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fde-tools/fde-tools-bsc1213945-set-rsa-key-size.patch

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From 7ab5a433c9fcc8cd56f8f9f7657b32282cb00ee8 Mon Sep 17 00:00:00 2001
From: Gary Lin <glin@suse.com>
Date: Fri, 6 Oct 2023 16:24:54 +0800
Subject: [PATCH 1/3] Set the RSA key size automatically
This commit utilizes the new pcr-oracle command, rsa-test, to detect the
highest RSA key size supported by the TPM chip and then uses the key
size for the TPM SRK and the private sign key.
Signed-off-by: Gary Lin <glin@suse.com>
---
share/grub2 | 1 +
share/tpm | 53 ++++++++++++++++++++++++++++++++++++++++++++++++---
sysconfig.fde | 4 ++++
3 files changed, 55 insertions(+), 3 deletions(-)
diff --git a/share/grub2 b/share/grub2
index aacd20c..97c8d86 100644
--- a/share/grub2
+++ b/share/grub2
@@ -82,6 +82,7 @@ function grub_update_early_config {
grub_set_control GRUB_ENABLE_CRYPTODISK "y"
grub_set_control GRUB_TPM2_SEALED_KEY "$sealed_key_file"
+ grub_set_control GRUB_TPM2_SRK_ALG "RSA${FDE_RSA_KEY_SIZE}"
# Do not clear the password implicitly; require fdectl or
# jeos firstboot to do so explicitly.
diff --git a/share/tpm b/share/tpm
index 0cc507a..0396e7e 100644
--- a/share/tpm
+++ b/share/tpm
@@ -42,13 +42,47 @@ function tpm_present_and_working {
return 0
}
+function tpm_set_rsa_key_size {
+
+ # Check if pcr-oracle supports rsa-test
+ # If pcr-oracle prints "Unknown action", fall back to default.
+ if pcr-oracle rsa-test 2>&1 | grep -q "Unknown action"; then
+ fde_set_variable FDE_RSA_KEY_SIZE "2048"
+ return 0
+ fi
+
+ # Find the highest supported RSA key size
+ sizes_to_test="4096 3072 2048"
+
+ for size in ${sizes_to_test}; do
+ if pcr-oracle --rsa-bits ${size} rsa-test > /dev/null 2>&1; then
+ fde_set_variable FDE_RSA_KEY_SIZE "${size}"
+ return 0
+ fi
+ done
+
+ fde_trace "Failed to find a valid RSA key size"
+ return 1
+}
+
function tpm_seal_key {
secret=$1
sealed_secret=$2
+ tpm_set_rsa_key_size
+ if [ $? -ne 0 ]; then
+ return 1
+ fi
+
+ opt_rsa_bits=
+ if [ -n "${FDE_RSA_KEY_SIZE}" -a ${FDE_RSA_KEY_SIZE} -ne 2048 ]; then
+ opt_rsa_bits="--rsa-bits ${FDE_RSA_KEY_SIZE}"
+ fi
+
echo "Sealing secret against PCR policy covering $FDE_SEAL_PCR_LIST" >&2
- pcr-oracle --input "$secret" --output "$sealed_secret" \
+ pcr-oracle ${opt_rsa_bits} \
+ --input "$secret" --output "$sealed_secret" \
--key-format tpm2.0 \
--algorithm "$FDE_SEAL_PCR_BANK" \
--from eventlog \
@@ -97,17 +131,22 @@ function tpm_test {
return $result
}
-
function tpm_seal_secret {
secret="$1"
sealed_secret="$2"
authorized_policy="$3"
+ opt_rsa_bits=
+ if [ -n "${FDE_RSA_KEY_SIZE}" -a ${FDE_RSA_KEY_SIZE} -ne 2048 ]; then
+ opt_rsa_bits="--rsa-bits ${FDE_RSA_KEY_SIZE}"
+ fi
+
# If we are expected to use an authorized policy, seal the secret
# against that, using pcr-oracle rather than the tpm2 tools
if [ -n "$authorized_policy" ]; then
- pcr-oracle --authorized-policy "$authorized_policy" \
