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Improve argon2 handling and KDF in general
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Previously it wasn't possible to use argon2 as KDF function without the tomb tools from extras/kdf-keys being available.
To change that behaviour introduce checks on the ARGON2 variable. Additionally add a fallback function to create a salt that is compatible to tomb-kdb-pbkdf2-gensalt.

Options specific for the different supported KDF algorithm are reorganized. Some options align between the various KDF and some are unique to them.
The output of -h is enhanced with the various --kdf options and depends on the available optional tools. argon2 specific cli arguments won't be displayed if argon2 is not available.

Add case for results beside argon2 and pbkdf2. Key creation won't be stopped, just a warning is issued that the resulting key won't be protected via KDF.

Regarding the cli options. The argument for the suboption --kdf is made optional. In that regard one needs to make sure, that if --kdf is the last option before an argument one needs to use - to separate or use -k.
Example: tomb forge --kdf - testkey.tomb
Example: tomb forge --kdf -k testkey.tomb
Example: tomb forge -k testkey.tomb --kdf

Additonally the kdf options are reorganized, which is a possible breaking change for scripts or GUI helpers.
* --kdftype is changed to --kdf
* --kdfiter is introduced as replacement the for previous --kdf definition
* --kdfpar is introduced to support the parallelism option of argon2
Only --kdf is mandatory to get a key which is protected with KDF. For every other option safe defaults are set and can be optionally adjusted.
KDF related subcommand options are removed where they don't come into play. gen_key() is only called in forge and passwd.

Closes #526
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@Narrat
Narrat committed Jul 25, 2024
1 parent 857895a commit 79b73d3
Showing 1 changed file with 58 additions and 31 deletions.
89 changes: 58 additions & 31 deletions tomb
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Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,7 @@ typeset -i SPHINX=1
typeset -i RESIZER=1
typeset -i RECOLL=1
typeset -i QRENCODE=1
typeset -i ARGON2=1

# Default mount options
typeset MOUNTOPTS="rw,noatime,nodev"
Expand Down Expand Up @@ -840,8 +841,13 @@ usage() {
_print " --sphx-host host associated with the key (for use with pitchforkedsphinx)"
}

[[ $KDF == 1 ]] && {
_print " --kdf forge keys armored against dictionary attacks"
[[ $KDF == 1 ]] || [[ $ARGON2 == 1 ]] && {
_print " --kdf forge keys armored against dictionary attacks (pbkdf2 (default), argon2)"
_print " --kdfiter Number of iterations (meaning depending on KDF algorithm) (pbkdf2, argon2)"
}
[[ $ARGON2 == 1 ]] && {
_print " --kdfmem memory to be used (argon2)"
_print " --kdfpar number of threads (argon2)"
}

echo
Expand Down Expand Up @@ -1313,11 +1319,14 @@ get_lukskey() {
kdf_salt="${firstline[(ws:_:)3]}"
kdf_ic="${firstline[(ws:_:)4]}"
kdf_mem="${firstline[(ws:_:)5]}"
kdf_par="${firstline[(ws:_:)6]}"
# ToDo also parse kdf_len?
_message "Unlocking KDF key protection (::1 kdf::)" $kdf_hash
_verbose "KDF salt: $kdf_salt"
_verbose "KDF ic: $kdf_ic"
_verbose "KDF mem: $kdf_mem"
_password=$(argon2 $kdf_salt -m $kdf_mem -t $kdf_ic -l 64 -r 2>/dev/null <<<$_password)
_verbose "KDF # threads: $kdf_par"
_password=$(argon2 $kdf_salt -m $kdf_mem -t $kdf_ic -p $kdf_par -l 64 -r 2>/dev/null <<<$_password)
;;

*)
Expand Down Expand Up @@ -1589,50 +1598,68 @@ gen_key() {
fi

header=""
[[ $KDF == 1 ]] && {
[[ $KDF == 1 ]] || [[ $ARGON2 == 1 ]] && {
{ option_is_set --kdf } && {
# KDF is a new key strenghtening technique against brute forcing
# KDF is a key strengthening technique against brute forcing
# see: https://github.com/dyne/Tomb/issues/82
itertime="`option_value --kdf`"
# Two algorithm currently supported:
# * pbkdf2 (covers against time)
# * argon2 (covers against time, memory and parallelismn)

# --kdfiter takes one parameter: time cost in seconds
# (argon2 has a default of 3 iterations;
# the resulting itertime with this default is considered safe enough for pbkdf2)
itertime="`option_value --kdfiter`"
itertime=${itertime:-3}

# removing support of floating points because they can't be type checked well
# if [[ "$itertime" != <-> ]]; then
# unset tombpass
# unset tombpasstmp
# _warning "Wrong argument for --kdf: must be an integer number (iteration seconds)."
# _warning "Wrong argument for --kdfiter: must be an integer number (iteration seconds)."
# _failure "Depending on the speed of machines using this tomb, use 1 to 10, or more"
# return 1
# fi
# # --kdf takes one parameter: iter time (on present machine) in seconds

kdftype="`option_value --kdftype`"
# Generating salt (either via tomb-kdb-pbkdf2 or a shell fallback)
if $(command -v tomb-kdb-pbkdf2-gensalt 1>/dev/null 2>/dev/null); then
kdfsalt=`tomb-kdb-pbkdf2-gensalt`
else
kdfsalt=$(LC_CTYPE=C tr -cd 'a-f0-9' < /dev/random | head -c 64)
fi
_message "kdf salt: ::1 kdfsalt::" $kdfsalt

