From: David Howells <dhowells@redhat.com> To: linux-security-module@vger.kernel.org Cc: dhowells@redhat.com, jforbes@redhat.com, jbohac@suse.cz, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 04/30] Enforce module signatures if the kernel is locked down Date: Thu, 22 Feb 2018 13:07:57 +0000 [thread overview] Message-ID: <30284.1519304877@warthog.procyon.org.uk> (raw) In-Reply-To: <151024866805.28329.10437019941463042267.stgit@warthog.procyon.org.uk> I'm considering folding the attached changes into this patch. It adjusts the errors generated: (1) If there's no signature (ENODATA) or we can't check it (ENOPKG, ENOKEY), then: (a) If signatures are enforced then EKEYREJECTED is returned. (b) If IMA will have validated the image, return 0 (okay). (c) If there's no signature or we can't check it, but the kernel is locked down then EPERM is returned (this is then consistent with other lockdown cases). (2) If the signature is unparseable (EBADMSG, EINVAL), the signature fails the check (EKEYREJECTED) or a system error occurs (eg. ENOMEM), we return the error we got. Note that the X.509 code doesn't check for key expiry as the RTC might not be valid or might not have been transferred to the kernel's clock yet. David --- diff --git a/kernel/module.c b/kernel/module.c index 1eb06a0ccbfb..62419cf48ef6 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -2769,8 +2769,9 @@ static inline void kmemleak_load_module(const struct module *mod, static int module_sig_check(struct load_info *info, int flags, bool can_do_ima_check) { - int err = -ENOKEY; + int err = -ENODATA; const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1; + const char *reason; const void *mod = info->hdr; /* @@ -2785,18 +2786,42 @@ static int module_sig_check(struct load_info *info, int flags, err = mod_verify_sig(mod, &info->len); } - if (!err) { + switch (err) { + case 0: info->sig_ok = true; return 0; - } - /* Not having a signature is only an error if we're strict. */ - if (err == -ENOKEY && !sig_enforce && - (!can_do_ima_check || !is_ima_appraise_enabled()) && - !kernel_is_locked_down("Loading of unsigned modules")) - err = 0; + /* We don't permit modules to be loaded into trusted kernels + * without a valid signature on them, but if we're not + * enforcing, certain errors are non-fatal. + */ + case -ENODATA: + reason = "Loading of unsigned module"; + goto decide; + case -ENOPKG: + reason = "Loading of module with unsupported crypto"; + goto decide; + case -ENOKEY: + reason = "Loading of module with unavailable key"; + decide: + if (sig_enforce) { + pr_notice("%s is rejected\n", reason); + return -EKEYREJECTED; + } - return err; + if (can_do_ima_check && is_ima_appraise_enabled()) + return 0; + if (kernel_is_locked_down(reason)) + return -EPERM; + return 0; + + /* All other errors are fatal, including nomem, unparseable + * signatures and signature check failures - even if signatures + * aren't required. + */ + default: + return err; + } } #else /* !CONFIG_MODULE_SIG */ static int module_sig_check(struct load_info *info, int flags,
WARNING: multiple messages have this Message-ID (diff)
From: dhowells@redhat.com (David Howells) To: linux-security-module@vger.kernel.org Subject: [PATCH 04/30] Enforce module signatures if the kernel is locked down Date: Thu, 22 Feb 2018 13:07:57 +0000 [thread overview] Message-ID: <30284.1519304877@warthog.procyon.org.uk> (raw) In-Reply-To: <151024866805.28329.10437019941463042267.stgit@warthog.procyon.org.uk> I'm considering folding the attached changes into this patch. It adjusts the errors generated: (1) If there's no signature (ENODATA) or we can't check it (ENOPKG, ENOKEY), then: (a) If signatures are enforced then EKEYREJECTED is returned. (b) If IMA will have validated the image, return 0 (okay). (c) If there's no signature or we can't check it, but the kernel is locked down then EPERM is returned (this is then consistent with other lockdown cases). (2) If the signature is unparseable (EBADMSG, EINVAL), the signature fails the check (EKEYREJECTED) or a system error occurs (eg. ENOMEM), we return the error we got. Note that the X.509 code doesn't check for key expiry as the RTC might not be valid or might not have been transferred to the kernel's clock yet. David --- diff --git