+ pcr-oracle ${opt_rsa_bits} \
+ --authorized-policy "$authorized_policy" \
--key-format tpm2.0 \
--input $secret \
--output $sealed_secret \
@@ -157,6 +196,14 @@ function tpm_create_authorized_policy {
extra_opts=
if [ ! -f "$secret_key" ]; then
extra_opts="--rsa-generate-key"
+
+ tpm_set_rsa_key_size
+ if [ $? -ne 0 ]; then
+ return 1
+ fi
+ if [ -n "${FDE_RSA_KEY_SIZE}" -a ${FDE_RSA_KEY_SIZE} -ne 2048 ]; then
+ extra_opts="${extra_opts} --rsa-bits ${FDE_RSA_KEY_SIZE}"
+ fi
fi
pcr-oracle $extra_opts \
diff --git a/sysconfig.fde b/sysconfig.fde
index a3435fe..f3ee38b 100644
--- a/sysconfig.fde
+++ b/sysconfig.fde
@@ -36,3 +36,7 @@ FDE_DEVS=""
# the bootloader update
# Set to yes/no
FDE_TPM_AUTO_UPDATE="yes"
+
+# The RSA key size to be used for SRK and the private sign key
+# NOTE: Do not touch this variable. It's updated by fdectl automatically.
+FDE_RSA_KEY_SIZE="2048"
--
2.35.3
From bee71824675721ae73ce770c0e846f0aba48b441 Mon Sep 17 00:00:00 2001
From: Gary Lin <glin@suse.com>
Date: Fri, 3 Nov 2023 15:04:00 +0800
Subject: [PATCH 2/3] Detect the RSA sizes supported by the bootloader
The bootloader may not support the SRK algorithm other than RSA2048.
Use the bootloader specific function to detect the supported RSA sizes.
Signed-off-by: Gary Lin <glin@suse.com>
---
share/grub2 | 19 +++++++++++++++++++
share/systemd-boot | 8 ++++++++
share/tpm | 2 +-
3 files changed, 28 insertions(+), 1 deletion(-)
diff --git a/share/grub2 b/share/grub2
index 97c8d86..cde7680 100644
--- a/share/grub2
+++ b/share/grub2
@@ -33,6 +33,7 @@ alias bootloader_commit_config=grub_commit_config
alias bootloader_get_keyslots=grub_get_keyslots
alias bootloader_remove_keyslots=grub_remove_keyslots
alias bootloader_wipe=grub_wipe
+alias bootloader_rsa_sizes=grub_rsa_sizes
##################################################################
# Edit a variable in /etc/default/grub
@@ -224,3 +225,21 @@ function grub_wipe {
grub_remove_keyslots ${luks_dev}
}
+
+function grub_rsa_sizes {
+
+ # Check if the shim-install script supports the SRK algorithm selection.
+ if ! grep -q "GRUB_TPM2_SRK_ALG" "/usr/sbin/shim-install"; then
+ echo "2048"
+ return 0
+ fi
+
+ # Check if grub2 supports the RSA4096 SRK.
+ if grub2-protect --help | grep -q "RSA4096"; then
+ echo "4096 3072 2048"
+ return 0
+ fi
+
+ # TPM 2.0 should at least support RSA2048.
+ echo "2048"
+}
diff --git a/share/systemd-boot b/share/systemd-boot
index a9475a7..27cb088 100644
--- a/share/systemd-boot
+++ b/share/systemd-boot
@@ -36,6 +36,7 @@ alias bootloader_commit_config=systemd_commit_config
alias bootloader_get_keyslots=systemd_get_keyslots
alias bootloader_remove_keyslots=systemd_remove_keyslots
alias bootloader_wipe=systemd_wipe
+alias bootloader_rsa_sizes=systemd_rsa_sizes
function not_implemented {
@@ -175,3 +176,10 @@ function systemd_wipe {
not_implemented
}
+
+##################################################################
+# This function lists all the supported RSA key sizes for SRK.
