From b69a2afd5afce9bf6d56e349d6ab592c916e20f2 Mon Sep 17 00:00:00 2001 From: Jonathan McDowell Date: Thu, 30 Jun 2022 08:36:12 +0000 Subject: [PATCH 1/2] x86/kexec: Carry forward IMA measurement log on kexec On kexec file load, the 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 use the setup_data mechanism to pass the IMA buffer to the new kernel. Signed-off-by: Jonathan McDowell Signed-off-by: Borislav Petkov Reviewed-by: Mimi Zohar # IMA function definitions Link: https://lore.kernel.org/r/YmKyvlF3my1yWTvK@noodles-fedora-PC23Y6EG --- arch/x86/Kconfig | 1 + arch/x86/include/uapi/asm/bootparam.h | 9 ++++ arch/x86/kernel/e820.c | 6 +-- arch/x86/kernel/kexec-bzimage64.c | 42 +++++++++++++++++- arch/x86/kernel/setup.c | 63 +++++++++++++++++++++++++++ drivers/of/kexec.c | 13 +++--- include/linux/ima.h | 5 +++ include/linux/of.h | 2 - security/integrity/ima/ima_kexec.c | 2 +- 9 files changed, 127 insertions(+), 16 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index be0b95e51df663..670e0edc074f16 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2033,6 +2033,7 @@ 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 bea5cdcdf53252..ca0796ac4403c0 100644 --- a/arch/x86/include/uapi/asm/bootparam.h +++ b/arch/x86/include/uapi/asm/bootparam.h @@ -11,6 +11,7 @@ #define SETUP_APPLE_PROPERTIES 5 #define SETUP_JAILHOUSE 6 #define SETUP_CC_BLOB 7 +#define SETUP_IMA 8 #define SETUP_INDIRECT (1<<31) @@ -172,6 +173,14 @@ 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 f267205f2d5a41..9dac24680ff8ea 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 170d0fd68b1f40..c63974e9427236 100644 --- a/arch/x86/kernel/kexec-bzimage64.c +++ b/arch/x86/kernel/kexec-bzimage64.c @@ -186,11 +186,38 @@ setup_efi_state(struct boot_params *params, unsigned long params_load_addr, } #endif /* CONFIG_EFI */ +static void +setup_ima_state(const struct kimage *image, struct boot_params *params, + unsigned long params_load_addr, + unsigned int ima_setup_data_offset) +{ +#ifdef CONFIG_IMA_KEXEC + struct setup_data *sd = (void *)params + ima_setup_data_offset; + unsigned long setup_data_phys; + struct ima_setup_data *ima; + + if (!image->ima_buffer_size) + return; + + sd->type = SETUP_IMA; + sd->len = sizeof(*ima); + + ima = (void *)sd + sizeof(struct setup_data); + 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, unsigned int efi_map_offset, unsigned int efi_map_sz, - unsigned int efi_setup_data_offset) + unsigned int setup_data_offset) { unsigned int nr_e820_entries; unsigned long long mem_k, start, end; @@ -245,8 +272,15 @@ setup_boot_parameters(struct kimage *image, struct boot_params *params, #ifdef CONFIG_EFI /* Setup EFI state */ setup_efi_state(params, params_load_addr, efi_map_offset, efi_map_sz, - efi_setup_data_offset); + setup_data_offset); + setup_data_offset += sizeof(struct setup_data) + + sizeof(struct efi_setup_data); #endif + + /* Setup IMA log buffer state */ + setup_ima_state(image, params, params_load_addr, + setup_data_offset); + /* Setup EDD info */ memcpy(params->eddbuf, boot_params.eddbuf, EDDMAXNR * sizeof(struct edd_info)); @@ -403,6 +437,10 @@ static void *bzImage64_load(struct kimage *image, char *kernel, sizeof(struct setup_data) + sizeof(struct efi_setup_data); + if (IS_ENABLED(CONFIG_IMA_KEXEC)) + kbuf.bufsz += sizeof(struct setup_data) + + sizeof(struct ima_setup_data); + params = kzalloc(kbuf.bufsz, GFP_KERNEL); if (!params) return ERR_PTR(-ENOMEM); diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index