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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
Subject: [PATCH 03/27] Enforce module signatures if the kernel is locked down
Date: Thu, 28 Feb 2019 15:11:39 -0800
Message-ID: <20190228231203.212359-3-matthewgarrett@google.com> (raw)
In-Reply-To: <20190228231203.212359-1-matthewgarrett@google.com>

From: David Howells <dhowells@redhat.com>

If the kernel is locked down, require that all modules have valid
signatures that we can verify or that IMA can validate the file.

I have adjusted 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.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jiri Bohac <jbohac@suse.cz>
cc: "Lee, Chun-Yi" <jlee@suse.com>
cc: James Morris <james.l.morris@oracle.com>
---
 kernel/module.c | 56 +++++++++++++++++++++++++++++++++++++------------
 1 file changed, 43 insertions(+), 13 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index 2ad1b5239910..afa5489be39f 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -64,6 +64,7 @@
 #include <linux/bsearch.h>
 #include <linux/dynamic_debug.h>
 #include <linux/audit.h>
+#include <linux/ima.h>
 #include <uapi/linux/module.h>
 #include "module-internal.h"
 
@@ -2765,10 +2766,12 @@ static inline void kmemleak_load_module(const struct module *mod,
 #endif
 
 #ifdef CONFIG_MODULE_SIG
-static int module_sig_check(struct load_info *info, int flags)
+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;
 
 	/*
@@ -2783,19 +2786,46 @@ static int module_sig_check(struct load_info *info, int flags)
 		err = mod_verify_sig(mod, info);
 	}
 
-	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 && !is_module_sig_enforced())
-		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 (is_module_sig_enforced()) {
+			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)
+static int module_sig_check(struct load_info *info, int flags,
+			    bool can_do_ima_check)
 {
 	return 0;
 }
@@ -3658,7 +3688,7 @@ static int unknown_module_param_cb(char *param, char *val, const char *modname,
 /* Allocate and load the module: note that size of section 0 is always
    zero, and we rely on this for optional sections. */
 static int load_module(struct load_info *info, const char __user *uargs,
-		       int flags)
+		       int flags, bool can_do_ima_check)
 {
 	struct module *mod;
 	long err = 0;
@@ -3677,7 +3707,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
 		goto free_copy;
 	}
 
-	err = module_sig_check(info, flags);
+	err = module_sig_check(info, flags, can_do_ima_check);
 	if (err)
 		goto free_copy;
 
@@ -3872,7 +3902,7 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
 	if (err)
 		return err;
 
-	return load_module(&info, uargs, 0);
+	return load_module(&info, uargs, 0, false);
 }
 
 SYSCALL_DEFINE3(finit_module, int, fd, const char __user *, uargs, int, flags)
@@ -3899,7 +3929,7 @@ SYSCALL_DEFINE3(finit_module, int, fd, const char __user *, uargs, int, flags)
 	info.hdr = hdr;
 	info.len = size;
 
-	return load_module(&info, uargs, flags);
+	return load_module(&info, uargs, flags, true);
 }
 
 static inline int within(unsigned long addr, void *start, unsigned long size)
-- 
2.21.0.352.gf09ad66450-goog