+##################################################################
+function systemd_rsa_sizes {
+ echo "2048"
+}
diff --git a/share/tpm b/share/tpm
index 0396e7e..00a0016 100644
--- a/share/tpm
+++ b/share/tpm
@@ -52,7 +52,7 @@ function tpm_set_rsa_key_size {
fi
# Find the highest supported RSA key size
- sizes_to_test="4096 3072 2048"
+ sizes_to_test=$(bootloader_rsa_sizes)
for size in ${sizes_to_test}; do
if pcr-oracle --rsa-bits ${size} rsa-test > /dev/null 2>&1; then
--
2.35.3
From 8912fa960fcecd218b05df45dae471180ebac156 Mon Sep 17 00:00:00 2001
From: Gary Lin <glin@suse.com>
Date: Wed, 22 Nov 2023 15:35:26 +0800
Subject: [PATCH 3/3] Refactor the RSA key size code to make it more flexible
Originally, FDE_RSA_KEY_SIZE was updated automatically and used as a
global variable for both tpm and grub2 scripts. However, there may be a
case that the user has to stick to a specific RSA key size due to some
bug or defect. This commit refactors the RSA key size code to make
FDE_RSA_KEY_SIZE empty by default and honor the user setting if the size
is specified.
Signed-off-by: Gary Lin <glin@suse.com>
---
share/grub2 | 5 ++--
share/tpm | 79 ++++++++++++++++++++++++++++++---------------------
sysconfig.fde | 5 ++--
3 files changed, 52 insertions(+), 37 deletions(-)
diff --git a/share/grub2 b/share/grub2
index cde7680..95d4b15 100644
--- a/share/grub2
+++ b/share/grub2
@@ -79,11 +79,12 @@ function grub_get_fde_password {
##################################################################
function grub_update_early_config {
- sealed_key_file="$1"
+ local sealed_key_file="$1"
+ local rsa_key_size=$(tpm_get_rsa_key_size)
grub_set_control GRUB_ENABLE_CRYPTODISK "y"
grub_set_control GRUB_TPM2_SEALED_KEY "$sealed_key_file"
- grub_set_control GRUB_TPM2_SRK_ALG "RSA${FDE_RSA_KEY_SIZE}"
+ grub_set_control GRUB_TPM2_SRK_ALG "RSA${rsa_key_size}"
# Do not clear the password implicitly; require fdectl or
# jeos firstboot to do so explicitly.
diff --git a/share/tpm b/share/tpm
index 00a0016..43747e7 100644
--- a/share/tpm
+++ b/share/tpm
@@ -42,13 +42,28 @@ function tpm_present_and_working {
return 0
}
-function tpm_set_rsa_key_size {
+function tpm_get_rsa_key_size {
+
+ declare -g __fde_rsa_key_size
+
+ if [ -n "$__fde_rsa_key_size" ]; then
+ echo "$__fde_rsa_key_size"
+ return
+ fi
+
+ if [ -n "$FDE_RSA_KEY_SIZE" ]; then
+ # TODO validate $FDE_RSA_KEY_SIZE
+ __fde_rsa_key_size="${FDE_RSA_KEY_SIZE}"
+ echo "$__fde_rsa_key_size"