bd6c6fd373aeed..53f863f28b4c2f 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -11,6 +11,7 @@ #include #include #include +#include #include #include #include @@ -140,6 +141,11 @@ __visible unsigned long mmu_cr4_features __ro_after_init; __visible unsigned long mmu_cr4_features __ro_after_init = X86_CR4_PAE; #endif +#ifdef CONFIG_IMA +static phys_addr_t ima_kexec_buffer_phys; +static size_t ima_kexec_buffer_size; +#endif + /* Boot loader ID and version as integers, for the benefit of proc_dointvec */ int bootloader_type, bootloader_version; @@ -330,6 +336,60 @@ static void __init reserve_initrd(void) } #endif /* CONFIG_BLK_DEV_INITRD */ +static void __init add_early_ima_buffer(u64 phys_addr) +{ +#ifdef CONFIG_IMA + 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; + } + + if (data->size) { + memblock_reserve(data->addr, data->size); + ima_kexec_buffer_phys = data->addr; + ima_kexec_buffer_size = data->size; + } + + early_memunmap(data, sizeof(*data)); +#else + pr_warn("Passed IMA kexec data, but CONFIG_IMA not set. Ignoring.\n"); +#endif +} + +#if defined(CONFIG_HAVE_IMA_KEXEC) && !defined(CONFIG_OF_FLATTREE) +int __init ima_free_kexec_buffer(void) +{ + int rc; + + if (!ima_kexec_buffer_size) + return -ENOENT; + + rc = memblock_phys_free(ima_kexec_buffer_phys, + ima_kexec_buffer_size); + if (rc) + return rc; + + ima_kexec_buffer_phys = 0; + ima_kexec_buffer_size = 0; + + return 0; +} + +int __init ima_get_kexec_buffer(void **addr, size_t *size) +{ + if (!ima_kexec_buffer_size) + return -ENOENT; + + *addr = __va(ima_kexec_buffer_phys); + *size = ima_kexec_buffer_size; + + return 0; +} +#endif + static void __init parse_setup_data(void) { struct setup_data *data; @@ -355,6 +415,9 @@ 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/drivers/of/kexec.c b/drivers/of/kexec.c index 8d374cc552be5f..f2e58ddfaed250 100644 --- a/drivers/of/kexec.c +++ b/drivers/of/kexec.c @@ -9,6 +9,7 @@ * Copyright (C) 2016 IBM Corporation */ +#include #include #include #include @@ -115,6 +116,7 @@ static int do_get_kexec_buffer(const void *prop, int len, unsigned long *addr, return 0; } +#ifdef CONFIG_HAVE_IMA_KEXEC /** * ima_get_kexec_buffer - get IMA buffer from the previous kernel * @addr: On successful return, set to point to the buffer contents. @@ -122,16 +124,13 @@ static int do_get_kexec_buffer(const void *prop, int len, unsigned long *addr, * * Return: 0 on success, negative errno on error. */ -int ima_get_kexec_buffer(void **addr, size_t *size) +int __init ima_get_kexec_buffer(void **addr, size_t *size) { int ret, len; unsigned long tmp_addr; size_t tmp_size; const void *prop; - if (!IS_ENABLED(CONFIG_HAVE_IMA_KEXEC)) - return -ENOTSUPP; - prop = of_get_property(of_chosen, "linux,ima-kexec-buffer", &len); if (!prop) return -ENOENT; @@ -149,16 +148,13 @@ int ima_get_kexec_buffer(void **addr, size_t *size) /** * ima_free_kexec_buffer - free memory used by the IMA buffer */ -int ima_free_kexec_buffer(void) +int __init ima_free_kexec_buffer(void) { int ret; unsigned long addr; size_t size; struct property *prop; - if (!IS_ENABLED(CONFIG_HAVE_IMA_KEXEC)) - return -ENOTSUPP; - prop = of_find_property(of_chosen, "linux,ima-kexec-buffer", NULL); if (!prop) return -ENOENT; @@ -173,6 +169,7 @@ int ima_free_kexec_buffer(void) return memblock_phys_free(addr, size); } +#endif /** * remove_ima_buffer - remove the IMA buffer property and reservation from @fdt diff --git a/include/linux/ima.h b/include/linux/ima.h index 426b1744215e39..81708ca0ebc74e 