7 files changed, 157 insertions, 1 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index ad7e2e5088c1..9b2b8d3ae3e0 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1582,6 +1582,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         log everything. Information is printed at KERN_DEBUG
                         so loglevel=8 may also need to be specified.
 
+        module.sig_enforce
+                        [KNL] When CONFIG_MODULE_SIG is set, this means that
+                        modules without (valid) signatures will fail to load.
+                        Note that if CONFIG_MODULE_SIG_ENFORCE is set, that
+                        is always true, so this option does nothing.
+
         mousedev.tap_time=
                         [MOUSE] Maximum time between finger touching and
                         leaving touchpad surface for touch to be considered
diff --git a/include/linux/module.h b/include/linux/module.h
index fbcafe2ee13e..7760c6d344a3 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -21,6 +21,9 @@
 #include <linux/percpu.h>
 #include <asm/module.h>
 
+/* In stripped ARM and x86-64 modules, ~ is surprisingly rare. */
+#define MODULE_SIG_STRING "~Module signature appended~\n"
+
 /* Not Yet Implemented */
 #define MODULE_SUPPORTED_DEVICE(name)
 
@@ -260,6 +263,11 @@ struct module
         const unsigned long *unused_gpl_crcs;
 #endif
 
+#ifdef CONFIG_MODULE_SIG
+        /* Signature was verified. */
+        bool sig_ok;
+#endif
+
         /* symbols that will be GPL-only in the near future. */
         const struct kernel_symbol *gpl_future_syms;
         const unsigned long *gpl_future_crcs;
diff --git a/init/Kconfig b/init/Kconfig
index 66cc885abbc6..fa8ccad1ea43 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1585,6 +1585,20 @@ config MODULE_SRCVERSION_ALL
           the version).  With this option, such a "srcversion" field
           will be created for all modules.  If unsure, say N.
 
+config MODULE_SIG
+        bool "Module signature verification"
+        depends on MODULES
+        help
+          Check modules for valid signatures upon load: the signature
+          is simply appended to the module. For more information see
+          Documentation/module-signing.txt.
+
+config MODULE_SIG_FORCE
+        bool "Require modules to be validly signed"
+        depends on MODULE_SIG
+        help
+          Reject unsigned modules or signed modules for which we don't have a
+          key.  Without this, such modules will simply taint the kernel.
 endif # MODULES
 
 config INIT_ALL_POSSIBLE
diff --git a/kernel/Makefile b/kernel/Makefile
index c0cc67ad764c..08ba8a6abd1c 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -55,6 +55,7 @@ obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock.o
 obj-$(CONFIG_PROVE_LOCKING) += spinlock.o
 obj-$(CONFIG_UID16) += uid16.o
 obj-$(CONFIG_MODULES) += module.o
+obj-$(CONFIG_MODULE_SIG) += module_signing.o
 obj-$(CONFIG_KALLSYMS) += kallsyms.o
 obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
 obj-$(CONFIG_KEXEC) += kexec.o
diff --git a/kernel/module-internal.h b/kernel/module-internal.h
new file mode 100644
index 000000000000..033c17fd70ef
--- /dev/null
+++ b/kernel/module-internal.h
@@ -0,0 +1,13 @@
+/* Module internals
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+extern int mod_verify_sig(const void *mod, unsigned long modlen,
+                          const void *sig, unsigned long siglen);
diff --git a/kernel/module.c b/kernel/module.c
index 74bc19562ca3..68c564edb2c1 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -58,6 +58,7 @@
 #include <linux/jump_label.h>
 #include <linux/pfn.h>
 #include <linux/bsearch.h>
+#include "module-internal.h"
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/module.h>
@@ -102,6 +103,43 @@ static LIST_HEAD(modules);
 struct list_head *kdb_modules = &modules; /* kdb needs the list of modules */
 #endif /* CONFIG_KGDB_KDB */
 
