diff mbox series

[v10,01/12] MODSIGN: Export module signature definitions

Message ID 20190418035120.2354-2-bauerman@linux.ibm.com (mailing list archive)
State New, archived
Headers show
Series Appended signatures support for IMA appraisal | expand

Commit Message

Thiago Jung Bauermann April 18, 2019, 3:51 a.m. UTC
IMA will use the module_signature format for append signatures, so export
the relevant definitions and factor out the code which verifies that the
appended signature trailer is valid.

Also, create a CONFIG_MODULE_SIG_FORMAT option so that IMA can select it
and be able to use mod_check_sig() without having to depend on either
CONFIG_MODULE_SIG or CONFIG_MODULES.

Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Cc: Jessica Yu <jeyu@kernel.org>
---
 include/linux/module.h           |  3 --
 include/linux/module_signature.h | 44 +++++++++++++++++++++++++
 init/Kconfig                     |  6 +++-
 kernel/Makefile                  |  1 +
 kernel/module.c                  |  1 +
 kernel/module_signature.c        | 45 +++++++++++++++++++++++++
 kernel/module_signing.c          | 56 +++++---------------------------
 scripts/Makefile                 |  2 +-
 8 files changed, 105 insertions(+), 53 deletions(-)

Comments

Mimi Zohar May 9, 2019, 3:42 p.m. UTC | #1
On Thu, 2019-04-18 at 00:51 -0300, Thiago Jung Bauermann wrote:
> IMA will use the module_signature format for append signatures, so export
> the relevant definitions and factor out the code which verifies that the
> appended signature trailer is valid.
> 
> Also, create a CONFIG_MODULE_SIG_FORMAT option so that IMA can select it
> and be able to use mod_check_sig() without having to depend on either
> CONFIG_MODULE_SIG or CONFIG_MODULES.
> 
> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
> Cc: Jessica Yu <jeyu@kernel.org>

Just a couple minor questions/comments below.

Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>

> ---

< snip >


> diff --git a/init/Kconfig b/init/Kconfig
> index 4592bf7997c0..a71019553ee1 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1906,7 +1906,7 @@ config MODULE_SRCVERSION_ALL
>  config MODULE_SIG
>  	bool "Module signature verification"
>  	depends on MODULES
> -	select SYSTEM_DATA_VERIFICATION
> +	select MODULE_SIG_FORMAT
>  	help
>  	  Check modules for valid signatures upon load: the signature
>  	  is simply appended to the module. For more information see
> @@ -2036,6 +2036,10 @@ config TRIM_UNUSED_KSYMS
>  
>  endif # MODULES
>  
> +config MODULE_SIG_FORMAT
> +	def_bool n
> +	select SYSTEM_DATA_VERIFICATION

Normally Kconfigs, in the same file, are defined before they are used.
 I'm not sure if that is required or just a convention.


>  config MODULES_TREE_LOOKUP
>  	def_bool y
>  	depends on PERF_EVENTS || TRACING
> diff --git a/kernel/Makefile b/kernel/Makefile
> index 6c57e78817da..d2f2488f80ab 100644
> --- a/kernel/Makefile
> +++ b/kernel/Makefile
> @@ -57,6 +57,7 @@ endif
>  obj-$(CONFIG_UID16) += uid16.o
>  obj-$(CONFIG_MODULES) += module.o
>  obj-$(CONFIG_MODULE_SIG) += module_signing.o
> +obj-$(CONFIG_MODULE_SIG_FORMAT) += module_signature.o
>  obj-$(CONFIG_KALLSYMS) += kallsyms.o
>  obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
>  obj-$(CONFIG_CRASH_CORE) += crash_core.o
> diff --git a/kernel/module.c b/kernel/module.c
> index 985caa467aef..326ddeb364dd 100644
> --- a/kernel/module.c
> +++ b/kernel/module.c
> @@ -19,6 +19,7 @@
>  #include <linux/export.h>
>  #include <linux/extable.h>
>  #include <linux/moduleloader.h>
> +#include <linux/module_signature.h>
>  #include <linux/trace_events.h>
>  #include <linux/init.h>
>  #include <linux/kallsyms.h>
> diff --git a/kernel/module_signature.c b/kernel/module_signature.c
> new file mode 100644
> index 000000000000..6d5e59f27f55
> --- /dev/null
> +++ b/kernel/module_signature.c
> @@ -0,0 +1,45 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Module signature checker
> + *
> + * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
> + * Written by David Howells (dhowells@redhat.com)
> + */
> +
> +#include <linux/errno.h>
> +#include <linux/printk.h>
> +#include <linux/module_signature.h>
> +#include <asm/byteorder.h>
> +
> +/**
> + * mod_check_sig - check that the given signature is sane
> + *
> + * @ms:		Signature to check.
> + * @file_len:	Size of the file to which @ms is appended.

