From 02bdaed98f9a17a06f71ce7e21d9af2bd6547dfc Mon Sep 17 00:00:00 2001 From: Dimitri John Ledkov Date: Wed, 22 Jul 2020 11:31:43 +0100 Subject: [PATCH 333/336] linuxefi: fail kernel validation without shim protocol. If certificates that signed grub are installed into db, grub can be booted directly. It will then boot any kernel without signature validation. The booted kernel will think it was booted in secureboot mode and will implement lockdown, yet it could have been tampered. This version of the patch skips calling verification, when booted without secureboot. And is indented with gnu ident. CVE-2020-15705 Reported-by: Mathieu Trudel-Lapierre Signed-off-by: Dimitri John Ledkov --- grub-core/loader/arm64/linux.c | 12 ++++++++---- grub-core/loader/efi/chainloader.c | 4 +--- grub-core/loader/efi/linux.c | 1 + grub-core/loader/i386/efi/linux.c | 13 ++++++++----- 4 files changed, 18 insertions(+), 12 deletions(-) diff --git a/grub-core/loader/arm64/linux.c b/grub-core/loader/arm64/linux.c index 1eb332a892c..d0a428d05fc 100644 --- a/grub-core/loader/arm64/linux.c +++ b/grub-core/loader/arm64/linux.c @@ -439,11 +439,15 @@ grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)), grub_dprintf ("linux", "kernel @ %p\n", kernel_addr); - rc = grub_linuxefi_secure_validate (kernel_addr, kernel_size); - if (rc < 0) + if (grub_efi_secure_boot ()) { - grub_error (GRUB_ERR_INVALID_COMMAND, N_("%s has invalid signature"), argv[0]); - goto fail; + rc = grub_linuxefi_secure_validate (kernel_addr, kernel_size); + if (rc <= 0) + { + grub_error (GRUB_ERR_INVALID_COMMAND, + N_("%s has invalid signature"), argv[0]); + goto fail; + } } pe = (void *)((unsigned long)kernel_addr + lh.hdr_offset); diff --git a/grub-core/loader/efi/chainloader.c b/grub-core/loader/efi/chainloader.c index dbcdf333b62..001766bdf68 100644 --- a/grub-core/loader/efi/chainloader.c +++ b/grub-core/loader/efi/chainloader.c @@ -1082,9 +1082,7 @@ grub_cmd_chainloader (grub_command_t cmd __attribute__ ((unused)), return 0; } - - grub_file_close (file); - grub_device_close (dev); + // -1 fall-through to fail fail: if (dev) diff --git a/grub-core/loader/efi/linux.c b/grub-core/loader/efi/linux.c index 7fe7201a388..d9b5380cfd3 100644 --- a/grub-core/loader/efi/linux.c +++ b/grub-core/loader/efi/linux.c @@ -33,6 +33,7 @@ struct grub_efi_shim_lock }; typedef struct grub_efi_shim_lock grub_efi_shim_lock_t; +// Returns 1 on success, -1 on error, 0 when not available int grub_linuxefi_secure_validate (void *data, grub_uint32_t size) { diff --git a/grub-core/loader/i386/efi/linux.c b/grub-core/loader/i386/efi/linux.c index 95dbb9e20af..c146bc58e3d 100644 --- a/grub-core/loader/i386/efi/linux.c +++ b/grub-core/loader/i386/efi/linux.c @@ -201,12 +201,15 @@ grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)), goto fail; } - rc = grub_linuxefi_secure_validate (kernel, filelen); - if (rc < 0) + if (grub_efi_secure_boot ()) { - grub_error (GRUB_ERR_INVALID_COMMAND, N_("%s has invalid signature"), - argv[0]); - goto fail; + rc = grub_linuxefi_secure_validate (kernel, filelen); + if (rc <= 0) + { + grub_error (GRUB_ERR_INVALID_COMMAND, + N_("%s has invalid signature"), argv[0]); + goto fail; + } } params = grub_efi_allocate_pages_max (0x3fffffff, -- 2.26.2