Merge branch 'modules-next' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux

Pull module signing support from Rusty Russell:
 "module signing is the highlight, but it's an all-over David Howells frenzy..."

Hmm "Magrathea: Glacier signing key". Somebody has been reading too much HHGTTG.

* 'modules-next' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux: (37 commits)
  X.509: Fix indefinite length element skip error handling
  X.509: Convert some printk calls to pr_devel
  asymmetric keys: fix printk format warning
  MODSIGN: Fix 32-bit overflow in X.509 certificate validity date checking
  MODSIGN: Make mrproper should remove generated files.
  MODSIGN: Use utf8 strings in signer's name in autogenerated X.509 certs
  MODSIGN: Use the same digest for the autogen key sig as for the module sig
  MODSIGN: Sign modules during the build process
  MODSIGN: Provide a script for generating a key ID from an X.509 cert
  MODSIGN: Implement module signature checking
  MODSIGN: Provide module signing public keys to the kernel
  MODSIGN: Automatically generate module signing keys if missing
  MODSIGN: Provide Kconfig options
  MODSIGN: Provide gitignore and make clean rules for extra files
  MODSIGN: Add FIPS policy
  module: signature checking hook
  X.509: Add a crypto key parser for binary (DER) X.509 certificates
  MPILIB: Provide a function to read raw data into an MPI
  X.509: Add an ASN.1 decoder
  X.509: Add simple ASN.1 grammar compiler
  ...