"name" is missing.

Mimi

> + */
Thiago Jung Bauermann May 28, 2019, 7:03 p.m. UTC | #2
Mimi Zohar <zohar@linux.ibm.com> writes:

> On Thu, 2019-04-18 at 00:51 -0300, Thiago Jung Bauermann wrote:
>> IMA will use the module_signature format for append signatures, so export
>> the relevant definitions and factor out the code which verifies that the
>> appended signature trailer is valid.
>> 
>> Also, create a CONFIG_MODULE_SIG_FORMAT option so that IMA can select it
>> and be able to use mod_check_sig() without having to depend on either
>> CONFIG_MODULE_SIG or CONFIG_MODULES.
>> 
>> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
>> Cc: Jessica Yu <jeyu@kernel.org>
>
> Just a couple minor questions/comments below.
>
> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>

Thanks for your review and your comments!

>> diff --git a/init/Kconfig b/init/Kconfig
>> index 4592bf7997c0..a71019553ee1 100644
>> --- a/init/Kconfig
>> +++ b/init/Kconfig
>> @@ -1906,7 +1906,7 @@ config MODULE_SRCVERSION_ALL
>>  config MODULE_SIG
>>  	bool "Module signature verification"
>>  	depends on MODULES
>> -	select SYSTEM_DATA_VERIFICATION
>> +	select MODULE_SIG_FORMAT
>>  	help
>>  	  Check modules for valid signatures upon load: the signature
>>  	  is simply appended to the module. For more information see
>> @@ -2036,6 +2036,10 @@ config TRIM_UNUSED_KSYMS
>>  
>>  endif # MODULES
>>  
>> +config MODULE_SIG_FORMAT
>> +	def_bool n
>> +	select SYSTEM_DATA_VERIFICATION
>
> Normally Kconfigs, in the same file, are defined before they are used.
>  I'm not sure if that is required or just a convention.

I think it's a convention, because it seemed to work in the current way.
For the next version I moved the config MODULE_SIG_FORMAT definition to
just before "menuconfig MODULES"

>> diff --git a/kernel/module_signature.c b/kernel/module_signature.c
>> new file mode 100644
>> index 000000000000..6d5e59f27f55
>> --- /dev/null
>> +++ b/kernel/module_signature.c
>> @@ -0,0 +1,45 @@
>> +// SPDX-License-Identifier: GPL-2.0+
>> +/*
>> + * Module signature checker
>> + *
>> + * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
>> + * Written by David Howells (dhowells@redhat.com)
>> + */
>> +
>> +#include <linux/errno.h>
>> +#include <linux/printk.h>
>> +#include <linux/module_signature.h>
>> +#include <asm/byteorder.h>
>> +
>> +/**
>> + * mod_check_sig - check that the given signature is sane
>> + *
>> + * @ms:		Signature to check.
>> + * @file_len:	Size of the file to which @ms is appended.
>
> "name" is missing.