a/kernel/module.c b/kernel/module.c index 1eb06a0ccbfb..62419cf48ef6 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -2769,8 +2769,9 @@ static inline void kmemleak_load_module(const struct module *mod, static int module_sig_check(struct load_info *info, int flags, bool can_do_ima_check) { - int err = -ENOKEY; + int err = -ENODATA; const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1; + const char *reason; const void *mod = info->hdr; /* @@ -2785,18 +2786,42 @@ static int module_sig_check(struct load_info *info, int flags, err = mod_verify_sig(mod, &info->len); } - if (!err) { + switch (err) { + case 0: info->sig_ok = true; return 0; - } - /* Not having a signature is only an error if we're strict. */ - if (err == -ENOKEY && !sig_enforce && - (!can_do_ima_check || !is_ima_appraise_enabled()) && - !kernel_is_locked_down("Loading of unsigned modules")) - err = 0; + /* We don't permit modules to be loaded into trusted kernels + * without a valid signature on them, but if we're not + * enforcing, certain errors are non-fatal. + */ + case -ENODATA: + reason = "Loading of unsigned module"; + goto decide; + case -ENOPKG: + reason = "Loading of module with unsupported crypto"; + goto decide; + case -ENOKEY: + reason = "Loading of module with unavailable key"; + decide: + if (sig_enforce) { + pr_notice("%s is rejected\n", reason); + return -EKEYREJECTED; + } - return err; + if (can_do_ima_check && is_ima_appraise_enabled()) + return 0; + if (kernel_is_locked_down(reason)) + return -EPERM; + return 0; + + /* All other errors are fatal, including nomem, unparseable + * signatures and signature check failures - even if signatures + * aren't required. + */ + default: + return err; + } } #else /* !CONFIG_MODULE_SIG */ static int module_sig_check(struct load_info *info, int flags, -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo at vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
next prev parent reply other threads:[~2018-02-22 13:08 UTC|newest] Thread overview: 130+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-11-09 17:30 [PATCH 00/30] security, efi: Add kernel lockdown David Howells 2017-11-09 17:30 ` David Howells 2017-11-09 17:30 ` [PATCH 01/30] Add the ability to lock down access to the running kernel image David Howells 2017-11-09 17:30 ` David Howells 2017-11-09 17:30 ` [PATCH 02/30] Add a SysRq option to lift kernel lockdown David Howells 2017-11-09 17:30 ` David Howells 2017-11-09 17:30 ` David Howells 2017-11-09 17:31 ` [PATCH 03/30] ima: require secure_boot rules in lockdown mode David Howells 2017-11-09 17:31 ` David Howells 2017-11-09 17:31 ` [PATCH 04/30] Enforce module signatures if the kernel is locked down David Howells 2017-11-09 17:31 ` David Howells 2017-11-09 17:31 ` David Howells 2017-11-09 17:31 ` [PATCH 05/30] Restrict /dev/{mem, kmem, port} when " David Howells 2017-11-09 17:31 ` David Howells 2017-11-09 17:31 ` [PATCH 06/30] kexec: Disable at runtime if " David Howells 2017-11-09 17:31 ` David Howells 2017-11-09 17:31 ` [PATCH 07/30] Copy secure_boot flag in boot params across kexec reboot David Howells 2017-11-09 17:31 ` David Howells 2017-11-09 17:31 ` [PATCH 08/30] kexec_file: Restrict at runtime if the kernel is locked down David Howells 2017-11-09 17:31 ` David Howells 2018-01-11 11:59 ` Jiri Bohac 2018-01-11 11:59 ` Jiri Bohac 2018-01-11 11:59 ` Jiri Bohac 2018-01-11 12:01 ` [PATCH 08a/30] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE Jiri Bohac 2018-01-11 12:01 ` Jiri Bohac 2018-01-11 12:01 ` Jiri Bohac 2018-01-11 12:02 ` [PATCH 08b/30] kexec_file: Restrict at runtime if the kernel is locked down Jiri Bohac 2018-01-11 12:02 ` Jiri Bohac 2018-01-16 16:31 ` [PATCH 08a/30] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE David Howells 2018-01-16 16:31 ` David Howells 2018-01-16 16:31 ` David Howells 2018-01-16 19:39 ` Jiri Bohac 2018-01-16 19:39 ` Jiri Bohac 2018-01-17 16:34 ` David Howells 2018-01-17 16:34 ` David Howells 2018-01-19 12:54 ` Jiri Bohac 2018-01-19 12:54 ` Jiri Bohac 2018-01-19 12:54 ` Jiri Bohac 2018-02-21 16:20 ` David Howells 2018-02-21 16:20 ` David Howells 2018-01-11 12:43 ` [PATCH 08/30] kexec_file: Restrict at runtime if the kernel is locked down David Howells 2018-01-11 12:43 ` David Howells 