From: Matthew Garrett <matthewgarrett@google.com> To: jmorris@namei.org Cc: linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, dhowells@redhat.com, linux-api@vger.kernel.org, luto@kernel.org, Jiri Bohac <jbohac@suse.cz>, Matthew Garrett <mjg59@google.com>, kexec@lists.infradead.org Subject: [PATCH V32 06/27] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE Date: Wed, 3 Apr 2019 17:32:28 -0700 [thread overview] Message-ID: <20190404003249.14356-7-matthewgarrett@google.com> (raw) In-Reply-To: <20190404003249.14356-1-matthewgarrett@google.com> From: Jiri Bohac <jbohac@suse.cz> This is a preparatory patch for kexec_file_load() lockdown. A locked down kernel needs to prevent unsigned kernel images from being loaded with kexec_file_load(). Currently, the only way to force the signature verification is compiling with KEXEC_VERIFY_SIG. This prevents loading usigned images even when the kernel is not locked down at runtime. This patch splits KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE. Analogous to the MODULE_SIG and MODULE_SIG_FORCE for modules, KEXEC_SIG turns on the signature verification but allows unsigned images to be loaded. KEXEC_SIG_FORCE disallows images without a valid signature. [Modified by David Howells such that: (1) verify_pefile_signature() differentiates between no-signature and sig-didn't-match in its returned errors. (2) kexec fails with EKEYREJECTED and logs an appropriate message if signature checking is enforced and an signature is not found, uses unsupported crypto or has no matching key. (3) kexec fails with EKEYREJECTED if there is a signature for which we have a key, but signature doesn't match - even if in non-forcing mode. (4) kexec fails with EBADMSG or some other error if there is a signature which cannot be parsed - even if in non-forcing mode. (5) kexec fails with ELIBBAD if the PE file cannot be parsed to extract the signature - even if in non-forcing mode. ] Signed-off-by: Jiri Bohac <jbohac@suse.cz> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Matthew Garrett <mjg59@google.com> Reviewed-by: Jiri Bohac <jbohac@suse.cz> cc: kexec@lists.infradead.org --- arch/x86/Kconfig | 20 ++++++++--- crypto/asymmetric_keys/verify_pefile.c | 4 ++- include/linux/kexec.h | 4 +-- kernel/kexec_file.c | 48 ++++++++++++++++++++++---- 4 files changed, 61 insertions(+), 15 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 4b4a7f32b68e..735d04a4b18f 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2016,20 +2016,30 @@ config KEXEC_FILE config ARCH_HAS_KEXEC_PURGATORY def_bool KEXEC_FILE -config KEXEC_VERIFY_SIG +config KEXEC_SIG bool "Verify kernel signature during kexec_file_load() syscall" depends on KEXEC_FILE ---help--- - This option makes kernel signature verification mandatory for - the kexec_file_load() syscall. - In addition to that option, you need to enable signature + This option makes the kexec_file_load() syscall check for a valid + signature of the kernel image. The image can still be loaded without + a valid signature unless you also enable KEXEC_SIG_FORCE, though if + there's a signature that we can check, then it must be valid. + + In addition to this option, you need to enable signature verification for the corresponding kernel image type being loaded in order for this to work. +config KEXEC_SIG_FORCE + bool "Require a valid signature in kexec_file_load() syscall" + depends on KEXEC_SIG + ---help--- + This option makes kernel signature verification mandatory for + the kexec_file_load() syscall. + config KEXEC_BZIMAGE_VERIFY_SIG bool "Enable bzImage signature verification support" - depends on KEXEC_VERIFY_SIG + depends on KEXEC_SIG depends on SIGNED_PE_FILE_VERIFICATION select SYSTEM_TRUSTED_KEYRING ---help--- diff --git a/crypto/asymmetric_keys/verify_pefile.c b/crypto/asymmetric_keys/verify_pefile.c index d178650fd524..4473cea1e877 100644 --- a/crypto/asymmetric_keys/verify_pefile.c +++ b/crypto/asymmetric_keys/verify_pefile.c @@ -100,7 +100,7 @@ static int pefile_parse_binary(const void *pebuf, unsigned int pelen, if (!ddir->certs.virtual_address || !ddir->certs.size) { pr_debug("Unsigned PE binary\n"); - return -EKEYREJECTED; + return -ENODATA; } chkaddr(ctx->header_size, ddir->certs.virtual_address, @@ -408,6 +408,8 @@ static int pefile_digest_pe(const void *pebuf, unsigned int pelen, * (*) 0 if at least one signature chain intersects with the keys in the trust * keyring, or: * + * (*) -ENODATA if there is no signature present. + * * (*) -ENOPKG if a suitable crypto module couldn't be found for a check on a * chain. * diff --git a/include/linux/kexec.h b/include/linux/kexec.h index b9b1bc5f9669..58b27c7bdc2b 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -125,7 +125,7 @@ typedef void *(kexec_load_t)(struct kimage *image, char *kernel_buf, unsigned long cmdline_len); typedef int (kexec_cleanup_t)(void *loader_data); -#ifdef CONFIG_KEXEC_VERIFY_SIG +#ifdef CONFIG_KEXEC_SIG typedef int (kexec_verify_sig_t)(const char *kernel_buf, unsigned long kernel_len); #endif @@ -134,7 +134,7 @@ struct kexec_file_ops { kexec_probe_t *probe; kexec_load_t *load; kexec_cleanup_t *cleanup; -#ifdef CONFIG_KEXEC_VERIFY_SIG +#ifdef CONFIG_KEXEC_SIG kexec_verify_sig_t *verify_sig; #endif }; diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c index f1d0e00a3971..67f3a866eabe 100644 --- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -90,7 +90,7 @@ int __weak arch_kimage_file_post_load_cleanup(struct kimage *image) return kexec_image_post_load_cleanup_default(image); } -#ifdef CONFIG_KEXEC_VERIFY_SIG +#ifdef CONFIG_KEXEC_SIG static int kexec_image_verify_sig_default(struct kimage *image, void *buf, unsigned long buf_len) { @@ -188,7 +188,8 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd, const char __user *cmdline_ptr, unsigned long cmdline_len, unsigned flags) { - int ret = 0; + const char *reason; + int ret; void *ldata; loff_t size; @@ -207,15 +208,48 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd, if (ret) goto out; -#ifdef CONFIG_KEXEC_VERIFY_SIG +#ifdef CONFIG_KEXEC_SIG ret = arch_kexec_kernel_verify_sig(image, image->kernel_buf, image->kernel_buf_len); - if (ret) { - pr_debug("kernel signature verification failed.\n"); +#else + ret = -ENODATA; +#endif + + switch (ret) { + case 0: + break; + + /* Certain verification errors are non-fatal if we're not + * checking errors, provided we aren't mandating that there + * must be a valid signature. + */ + case -ENODATA: + reason = "kexec of unsigned image"; + goto decide; + case -ENOPKG: + reason = "kexec of image with unsupported crypto"; + goto decide; + case -ENOKEY: + reason = "kexec of image with unavailable key"; + decide: + if (IS_ENABLED(CONFIG_KEXEC_SIG_FORCE)) { + pr_notice("%s rejected\n", reason); + ret = -EKEYREJECTED; + goto out; + } + + ret = 0; + break; + + /* All other errors are fatal, including nomem, unparseable + * signatures and signature check failures - even if signatures + * aren't required. + */ + default: + pr_notice("kernel signature verification failed (%d).\n", ret); goto out; } - pr_debug("kernel signature verification successful.\n"); -#endif + /* It is possible that there no initramfs is being loaded */ if (!(flags & KEXEC_FILE_NO_INITRAMFS)) { ret = kernel_read_file_from_fd(initrd_fd, &image->initrd_buf, -- 2.21.0.392.gf8f6787159e-goog
WARNING: multiple messages have this Message-ID (diff)