+ return
+ fi
# Check if pcr-oracle supports rsa-test
# If pcr-oracle prints "Unknown action", fall back to default.
if pcr-oracle rsa-test 2>&1 | grep -q "Unknown action"; then
- fde_set_variable FDE_RSA_KEY_SIZE "2048"
- return 0
+ __fde_rsa_key_size="2048"
+ echo "$__fde_rsa_key_size"
+ return
fi
# Find the highest supported RSA key size
@@ -56,28 +71,27 @@ function tpm_set_rsa_key_size {
for size in ${sizes_to_test}; do
if pcr-oracle --rsa-bits ${size} rsa-test > /dev/null 2>&1; then
- fde_set_variable FDE_RSA_KEY_SIZE "${size}"
- return 0
+ __fde_rsa_key_size="${size}"
+ echo "$__fde_rsa_key_size"
+ return
fi
done
- fde_trace "Failed to find a valid RSA key size"
- return 1
+ fde_trace "Failed to find a valid RSA key size. Fall back to 2048"
+ __fde_rsa_key_size="2048"
+ echo "$__fde_rsa_key_size"
}
function tpm_seal_key {
- secret=$1
- sealed_secret=$2
+ local secret=$1
+ local sealed_secret=$2
- tpm_set_rsa_key_size
- if [ $? -ne 0 ]; then
- return 1
- fi
+ local opt_rsa_bits=
+ local rsa_size=$(tpm_get_rsa_key_size)
- opt_rsa_bits=
- if [ -n "${FDE_RSA_KEY_SIZE}" -a ${FDE_RSA_KEY_SIZE} -ne 2048 ]; then
- opt_rsa_bits="--rsa-bits ${FDE_RSA_KEY_SIZE}"
+ if [ -n "$rsa_size" -a "$rsa_size" -ne 2048 ]; then
+ opt_rsa_bits="--rsa-bits ${rsa_size}"
fi
echo "Sealing secret against PCR policy covering $FDE_SEAL_PCR_LIST" >&2
@@ -133,13 +147,15 @@ function tpm_test {
function tpm_seal_secret {
- secret="$1"
- sealed_secret="$2"
- authorized_policy="$3"
+ local secret="$1"
+ local sealed_secret="$2"
+ local authorized_policy="$3"
+
+ local opt_rsa_bits=
+ local rsa_size=$(tpm_get_rsa_key_size)
- opt_rsa_bits=
- if [ -n "${FDE_RSA_KEY_SIZE}" -a ${FDE_RSA_KEY_SIZE} -ne 2048 ]; then
- opt_rsa_bits="--rsa-bits ${FDE_RSA_KEY_SIZE}"
+ if [ -n "$rsa_size" -a "$rsa_size" -ne 2048 ]; then
+ opt_rsa_bits="--rsa-bits ${rsa_size}"
fi
# If we are expected to use an authorized policy, seal the secret
@@ -188,21 +204,18 @@ function tpm_set_authorized_policy_paths {
function tpm_create_authorized_policy {
- secret_key="$1"
- output_policy="$2"
- public_key="$3"
+ local secret_key="$1"
+ local output_policy="$2"
+ local public_key="$3"
# Generate the private key if it does not exist
- extra_opts=
+ local extra_opts=
if [ ! -f "$secret_key" ]; then
- extra_opts="--rsa-generate-key"
+ local rsa_size=$(tpm_get_rsa_key_size)
- tpm_set_rsa_key_size
- if [ $? -ne 0 ]; then
- return 1
- fi
- if [ -n "${FDE_RSA_KEY_SIZE}" -a ${FDE_RSA_KEY_SIZE} -ne 2048 ]; then
- extra_opts="${extra_opts} --rsa-bits ${FDE_RSA_KEY_SIZE}"
+ extra_opts="--rsa-generate-key"
+ if [ -n "$rsa_size" -a "$rsa_size" -ne 2048 ]; then
+ extra_opts="${extra_opts} --rsa-bits ${rsa_size}"
fi
fi
diff --git a/sysconfig.fde b/sysconfig.fde
index f3ee38b..741f5b4 100644
--- a/sysconfig.fde
+++ b/sysconfig.fde
@@ -38,5 +38,6 @@ FDE_DEVS=""
FDE_TPM_AUTO_UPDATE="yes"
# The RSA key size to be used for SRK and the private sign key
-# NOTE: Do not touch this variable. It's updated by fdectl automatically.
-FDE_RSA_KEY_SIZE="2048"
+# Expected values: 2048, 3072, 4096, or just leave it empty to let fdectl
+# to determine the size at runtime
+FDE_RSA_KEY_SIZE=""
--
2.35.3
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