100644 --- a/include/linux/ima.h +++ b/include/linux/ima.h @@ -140,6 +140,11 @@ static inline int ima_measure_critical_data(const char *event_label, #endif /* CONFIG_IMA */ +#ifdef CONFIG_HAVE_IMA_KEXEC +int __init ima_free_kexec_buffer(void); +int __init ima_get_kexec_buffer(void **addr, size_t *size); +#endif + #ifdef CONFIG_IMA_SECURE_AND_OR_TRUSTED_BOOT extern bool arch_ima_get_secureboot(void); extern const char * const *arch_get_ima_policy(void); diff --git a/include/linux/of.h b/include/linux/of.h index f0a5d6b10c5a7a..20a4e7cb7afe5c 100644 --- a/include/linux/of.h +++ b/include/linux/of.h @@ -441,8 +441,6 @@ void *of_kexec_alloc_and_setup_fdt(const struct kimage *image, unsigned long initrd_load_addr, unsigned long initrd_len, const char *cmdline, size_t extra_fdt_size); -int ima_get_kexec_buffer(void **addr, size_t *size); -int ima_free_kexec_buffer(void); #else /* CONFIG_OF */ static inline void of_core_init(void) diff --git a/security/integrity/ima/ima_kexec.c b/security/integrity/ima/ima_kexec.c index 13753136f03f08..419dc405c8310b 100644 --- a/security/integrity/ima/ima_kexec.c +++ b/security/integrity/ima/ima_kexec.c @@ -137,7 +137,7 @@ void ima_add_kexec_buffer(struct kimage *image) /* * 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; From 68b8e9713c8ec90af93c16e1de51cca18cefdb56 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Sun, 10 Jul 2022 19:29:21 +0200 Subject: [PATCH 2/2] x86/setup: Use rng seeds from setup_data Currently, the only way x86 can get an early boot RNG seed is via EFI, which is generally always used now for physical machines, but is very rarely used in VMs, especially VMs that are optimized for starting "instantaneously", such as Firecracker's MicroVM. For tiny fast booting VMs, EFI is not something you generally need or want. Rather, the image loader or firmware should be able to pass a single random seed, exactly as device tree platforms do with the "rng-seed" property. Additionally, this is something that bootloaders can append, with their own seed file management, which is something every other major OS ecosystem has that Linux does not (yet). Add SETUP_RNG_SEED, similar to the other eight setup_data entries that are parsed at boot. It also takes care to zero out the seed immediately after using, in order to retain forward secrecy. This all takes about 7 trivial lines of code. Then, on kexec_file_load(), a new fresh seed is generated and passed to the next kernel, just as is done on device tree architectures when using kexec. And, importantly, I've tested that QEMU is able to properly pass SETUP_RNG_SEED as well, making this work for every step of the way. This code too is pretty straight forward. Together these measures ensure that VMs and nested kexec()'d kernels always receive a proper boot time RNG seed at the earliest possible stage from their parents: - Host [already has strongly initialized RNG] - QEMU [passes fresh seed in SETUP_RNG_SEED field] - Linux [uses parent's seed and gathers entropy of its own] - kexec [passes this in SETUP_RNG_SEED field] - Linux [uses parent's seed and gathers entropy of its own] - kexec [passes this in SETUP_RNG_SEED field] - Linux [uses parent's seed and gathers entropy of its own] - kexec [passes this in SETUP_RNG_SEED field] - ... I've verified in several scenarios that this works quite well from a host kernel to QEMU and down inwards, mixing and matching loaders, with every layer providing a seed to the next. [ bp: Massage commit