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tpmr: Use at_exit for cleanup traps

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Multiple traps overwrite each other.  While no tpmr functions have more
than one trap right now, it is fragile, and the quoting is complex due
to double expansion.  Use at_exit to add exit handlers that accumulate
and do not require special quoting.

Signed-off-by: Jonathon Hall <jonathon.hall@puri.sm>
This commit is contained in:
Jonathon Hall 2023-03-10 17:50:43 -05:00
parent decd45f361
commit 55b3fcfe1a
No known key found for this signature in database
GPG Key ID: 1E9C3CA91AE25114
2 changed files with 42 additions and 8 deletions
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16
initrd/bin/tpmr
View File

@ -226,9 +226,9 @@ tpm2_startsession() {
tpm2 sessionconfig -Q --disable-encrypt "/tmp/$DEC_SESSION_FILE"
}
# Trap EXIT with cleanup_session() to release a TPM2 session and delete the
# Use cleanup_session() with at_exit to release a TPM2 session and delete the
# session file. E.g.:
# trap "cleanup_session '$SESSION_FILE'" EXIT
# at_exit cleanup_session "$SESSION_FILE"
cleanup_session() {
TRACE "Under /bin/tpmr:cleanup_session"
session_file="$1"
@ -243,8 +243,8 @@ cleanup_session() {
}
# Clean up a file by shredding it. No-op if the file wasn't created. Use with
# trap EXIT, e.g.:
# trap "cleanup_shred '$FILE'" EXIT
# at_exit, e.g.:
# at_exit cleanup_shred "$FILE"
cleanup_shred() {
TRACE "Under /bin/tpmr:cleanup_shred"
shred -n 10 -z -u "$1" 2>/dev/null || true
@ -281,7 +281,7 @@ tpm2_seal() {
rm -f "$TRIAL_SESSION" "$AUTH_POLICY"
tpm2 startauthsession -g sha256 -S "$TRIAL_SESSION"
# We have to clean up the session
trap "cleanup_session '$TRIAL_SESSION'" EXIT
at_exit cleanup_session "$TRIAL_SESSION"
# Save the policy hash in case the password policy is not used (we have
# to get this from the last step, whichever it is).
tpm2 policypcr -Q -l "sha256:$pcrl" -f "$pcrf" -S "$TRIAL_SESSION" -L "$AUTH_POLICY"
@ -334,7 +334,7 @@ tpm1_seal() {
tpm_password="$7" # Owner password - will prompt if needed and not empty
sealed_file="$SECRET_DIR/tpm1_seal_sealed.bin"
trap "cleanup_shred '$sealed_file'" EXIT
at_exit cleanup_shred "$sealed_file"
POLICY_ARGS=()
@ -412,7 +412,7 @@ tpm2_unseal() {
POLICY_SESSION=/tmp/unsealfile_policy.session
rm -f "$POLICY_SESSION"
tpm2 startauthsession -Q -g sha256 -S "$POLICY_SESSION" --policy-session
trap "cleanup_session '$POLICY_SESSION'" EXIT
at_exit cleanup_session "$POLICY_SESSION"
# Check the PCR policy
tpm2 policypcr -Q -l "sha256:$pcrl" -S "$POLICY_SESSION"
UNSEAL_PASS_SUFFIX=""
@ -442,7 +442,7 @@ tpm1_unseal() {
# correct either, so just ignore it in TPM1.
sealed_file="$SECRET_DIR/tpm1_unseal_sealed.bin"
trap "cleanup_shred '$sealed_file'" EXIT
at_exit cleanup_shred "$sealed_file"
rm -f "$sealed_file"

34
initrd/etc/functions
View File

@ -576,3 +576,37 @@ generate_random_mac_address()
#Borrowed from https://stackoverflow.com/questions/42660218/bash-generate-random-mac-address-unicast
hexdump -n 6 -ve '1/1 "%.2x "' /dev/urandom | awk -v a="2,6,a,e" -v r="$RANDOM" 'BEGIN{srand(r);}NR==1{split(a,b,",");r=int(rand()*4+1);printf "%s%s:%s:%s:%s:%s:%s\n",substr($1,0,1),b[r],$2,$3,$4,$5,$6}'
}
# Add a command to be invoked at exit. (Note that trap EXIT replaces any
# existing handler.) Commands are invoked in reverse order, so they can be used
# to clean up resources, etc.
# The parameters are all executed as-is and do _not_ require additional quoting
# (unlike trap). E.g.:
# at_exit shred "$file" #<-- file is expanded when calling at_exit, no extra quoting needed
at_exit() {
AT_EXIT_HANDLERS+=("$@") # Command and args
AT_EXIT_HANDLERS+=("$#") # Number of elements in this command
}
# Array of all exit handler command arguments with lengths of each command at
# the end. For example:
# at_exit echo hello
# at_exit echo a b c
# results in:
# AT_EXIT_HANDLERS=(echo hello 2 echo a b c 4)
AT_EXIT_HANDLERS=()
# Each handler is an array AT_EXIT_HANDLER_{i}
run_at_exit_handlers() {
local cmd_pos cmd_len
cmd_pos="${#AT_EXIT_HANDLERS[@]}"
# Silence trace if there are no handlers, this is common and occurs a lot
[ "$cmd_pos" -gt 0 ] && DEBUG "Running at_exit handlers"
while [ "$cmd_pos" -gt 0 ]; do
cmd_pos="$((cmd_pos-1))"
cmd_len="${AT_EXIT_HANDLERS[$cmd_pos]}"
cmd_pos="$((cmd_pos-cmd_len))"
"${AT_EXIT_HANDLERS[@]:$cmd_pos:$cmd_len}"
done
}
trap run_at_exit_handlers EXIT