OK, I took a look at the module.c parts of David and Dmitry's patchsets,
and didn't really like either, but I stole parts of David's to make
this.
So, here's the module.c part of module signing. I hope you two got time
to discuss the signature format details? Mimi suggested a scheme where
the private key would never be saved on disk (even temporarily), but I
didn't see patches. Frankly it's something we can do later; let's aim
at getting the format right for the next merge window.
Cheers,
Rusty.
---
This patch doesn't compile: we need to implement:
int mod_verify_sig(const void *mod, unsigned long modlen,
const void *sig, unsigned long siglen,
bool *sig_ok);
Also, we need to actually append the signatures during build.
diff --git a/Documentation/kernel-parameters.txt
b/Documentation/kernel-parameters.txt
index ad7e2e5..9b2b8d3 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 fbcafe2..7760c6d 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 af6c7f8..7452e19 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/module.c b/kernel/module.c
index 4edbd9c..3cbd1a4 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -102,6 +102,43 @@ 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_ENFORCE
+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_ENFORCE */
+#endif /* CONFIG_MODULE_SIG */
/* Block module loading/unloading? */
int modules_disabled = 0;
@@ -136,6 +173,7 @@ 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;
@@ -2399,7 +2437,50 @@ 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,
+ void *mod, unsigned long *len)
+{
+ int err;
+ unsigned long i, siglen;
+ char *sig = NULL;
+
+ /* This is not a valid module: ELF header is larger anyway. */
+ if (*len < sizeof(MODULE_SIG_STRING))
+ return -ENOEXEC;
+
+ for (i = 0; i < *len - (sizeof(MODULE_SIG_STRING)-1); i++) {
+ /* Our memcmp is dumb, speed it up a little. */
+ if (((char *)mod)[i] != MODULE_SIG_STRING[0])
+ continue;
+ if (memcmp(mod, MODULE_SIG_STRING, strlen(MODULE_SIG_STRING)))
+ continue;
+
+ sig = mod + i + strlen(MODULE_SIG_STRING);
+ siglen = *len - i - strlen(MODULE_SIG_STRING);
+ *len = i;
+ break;
+ }
+
+ if (!sig)
+ err = 0;
+ else
+ err = mod_verify_sig(mod, len, sig, siglen, &info->sig_ok);
+
+ /* Not having a signature is only an error if we're strict. */
+ if (!err && !info->sig_ok && sig_enforce)
+ err = -EKEYREJECTED;
+ 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)
@@ -2419,6 +2500,10 @@ 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
@@ -2886,6 +2971,12 @@ 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)
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