message. ] Signed-off-by: Jason A. Donenfeld Signed-off-by: Borislav Petkov Acked-by: H. Peter Anvin (Intel) Link: https://lore.kernel.org/r/20220630113300.1892799-1-Jason@zx2c4.com --- arch/x86/include/uapi/asm/bootparam.h | 6 ++--- arch/x86/kernel/kexec-bzimage64.c | 38 ++++++++++++++++++++++++--- arch/x86/kernel/setup.c | 10 +++++++ 3 files changed, 47 insertions(+), 7 deletions(-) diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h index be2b9ce52c7638..34229062404018 100644 --- a/arch/x86/include/uapi/asm/bootparam.h +++ b/arch/x86/include/uapi/asm/bootparam.h @@ -12,11 +12,11 @@ #define SETUP_JAILHOUSE 6 #define SETUP_CC_BLOB 7 #define SETUP_IMA 8 +#define SETUP_RNG_SEED 9 +#define SETUP_ENUM_MAX SETUP_RNG_SEED #define SETUP_INDIRECT (1<<31) - -/* SETUP_INDIRECT | max(SETUP_*) */ -#define SETUP_TYPE_MAX (SETUP_INDIRECT | SETUP_CC_BLOB) +#define SETUP_TYPE_MAX (SETUP_ENUM_MAX | SETUP_INDIRECT) /* ram_size flags */ #define RAMDISK_IMAGE_START_MASK 0x07FF diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c index c63974e9427236..b9bdb40364a62d 100644 --- a/arch/x86/kernel/kexec-bzimage64.c +++ b/arch/x86/kernel/kexec-bzimage64.c @@ -18,6 +18,7 @@ #include #include #include +#include #include #include @@ -110,6 +111,26 @@ static int setup_e820_entries(struct boot_params *params) return 0; } +enum { RNG_SEED_LENGTH = 32 }; + +static void +setup_rng_seed(struct boot_params *params, unsigned long params_load_addr, + unsigned int rng_seed_setup_data_offset) +{ + struct setup_data *sd = (void *)params + rng_seed_setup_data_offset; + unsigned long setup_data_phys; + + if (!rng_is_initialized()) + return; + + sd->type = SETUP_RNG_SEED; + sd->len = RNG_SEED_LENGTH; + get_random_bytes(sd->data, RNG_SEED_LENGTH); + setup_data_phys = params_load_addr + rng_seed_setup_data_offset; + sd->next = params->hdr.setup_data; + params->hdr.setup_data = setup_data_phys; +} + #ifdef CONFIG_EFI static int setup_efi_info_memmap(struct boot_params *params, unsigned long params_load_addr, @@ -277,9 +298,16 @@ setup_boot_parameters(struct kimage *image, struct boot_params *params, sizeof(struct efi_setup_data); #endif - /* Setup IMA log buffer state */ - setup_ima_state(image, params, params_load_addr, - setup_data_offset); + if (IS_ENABLED(CONFIG_IMA_KEXEC)) { + /* Setup IMA log buffer state */ + setup_ima_state(image, params, params_load_addr, + setup_data_offset); + setup_data_offset += sizeof(struct setup_data) + + sizeof(struct ima_setup_data); + } + + /* Setup RNG seed */ + setup_rng_seed(params, params_load_addr, setup_data_offset); /* Setup EDD info */ memcpy(params->eddbuf, boot_params.eddbuf, @@ -435,7 +463,9 @@ 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) + + RNG_SEED_LENGTH; if (IS_ENABLED(CONFIG_IMA_KEXEC)) kbuf.bufsz += sizeof(struct setup_data) + diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 53f863f28b4c2f..216fee7144eefd 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -24,6 +24,7 @@ #include #include #include +#include #include @@ -418,6 +419,15 @@ static void __init parse_setup_data(void) case SETUP_IMA: add_early_ima_buffer(pa_data); break; + case SETUP_RNG_SEED: + data = early_memremap(pa_data, data_len); + add_bootloader_randomness(data->data, data->len); + /* Zero seed for forward secrecy. */ + memzero_explicit(data->data, data->len); + /* Zero length in case we find ourselves back here by accident. */ + memzero_explicit(&data->len, sizeof(data->len)); + early_memunmap(data, data_len); + break; default: break; }