Fixed.
diff mbox series

Patch

diff --git a/include/linux/module.h b/include/linux/module.h
index 73ee2b10e816..cd919ec972d6 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -25,9 +25,6 @@ 
 #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)
 
diff --git a/include/linux/module_signature.h b/include/linux/module_signature.h
new file mode 100644
index 000000000000..523617fc5b6a
--- /dev/null
+++ b/include/linux/module_signature.h
@@ -0,0 +1,44 @@ 
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Module signature handling.
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#ifndef _LINUX_MODULE_SIGNATURE_H
+#define _LINUX_MODULE_SIGNATURE_H
+
+/* In stripped ARM and x86-64 modules, ~ is surprisingly rare. */
+#define MODULE_SIG_STRING "~Module signature appended~\n"
+
+enum pkey_id_type {
+	PKEY_ID_PGP,		/* OpenPGP generated key ID */
+	PKEY_ID_X509,		/* X.509 arbitrary subjectKeyIdentifier */
+	PKEY_ID_PKCS7,		/* Signature in PKCS#7 message */
+};
+
+/*
+ * 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 {
+	u8	algo;		/* Public-key crypto algorithm [0] */
+	u8	hash;		/* Digest algorithm [0] */
+	u8	id_type;	/* Key identifier type [PKEY_ID_PKCS7] */
+	u8	signer_len;	/* Length of signer's name [0] */
+	u8	key_id_len;	/* Length of key identifier [0] */
+	u8	__pad[3];
+	__be32	sig_len;	/* Length of signature data */
+};
+
+int mod_check_sig(const struct module_signature *ms, size_t file_len,
+		  const char *name);
+
+#endif /* _LINUX_MODULE_SIGNATURE_H */
diff --git a/init/Kconfig b/init/Kconfig
index 4592bf7997c0..a71019553ee1 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1906,7 +1906,7 @@  config MODULE_SRCVERSION_ALL
 config MODULE_SIG
 	bool "Module signature verification"
 	depends on MODULES
-	select SYSTEM_DATA_VERIFICATION
+	select MODULE_SIG_FORMAT
 	help
 	  Check modules for valid signatures upon load: the signature
 	  is simply appended to the module. For more information see
@@ -2036,6 +2036,10 @@  config TRIM_UNUSED_KSYMS
 
 endif # MODULES
 
+config MODULE_SIG_FORMAT
+	def_bool n
+	select SYSTEM_DATA_VERIFICATION
+
 config MODULES_TREE_LOOKUP
 	def_bool y
 	depends on PERF_EVENTS || TRACING
diff --git a/kernel/Makefile b/kernel/Makefile
index 6c57e78817da..d2f2488f80ab 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -57,6 +57,7 @@  endif
 obj-$(CONFIG_UID16) += uid16.o
 obj-$(CONFIG_MODULES) += module.o
 obj-$(CONFIG_MODULE_SIG) += module_signing.o
+obj-$(CONFIG_MODULE_SIG_FORMAT) += module_signature.o
 obj-$(CONFIG_KALLSYMS) += kallsyms.o
 obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o
 obj-$(CONFIG_CRASH_CORE) += crash_core.o
diff --git a/kernel/module.c b/kernel/module.c
index 985caa467aef..326ddeb364dd 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -19,6 +19,7 @@ 
 #include <linux/export.h>
 #include <linux/extable.h>
 #include <linux/moduleloader.h>
+#include <linux/module_signature.h>
 #include <linux/trace_events.h>
 #include <linux/init.h>
 #include <linux/kallsyms.h>
diff --git a/kernel/module_signature.c b/kernel/module_signature.c
new file mode 100644
index 000000000000..6d5e59f27f55
--- /dev/null
+++ b/kernel/module_signature.c
@@ -0,0 +1,45 @@ 
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Module signature checker
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/errno.h>
+#include <linux/printk.h>
+#include <linux/module_signature.h>
+#include <asm/byteorder.h>
+
+/**
+ * mod_check_sig - check that the given signature is sane
+ *
+ * @ms:		Signature to check.
+ * @file_len:	Size of the file to which @ms is appended.
+ */
+int mod_check_sig(const struct module_signature *ms, size_t file_len,
+		  const char *name)
+{
+	if (be32_to_cpu(ms->sig_len) >= file_len - sizeof(*ms))
+		return -EBADMSG;
+
+	if (ms->id_type != PKEY_ID_PKCS7) {
+		pr_err("%s: Module is not signed with expected PKCS#7 message\n",
+		       name);
+		return -ENOPKG;
+	}
+
+	if (ms->algo != 0 ||
+	    ms->hash != 0 ||
+	    ms->signer_len != 0 ||
+	    ms->key_id_len != 0 ||
+	    ms->__pad[0] != 0 ||
+	    ms->__pad[1] != 0 ||
+	    ms->__pad[2] != 0) {
+		pr_err("%s: PKCS#7 signature info has unexpected non-zero params\n",
+		       name);
+		return -EBADMSG;
+	}
+
+	return 0;
+}
diff --git a/kernel/module_signing.c b/kernel/module_signing.c
index 6b9a926fd86b..cdd04a6b8074 100644
--- a/kernel/module_signing.c
+++ b/kernel/module_signing.c
@@ -11,37 +11,13 @@ 
 