# --kdf takes one optional parameter: what KDF
# (pbkdf being the default)
kdftype="`option_value --kdf`"
kdftype=${kdftype:-pbkdf2}
case ${kdftype} in
pbkdf2)
pbkdf2)
local -i microseconds
microseconds=$(( itertime * 1000000 ))
_success "Using KDF, iteration time: ::1 microseconds::" $microseconds
_message "generating salt"
pbkdf2_salt=`tomb-kdb-pbkdf2-gensalt`
_success "Using pbkdf2 as KDF, iteration time: ::1 microseconds::" $microseconds
_message "calculating iterations"
pbkdf2_iter=`tomb-kdb-pbkdf2-getiter $microseconds`
_message "encoding the password"
# We use a length of 64bytes = 512bits (more than needed!?)
tombpass=`tomb-kdb-pbkdf2 $pbkdf2_salt $pbkdf2_iter 64 <<<"${tombpass}"`

header="_KDF_pbkdf2sha1_${pbkdf2_salt}_${pbkdf2_iter}_64\n"
tombpass=`tomb-kdb-pbkdf2 $kdfsalt $pbkdf2_iter 64 <<<"${tombpass}"`
header="_KDF_pbkdf2sha1_${kdfsalt}_${pbkdf2_iter}_64\n"
;;
argon2)
_success "Using KDF Argon2"
argon2)
_success "Using Argon2 as KDF"
_message "iterations: ::1 kdfiterations::" $itertime
kdfmem="`option_value --kdfmem`"
kdfmem=${kdfmem:-18}
_message "memory used: 2^::1 kdfmemory::" $kdfmem
itertime="`option_value --kdf`"
itertime=${itertime:-3}
kdfsalt=`tomb-kdb-pbkdf2-gensalt`
_message "kdf salt: ::1 kdfsalt::" $kdfsalt
_message "kdf iterations: ::1 kdfiterations::" $itertime
tombpass=`argon2 $kdfsalt -m $kdfmem -t $itertime -l 64 -r <<<"${tombpass}"`
header="_KDF_argon2_${kdfsalt}_${itertime}_${kdfmem}_64\n"
kdfpar="`option_value --kdfpar`"
kdfpar=${kdfpar:-1}
_message "parallelismn: ::1 kdfparallel::" $kdfpar
tombpass=`argon2 $kdfsalt -m $kdfmem -t $itertime -p $kdfpar -l 64 -r <<<"${tombpass}"`
header="_KDF_argon2_${kdfsalt}_${itertime}_${kdfmem}_${kdfpar}_64\n"
;;
*)
_warning "unrecognized KDF ::1::" $kdftype
_warning "key won\'t be protected via a KDF implementation"
;;
esac
}
Expand Down Expand Up @@ -2095,7 +2122,7 @@ forge_key() {
$destkey $algo

[[ $KDF == 1 ]] && { ! option_is_set -g } && {
_message "Using KDF to protect the key password (`option_value --kdf` rounds)"
_message "Using KDF to protect the key password"
}

TOMBKEYFILE="$destkey" # Set global variable
Expand Down Expand Up @@ -3268,19 +3295,19 @@ main() {
main_opts=(q -quiet=q D -debug=D h -help=h v -version=v f -force=f -tmp: U: G: T: -no-color -unsafe g -gpgkey=g -sudo:)
subcommands_opts[__default]=""
# -o in open and mount is used to pass alternate mount options
subcommands_opts[open]="n -nohook=n k: -kdf: -kdftype: -kdfmem: o: -ignore-swap -tomb-pwd: r: R: -sphx-host: -sphx-user: p -preserve-ownership=p"
subcommands_opts[open]="n -nohook=n k: o: -ignore-swap -tomb-pwd: r: R: -sphx-host: -sphx-user: p -preserve-ownership=p"
subcommands_opts[mount]=${subcommands_opts[open]}

subcommands_opts[create]="" # deprecated, will issue warning

# -o in forge and lock is used to pass an alternate cipher.
subcommands_opts[forge]="-ignore-swap k: -kdf: -kdftype: -kdfmem: o: -tomb-pwd: -use-random r: R: -sphx-host: -sphx-user: "
subcommands_opts[forge]="-ignore-swap k: -kdf:: -kdfiter: -kdfmem: -kdfpar: o: -tomb-pwd: -use-random r: R: -sphx-host: -sphx-user: "
subcommands_opts[dig]="-ignore-swap s: -size=s "
subcommands_opts[lock]="-ignore-swap k: -kdf: -kdftype: -kdfmem: o: -tomb-pwd: r: R: -sphx-host: -sphx-user: -filesystem: "
subcommands_opts[setkey]="k: -ignore-swap -kdf: -kdftype: -kdfmem: -tomb-old-pwd: -tomb-pwd: r: R: -sphx-host: -sphx-user: "
subcommands_opts[lock]="-ignore-swap k: o: -tomb-pwd: r: R: -sphx-host: -sphx-user: -filesystem: "
subcommands_opts[setkey]="k: -ignore-swap -tomb-old-pwd: -tomb-pwd: r: R: -sphx-host: -sphx-user: "
subcommands_opts[engrave]="k: "

subcommands_opts[passwd]="k: -ignore-swap -kdf: -kdftype: -kdfmem: -tomb-old-pwd: -tomb-pwd: r: R: -sphx-host: -sphx-user: "
subcommands_opts[passwd]="k: -ignore-swap -kdf:: -kdfiter: -kdfmem: -kdfpar: -tomb-old-pwd: -tomb-pwd: r: R: -sphx-host: -sphx-user: "
subcommands_opts[close]=""
subcommands_opts[help]=""
subcommands_opts[slam]=""
Expand Down

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