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authorLinus Torvalds <torvalds@linux-foundation.org>2015-09-08 12:41:25 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-09-08 12:41:25 -0700
commitb793c005ceabf6db0b17494b0ec67ade6796bb34 (patch)
tree080c884f04254403ec9564742f591a9fd9b7e95a /Documentation/module-signing.txt
parent6f0a2fc1feb19bd142961a39dc118e7e55418b3f (diff)
parent07f081fb5057b2ea98baeca3a47bf0eb33e94aa1 (diff)
Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security
Pull security subsystem updates from James Morris: "Highlights: - PKCS#7 support added to support signed kexec, also utilized for module signing. See comments in 3f1e1bea. ** NOTE: this requires linking against the OpenSSL library, which must be installed, e.g. the openssl-devel on Fedora ** - Smack - add IPv6 host labeling; ignore labels on kernel threads - support smack labeling mounts which use binary mount data - SELinux: - add ioctl whitelisting (see http://kernsec.org/files/lss2015/vanderstoep.pdf) - fix mprotect PROT_EXEC regression caused by mm change - Seccomp: - add ptrace options for suspend/resume" * 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security: (57 commits) PKCS#7: Add OIDs for sha224, sha284 and sha512 hash algos and use them Documentation/Changes: Now need OpenSSL devel packages for module signing scripts: add extract-cert and sign-file to .gitignore modsign: Handle signing key in source tree modsign: Use if_changed rule for extracting cert from module signing key Move certificate handling to its own directory sign-file: Fix warning about BIO_reset() return value PKCS#7: Add MODULE_LICENSE() to test module Smack - Fix build error with bringup unconfigured sign-file: Document dependency on OpenSSL devel libraries PKCS#7: Appropriately restrict authenticated attributes and content type KEYS: Add a name for PKEY_ID_PKCS7 PKCS#7: Improve and export the X.509 ASN.1 time object decoder modsign: Use extract-cert to process CONFIG_SYSTEM_TRUSTED_KEYS extract-cert: Cope with multiple X.509 certificates in a single file sign-file: Generate CMS message as signature instead of PKCS#7 PKCS#7: Support CMS messages also [RFC5652] X.509: Change recorded SKID & AKID to not include Subject or Issuer PKCS#7: Check content type and versions MAINTAINERS: The keyrings mailing list has moved ...
Diffstat (limited to 'Documentation/module-signing.txt')
-rw-r--r--Documentation/module-signing.txt56
1 files changed, 44 insertions, 12 deletions
diff --git a/Documentation/module-signing.txt b/Documentation/module-signing.txt
index c72702ec1ded..a78bf1ffa68c 100644
--- a/Documentation/module-signing.txt
+++ b/Documentation/module-signing.txt
@@ -89,6 +89,32 @@ This has a number of options available:
their signatures checked without causing a dependency loop.
+ (4) "File name or PKCS#11 URI of module signing key" (CONFIG_MODULE_SIG_KEY)
+
+ Setting this option to something other than its default of
+ "certs/signing_key.pem" will disable the autogeneration of signing keys
+ and allow the kernel modules to be signed with a key of your choosing.
+ The string provided should identify a file containing both a private key
+ and its corresponding X.509 certificate in PEM form, or — on systems where
+ the OpenSSL ENGINE_pkcs11 is functional — a PKCS#11 URI as defined by
+ RFC7512. In the latter case, the PKCS#11 URI should reference both a
+ certificate and a private key.
+
+ If the PEM file containing the private key is encrypted, or if the
+ PKCS#11 token requries a PIN, this can be provided at build time by
+ means of the KBUILD_SIGN_PIN variable.
+
+
+ (5) "Additional X.509 keys for default system keyring" (CONFIG_SYSTEM_TRUSTED_KEYS)
+
+ This option can be set to the filename of a PEM-encoded file containing
+ additional certificates which will be included in the system keyring by
+ default.
+
+Note that enabling module signing adds a dependency on the OpenSSL devel
+packages to the kernel build processes for the tool that does the signing.
+
+
=======================
GENERATING SIGNING KEYS
=======================
@@ -100,16 +126,16 @@ it can be deleted or stored securely. The public key gets built into the
kernel so that it can be used to check the signatures as the modules are
loaded.
-Under normal conditions, the kernel build will automatically generate a new
-keypair using openssl if one does not exist in the files:
+Under normal conditions, when CONFIG_MODULE_SIG_KEY is unchanged from its
+default, the kernel build will automatically generate a new keypair using
+openssl if one does not exist in the file:
- signing_key.priv
- signing_key.x509
+ certs/signing_key.pem
during the building of vmlinux (the public part of the key needs to be built
into vmlinux) using parameters in the:
- x509.genkey
+ certs/x509.genkey
file (which is also generated if it does not already exist).
@@ -135,8 +161,12 @@ kernel sources tree and the openssl command. The following is an example to
generate the public/private key files:
openssl req -new -nodes -utf8 -sha256 -days 36500 -batch -x509 \
- -config x509.genkey -outform DER -out signing_key.x509 \
- -keyout signing_key.priv
+ -config x509.genkey -outform PEM -out kernel_key.pem \
+ -keyout kernel_key.pem
+
+The full pathname for the resulting kernel_key.pem file can then be specified
+in the CONFIG_MODULE_SIG_KEY option, and the certificate and key therein will
+be used instead of an autogenerated keypair.
=========================
@@ -152,10 +182,9 @@ in a keyring called ".system_keyring" that can be seen by:
302d2d52 I------ 1 perm 1f010000 0 0 asymmetri Fedora kernel signing key: d69a84e6bce3d216b979e9505b3e3ef9a7118079: X509.RSA a7118079 []
...
-Beyond the public key generated specifically for module signing, any file
-placed in the kernel source root directory or the kernel build root directory
-whose name is suffixed with ".x509" will be assumed to be an X.509 public key
-and will be added to the keyring.
+Beyond the public key generated specifically for module signing, additional
+trusted certificates can be provided in a PEM-encoded file referenced by the
+CONFIG_SYSTEM_TRUSTED_KEYS configuration option.
Further, the architecture code may take public keys from a hardware store and
add those in also (e.g. from the UEFI key database).
@@ -181,7 +210,7 @@ To manually sign a module, use the scripts/sign-file tool available in
the Linux kernel source tree. The script requires 4 arguments:
1. The hash algorithm (e.g., sha256)
- 2. The private key filename
+ 2. The private key filename or PKCS#11 URI
3. The public key filename
4. The kernel module to be signed
@@ -194,6 +223,9 @@ The hash algorithm used does not have to match the one configured, but if it
doesn't, you should make sure that hash algorithm is either built into the
kernel or can be loaded without requiring itself.
+If the private key requires a passphrase or PIN, it can be provided in the
+$KBUILD_SIGN_PIN environment variable.
+
============================
SIGNED MODULES AND STRIPPING