status_t status; + + status = efi_call_phys5(sys_table->runtime->get_variable, + L"SecureBoot", &var_guid, NULL, &datasize, &sb); + + if (status != EFI_SUCCESS) + return 0; + + if (sb == 0) + return 0; + + + status = efi_call_phys5(sys_table->runtime->get_variable, + L"SetupMode", &var_guid, NULL, &datasize, + &setup); + + if (status != EFI_SUCCESS) + return 0; + + if (setup == 1) + return 0; + + return 1; +} + /* * Because the x86 boot code expects to be passed a boot_params we * need to create one ourselves (usually the bootloader would create @@ -1018,6 +1048,8 @@ struct boot_params *efi_main(void *handle, efi_system_table_t *_table, if (sys_table->hdr.signature != EFI_SYSTEM_TABLE_SIGNATURE) goto fail; + boot_params->secure_boot = get_secure_boot(sys_table); + setup_graphics(boot_params); status = efi_call_phys3(sys_table->boottime->allocate_pool, diff --git a/arch/x86/include/asm/bootparam.h b/arch/x86/include/asm/bootparam.h index 2ad874c..c7338e0 100644 --- a/arch/x86/include/asm/bootparam.h +++ b/arch/x86/include/asm/bootparam.h @@ -114,7 +114,8 @@ struct boot_params { __u8 eddbuf_entries; /* 0x1e9 */ __u8 edd_mbr_sig_buf_entries; /* 0x1ea */ __u8 kbd_status; /* 0x1eb */ - __u8 _pad6[5]; /* 0x1ec */ + __u8 secure_boot; /* 0x1ec */ + __u8 _pad6[4]; /* 0x1ed */ struct setup_header hdr; /* setup header */ /* 0x1f1 */ __u8 _pad7[0x290-0x1f1-sizeof(struct setup_header)]; __u32 edd_mbr_sig_buffer[EDD_MBR_SIG_MAX]; /* 0x290 */ diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index f4b9b80..239bf2a 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -947,6 +947,9 @@ void __init setup_arch(char **cmdline_p) io_delay_init(); + if (boot_params.secure_boot) + secureboot_enable(); + /* * Parse the ACPI tables for possible boot-time SMP configuration. */ diff --git a/include/linux/cred.h b/include/linux/cred.h index ebbed2c..a24faf1 100644 --- a/include/linux/cred.h +++ b/include/linux/cred.h @@ -170,6 +170,8 @@ extern int set_security_override_from_ctx(struct cred *, const char *); extern int set_create_files_as(struct cred *, struct inode *); extern void __init cred_init(void); +extern void secureboot_enable(void); + /* * check for validity of credentials */ -- 1.7.11.4 From 3acf1ceb5f6f3be9103c9da16ddc24afc6d8b02a Mon Sep 17 00:00:00 2001 From: Josh Boyer Date: Thu, 20 Sep 2012 10:41:04 -0400 Subject: [PATCH 09/14] acpi: Ignore acpi_rsdp kernel parameter in a secure boot environment This option allows userspace to pass the RSDP address to the kernel. This could potentially be used to circumvent the secure boot trust model. We ignore the setting if we don't have the CAP_COMPROMISE_KERNEL capability. Signed-off-by: Josh Boyer --- drivers/acpi/osl.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c index 9eaf708..f94341b 100644 --- a/drivers/acpi/osl.c +++ b/drivers/acpi/osl.c @@ -246,7 +246,7 @@ early_param("acpi_rsdp", setup_acpi_rsdp); acpi_physical_address __init acpi_os_get_root_pointer(void) { #ifdef CONFIG_KEXEC - if (acpi_rsdp) + if (acpi_rsdp && capable(CAP_COMPROMISE_KERNEL)) return acpi_rsdp; #endif -- 1.7.11.4 From 03fb06d272ddc1062e610521c5cfdbe42f251209 Mon Sep 17 00:00:00 2001 From: Josh Boyer Date: Thu, 20 Sep 2012 10:41:05 -0400 Subject: [PATCH 10/14] SELinux: define mapping for new Secure Boot capability Add the name of the new Secure Boot capability. This allows SELinux policies to properly map CAP_COMPROMISE_KERNEL to the appropriate capability class. Signed-off-by: Josh Boyer --- security/selinux/include/classmap.