  parent reply index

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-28 21:28 [PULL REQUEST] Lock down patches Matthew Garrett
2019-02-28 22:20 ` Mimi Zohar
2019-02-28 23:13   ` Matthew Garrett
2019-03-01  0:05     ` Mimi Zohar
2019-03-01  1:01       ` Matthew Garrett
2019-03-01  1:44         ` Mimi Zohar
2019-03-01  3:33           ` Matthew Garrett
2019-03-01  4:16             ` Mimi Zohar
2019-02-28 22:44 ` [PATCH 01/27] Add the ability to lock down access to the running kernel image Matthew Garrett
2019-02-28 22:44   ` [PATCH 02/27] Add a SysRq option to lift kernel lockdown Matthew Garrett
2019-02-28 23:10 ` [PATCH 01/27] Add the ability to lock down access to the running kernel image Matthew Garrett
2019-02-28 23:10   ` [PATCH 02/27] Add a SysRq option to lift kernel lockdown Matthew Garrett
2019-02-28 23:11 ` [PATCH 01/27] Add the ability to lock down access to the running kernel image Matthew Garrett
2019-02-28 23:11   ` [PATCH 02/27] Add a SysRq option to lift kernel lockdown Matthew Garrett
2019-02-28 23:11 ` [PATCH 01/27] Add the ability to lock down access to the running kernel image Matthew Garrett
2019-02-28 23:11   ` [PATCH 02/27] Add a SysRq option to lift kernel lockdown Matthew Garrett
2019-02-28 23:11   ` Matthew Garrett [this message]
2019-02-28 23:11   ` [PATCH 04/27] Restrict /dev/{mem,kmem,port} when the kernel is locked down Matthew Garrett
2019-02-28 23:11   ` [PATCH 05/27] kexec_load: Disable at runtime if " Matthew Garrett
2019-02-28 23:11   ` [PATCH 06/27] Copy secure_boot flag in boot params across kexec reboot Matthew Garrett
2019-02-28 23:11   ` [PATCH 07/27] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE Matthew Garrett
2019-02-28 23:11   ` [PATCH 08/27] kexec_file: Restrict at runtime if the kernel is locked down Matthew Garrett
2019-03-01  2:05     ` Mimi Zohar
2019-02-28 23:11   ` [PATCH 09/27] hibernate: Disable when " Matthew Garrett
2019-03-19 22:15     ` Pavel Machek
2019-02-28 23:11   ` [PATCH 10/27] uswsusp: " Matthew Garrett
2019-02-28 23:11   ` [PATCH 11/27] PCI: Lock down BAR access " Matthew Garrett
2019-02-28 23:11   ` [PATCH 12/27] x86: Lock down IO port " Matthew Garrett
2019-02-28 23:11   ` [PATCH 13/27] x86/msr: Restrict MSR " Matthew Garrett
2019-02-28 23:11   ` [PATCH 14/27] ACPI: Limit access to custom_method " Matthew Garrett
2019-02-28 23:11   ` [PATCH 15/27] acpi: Ignore acpi_rsdp kernel param when the kernel has been " Matthew Garrett
2019-02-28 23:11   ` [PATCH 16/27] acpi: Disable ACPI table override if the kernel is " Matthew Garrett
2019-02-28 23:11   ` [PATCH 17/27] acpi: Disable APEI error injection " Matthew Garrett
2019-02-28 23:11   ` [PATCH 18/27] Prohibit PCMCIA CIS storage when " Matthew Garrett
2019-02-28 23:11   ` [PATCH 19/27] Lock down TIOCSSERIAL Matthew Garrett
2019-02-28 23:11   ` [PATCH 20/27] Lock down module params that specify hardware parameters (eg. ioport) Matthew Garrett
2019-02-28 23:11   ` [PATCH 21/27] x86/mmiotrace: Lock down the testmmiotrace module Matthew Garrett
2019-02-28 23:11   ` [PATCH 22/27] Lock down /proc/kcore Matthew Garrett
2019-02-28 23:11   ` [PATCH 23/27] Lock down kprobes Matthew Garrett
2019-02-28 23:12   ` [PATCH 24/27] bpf: Restrict kernel image access functions when the kernel is locked down Matthew Garrett
2019-02-28 23:12   ` [PATCH 25/27] Lock down perf Matthew Garrett
2019-02-28 23:12   ` [PATCH 26/27] debugfs: Restrict debugfs when the kernel is locked down Matthew Garrett
2019-02-28 23:12   ` [PATCH 27/27] lockdown: Print current->comm in restriction messages Matthew Garrett
2019-02-28 23:24 ` [PULL REQUEST] Lock down patches Randy Dunlap
2019-03-04 22:10 ` Matthew Garrett
  -- strict thread matches above, loose matches on Subject: below --
2019-03-06 23:58 [PULL REQUEST] Kernel lockdown patches for 5.2 Matthew Garrett
2019-03-06 23:58 ` [PATCH 03/27] Enforce module signatures if the kernel is locked down Matthew Garrett
2019-03-08 23:00   ` James Morris
2019-03-08 23:30     ` Matthew Garrett
2019-03-09  4:45       ` James Morris
2017-10-19 14:50 [PATCH 00/27] security, efi: Add kernel lockdown David Howells
2017-10-19 14:50 ` [PATCH 03/27] Enforce module signatures if the kernel is locked down David Howells
2017-10-20  6:33   ` joeyli
2017-10-20 23:21   ` James Morris
2017-10-27 18:48   ` Mimi Zohar
2017-10-30 17:00   ` David Howells
2017-10-30 17:52     ` Mimi Zohar
2017-11-02 17:22   ` David Howells
2017-11-02 19:13     ` Mimi Zohar
2017-11-02 21:30     ` David Howells
2017-11-02 21:41       ` Mimi Zohar
2017-11-02 22:01       ` David Howells
2017-11-02 22:18         ` Mimi Zohar

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