Re: [PATCH] Carry forward IMA measurement log on kexec on x86_64
From: Mimi Zohar
Date: Mon Apr 25 2022 - 12:30:16 EST
Hi Jonathan,
On Fri, 2022-04-22 at 13:50 +0000, Jonathan McDowell wrote:
> On kexec file load Integrity Measurement Architecture (IMA) subsystem
> may verify the IMA signature of the kernel and initramfs, and measure
> it. The command line parameters passed to the kernel in the kexec call
> may also be measured by IMA. A remote attestation service can verify
> a TPM quote based on the TPM event log, the IMA measurement list, and
> the TPM PCR data. This can be achieved only if the IMA measurement log
> is carried over from the current kernel to the next kernel across
> the kexec call.
>
> powerpc and ARM64 both achieve this using device tree with a
> "linux,ima-kexec-buffer" node. x86 platforms generally don't make use of
> device tree, so the IMA infrastructure is extended to allow non device
> tree platforms to provide a log buffer. x86 then passes the IMA buffer
> to the new kernel via the setup_data mechanism.
>
> Signed-off-by: Jonathan McDowell <noodles@xxxxxx>
FYI, after applying, building, and booting a kernel with this patch,
"kexec -s -l /boot/vmlinuz-5.18.0-rc4+ --reuse-cmdline --
initrd=/boot/initramfs-5.18.0-rc4+.img" properly loads the kernel, but
"kexec -s -e" fails to reboot, at least on a test laptop even with only
the "boot_aggregate" measurement record.
Without enabling CONFIG_IMA_KEXEC, kexec boots properly.
thanks,
Mimi
> ---
> arch/x86/Kconfig | 1 +
> arch/x86/include/uapi/asm/bootparam.h | 9 ++++
> arch/x86/kernel/e820.c | 6 +--
> arch/x86/kernel/kexec-bzimage64.c | 37 ++++++++++++++++-
> arch/x86/kernel/setup.c | 26 ++++++++++++
> include/linux/ima.h | 1 +
> security/integrity/ima/ima_kexec.c | 59 ++++++++++++++++++++++++++-
> 7 files changed, 134 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index b0142e01002e..bde4959d9bdc 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -2017,6 +2017,7 @@ config KEXEC_FILE
> bool "kexec file based system call"
> select KEXEC_CORE
> select BUILD_BIN2C
> + select HAVE_IMA_KEXEC if IMA
> depends on X86_64
> depends on CRYPTO=y
> depends on CRYPTO_SHA256=y
> diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h
> index b25d3f82c2f3..2f7b138a9388 100644
> --- a/arch/x86/include/uapi/asm/bootparam.h
> +++ b/arch/x86/include/uapi/asm/bootparam.h
> @@ -10,6 +10,7 @@
> #define SETUP_EFI 4
> #define SETUP_APPLE_PROPERTIES 5
> #define SETUP_JAILHOUSE 6
> +#define SETUP_IMA 7
>
> #define SETUP_INDIRECT (1<<31)
>
> @@ -171,6 +172,14 @@ struct jailhouse_setup_data {
> } __attribute__((packed)) v2;
> } __attribute__((packed));
>
> +/*
> + * IMA buffer setup data information from the previous kernel during kexec
> + */
> +struct ima_setup_data {
> + __u64 addr;
> + __u64 size;
> +} __attribute__((packed));
> +
> /* The so-called "zeropage" */
> struct boot_params {
> struct screen_info screen_info; /* 0x000 */
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index f267205f2d5a..9dac24680ff8 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -1017,10 +1017,10 @@ void __init e820__reserve_setup_data(void)
> e820__range_update(pa_data, sizeof(*data)+data->len, E820_TYPE_RAM, E820_TYPE_RESERVED_KERN);
>
> /*
> - * SETUP_EFI is supplied by kexec and does not need to be
> - * reserved.
> + * SETUP_EFI and SETUP_IMA are supplied by kexec and do not need
> + * to be reserved.
