On Mon, 2020-11-02 at 15:20 +0800, Chester Lin wrote:

On Fri, Oct 30, 2020 at 12:53:25PM +0100, Ard Biesheuvel wrote:

quoted

On Fri, 30 Oct 2020 at 07:09, Chester Lin [off-list ref] wrote:

quoted

Add arm64 IMA arch support. The code and arch policy is mainly inherited
from x86.

Signed-off-by: Chester Lin <redacted>
---
 arch/arm64/Kconfig           |  1 +
 arch/arm64/kernel/Makefile   |  2 ++
 arch/arm64/kernel/ima_arch.c | 43 ++++++++++++++++++++++++++++++++++++
 3 files changed, 46 insertions(+)
 create mode 100644 arch/arm64/kernel/ima_arch.c

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index a42e8d13cc88..496a4a26afc6 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig

@@ -201,6 +201,7 @@ config ARM64
        select SWIOTLB
        select SYSCTL_EXCEPTION_TRACE
        select THREAD_INFO_IN_TASK
+       imply IMA_SECURE_AND_OR_TRUSTED_BOOT if EFI
        help
          ARM 64-bit (AArch64) Linux support.

diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index bbaf0bc4ad60..0f6cbb50668c 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile

@@ -69,3 +69,5 @@ extra-y                                       += $(head-y) vmlinux.lds
 ifeq ($(CONFIG_DEBUG_EFI),y)
 AFLAGS_head.o += -DVMLINUX_PATH="\"$(realpath $(objtree)/vmlinux)\""
 endif
+
+obj-$(CONFIG_IMA_SECURE_AND_OR_TRUSTED_BOOT)   += ima_arch.o

diff --git a/arch/arm64/kernel/ima_arch.c b/arch/arm64/kernel/ima_arch.c
new file mode 100644
index 000000000000..564236d77adc
--- /dev/null
+++ b/arch/arm64/kernel/ima_arch.c

@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2018 IBM Corporation
+ */
+#include <linux/efi.h>
+#include <linux/module.h>
+#include <linux/ima.h>
+
+bool arch_ima_get_secureboot(void)
+{
+       static bool sb_enabled;
+       static bool initialized;
+
+       if (!initialized & efi_enabled(EFI_BOOT)) {
+               sb_enabled = ima_get_efi_secureboot();
+               initialized = true;
+       }
+
+       return sb_enabled;
+}
+
+/* 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",
+#endif /* CONFIG_KEXEC_SIG */
+       "measure func=KEXEC_KERNEL_CHECK",
+#if !IS_ENABLED(CONFIG_MODULE_SIG)
+       "appraise func=MODULE_CHECK appraise_type=imasig",
+#endif
+       "measure func=MODULE_CHECK",
+       NULL
+};
+
+const char * const *arch_get_ima_policy(void)
+{
+       if (IS_ENABLED(CONFIG_IMA_ARCH_POLICY) && arch_ima_get_secureboot()) {
+               if (IS_ENABLED(CONFIG_MODULE_SIG))
+                       set_module_sig_enforced();
+               return sb_arch_rules;
+       }
+       return NULL;
+}
--

2.28.0

Can we move all this stuff into security/integrity/ima/ima_efi.c instead?

Actually I hesitated to move all this stuff into ima_efi.c when coding v3
because I haven't figured out a clear picture to achieve it. Since each
architecture could still have different details to trigger secure boot detection
and define their arch-specific rules [e.g. Having boot_params in x86_64 creates
more conditions that need to be determined before calling get_sb_mode()], moving
all this stuff seems to decrease the flexibility. Besides, it might also affect
the consistency of ima_arch as well, for example, ppc and s390 still use these
function prototypes defined in ima.h. Since these functions are already referred
by non-EFI architectures, why don't we still reuse these prototypes? For example,
we could remain a smaller arch_ima_get_secureboot() and the arch-specific rules
but move the major part of arch_get_ima_policy() into ima_efi.c. For example,
we could implement an efi_ima_policy() for arch_get_ima_policy() to call so that
the arch_get_ima_policy() doesn't have to know some details such as checking
conditions or calling set_module_sig_enforced().

Please feel free to let me know if any suggestions.

Yes, that is the point and the reason for defining ima_efi.c and
conditionally including it only for EFI systems.  The existing ppc and
s390 code should remain unaffected by this change.

thanks,

Mimi


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