5 files changed, 578 insertions, 27 deletions

diff --git a/kernel/Makefile b/kernel/Makefile
index 5404911eaee..0dfeca4324e 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -54,6 +54,7 @@ obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock.o
 obj-$(CONFIG_PROVE_LOCKING) += spinlock.o
 obj-$(CONFIG_UID16) += uid16.o
 obj-$(CONFIG_MODULES) += module.o
+obj-$(CONFIG_MODULE_SIG) += module_signing.o modsign_pubkey.o
 obj-$(CONFIG_KALLSYMS) += kallsyms.o
 obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
 obj-$(CONFIG_KEXEC) += kexec.o
@@ -130,3 +131,79 @@ quiet_cmd_timeconst  = TIMEC   $@
 targets += timeconst.h
 $(obj)/timeconst.h: $(src)/timeconst.pl FORCE
 	$(call if_changed,timeconst)
+
+ifeq ($(CONFIG_MODULE_SIG),y)
+#
+# Pull the signing certificate and any extra certificates into the kernel
+#
+extra_certificates:
+	touch $@
+
+kernel/modsign_pubkey.o: signing_key.x509 extra_certificates
+
+###############################################################################
+#
+# If module signing is requested, say by allyesconfig, but a key has not been
+# supplied, then one will need to be generated to make sure the build does not
+# fail and that the kernel may be used afterwards.
+#
+###############################################################################
+sign_key_with_hash :=
+ifeq ($(CONFIG_MODULE_SIG_SHA1),y)
+sign_key_with_hash := -sha1
+endif
+ifeq ($(CONFIG_MODULE_SIG_SHA224),y)
+sign_key_with_hash := -sha224
+endif
+ifeq ($(CONFIG_MODULE_SIG_SHA256),y)
+sign_key_with_hash := -sha256
+endif
+ifeq ($(CONFIG_MODULE_SIG_SHA384),y)
+sign_key_with_hash := -sha384
+endif
+ifeq ($(CONFIG_MODULE_SIG_SHA512),y)
+sign_key_with_hash := -sha512
+endif
+ifeq ($(sign_key_with_hash),)
+$(error Could not determine digest type to use from kernel config)
+endif
+
+signing_key.priv signing_key.x509: x509.genkey
+	@echo "###"
+	@echo "### Now generating an X.509 key pair to be used for signing modules."
+	@echo "###"
+	@echo "### If this takes a long time, you might wish to run rngd in the"
+	@echo "### background to keep the supply of entropy topped up.  It"
+	@echo "### needs to be run as root, and should use a hardware random"
+	@echo "### number generator if one is available, eg:"
+	@echo "###"
+	@echo "###     rngd -r /dev/hwrandom"
+	@echo "###"
+	openssl req -new -nodes -utf8 $(sign_key_with_hash) -days 36500 -batch \
+		-x509 -config x509.genkey \
+		-outform DER -out signing_key.x509 \
+		-keyout signing_key.priv
+	@echo "###"
+	@echo "### Key pair generated."
+	@echo "###"
+
+x509.genkey:
+	@echo Generating X.509 key generation config
+	@echo  >x509.genkey "[ req ]"
+	@echo >>x509.genkey "default_bits = 4096"
+	@echo >>x509.genkey "distinguished_name = req_distinguished_name"
+	@echo >>x509.genkey "prompt = no"
+	@echo >>x509.genkey "string_mask = utf8only"
+	@echo >>x509.genkey "x509_extensions = myexts"
+	@echo >>x509.genkey
+	@echo >>x509.genkey "[ req_distinguished_name ]"
+	@echo >>x509.genkey "O = Magrathea"
+	@echo >>x509.genkey "CN = Glacier signing key"
+	@echo >>x509.genkey "emailAddress = slartibartfast@magrathea.h2g2"
+	@echo >>x509.genkey
+	@echo >>x509.genkey "[ myexts ]"
+	@echo >>x509.genkey "basicConstraints=critical,CA:FALSE"
+	@echo >>x509.genkey "keyUsage=digitalSignature"
+	@echo >>x509.genkey "subjectKeyIdentifier=hash"
+	@echo >>x509.genkey "authorityKeyIdentifier=keyid"
+endif
diff --git a/kernel/modsign_pubkey.c b/kernel/modsign_pubkey.c
new file mode 100644
index 00000000000..4646eb2c382
--- /dev/null
+++ b/kernel/modsign_pubkey.c
@@ -0,0 +1,113 @@
