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Implement muli-user authentication for yubikey pba, i.e. multiple users can now share a single luks keyslot.

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This is achieved by having multiple lines per storage file, one for each user (if the feature is enabled); each of these
lines has the same format as would be the case for the userless authentication, except that they are prepended with a
SHA-512 of the user's id.
This commit is contained in:
Moritz Maxeiner 2014-01-29 17:20:05 +01:00
parent 20cfaf0faa
commit e96f58ef5c
1 changed files with 60 additions and 16 deletions
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76
nixos/modules/system/boot/luksroot.nix
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@ -68,39 +68,69 @@ let
mount -t ${yubikey.storage.fsType} ${toString yubikey.storage.device} ${yubikey.storage.mountPoint}
local uuid_r
uuid_r="$(take 32 ${yubikey.storage.mountPoint}${yubikey.storage.path})"
local uuid_luks
uuid_luks="$(cryptsetup luksUUID ${device} | take 36 | tr -d '-')"
local k_user
local challenge
local k_blob
local aes_blob_decrypted
local checksum_correct
local checksum
local uuid_luks
local user_record
uuid_luks="$(cryptsetup luksUUID ${device} | take 36 | tr -d '-')"
${optionalString (!yubikey.multiUser) ''
user_record="$(cat ${yubikey.storage.mountPoint}${yubikey.storage.path})"
uuid_r="$(echo -n $user_record | take 32)"
''}
for try in $(seq 3); do
${optionalString yubikey.multiUser ''
local user_id
echo -n "Enter user id: "
read -s user_id
echo
''}
${optionalString yubikey.twoFactor ''
echo -n "Enter two-factor passphrase: "
read -s k_user
echo
''}
challenge="$(echo -n $k_user$uuid_r$uuid_luks | openssl-wrap dgst -binary -sha1 | rbtohex)"
${optionalString yubikey.multiUser ''
local user_id_hash
user_id_hash="$(echo -n $user_id | openssl-wrap dgst -binary -sha512 | rbtohex)"
k_blob="$(ykchalresp -${toString yubikey.slot} -x $challenge 2>/dev/null)"
user_record="$(sed -n -e /^$user_id_hash[^$]*$/p ${yubikey.storage.mountPoint}${yubikey.storage.path} | tr -d '\n')"
aes_blob_decrypted="$(drop 32 ${yubikey.storage.mountPoint}${yubikey.storage.path} | hextorb | openssl-wrap enc -d -aes-256-ctr -K $k_blob -iv $uuid_r | rbtohex)"
if [ ! -z "$user_record" ]; then
user_record="$(echo -n $user_record | drop 128)"
uuid_r="$(echo -n $user_record | take 32)"
''}
checksum="$(echo -n $aes_blob_decrypted | drop 168)"
if [ "$(echo -n $aes_blob_decrypted | hextorb | take 84 | openssl-wrap dgst -binary -sha512 | rbtohex)" == "$checksum" ]; then
checksum_correct=1
break
challenge="$(echo -n $k_user$uuid_r$uuid_luks | openssl-wrap dgst -binary -sha1 | rbtohex)"
k_blob="$(ykchalresp -${toString yubikey.slot} -x $challenge 2>/dev/null)"
aes_blob_decrypted="$(echo -n $user_record | drop 32 | hextorb | openssl-wrap enc -d -aes-256-ctr -K $k_blob -iv $uuid_r | rbtohex)"
checksum="$(echo -n $aes_blob_decrypted | drop 168)"
if [ "$(echo -n $aes_blob_decrypted | hextorb | take 84 | openssl-wrap dgst -binary -sha512 | rbtohex)" == "$checksum" ]; then
checksum_correct=1
break
else
checksum_correct=0
echo "Authentication failed!"
fi
${optionalString yubikey.multiUser ''
else
checksum_correct=0
echo "Authentication failed!"
checksum_correct=0
echo "Authentication failed!"
fi
''}
done
if [ "$checksum_correct" != "1" ]; then
@ -139,8 +169,16 @@ let
local new_k_blob
new_k_blob="$(echo -n $new_challenge | hextorb | openssl-wrap dgst -binary -sha1 -mac HMAC -macopt hexkey:$k_yubi | rbtohex)"
echo -n "$new_uuid_r" > ${yubikey.storage.mountPoint}${yubikey.storage.path}
echo -n "$k_yubi$k_luks$checksum" | hextorb | openssl-wrap enc -e -aes-256-ctr -K "$new_k_blob" -iv "$new_uuid_r" | rbtohex >> ${yubikey.storage.mountPoint}${yubikey.storage.path}
local new_aes_blob
new_aes_blob=$(echo -n "$k_yubi$k_luks$checksum" | hextorb | openssl-wrap enc -e -aes-256-ctr -K "$new_k_blob" -iv "$new_uuid_r" | rbtohex)
${optionalString yubikey.multiUser ''
sed -i -e "s|^$user_id_hash$user_record|$user_id_hash$new_uuid_r$new_aes_blob|1"
''}
${optionalString (!yubikey.multiUser) ''
echo -n "$new_uuid_r$new_aes_blob" > ${yubikey.storage.mountPoint}${yubikey.storage.path}
''}
else
echo "Warning: Could not obtain new UUID, current challenge persists!"
fi
@ -298,6 +336,12 @@ in
description = "Whether to use a passphrase and a Yubikey (true), or only a Yubikey (false)";
};
multiUser = mkOption {
default = false;
type = types.bool;
description = "Whether to allow multiple users to authenticate with a Yubikey";
};
slot = mkOption {
default = 2;
type = types.int;