 #include <linux/kernel.h>
 #include <linux/errno.h>
+#include <linux/module.h>
+#include <linux/module_signature.h>
 #include <linux/string.h>
 #include <linux/verification.h>
 #include <crypto/public_key.h>
 #include "module-internal.h"
 
-enum pkey_id_type {
-	PKEY_ID_PGP,		/* OpenPGP generated key ID */
-	PKEY_ID_X509,		/* X.509 arbitrary subjectKeyIdentifier */
-	PKEY_ID_PKCS7,		/* Signature in PKCS#7 message */
-};
-
-/*
- * 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 {
-	u8	algo;		/* Public-key crypto algorithm [0] */
-	u8	hash;		/* Digest algorithm [0] */
-	u8	id_type;	/* Key identifier type [PKEY_ID_PKCS7] */
-	u8	signer_len;	/* Length of signer's name [0] */
-	u8	key_id_len;	/* Length of key identifier [0] */
-	u8	__pad[3];
-	__be32	sig_len;	/* Length of signature data */
-};
-
 /*
  * Verify the signature on a module.
  */
@@ -49,6 +25,7 @@  int mod_verify_sig(const void *mod, struct load_info *info)
 {
 	struct module_signature ms;
 	size_t sig_len, modlen = info->len;
+	int ret;
 
 	pr_devel("==>%s(,%zu)\n", __func__, modlen);
 
@@ -56,32 +33,15 @@  int mod_verify_sig(const void *mod, struct load_info *info)
 		return -EBADMSG;
 
 	memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms));
-	modlen -= sizeof(ms);
+
+	ret = mod_check_sig(&ms, modlen, info->name);
+	if (ret)
+		return ret;
 
 	sig_len = be32_to_cpu(ms.sig_len);
-	if (sig_len >= modlen)
-		return -EBADMSG;
-	modlen -= sig_len;
+	modlen -= sig_len + sizeof(ms);
 	info->len = modlen;
 
-	if (ms.id_type != PKEY_ID_PKCS7) {
-		pr_err("%s: Module is not signed with expected PKCS#7 message\n",
-		       info->name);
-		return -ENOPKG;
-	}
-
-	if (ms.algo != 0 ||
-	    ms.hash != 0 ||
-	    ms.signer_len != 0 ||
-	    ms.key_id_len != 0 ||
-	    ms.__pad[0] != 0 ||
-	    ms.__pad[1] != 0 ||
-	    ms.__pad[2] != 0) {
-		pr_err("%s: PKCS#7 signature info has unexpected non-zero params\n",
-		       info->name);
-		return -EBADMSG;
-	}
-
 	return verify_pkcs7_signature(mod, modlen, mod + modlen, sig_len,
 				      VERIFY_USE_SECONDARY_KEYRING,
 				      VERIFYING_MODULE_SIGNATURE,
diff --git a/scripts/Makefile b/scripts/Makefile
index 9d442ee050bd..52098b080ab7 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -17,7 +17,7 @@  hostprogs-$(CONFIG_VT)           += conmakehash
 hostprogs-$(BUILD_C_RECORDMCOUNT) += recordmcount
 hostprogs-$(CONFIG_BUILDTIME_EXTABLE_SORT) += sortextable
 hostprogs-$(CONFIG_ASN1)	 += asn1_compiler
-hostprogs-$(CONFIG_MODULE_SIG)	 += sign-file
+hostprogs-$(CONFIG_MODULE_SIG_FORMAT) += sign-file
 hostprogs-$(CONFIG_SYSTEM_TRUSTED_KEYRING) += extract-cert
 hostprogs-$(CONFIG_SYSTEM_EXTRA_CERTIFICATE) += insert-sys-cert