+/* Public keys for module signature verification
+ *
+ * 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/sched.h>
+#include <linux/cred.h>
+#include <linux/err.h>
+#include <keys/asymmetric-type.h>
+#include "module-internal.h"
+
+struct key *modsign_keyring;
+
+extern __initdata const u8 modsign_certificate_list[];
+extern __initdata const u8 modsign_certificate_list_end[];
+asm(".section .init.data,\"aw\"\n"
+    "modsign_certificate_list:\n"
+    ".incbin \"signing_key.x509\"\n"
+    ".incbin \"extra_certificates\"\n"
+    "modsign_certificate_list_end:"
+    );
+
+/*
+ * We need to make sure ccache doesn't cache the .o file as it doesn't notice
+ * if modsign.pub changes.
+ */
+static __initdata const char annoy_ccache[] = __TIME__ "foo";
+
+/*
+ * Load the compiled-in keys
+ */
+static __init int module_verify_init(void)
+{
+	pr_notice("Initialise module verification\n");
+
+	modsign_keyring = key_alloc(&key_type_keyring, ".module_sign",
+				    KUIDT_INIT(0), KGIDT_INIT(0),
+				    current_cred(),
+				    (KEY_POS_ALL & ~KEY_POS_SETATTR) |
+				    KEY_USR_VIEW | KEY_USR_READ,
+				    KEY_ALLOC_NOT_IN_QUOTA);
+	if (IS_ERR(modsign_keyring))
+		panic("Can't allocate module signing keyring\n");
+
+	if (key_instantiate_and_link(modsign_keyring, NULL, 0, NULL, NULL) < 0)
+		panic("Can't instantiate module signing keyring\n");
+
+	return 0;
+}
+
+/*
+ * Must be initialised before we try and load the keys into the keyring.
+ */
+device_initcall(module_verify_init);
+
+/*
+ * Load the compiled-in keys
+ */
+static __init int load_module_signing_keys(void)
+{
+	key_ref_t key;
+	const u8 *p, *end;
+	size_t plen;
+
+	pr_notice("Loading module verification certificates\n");
+
+	end = modsign_certificate_list_end;
+	p = modsign_certificate_list;
+	while (p < end) {
+		/* Each cert begins with an ASN.1 SEQUENCE tag and must be more
+		 * than 256 bytes in size.
+		 */
+		if (end - p < 4)
+			goto dodgy_cert;
+		if (p[0] != 0x30 &&
+		    p[1] != 0x82)
+			goto dodgy_cert;
+		plen = (p[2] << 8) | p[3];
+		plen += 4;
+		if (plen > end - p)
+			goto dodgy_cert;
+
+		key = key_create_or_update(make_key_ref(modsign_keyring, 1),
+					   "asymmetric",
+					   NULL,
+					   p,
+					   plen,
+					   (KEY_POS_ALL & ~KEY_POS_SETATTR) |
+					   KEY_USR_VIEW,
+					   KEY_ALLOC_NOT_IN_QUOTA);
+		if (IS_ERR(key))
+			pr_err("MODSIGN: Problem loading in-kernel X.509 certificate (%ld)\n",
+			       PTR_ERR(key));
+		else
+			pr_notice("MODSIGN: Loaded cert '%s'\n",
+				  key_ref_to_ptr(key)->description);
+		p += plen;
+	}
+
+	return 0;
+
+dodgy_cert:
+	pr_err("MODSIGN: Problem parsing in-kernel X.509 certificate list\n");
+	return 0;
+}
+late_initcall(load_module_signing_keys);
diff --git a/kernel/module-internal.h b/kernel/module-internal.h
new file mode 100644
index 00000000000..6114a13419b
--- /dev/null
+++ b/kernel/module-internal.h
@@ -0,0 +1,15 @@
+/* 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 struct key *modsign_keyring;
+
+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 4edbd9c11ac..0e2da8695f8 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -58,6 +58,8 @@
 #include <linux/jump_label.h>
 #include <linux/pfn.h>
 #include <linux/bsearch.h>
+#include <linux/fips.h>
+#include "module-internal.h"
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/module.h>
@@ -102,6 +104,43 @@ 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 +175,7 @@ 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;
@@ -1949,26 +1989,6 @@ static int simplify_symbols(struct module *mod, const struct load_info *info)
 	return ret;
 }
 