From: Matthew Garrett <matthewgarrett@google.com> To: jmorris@namei.org Cc: Jiri Bohac <jbohac@suse.cz>, linux-api@vger.kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Matthew Garrett <mjg59@google.com>, dhowells@redhat.com, linux-security-module@vger.kernel.org, luto@kernel.org Subject: [PATCH V32 06/27] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE Date: Wed, 3 Apr 2019 17:32:28 -0700 [thread overview] Message-ID: <20190404003249.14356-7-matthewgarrett@google.com> (raw) In-Reply-To: <20190404003249.14356-1-matthewgarrett@google.com> From: Jiri Bohac <jbohac@suse.cz> This is a preparatory patch for kexec_file_load() lockdown. A locked down kernel needs to prevent unsigned kernel images from being loaded with kexec_file_load(). Currently, the only way to force the signature verification is compiling with KEXEC_VERIFY_SIG. This prevents loading usigned images even when the kernel is not locked down at runtime. This patch splits KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE. Analogous to the MODULE_SIG and MODULE_SIG_FORCE for modules, KEXEC_SIG turns on the signature verification but allows unsigned images to be loaded. KEXEC_SIG_FORCE disallows images without a valid signature. [Modified by David Howells such that: (1) verify_pefile_signature() differentiates between no-signature and sig-didn't-match in its returned errors. (2) kexec fails with EKEYREJECTED and logs an appropriate message if signature checking is enforced and an signature is not found, uses unsupported crypto or has no matching key. (3) kexec fails with EKEYREJECTED if there is a signature for which we have a key, but signature doesn't match - even if in non-forcing mode. (4) kexec fails with EBADMSG or some other error if there is a signature which cannot be parsed - even if in non-forcing mode. (5) kexec fails with ELIBBAD if the PE file cannot be parsed to extract the signature - even if in non-forcing mode. ] Signed-off-by: Jiri Bohac <jbohac@suse.cz> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Matthew Garrett <mjg59@google.com> Reviewed-by: Jiri Bohac <jbohac@suse.cz> cc: kexec@lists.infradead.org --- arch/x86/Kconfig | 20 ++++++++--- crypto/asymmetric_keys/verify_pefile.c | 4 ++- include/linux/kexec.h | 4 +-- kernel/kexec_file.c | 48 ++++++++++++++++++++++---- 4 files changed, 61 insertions(+), 15 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 4b4a7f32b68e..735d04a4b18f 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2016,20 +2016,30 @@ config KEXEC_FILE config ARCH_HAS_KEXEC_PURGATORY def_bool KEXEC_FILE -config KEXEC_VERIFY_SIG +config KEXEC_SIG bool "Verify kernel signature during kexec_file_load() syscall" depends on KEXEC_FILE ---help--- - This option makes kernel signature verification mandatory for - the kexec_file_load() syscall. - In addition to that option, you need to enable signature + This option makes the kexec_file_load() syscall check for a valid + signature of the kernel image. The image can still be loaded without + a valid signature unless you also enable KEXEC_SIG_FORCE, though if + there's a signature that we can check, then it must be valid. + + In addition to this option, you need to enable signature verification for the corresponding kernel image type being loaded in order for this to work. +config KEXEC_SIG_FORCE + bool "Require a valid signature in kexec_file_load() syscall" + depends on KEXEC_SIG + ---help--- + This option makes kernel signature verification mandatory for + the kexec_file_load() syscall. + config KEXEC_BZIMAGE_VERIFY_SIG bool "Enable bzImage signature verification support" - depends on KEXEC_VERIFY_SIG + depends on KEXEC_SIG depends on SIGNED_PE_FILE_VERIFICATION select SYSTEM_TRUSTED_KEYRING ---help--- diff --git a/crypto/asymmetric_keys/verify_pefile.c b/crypto/asymmetric_keys/verify_pefile.c index d178650fd524..4473cea1e877 