+#ifdef CONFIG_MODULE_SIG
+#ifdef CONFIG_MODULE_SIG_FORCE
+static bool sig_enforce = true;
+#else
+static bool sig_enforce = false;
+
+static int param_set_bool_enable_only(const char *val,
+                                      const struct kernel_param *kp)
+{
+        int err;
+        bool test;
+        struct kernel_param dummy_kp = *kp;
+
+        dummy_kp.arg = &test;
+
+        err = param_set_bool(val, &dummy_kp);
+        if (err)
+                return err;
+
+        /* Don't let them unset it once it's set! */
+        if (!test && sig_enforce)
+                return -EROFS;
+
+        if (test)
+                sig_enforce = true;
+        return 0;
+}
+
+static const struct kernel_param_ops param_ops_bool_enable_only = {
+        .set = param_set_bool_enable_only,
+        .get = param_get_bool,
+};
+#define param_check_bool_enable_only param_check_bool
+
+module_param(sig_enforce, bool_enable_only, 0644);
+#endif /* !CONFIG_MODULE_SIG_FORCE */
+#endif /* CONFIG_MODULE_SIG */
 
 /* Block module loading/unloading? */
 int modules_disabled = 0;
@@ -136,6 +174,7 @@ struct load_info {
         unsigned long symoffs, stroffs;
         struct _ddebug *debug;
         unsigned int num_debug;
+        bool sig_ok;
         struct {
                 unsigned int sym, str, mod, vers, info, pcpu;
         } index;
@@ -2379,7 +2418,49 @@ static inline void kmemleak_load_module(const struct module *mod,
 }
 #endif
 
-/* Sets info->hdr and info->len. */
+#ifdef CONFIG_MODULE_SIG
+static int module_sig_check(struct load_info *info,
+                            const void *mod, unsigned long *len)
+{
+        int err = -ENOKEY;
+        const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1;
+        const void *p = mod, *end = mod + *len;
+
+        /* Poor man's memmem. */
+        while ((p = memchr(p, MODULE_SIG_STRING[0], end - p))) {
+                if (p + markerlen > end)
+                        break;
+
+                if (memcmp(p, MODULE_SIG_STRING, markerlen) == 0) {
+                        const void *sig = p + markerlen;
+                        /* Truncate module up to signature. */
+                        *len = p - mod;
+                        err = mod_verify_sig(mod, *len, sig, end - sig);
+                        break;
+                }
+                p++;
+        }
+
+        if (!err) {
+                info->sig_ok = true;
+                return 0;
+        }
+
+        /* Not having a signature is only an error if we're strict. */
+        if (err == -ENOKEY && !sig_enforce)
+                err = 0;
+
+        return err;
+}
+#else /* !CONFIG_MODULE_SIG */
+static int module_sig_check(struct load_info *info,
+                            void *mod, unsigned long *len)
+{
+        return 0;
+}
+#endif /* !CONFIG_MODULE_SIG */
+
+/* Sets info->hdr, info->len and info->sig_ok. */
 static int copy_and_check(struct load_info *info,
                           const void __user *umod, unsigned long len,
                           const char __user *uargs)
@@ -2399,6 +2480,10 @@ static int copy_and_check(struct load_info *info,
                 goto free_hdr;
         }
 
+        err = module_sig_check(info, hdr, &len);
+        if (err)
+                goto free_hdr;
+
         /* Sanity checks against insmoding binaries or wrong arch,
            weird elf version */
         if (memcmp(hdr->e_ident, ELFMAG, SELFMAG) != 0
@@ -2884,6 +2969,12 @@ static struct module *load_module(void __user *umod,
                 goto free_copy;
         }
 
+#ifdef CONFIG_MODULE_SIG
+        mod->sig_ok = info.sig_ok;
+        if (!mod->sig_ok)
+                add_taint_module(mod, TAINT_FORCED_MODULE);
+#endif
+
         /* Now module is in final location, initialize linked lists, etc. */
         err = module_unload_init(mod);
         if (err)
diff --git a/kernel/module_signing.c b/kernel/module_signing.c
new file mode 100644
index 000000000000..499728aecafb
--- /dev/null
+++ b/kernel/module_signing.c
@@ -0,0 +1,23 @@
+/* Module signature checker
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/kernel.h>
+#include <linux/err.h>
+#include "module-internal.h"
+
+/*
+ * Verify the signature on a module.
+ */
+int mod_verify_sig(const void *mod, unsigned long modlen,
+                   const void *sig, unsigned long siglen)
+{
+        return -ENOKEY;
+}