File 0009-appendedsig-documentation.patch of Package grub2
From e57bcf83765291da62ad92f330cc1ffb535d4017 Mon Sep 17 00:00:00 2001
From: Sudhakar Kuppusamy <sudhakar@linux.ibm.com>
Date: Tue, 25 Feb 2025 02:47:03 +0530
Subject: [PATCH 9/9] appendedsig: documentation
This explains how static and dynamic key appended signatures can be used to form part of
a secure boot chain, and documents the commands and variables introduced.
Signed-off-by: Sudhakar Kuppusamy <sudhakar@linux.ibm.com>
Reviewed-by: Avnish Chouhan <avnish@linux.ibm.com>
---
docs/grub.texi | 113 +++++++++++++++++++++++++++++++++----------------
1 file changed, 76 insertions(+), 37 deletions(-)
diff --git a/docs/grub.texi b/docs/grub.texi
index e89007920c..9aaea72826 100644
--- a/docs/grub.texi
+++ b/docs/grub.texi
@@ -4373,7 +4373,9 @@ you forget a command, you can run the command @command{help}
* date:: Display or set current date and time
* devicetree:: Load a device tree blob
* distrust:: Remove a pubkey from trusted keys
-* distrust_certificate:: Remove a certificate from the list of trusted certificates
+* distrusted_certificate:: Remove a certificate from the trusted list
+* distrusted_list:: List distrusted certificates and binary/certificate hashes
+* distrusted_signature:: Add a binary hash to the distrusted list
* drivemap:: Map a drive to another
* echo:: Display a line of text
* efitextmode:: Set/Get text output mode resolution
@@ -4390,7 +4392,6 @@ you forget a command, you can run the command @command{help}
* hexdump:: Show raw contents of a file or memory
* insmod:: Insert a module
* keystatus:: Check key modifier status
-* list_certificates:: List trusted certificates
* list_env:: List variables in environment block
* list_trusted:: List trusted public keys
* load_env:: Load variables from environment block
@@ -4429,7 +4430,9 @@ you forget a command, you can run the command @command{help}
* test:: Check file types and compare values
* true:: Do nothing, successfully
* trust:: Add public key to list of trusted keys
-* trust_certificate:: Add an x509 certificate to the list of trusted certificates
+* trusted_certificate:: Add an x509 certificate to the trusted list
+* trusted_list:: List trusted certificates and binary hashes
+* trusted_signature:: Add a binary hash to the trusted list.
* unset:: Unset an environment variable
@comment * vbeinfo:: List available video modes
* verify_appended:: Verify appended digital signature
@@ -4775,16 +4778,15 @@ These keys are used to validate signatures when environment variable
GPG-style digital signatures}, for more information.
@end deffn
+@node distrusted_certificate
+@subsection distrusted_certificate
-@node distrust_certificate
-@subsection distrust_certificate
-
-@deffn Command distrust_certificate cert_number
+@deffn Command distrusted_certificate cert_number
Remove the x509 certificate numbered @var{cert_number} from GRUB's keyring of
trusted x509 certificates for verifying appended signatures.
@var{cert_number} is the certificate number as listed by
-@command{list_certificates} (@pxref{list_certificates}).
+@command{trusted_list} (@pxref{trusted_list}).
These certificates are used to validate appended signatures when environment
variable @code{check_appended_signatures} is set to @code{enforce}
@@ -4793,6 +4795,27 @@ variable @code{check_appended_signatures} is set to @code{enforce}
information.
@end deffn
+@node distrusted_list
+@subsection distrusted_list
+
+@deffn Command distrusted_list
+List all the distrusted x509 certificates and binary/certificate hashes.
+The output is a numbered list of certificates and binary/certificate hashes,
+showing the certificate's serial number and Common Name.
+@end deffn
+
+@node distrusted_signature
+@subsection distrusted_signature
+
+@deffn Command distrusted_signature
+Read a binary hash from the file @var{binary hash file}
+and add it to GRUB's internal distrusted list. These hash are used to
+restrict validation of linux image integrity using trusted list if appended
+signatures validation failed when the environment variable
+@code{check_appended_signatures} is set to @code{enforce}.
+
+See @xref{Using appended signatures} for more information.
+@end deffn
@node drivemap
@subsection drivemap
@@ -5069,22 +5092,6 @@ without any options, the @command{keystatus} command returns true if and
only if checking key modifier status is supported.
@end deffn
-
-@node list_certificates
-@subsection list_certificates
-
-@deffn Command list_certificates
-List all x509 certificates trusted by GRUB for validating appended signatures.
