From: Vivek Goyal Date: Fri, 8 Aug 2014 21:26:13 +0000 (-0700) Subject: kexec: verify the signature of signed PE bzImage X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=8e7d838103feac320baf9e68d73f954840ac1eea;p=GitHub%2FLineageOS%2FG12%2Fandroid_kernel_amlogic_linux-4.9.git kexec: verify the signature of signed PE bzImage This is the final piece of the puzzle of verifying kernel image signature during kexec_file_load() syscall. This patch calls into PE file routines to verify signature of bzImage. If signature are valid, kexec_file_load() succeeds otherwise it fails. Two new config options have been introduced. First one is CONFIG_KEXEC_VERIFY_SIG. This option enforces that kernel has to be validly signed otherwise kernel load will fail. If this option is not set, no signature verification will be done. Only exception will be when secureboot is enabled. In that case signature verification should be automatically enforced when secureboot is enabled. But that will happen when secureboot patches are merged. Second config option is CONFIG_KEXEC_BZIMAGE_VERIFY_SIG. This option enables signature verification support on bzImage. If this option is not set and previous one is set, kernel image loading will fail because kernel does not have support to verify signature of bzImage. I tested these patches with both "pesign" and "sbsign" signed bzImages. I used signing_key.priv key and signing_key.x509 cert for signing as generated during kernel build process (if module signing is enabled). Used following method to sign bzImage. pesign ====== - Convert DER format cert to PEM format cert openssl x509 -in signing_key.x509 -inform DER -out signing_key.x509.PEM -outform PEM - Generate a .p12 file from existing cert and private key file openssl pkcs12 -export -out kernel-key.p12 -inkey signing_key.priv -in signing_key.x509.PEM - Import .p12 file into pesign db pk12util -i /tmp/kernel-key.p12 -d /etc/pki/pesign - Sign bzImage pesign -i /boot/vmlinuz-3.16.0-rc3+ -o /boot/vmlinuz-3.16.0-rc3+.signed.pesign -c "Glacier signing key - Magrathea" -s sbsign ====== sbsign --key signing_key.priv --cert signing_key.x509.PEM --output /boot/vmlinuz-3.16.0-rc3+.signed.sbsign /boot/vmlinuz-3.16.0-rc3+ Patch details: Well all the hard work is done in previous patches. Now bzImage loader has just call into that code and verify whether bzImage signature are valid or not. Also create two config options. First one is CONFIG_KEXEC_VERIFY_SIG. This option enforces that kernel has to be validly signed otherwise kernel load will fail. If this option is not set, no signature verification will be done. Only exception will be when secureboot is enabled. In that case signature verification should be automatically enforced when secureboot is enabled. But that will happen when secureboot patches are merged. Second config option is CONFIG_KEXEC_BZIMAGE_VERIFY_SIG. This option enables signature verification support on bzImage. If this option is not set and previous one is set, kernel image loading will fail because kernel does not have support to verify signature of bzImage. Signed-off-by: Vivek Goyal Cc: Borislav Petkov Cc: Michael Kerrisk Cc: Yinghai Lu Cc: Eric Biederman Cc: H. Peter Anvin Cc: Matthew Garrett Cc: Greg Kroah-Hartman Cc: Dave Young Cc: WANG Chao Cc: Baoquan He Cc: Andy Lutomirski Cc: Matt Fleming Cc: David Howells Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 9558b9fcafbf..4aafd322e21e 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1599,6 +1599,28 @@ config KEXEC interface is strongly in flux, so no good recommendation can be made. +config KEXEC_VERIFY_SIG + bool "Verify kernel signature during kexec_file_load() syscall" + depends on KEXEC + ---help--- + This option makes kernel signature verification mandatory for + kexec_file_load() syscall. If