| 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 |
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 > + */
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 --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
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(-)