-int __weak apply_relocate(Elf_Shdr *sechdrs,
-			  const char *strtab,
-			  unsigned int symindex,
-			  unsigned int relsec,
-			  struct module *me)
-{
-	pr_err("module %s: REL relocation unsupported\n", me->name);
-	return -ENOEXEC;
-}
-
-int __weak apply_relocate_add(Elf_Shdr *sechdrs,
-			      const char *strtab,
-			      unsigned int symindex,
-			      unsigned int relsec,
-			      struct module *me)
-{
-	pr_err("module %s: RELA relocation unsupported\n", me->name);
-	return -ENOEXEC;
-}
-
 static int apply_relocations(struct module *mod, const struct load_info *info)
 {
 	unsigned int i;
@@ -2399,7 +2419,52 @@ 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 < 0 && fips_enabled)
+		panic("Module verification failed with error %d in FIPS mode\n",
+		      err);
+	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)
@@ -2419,6 +2484,10 @@ 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
@@ -2730,6 +2799,10 @@ static int check_module_license_and_versions(struct module *mod)
 	if (strcmp(mod->name, "driverloader") == 0)
 		add_taint_module(mod, TAINT_PROPRIETARY_MODULE);
 
+	/* lve claims to be GPL but upstream won't provide source */
+	if (strcmp(mod->name, "lve") == 0)
+		add_taint_module(mod, TAINT_PROPRIETARY_MODULE);
+
 #ifdef CONFIG_MODVERSIONS
 	if ((mod->num_syms && !mod->crcs)
 	    || (mod->num_gpl_syms && !mod->gpl_crcs)
@@ -2861,6 +2934,20 @@ static int post_relocation(struct module *mod, const struct load_info *info)
 	return module_finalize(info->hdr, info->sechdrs, mod);
 }
 
+/* Is this module of this name done loading?  No locks held. */
+static bool finished_loading(const char *name)
+{
+	struct module *mod;
+	bool ret;
+
+	mutex_lock(&module_mutex);
+	mod = find_module(name);
+	ret = !mod || mod->state != MODULE_STATE_COMING;
+	mutex_unlock(&module_mutex);
+
+	return ret;
+}
+
 /* Allocate and load the module: note that size of section 0 is always
    zero, and we rely on this for optional sections. */
 static struct module *load_module(void __user *umod,
@@ -2868,7 +2955,7 @@ static struct module *load_module(void __user *umod,
 				  const char __user *uargs)
 {
 	struct load_info info = { NULL, };
-	struct module *mod;
+	struct module *mod, *old;
 	long err;
 
 	pr_debug("load_module: umod=%p, len=%lu, uargs=%p\n",
@@ -2886,6 +2973,12 @@ 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)
@@ -2934,8 +3027,18 @@ static struct module *load_module(void __user *umod,
 	 * function to insert in a way safe to concurrent readers.
 	 * The mutex protects against concurrent writers.
 	 */
+again:
 	mutex_lock(&module_mutex);
-	if (find_module(mod->name)) {
+	if ((old = find_module(mod->name)) != NULL) {
+		if (old->state == MODULE_STATE_COMING) {
+			/* Wait in case it fails to load. */
+			mutex_unlock(&module_mutex);
+			err = wait_event_interruptible(module_wq,
+					       finished_loading(mod->name));
+			if (err)
+				goto free_arch_cleanup;
+			goto again;
+		}
 		err = -EEXIST;
 		goto unlock;
 	}
@@ -2975,7 +3078,7 @@ static struct module *load_module(void __user *umod,
 	/* Unlink carefully: kallsyms could be walking list. */
 	list_del_rcu(&mod->list);
 	module_bug_cleanup(mod);
-
+	wake_up_all(&module_wq);
  ddebug:
 	dynamic_debug_remove(info.debug);
  unlock:
@@ -3050,7 +3153,7 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
 		blocking_notifier_call_chain(&module_notify_list,
 					     MODULE_STATE_GOING, mod);
 		free_module(mod);
-		wake_up(&module_wq);
+		wake_up_all(&module_wq);
 		return ret;
 	}
 	if (ret > 0) {
@@ -3062,9 +3165,8 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
 		dump_stack();
 	}
 