2018-01-11 12:43 ` David Howells 2018-01-11 12:47 ` David Howells 2018-01-11 12:47 ` David Howells 2018-01-11 15:44 ` Jiri Bohac 2018-01-11 15:44 ` Jiri Bohac 2018-01-11 15:44 ` Jiri Bohac 2018-01-17 16:16 ` David Howells 2018-01-17 16:16 ` David Howells 2018-01-17 16:16 ` David Howells 2017-11-09 17:31 ` [PATCH 09/30] hibernate: Disable when " David Howells 2017-11-09 17:31 ` David Howells 2017-11-09 17:31 ` David Howells 2017-11-09 17:31 ` [PATCH 10/30] uswsusp: " David Howells 2017-11-09 17:31 ` David Howells 2017-11-09 17:32 ` [PATCH 11/30] PCI: Lock down BAR access " David Howells 2017-11-09 17:32 ` David Howells 2017-11-09 17:32 ` [PATCH 12/30] x86: Lock down IO port " David Howells 2017-11-09 17:32 ` David Howells 2017-11-09 17:32 ` [PATCH 13/30] x86/msr: Restrict MSR " David Howells 2017-11-09 17:32 ` David Howells 2017-11-09 17:32 ` [PATCH 14/30] asus-wmi: Restrict debugfs interface " David Howells 2017-11-09 17:32 ` David Howells 2017-11-09 17:32 ` [PATCH 15/30] ACPI: Limit access to custom_method " David Howells 2017-11-09 17:32 ` David Howells 2017-11-09 17:32 ` [PATCH 16/30] acpi: Ignore acpi_rsdp kernel param when the kernel has been " David Howells 2017-11-09 17:32 ` David Howells 2017-11-09 17:32 ` [PATCH 17/30] acpi: Disable ACPI table override if the kernel is " David Howells 2017-11-09 17:32 ` David Howells 2017-11-09 17:32 ` [PATCH 18/30] acpi: Disable APEI error injection " David Howells 2017-11-09 17:32 ` David Howells 2019-11-07 8:21 ` Joey Lee 2022-05-28 0:11 ` joeyli 2017-11-09 17:33 ` [PATCH 19/30] scsi: Lock down the eata driver David Howells 2017-11-09 17:33 ` David Howells 2017-11-09 17:33 ` [PATCH 20/30] Prohibit PCMCIA CIS storage when the kernel is locked down David Howells 2017-11-09 17:33 ` David Howells 2017-11-09 17:33 ` [PATCH 21/30] Lock down TIOCSSERIAL David Howells 2017-11-09 17:33 ` David Howells 2017-11-09 17:33 ` [PATCH 22/30] Lock down module params that specify hardware parameters (eg. ioport) David Howells 2017-11-09 17:33 ` David Howells 2017-11-09 17:33 ` [PATCH 23/30] x86/mmiotrace: Lock down the testmmiotrace module David Howells 2017-11-09 17:33 ` David Howells 2017-11-09 17:33 ` [PATCH 24/30] debugfs: Disallow use of debugfs files when the kernel is locked down David Howells 2017-11-09 17:33 ` David Howells 2017-11-09 17:33 ` [PATCH 25/30] Lock down /proc/kcore David Howells 2017-11-09 17:33 ` David Howells 2017-11-09 17:33 ` [PATCH 26/30] Lock down ftrace David Howells 2017-11-09 17:33 ` David Howells 2017-11-10 9:23 ` Jiri Kosina 2017-11-10 9:23 ` Jiri Kosina 2017-11-10 9:23 ` Jiri Kosina 2017-11-10 10:07 ` David Howells 2017-11-10 10:07 ` David Howells 2017-11-10 10:07 ` David Howells 2017-11-10 10:15 ` Jiri Kosina 2017-11-10 10:15 ` Jiri Kosina 2017-11-10 10:15 ` Jiri Kosina 2017-11-10 10:21 ` David Howells 2017-11-10 10:21 ` David Howells 2017-11-10 10:21 ` David Howells 2017-11-10 10:23 ` Jiri Kosina 2017-11-10 10:23 ` Jiri Kosina 2017-11-10 11:06 ` David Howells 2017-11-10 11:06 ` David Howells 2017-11-10 11:06 ` David Howells 2017-11-09 17:34 ` [PATCH 27/30] Lock down kprobes David Howells 2017-11-09 17:34 ` David Howells 2017-11-09 17:34 ` [PATCH 28/30] bpf: Restrict kernel image access functions when the kernel is locked down David Howells 2017-11-09 17:34 ` David Howells 2017-11-09 17:34 ` [PATCH 29/30] efi: Add an EFI_SECURE_BOOT flag to indicate secure boot mode David Howells 2017-11-09 17:34 ` David Howells 2017-11-09 17:34 ` [PATCH 30/30] efi: Lock down the kernel if booted in " David Howells 2017-11-09 17:34 ` David Howells 2017-11-09 17:34 ` David Howells 2018-02-22 13:07 ` David Howells [this message] 2018-02-22 13:07 ` [PATCH 04/30] Enforce module signatures if the kernel is locked down David Howells 2018-02-22 18:44 ` Jiri Bohac 2018-02-22 18:44 ` Jiri Bohac 2018-02-22 14:20 ` [PATCH 08/30] kexec_file: Restrict at runtime " David Howells 2018-02-22 14:20 ` David Howells 2018-02-22 19:08 ` Jiri Bohac 2018-02-22 19:08 ` Jiri Bohac 2018-02-22 14:21 ` David Howells 2018-02-22 14:21 ` David Howells 2018-02-22 19:14 ` Jiri Bohac 2018-02-22 19:14 ` Jiri Bohac 2018-03-03 1:18 ` [PATCH 00/30] security, efi: Add kernel lockdown Andrew Morton 2018-03-03 1:18 ` Andrew Morton
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