> */
> - if (data->type != SETUP_EFI)
> + if (data->type != SETUP_EFI && data->type != SETUP_IMA)
> e820__range_update_kexec(pa_data,
> sizeof(*data) + data->len,
> E820_TYPE_RAM, E820_TYPE_RESERVED_KERN);
> diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c
> index 170d0fd68b1f..07625da33075 100644
> --- a/arch/x86/kernel/kexec-bzimage64.c
> +++ b/arch/x86/kernel/kexec-bzimage64.c
> @@ -186,6 +186,32 @@ setup_efi_state(struct boot_params *params, unsigned long params_load_addr,
> }
> #endif /* CONFIG_EFI */
>
> +#ifdef CONFIG_IMA_KEXEC
> +static void
> +setup_ima_state(const struct kimage *image, struct boot_params *params,
> + unsigned long params_load_addr,
> + unsigned int ima_setup_data_offset)
> +{
> + struct setup_data *sd = (void *)params + ima_setup_data_offset;
> + struct ima_setup_data *ima = (void *)sd + sizeof(struct setup_data);
> + unsigned long setup_data_phys;
> +
> + if (!image->ima_buffer_size)
> + return;
> +
> + sd->type = SETUP_IMA;
> + sd->len = sizeof(*ima);
> +
> + ima->addr = image->ima_buffer_addr;
> + ima->size = image->ima_buffer_size;
> +
> + /* Add setup data */
> + setup_data_phys = params_load_addr + ima_setup_data_offset;
> + sd->next = params->hdr.setup_data;
> + params->hdr.setup_data = setup_data_phys;
> +}
> +#endif /* CONFIG_IMA_KEXEC */
> +
> static int
> setup_boot_parameters(struct kimage *image, struct boot_params *params,
> unsigned long params_load_addr,
> @@ -247,6 +273,13 @@ setup_boot_parameters(struct kimage *image, struct boot_params *params,
> setup_efi_state(params, params_load_addr, efi_map_offset, efi_map_sz,
> efi_setup_data_offset);
> #endif
> +
> +#ifdef CONFIG_IMA_KEXEC
> + /* Setup IMA log buffer state */
> + setup_ima_state(image, params, params_load_addr,
> + efi_setup_data_offset + ALIGN(efi_map_sz, 16) + sizeof(struct setup_data));
> +#endif
> +
> /* Setup EDD info */
> memcpy(params->eddbuf, boot_params.eddbuf,
> EDDMAXNR * sizeof(struct edd_info));
> @@ -401,7 +434,9 @@ static void *bzImage64_load(struct kimage *image, char *kernel,
> params_cmdline_sz = ALIGN(params_cmdline_sz, 16);
> kbuf.bufsz = params_cmdline_sz + ALIGN(efi_map_sz, 16) +
> sizeof(struct setup_data) +
> - sizeof(struct efi_setup_data);
> + sizeof(struct efi_setup_data) +
> + sizeof(struct setup_data) +
> + sizeof(struct ima_setup_data);
>
> params = kzalloc(kbuf.bufsz, GFP_KERNEL);
> if (!params)
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index c95b9ac5a457..8b0e7725f918 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -11,6 +11,7 @@
> #include <linux/dma-map-ops.h>
> #include <linux/dmi.h>
> #include <linux/efi.h>
> +#include <linux/ima.h>
> #include <linux/init_ohci1394_dma.h>
> #include <linux/initrd.h>
> #include <linux/iscsi_ibft.h>
> @@ -335,6 +336,28 @@ static void __init reserve_initrd(void)
> }
> #endif /* CONFIG_BLK_DEV_INITRD */
>
> +#ifdef CONFIG_IMA_KEXEC
> +static void __init add_early_ima_buffer(u64 phys_addr)
> +{
> + struct ima_setup_data *data;
> +
> + data = early_memremap(phys_addr + sizeof(struct setup_data),
> + sizeof(*data));
> + if (!data) {