100644 --- a/crypto/asymmetric_keys/verify_pefile.c +++ b/crypto/asymmetric_keys/verify_pefile.c @@ -100,7 +100,7 @@ static int pefile_parse_binary(const void *pebuf, unsigned int pelen, if (!ddir->certs.virtual_address || !ddir->certs.size) { pr_debug("Unsigned PE binary\n"); - return -EKEYREJECTED; + return -ENODATA; } chkaddr(ctx->header_size, ddir->certs.virtual_address, @@ -408,6 +408,8 @@ static int pefile_digest_pe(const void *pebuf, unsigned int pelen, * (*) 0 if at least one signature chain intersects with the keys in the trust * keyring, or: * + * (*) -ENODATA if there is no signature present. + * * (*) -ENOPKG if a suitable crypto module couldn't be found for a check on a * chain. * diff --git a/include/linux/kexec.h b/include/linux/kexec.h index b9b1bc5f9669..58b27c7bdc2b 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -125,7 +125,7 @@ typedef void *(kexec_load_t)(struct kimage *image, char *kernel_buf, unsigned long cmdline_len); typedef int (kexec_cleanup_t)(void *loader_data); -#ifdef CONFIG_KEXEC_VERIFY_SIG +#ifdef CONFIG_KEXEC_SIG typedef int (kexec_verify_sig_t)(const char *kernel_buf, unsigned long kernel_len); #endif @@ -134,7 +134,7 @@ struct kexec_file_ops { kexec_probe_t *probe; kexec_load_t *load; kexec_cleanup_t *cleanup; -#ifdef CONFIG_KEXEC_VERIFY_SIG +#ifdef CONFIG_KEXEC_SIG kexec_verify_sig_t *verify_sig; #endif }; diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c index f1d0e00a3971..67f3a866eabe 100644 --- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -90,7 +90,7 @@ int __weak arch_kimage_file_post_load_cleanup(struct kimage *image) return kexec_image_post_load_cleanup_default(image); } -#ifdef CONFIG_KEXEC_VERIFY_SIG +#ifdef CONFIG_KEXEC_SIG static int kexec_image_verify_sig_default(struct kimage *image, void *buf, unsigned long buf_len) { @@ -188,7 +188,8 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd, const char __user *cmdline_ptr, unsigned long cmdline_len, unsigned flags) { - int ret = 0; + const char *reason; + int ret; void *ldata; loff_t size; @@ -207,15 +208,48 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd, if (ret) goto out; -#ifdef CONFIG_KEXEC_VERIFY_SIG +#ifdef CONFIG_KEXEC_SIG ret = arch_kexec_kernel_verify_sig(image, image->kernel_buf, image->kernel_buf_len); - if (ret) { - pr_debug("kernel signature verification failed.\n"); +#else + ret = -ENODATA; +#endif + + switch (ret) { + case 0: + break; + + /* Certain verification errors are non-fatal if we're not + * checking errors, provided we aren't mandating that there + * must be a valid signature. + */ + case -ENODATA: + reason = "kexec of unsigned image"; + goto decide; + case -ENOPKG: + reason = "kexec of image with unsupported crypto"; + goto decide; + case -ENOKEY: + reason = "kexec of image with unavailable key"; + decide: + if (IS_ENABLED(CONFIG_KEXEC_SIG_FORCE)) { + pr_notice("%s rejected\n", reason); + ret = -EKEYREJECTED; + goto out; + } + + ret = 0; + break; + + /* All other errors are fatal, including nomem, unparseable + * signatures and signature check failures - even if signatures + * aren't required. + */ + default: + pr_notice("kernel signature verification failed (%d).\n", ret); goto out; } - pr_debug("kernel signature verification successful.\n"); -#endif + /* It is possible that there no initramfs is being loaded */ if (!(flags & KEXEC_FILE_NO_INITRAMFS)) { ret = kernel_read_file_from_fd(initrd_fd, &image->initrd_buf, -- 2.21.0.392.gf8f6787159e-goog _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec
next prev parent reply other threads:[~2019-04-04 0:33 UTC|newest] Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-04-04 0:32 [PATCH V32 0/27] Lockdown patches for 5.2 Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 01/27] Add the ability to lock down access to the running kernel image Matthew Garrett 2019-04-16 8:40 ` Andrew Donnellan 2019-04-16 8:40 ` Andrew Donnellan 2019-04-18 6:38 ` Daniel Axtens 2019-04-18 6:38 ` Daniel Axtens 2019-04-18 19:35 ` Matthew Garrett 2019-04-18 19:35 ` Matthew Garrett 2019-04-29 0:06 ` Daniel Axtens 2019-04-29 0:06 ` Daniel Axtens 2019-04-29 4:54 ` Daniel Axtens 2019-04-29 4:54 ` Daniel Axtens 2019-04-30 5:15 ` Andrew Donnellan 2019-04-30 5:15 ` Andrew Donnellan 2019-04-29 22:56 ` Matthew Garrett 2019-05-02 21:07 ` James Morris 2019-05-02 21:15 ` Matthew Garrett 2019-05-02 23:19 ` James Morris 2019-05-03 0:34 ` Andy Lutomirski 2019-04-04 0:32 ` [PATCH V32 02/27] Enforce module signatures if the kernel is locked down Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 03/27] Restrict /dev/{mem,kmem,port} when " Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 04/27] kexec_load: Disable at runtime if " Matthew Garrett 2019-04-04 0:32 ` Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 05/27] Copy secure_boot flag in boot params across kexec reboot Matthew Garrett 2019-04-04 0:32 ` Matthew Garrett 2019-04-04 0:32 ` Matthew Garrett 2019-04-04 0:32 ` Matthew Garrett [this message] 2019-04-04 0:32 ` [PATCH V32 06/27] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 07/27] kexec_file: Restrict at runtime if the kernel is locked down Matthew Garrett 2019-04-04 0:32 ` Matthew Garrett 2019-04-04 0:32 ` Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 08/27] hibernate: Disable when " Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 09/27] uswsusp: " Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 10/27] PCI: Lock down BAR access " Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 11/27] x86: Lock down IO port " Matthew Garrett 2019-04-04 7:49 ` Thomas Gleixner 2019-04-04 0:32 ` [PATCH V32 12/27] x86/msr: Restrict MSR " Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 13/27] ACPI: Limit access to custom_method " Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 14/27] acpi: Ignore acpi_rsdp kernel param when the kernel has been " Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 15/27] acpi: Disable ACPI table override if the kernel is " Matthew Garrett 2019-04-04 0:32 ` Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 16/27] Prohibit PCMCIA CIS storage when " Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 17/27] Lock down TIOCSSERIAL Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 18/27] Lock down module params that specify hardware parameters (eg. ioport) Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 19/27] x86/mmiotrace: Lock down the testmmiotrace module Matthew Garrett 2019-04-04 1:33 ` Steven Rostedt 2019-04-04 7:47 ` Thomas Gleixner 2019-04-04 0:32 ` [PATCH V32 20/27] Lock down /proc/kcore Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 21/27] Lock down tracing and perf kprobes when in confidentiality mode Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 22/27] bpf: Restrict bpf when kernel lockdown is " Matthew Garrett 2019-04-30 19:19 ` Jann Horn 2019-04-04 0:32 ` [PATCH V32 23/27] Lock down perf when " Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 24/27] kexec: Allow kexec_file() with appropriate IMA policy when locked down Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 25/27] lockdown: Print current->comm in restriction messages Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 26/27] debugfs: Restrict debugfs when the kernel is locked down Matthew Garrett 2019-04-04 0:32 ` [PATCH V32 27/27] tracefs: Restrict tracefs " Matthew Garrett 2019-04-04 13:39 ` Steven Rostedt 2019-04-04 20:09 ` Matthew Garrett
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