-The output is a numbered list of certificates, showing the certificate's serial
-number and Common Name.
-
-The certificate number can be used as an argument to
-@command{distrust_certificate} (@pxref{distrust_certificate}).
-
-See @xref{Using appended signatures} for more information.
-@end deffn
-
-
@node list_env
@subsection list_env
@@ -5936,17 +5943,17 @@ information.
@end deffn
-@node trust_certificate
-@subsection trust_certificate
+@node trusted_certificate
+@subsection trusted_certificate
-@deffn Command trust_certificate x509_certificate
+@deffn Command trusted_certificate x509_certificate
Read a DER-formatted x509 certificate from the file @var{x509_certificate}
and add it to GRUB's internal list of trusted x509 certificates. These
certificates are used to validate appended signatures when the environment
variable @code{check_appended_signatures} is set to @code{enforce}.
Note that if @code{check_appended_signatures} is set to @code{enforce}
-when @command{trust_certificate} is executed, then @var{x509_certificate}
+when @command{trusted_certificate} is executed, then @var{x509_certificate}
must itself bear an appended signature. (It is not sufficient that
@var{x509_certificate} be signed by a trusted certificate according to the
x509 rules: grub does not include support for validating signatures within x509
@@ -5955,6 +5962,32 @@ certificates themselves.)
See @xref{Using appended signatures} for more information.
@end deffn
+@node trusted_list
+@subsection trusted_list
+
+@deffn Command trusted_list
+List all x509 certificates and binary hases trusted by GRUB for validating
+appended signatures. The output is a numbered list of certificates and binary
+hashes, showing the certificate's serial number and Common Name.
+
+The certificate number can be used as an argument to
+@command{distrusted_certificate} (@pxref{distrusted_certificate}).
+
+See @xref{Using appended signatures} for more information.
+@end deffn
+
+@node trusted_signature
+@subsection trusted_signature
+
+@deffn Command trust_signature
+Read a binary hash from the file @var{binary hash file}
+and add it to GRUB's internal trusted list. These binary hash are used to
+validate linux image integrity if appended signatures validation failed
+when the environment variable @code{check_appended_signatures} is set
+to @code{enforce}.
+
+See @xref{Using appended signatures} for more information.
+@end deffn
@node unset
@subsection unset
@@ -5979,9 +6012,8 @@ only on PC BIOS platforms.
@deffn Command verify_appended file
Verifies an appended signature on @var{file} against the trusted certificates
-known to GRUB (See @pxref{list_certificates}, @pxref{trust_certificate}, and
-@pxref{distrust_certificate}).
-
+known to GRUB (See @pxref{trusted_list}, @pxref{trusted_certificate}, and
+@pxref{distrusted_certificate}).
Exit code @code{$?} is set to 0 if the signature validates
successfully. If validation fails, it is set to a non-zero value.
See @xref{Using appended signatures}, for more information.
@@ -6669,14 +6701,21 @@ To enable appended signature verification, load the appendedsig module and an
x509 certificate for verification. Building the appendedsig module into the
core grub image is recommended.
-Certificates can be managed at boot time using the @pxref{trust_certificate},
-@pxref{distrust_certificate} and @pxref{list_certificates} commands.
-Certificates can also be built in to the core image using the @code{--x509}
-parameter to @command{grub-install} or @command{grub-mkimage}.
+For static key, Certificates will be built in to the core image using
+the @code{--x509} parameter to @command{grub-install} or @command{grub-mkimage}.
+it can allow to list the trusted certificates and binary hashes at boot time using
+@pxref{trusted_list} and list distrusted certificates and binary/certificate hashes
+at boot time using @pxref{distrusted_list} commands.
+
+For dynamic key, loads the signature database (DB) and forbidden
+signature database (DBX) from platform keystore (PKS) and it can allow to list
+the trusted certificates and binary hashes at boot time using @pxref{trusted_list}
+and list distrusted certificates and binary/certificate hashes at boot time using
+@pxref{distrusted_list} commands.
-A file can be explictly verified using the @pxref{verify_appended} command.
+A file can be explicitly verified using the @pxref{verify_appended} command.
-Only signatures made with the SHA-256 or SHA-512 hash algorithm are supported,
+Only signatures made with the SHA-256, SHA-384 and SHA-512 hash algorithm are supported,
and only RSA signatures are supported.
A file can be signed with the @command{sign-file} utility supplied with the
--
2.48.1