> + pr_warn("setup: failed to memremap ima_setup_data entry\n");
> + return;
> + }
> + memblock_reserve(data->addr, data->size);
> + ima_set_kexec_buffer(data->addr, data->size);
> + early_memunmap(data, sizeof(*data));
> +}
> +#else
> +static void __init add_early_ima_buffer(u64 phys_addr)
> +{
> + pr_warn("Passed IMA kexec data, but CONFIG_IMA_KEXEC not set. Ignoring.\n");
> +}
> +#endif
> +
> static void __init parse_setup_data(void)
> {
> struct setup_data *data;
> @@ -360,6 +383,9 @@ static void __init parse_setup_data(void)
> case SETUP_EFI:
> parse_efi_setup(pa_data, data_len);
> break;
> + case SETUP_IMA:
> + add_early_ima_buffer(pa_data);
> + break;
> default:
> break;
> }
> diff --git a/include/linux/ima.h b/include/linux/ima.h
> index 426b1744215e..f58aed7acad4 100644
> --- a/include/linux/ima.h
> +++ b/include/linux/ima.h
> @@ -48,6 +48,7 @@ static inline void ima_appraise_parse_cmdline(void) {}
>
> #ifdef CONFIG_IMA_KEXEC
> extern void ima_add_kexec_buffer(struct kimage *image);
> +extern void ima_set_kexec_buffer(phys_addr_t phys_addr, size_t size);
> #endif
>
> #else
> diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c
> index 13753136f03f..419c50cfe6b9 100644
> --- a/security/integrity/ima/ima_kexec.c
> +++ b/security/integrity/ima/ima_kexec.c
> @@ -10,6 +10,7 @@
> #include <linux/seq_file.h>
> #include <linux/vmalloc.h>
> #include <linux/kexec.h>
> +#include <linux/memblock.h>
> #include <linux/of.h>
> #include <linux/ima.h>
> #include "ima.h"
> @@ -134,10 +135,66 @@ void ima_add_kexec_buffer(struct kimage *image)
> }
> #endif /* IMA_KEXEC */
>
> +#ifndef CONFIG_OF
> +static phys_addr_t ima_early_kexec_buffer_phys;
> +static size_t ima_early_kexec_buffer_size;
> +
> +void __init ima_set_kexec_buffer(phys_addr_t phys_addr, size_t size)
> +{
> + if (size == 0)
> + return;
> +
> + ima_early_kexec_buffer_phys = phys_addr;
> + ima_early_kexec_buffer_size = size;
> +}
> +
> +int __init ima_free_kexec_buffer(void)
> +{
> + int rc;
> +
> + if (!IS_ENABLED(CONFIG_HAVE_IMA_KEXEC))
> + return -ENOTSUPP;
> +
> + if (ima_early_kexec_buffer_size == 0)
> + return -ENOENT;
> +
> + rc = memblock_phys_free(ima_early_kexec_buffer_phys,
> + ima_early_kexec_buffer_size);
> + if (rc)
> + return rc;
> +
> + ima_early_kexec_buffer_phys = 0;
> + ima_early_kexec_buffer_size = 0;
> +
> + return 0;
> +}
> +
> +int __init ima_get_kexec_buffer(void **addr, size_t *size)
> +{
> + if (!IS_ENABLED(CONFIG_HAVE_IMA_KEXEC))
> + return -ENOTSUPP;
> +
> + if (ima_early_kexec_buffer_size == 0)
> + return -ENOENT;
> +
> + *addr = __va(ima_early_kexec_buffer_phys);
> + *size = ima_early_kexec_buffer_size;
> +
> + return 0;
> +}
> +
> +#else
> +
> +void __init ima_set_kexec_buffer(phys_addr_t phys_addr, size_t size)
> +{
> + pr_warn("CONFIG_OF enabled, ignoring call to set buffer details.\n");
> +}
> +#endif /* CONFIG_OF */
> +
> /*
> * Restore the measurement list from the previous kernel.
> */
> -void ima_load_kexec_buffer(void)
> +void __init ima_load_kexec_buffer(void)
> {
> void *kexec_buffer = NULL;
> size_t kexec_buffer_size = 0;