efi/arm*/libstub: Invoke EFI_RNG_PROTOCOL to seed the UEFI RNG table

Invoke the EFI_RNG_PROTOCOL protocol in the context of the stub and
install the Linux-specific RNG seed UEFI config table. This will be
picked up by the EFI routines in the core kernel to seed the kernel
entropy pool.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Reviewed-by: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20161112213237.8804-6-matt@codeblueprint.co.uk
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c
index 993aa56..b4f7d78 100644 (file)
--- a/drivers/firmware/efi/libstub/arm-stub.c
+++ b/drivers/firmware/efi/libstub/arm-stub.c
@@ -340,6 +340,8 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table,
        if (status != EFI_SUCCESS)
                pr_efi_err(sys_table, "Failed initrd from command line!\n");
 
+       efi_random_get_seed(sys_table);
+
        new_fdt_addr = fdt_addr;
        status = allocate_new_fdt_and_exit_boot(sys_table, handle,
                                &new_fdt_addr, dram_base + MAX_FDT_OFFSET,

diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
index fe1f225..b98824e 100644 (file)
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/drivers/firmware/efi/libstub/efistub.h
@@ -71,4 +71,6 @@ efi_status_t efi_random_alloc(efi_system_table_t *sys_table_arg,
 
 efi_status_t check_platform_features(efi_system_table_t *sys_table_arg);
 
+efi_status_t efi_random_get_seed(efi_system_table_t *sys_table_arg);
+
 #endif

diff --git a/drivers/firmware/efi/libstub/random.c b/drivers/firmware/efi/libstub/random.c
index f8e2e5a..3a3feac 100644 (file)
--- a/drivers/firmware/efi/libstub/random.c
+++ b/drivers/firmware/efi/libstub/random.c
@@ -143,3 +143,51 @@ efi_status_t efi_random_alloc(efi_system_table_t *sys_table_arg,
 
        return status;
 }
+
+#define RANDOM_SEED_SIZE       32
+
+efi_status_t efi_random_get_seed(efi_system_table_t *sys_table_arg)
+{
+       efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID;
+       efi_guid_t rng_algo_raw = EFI_RNG_ALGORITHM_RAW;
+       efi_guid_t rng_table_guid = LINUX_EFI_RANDOM_SEED_TABLE_GUID;
+       struct efi_rng_protocol *rng;
+       struct linux_efi_random_seed *seed;
+       efi_status_t status;
+
+       status = efi_call_early(locate_protocol, &rng_proto, NULL,
+                               (void **)&rng);
+       if (status != EFI_SUCCESS)
+               return status;
+
+       status = efi_call_early(allocate_pool, EFI_RUNTIME_SERVICES_DATA,
+                               sizeof(*seed) + RANDOM_SEED_SIZE,
+                               (void **)&seed);
+       if (status != EFI_SUCCESS)
+               return status;
+
+       status = rng->get_rng(rng, &rng_algo_raw, RANDOM_SEED_SIZE,
+                             seed->bits);
+       if (status == EFI_UNSUPPORTED)
+               /*
+                * Use whatever algorithm we have available if the raw algorithm
+                * is not implemented.
+                */
+               status = rng->get_rng(rng, NULL, RANDOM_SEED_SIZE,
+                                     seed->bits);
+
+       if (status != EFI_SUCCESS)
+               goto err_freepool;
+
+       seed->size = RANDOM_SEED_SIZE;
+       status = efi_call_early(install_configuration_table, &rng_table_guid,
+                               seed);
+       if (status != EFI_SUCCESS)
+               goto err_freepool;
+
+       return EFI_SUCCESS;
+
+err_freepool:
+       efi_call_early(free_pool, seed);
+       return status;
+}

diff --git a/include/linux/efi.h b/include/linux/efi.h
index 85e28b1..f5a821d 100644 (file)
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -589,6 +589,7 @@ void efi_native_runtime_setup(void);
 #define DEVICE_TREE_GUID                       EFI_GUID(0xb1b621d5, 0xf19c, 0x41a5,  0x83, 0x0b, 0xd9, 0x15, 0x2c, 0x69, 0xaa, 0xe0)
 #define EFI_PROPERTIES_TABLE_GUID              EFI_GUID(0x880aaca3, 0x4adc, 0x4a04,  0x90, 0x79, 0xb7, 0x47, 0x34, 0x08, 0x25, 0xe5)
 #define EFI_RNG_PROTOCOL_GUID                  EFI_GUID(0x3152bca5, 0xeade, 0x433d,  0x86, 0x2e, 0xc0, 0x1c, 0xdc, 0x29, 0x1f, 0x44)
+#define EFI_RNG_ALGORITHM_RAW                  EFI_GUID(0xe43176d7, 0xb6e8, 0x4827,  0xb7, 0x84, 0x7f, 0xfd, 0xc4, 0xb6, 0x85, 0x61)
 #define EFI_MEMORY_ATTRIBUTES_TABLE_GUID       EFI_GUID(0xdcfa911d, 0x26eb, 0x469f,  0xa2, 0x20, 0x38, 0xb7, 0xdc, 0x46, 0x12, 0x20)
 #define EFI_CONSOLE_OUT_DEVICE_GUID            EFI_GUID(0xd3b36f2c, 0xd551, 0x11d4,  0x9a, 0x46, 0x00, 0x90, 0x27, 0x3f, 0xc1, 0x4d)