kernel is signature can not be + verified, kexec_file_load() will fail. + + This option enforces signature verification at generic level. + One needs to enable signature verification for type of kernel + image being loaded to make sure it works. For example, enable + bzImage signature verification option to be able to load and + verify signatures of bzImage. Otherwise kernel loading will fail. + +config KEXEC_BZIMAGE_VERIFY_SIG + bool "Enable bzImage signature verification support" + depends on KEXEC_VERIFY_SIG + depends on SIGNED_PE_FILE_VERIFICATION + select SYSTEM_TRUSTED_KEYRING + ---help--- + Enable bzImage signature verification support. + config CRASH_DUMP bool "kernel crash dumps" depends on X86_64 || (X86_32 && HIGHMEM) diff --git a/arch/x86/kernel/kexec-bzimage64.c b/arch/x86/kernel/kexec-bzimage64.c index 623e6c58081f..9642b9b33655 100644 --- a/arch/x86/kernel/kexec-bzimage64.c +++ b/arch/x86/kernel/kexec-bzimage64.c @@ -19,6 +19,8 @@ #include #include #include +#include +#include #include #include @@ -525,8 +527,27 @@ int bzImage64_cleanup(void *loader_data) return 0; } +#ifdef CONFIG_KEXEC_BZIMAGE_VERIFY_SIG +int bzImage64_verify_sig(const char *kernel, unsigned long kernel_len) +{ + bool trusted; + int ret; + + ret = verify_pefile_signature(kernel, kernel_len, + system_trusted_keyring, &trusted); + if (ret < 0) + return ret; + if (!trusted) + return -EKEYREJECTED; + return 0; +} +#endif + struct kexec_file_ops kexec_bzImage64_ops = { .probe = bzImage64_probe, .load = bzImage64_load, .cleanup = bzImage64_cleanup, +#ifdef CONFIG_KEXEC_BZIMAGE_VERIFY_SIG + .verify_sig = bzImage64_verify_sig, +#endif }; diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c index 9330434da777..8b04018e5d1f 100644 --- a/arch/x86/kernel/machine_kexec_64.c +++ b/arch/x86/kernel/machine_kexec_64.c @@ -372,6 +372,17 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image) return image->fops->cleanup(image->image_loader_data); } +int arch_kexec_kernel_verify_sig(struct kimage *image, void *kernel, + unsigned long kernel_len) +{ + if (!image->fops || !image->fops->verify_sig) { + pr_debug("kernel loader does not support signature verification."); + return -EKEYREJECTED; + } + + return image->fops->verify_sig(kernel, kernel_len); +} + /* * Apply purgatory relocations. * diff --git a/include/linux/kexec.h b/include/linux/kexec.h index 9481703b0e7a..4b2a0e11cc5b 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -191,11 +191,14 @@ typedef void *(kexec_load_t)(struct kimage *image, char *kernel_buf, unsigned long initrd_len, char *cmdline, unsigned long cmdline_len); typedef int (kexec_cleanup_t)(void *loader_data); +typedef int (kexec_verify_sig_t)(const char *kernel_buf, + unsigned long kernel_len); struct kexec_file_ops { kexec_probe_t *probe; kexec_load_t *load; kexec_cleanup_t *cleanup; + kexec_verify_sig_t *verify_sig; }; /* kexec interface functions */ diff --git a/kernel/kexec.c b/kernel/kexec.c index f18c780f9716..0b49a0a58102 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -416,6 +416,12 @@ void __weak arch_kimage_file_post_load_cleanup(struct kimage *image) { } +int __weak arch_kexec_kernel_verify_sig(struct kimage *image, void *buf, + unsigned long buf_len) +{ + return -EKEYREJECTED; +} + /* Apply relocations of type RELA */ int __weak arch_kexec_apply_relocations_add(const Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, @@ -494,6 +500,15 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd, if (ret) goto out; +#ifdef CONFIG_KEXEC_VERIFY_SIG + ret = arch_kexec_kernel_verify_sig(image, image->kernel_buf, + image->kernel_buf_len); + if (ret) { + pr_debug("kernel signature verification failed.\n"); + 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 = copy_file_from_fd(initrd_fd, &image->initrd_buf,