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h index df2de54..70e2834 100644 --- a/security/selinux/include/classmap.h +++ b/security/selinux/include/classmap.h @@ -146,8 +146,8 @@ struct security_class_mapping secclass_map[] = { { "memprotect", { "mmap_zero", NULL } }, { "peer", { "recv", NULL } }, { "capability2", - { "mac_override", "mac_admin", "syslog", "wake_alarm", "block_suspend", - NULL } }, + { "mac_override", "mac_admin", "syslog", "wake_alarm", + "block_suspend", "compromise_kernel", NULL } }, { "kernel_service", { "use_as_override", "create_files_as", NULL } }, { "tun_socket", { COMMON_SOCK_PERMS, NULL } }, -- 1.7.11.4 From 0cfaa5ecf01f8eaaa2a84d88b7258a94ac9a1bfe Mon Sep 17 00:00:00 2001 From: Matthew Garrett Date: Tue, 4 Sep 2012 11:55:13 -0400 Subject: [PATCH 11/14] kexec: Disable in a secure boot environment kexec could be used as a vector for a malicious user to use a signed kernel to circumvent the secure boot trust model. In the long run we'll want to support signed kexec payloads, but for the moment we should just disable loading entirely in that situation. Signed-off-by: Matthew Garrett --- kernel/kexec.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/kexec.c b/kernel/kexec.c index 0668d58..8b976a5 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -944,7 +944,7 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments, int result; /* We only trust the superuser with rebooting the system. */ - if (!capable(CAP_SYS_BOOT)) + if (!capable(CAP_SYS_BOOT) || !capable(CAP_COMPROMISE_KERNEL)) return -EPERM; /* -- 1.7.11.4 From 895c46276788b3711aee05a1a1d685eff69d48b9 Mon Sep 17 00:00:00 2001 From: Josh Boyer Date: Mon, 25 Jun 2012 21:29:46 -0400 Subject: [PATCH 12/14] Documentation: kernel-parameters.txt remove capability.disable Remove the documentation for capability.disable. The code supporting this parameter was removed with: commit 5915eb53861c5776cfec33ca4fcc1fd20d66dd27 Author: Miklos Szeredi Date: Thu Jul 3 20:56:05 2008 +0200 security: remove dummy module Signed-off-by: Josh Boyer --- Documentation/kernel-parameters.txt | 6 ------ 1 file changed, 6 deletions(-) diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 93978d5..e3e5f8c 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -446,12 +446,6 @@ bytes respectively. Such letter suffixes can also be entirely omitted. possible to determine what the correct size should be. This option provides an override for these situations. - capability.disable= - [SECURITY] Disable capabilities. This would normally - be used only if an alternative security model is to be - configured. Potentially dangerous and should only be - used if you are entirely sure of the consequences. - ccw_timeout_log [S390] See Documentation/s390/CommonIO for details. -- 1.7.11.4 From 1cc529e97756554953187fe48b9b8cf0e24b9bc7 Mon Sep 17 00:00:00 2001 From: Josh Boyer Date: Fri, 5 Oct 2012 10:12:48 -0400 Subject: [PATCH] modsign: Always enforce module signing in a Secure Boot environment If a machine is booted into a Secure Boot environment, we need to protect the trust model. This requires that all modules be signed with a key that is in the kernel's _modsign keyring. The checks for this are already done via the 'sig_enforce' module parameter. Make this visible within the kernel and force it to be true. Signed-off-by: Josh Boyer --- kernel/cred.c | 8 ++++++++ kernel/module.c | 4 ++-- 2 files changed, 10 insertions(+), 2 deletions(-) diff --git a/kernel/cred.c b/kernel/cred.c index 7e6e83f..2b0b980 100644 --- a/kernel/cred.c +++ b/kernel/cred.c @@ -623,11 +623,19 @@ void __init cred_init(void) 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL); } +#ifdef CONFIG_MODULE_SIG +extern bool sig_enforce; +#endif + void __init secureboot_enable() { pr_info("Secure boot enabled\n"); cap_lower((&init_cred)->cap_bset, CAP_COMPROMISE_KERNEL); cap_lower((&init_cred)->cap_permitted, CAP_COMPROMISE_KERNEL); +#ifdef CONFIG_MODULE_SIG + /* Enable module signature enforcing */ + sig_enforce = true; +#endif } /* Dummy Secure Boot enable option to fake out UEFI SB=1 */ diff --git a/kernel/module.c b/kernel/module.c index de16959..7d4c50a 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -106,9 +106,9 @@ struct list_head *kdb_modules = &modules; /* kdb needs the list of modules */ #ifdef CONFIG_MODULE_SIG #ifdef CONFIG_MODULE_SIG_FORCE -static bool sig_enforce = true; +bool sig_enforce = true; #else -static bool sig_enforce = false; +bool sig_enforce = false; static int param_set_bool_enable_only(const char *val, const struct kernel_param *kp) -- 1.7.11.4