-	/* Now it's a first class citizen!  Wake up anyone waiting for it. */
+	/* Now it's a first class citizen! */
 	mod->state = MODULE_STATE_LIVE;
-	wake_up(&module_wq);
 	blocking_notifier_call_chain(&module_notify_list,
 				     MODULE_STATE_LIVE, mod);
 
@@ -3087,6 +3189,7 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
 	mod->init_ro_size = 0;
 	mod->init_text_size = 0;
 	mutex_unlock(&module_mutex);
+	wake_up_all(&module_wq);
 
 	return 0;
 }
diff --git a/kernel/module_signing.c b/kernel/module_signing.c
new file mode 100644
index 00000000000..6b09f6983ac
--- /dev/null
+++ b/kernel/module_signing.c
@@ -0,0 +1,243 @@
+/* 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 <crypto/public_key.h>
+#include <crypto/hash.h>
+#include <keys/asymmetric-type.h>
+#include "module-internal.h"
+
+/*
+ * Module signature information block.
+ *
+ * The constituents of the signature section are, in order:
+ *
+ *	- Signer's name
+ *	- Key identifier
+ *	- Signature data
+ *	- Information block
+ */
+struct module_signature {
+	enum pkey_algo		algo : 8;	/* Public-key crypto algorithm */
+	enum pkey_hash_algo	hash : 8;	/* Digest algorithm */
+	enum pkey_id_type	id_type : 8;	/* Key identifier type */
+	u8			signer_len;	/* Length of signer's name */
+	u8			key_id_len;	/* Length of key identifier */
+	u8			__pad[3];
+	__be32			sig_len;	/* Length of signature data */
+};
+
+/*
+ * Digest the module contents.
+ */
+static struct public_key_signature *mod_make_digest(enum pkey_hash_algo hash,
+						    const void *mod,
+						    unsigned long modlen)
+{
+	struct public_key_signature *pks;
+	struct crypto_shash *tfm;
+	struct shash_desc *desc;
+	size_t digest_size, desc_size;
+	int ret;
+
+	pr_devel("==>%s()\n", __func__);
+	
+	/* Allocate the hashing algorithm we're going to need and find out how
+	 * big the hash operational data will be.
+	 */
+	tfm = crypto_alloc_shash(pkey_hash_algo[hash], 0, 0);
+	if (IS_ERR(tfm))
+		return (PTR_ERR(tfm) == -ENOENT) ? ERR_PTR(-ENOPKG) : ERR_CAST(tfm);
+
+	desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
+	digest_size = crypto_shash_digestsize(tfm);
+
+	/* We allocate the hash operational data storage on the end of our
+	 * context data and the digest output buffer on the end of that.
+	 */
+	ret = -ENOMEM;
+	pks = kzalloc(digest_size + sizeof(*pks) + desc_size, GFP_KERNEL);
+	if (!pks)
+		goto error_no_pks;
+
+	pks->pkey_hash_algo	= hash;
+	pks->digest		= (u8 *)pks + sizeof(*pks) + desc_size;
+	pks->digest_size	= digest_size;
+
+	desc = (void *)pks + sizeof(*pks);
+	desc->tfm   = tfm;
+	desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
+
+	ret = crypto_shash_init(desc);
+	if (ret < 0)
+		goto error;
+
+	ret = crypto_shash_finup(desc, mod, modlen, pks->digest);
+	if (ret < 0)
+		goto error;
+
+	crypto_free_shash(tfm);
+	pr_devel("<==%s() = ok\n", __func__);
+	return pks;
+
+error:
+	kfree(pks);
+error_no_pks:
+	crypto_free_shash(tfm);
+	pr_devel("<==%s() = %d\n", __func__, ret);
+	return ERR_PTR(ret);
+}
+
+/*
+ * Extract an MPI array from the signature data.  This represents the actual
+ * signature.  Each raw MPI is prefaced by a BE 2-byte value indicating the
+ * size of the MPI in bytes.
+ *
+ * RSA signatures only have one MPI, so currently we only read one.
+ */
+static int mod_extract_mpi_array(struct public_key_signature *pks,
+				 const void *data, size_t len)
+{
+	size_t nbytes;
+	MPI mpi;
+
+	if (len < 3)
+		return -EBADMSG;
+	nbytes = ((const u8 *)data)[0] << 8 | ((const u8 *)data)[1];
+	data += 2;
+	len -= 2;
+	if (len != nbytes)
+		return -EBADMSG;
+
+	mpi = mpi_read_raw_data(data, nbytes);
+	if (!mpi)
+		return -ENOMEM;
+	pks->mpi[0] = mpi;
+	pks->nr_mpi = 1;
+	return 0;
+}
+
+/*
+ * Request an asymmetric key.
+ */
+static struct key *request_asymmetric_key(const char *signer, size_t signer_len,
+					  const u8 *key_id, size_t key_id_len)
+{
+	key_ref_t key;
+	size_t i;
+	char *id, *q;
+
+	pr_devel("==>%s(,%zu,,%zu)\n", __func__, signer_len, key_id_len);
+
+	/* Construct an identifier. */
+	id = kmalloc(signer_len + 2 + key_id_len * 2 + 1, GFP_KERNEL);
+	if (!id)
+		return ERR_PTR(-ENOKEY);
+
+	memcpy(id, signer, signer_len);
+
+	q = id + signer_len;
+	*q++ = ':';
+	*q++ = ' ';
+	for (i = 0; i < key_id_len; i++) {
+		*q++ = hex_asc[*key_id >> 4];
+		*q++ = hex_asc[*key_id++ & 0x0f];
+	}
+
+	*q = 0;
+
+	pr_debug("Look up: \"%s\"\n", id);
+
+	key = keyring_search(make_key_ref(modsign_keyring, 1),
+			     &key_type_asymmetric, id);
+	if (IS_ERR(key))
+		pr_warn("Request for unknown module key '%s' err %ld\n",
+			id, PTR_ERR(key));
+	kfree(id);
+
+	if (IS_ERR(key)) {
+		switch (PTR_ERR(key)) {
+			/* Hide some search errors */
+		case -EACCES:
+		case -ENOTDIR:
+		case -EAGAIN:
+			return ERR_PTR(-ENOKEY);
+		default:
+			return ERR_CAST(key);
+		}
+	}
+
+	pr_devel("<==%s() = 0 [%x]\n", __func__, key_serial(key_ref_to_ptr(key)));
+	return key_ref_to_ptr(key);
+}
+
+/*
+ * Verify the signature on a module.
+ */
+int mod_verify_sig(const void *mod, unsigned long modlen,
+		   const void *sig, unsigned long siglen)
+{
+	struct public_key_signature *pks;
+	struct module_signature ms;
+	struct key *key;
+	size_t sig_len;
+	int ret;
+
+	pr_devel("==>%s(,%lu,,%lu,)\n", __func__, modlen, siglen);
+
+	if (siglen <= sizeof(ms))
+		return -EBADMSG;
+
+	memcpy(&ms, sig + (siglen - sizeof(ms)), sizeof(ms));
+	siglen -= sizeof(ms);
+
+	sig_len = be32_to_cpu(ms.sig_len);
+	if (sig_len >= siglen ||
+	    siglen - sig_len != (size_t)ms.signer_len + ms.key_id_len)
+		return -EBADMSG;
+
+	/* For the moment, only support RSA and X.509 identifiers */
+	if (ms.algo != PKEY_ALGO_RSA ||
+	    ms.id_type != PKEY_ID_X509)
+		return -ENOPKG;
+
+	if (ms.hash >= PKEY_HASH__LAST ||
+	    !pkey_hash_algo[ms.hash])
+		return -ENOPKG;
+
+	key = request_asymmetric_key(sig, ms.signer_len,
+				     sig + ms.signer_len, ms.key_id_len);
+	if (IS_ERR(key))
+		return PTR_ERR(key);
+
+	pks = mod_make_digest(ms.hash, mod, modlen);
+	if (IS_ERR(pks)) {
+		ret = PTR_ERR(pks);
+		goto error_put_key;
+	}
+
+	ret = mod_extract_mpi_array(pks, sig + ms.signer_len + ms.key_id_len,
+				    sig_len);
+	if (ret < 0)
+		goto error_free_pks;
+
+	ret = verify_signature(key, pks);
+	pr_devel("verify_signature() = %d\n", ret);
+
+error_free_pks:
+	mpi_free(pks->rsa.s);
+	kfree(pks);
+error_put_key:
+	key_put(key);
+	pr_devel("<==%s() = %d\n", __func__, ret);
+	return ret;	
+}