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Unencrypted keys in user directory for single-password access (from #1399) #1585

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Unencrypted keys in user directory for single-password access (from #1399) #1585

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e1aa4e2
New style of crouton passwordless encryption
Timvrakas Apr 9, 2015
2ff8299
Further changes to passwordless encryption (as requested by @dnschneid).
Timvrakas May 22, 2015
71cc57d
Changed NOPASS to local.
Timvrakas May 27, 2015
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155 changes: 113 additions & 42 deletions host-bin/mount-chroot
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Original file line number Diff line number Diff line change
Expand Up @@ -9,11 +9,14 @@ APPLICATION="${0##*/}"
BINDIR="`dirname "\`readlink -f "$0"\`"`"
CHROOTS="`readlink -m "$BINDIR/../chroots"`"
CREATE=''
ENABLENOPASS=''
ENCRYPT=''
KEYFILE=''
PRINT=''
NOENC=''
ROOT="`readlink -m '/var/run/crouton'`"
MOUNTOPTS='rw,dev,exec,suid'
PAD='................'

USAGE="$APPLICATION [options] name [...]

Expand Down Expand Up @@ -60,27 +63,46 @@ addtrap "stty echo 2>/dev/null"

# Function to prompt the user for a passphrase. Sets $passphrase.
promptNewPassphrase() {
echo_tty -n "Choose an encryption passphrase for $NAME: "
[ -t 0 ] && stty -echo
while [ -z "$passphrase" ]; do
local NOPASS=''
if [ "$KEYFILE" != "$CHROOTSRC/.ecryptfs" ]; then
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Actually, I think this should still be enforced if keyfile wasn't set by the user.

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About this... I wasn't sure if the warning about secure location was enough, or the blank passphrase should be linked to the -k flag. Right now they are independent features. I get the secure location thing, but seeing as the crouton default is no encryption at all, it feels like overkill.

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The point of the -e flag is to make your chroot install more secure. If we allow blank passwords without further configuration, then people will assume that even with a blank passphrase, things are fine (they will ignore the later warnings). Unless you see actual value in allowing co-located unencrypted passphrases, I'd rather disallow it to avoid any chance of a false sense of security.

ENABLENOPASS='y'
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Does ENABLENOPASS need to be a global variable if you redetermine it each time?

fi
while [ -z "$passphrase" -a -z "$NOPASS" ]; do
[ -t 0 ] && stty -echo
echo_tty -n "Choose an encryption passphrase for $NAME: "
read -r passphrase
if [ -z "$passphrase" ]; then
echo_tty ''
echo_tty -n 'You must specify a passphrase: '
continue
fi
echo_tty ''
echo_tty -n 'Please confirm your passphrase: '
read -r confirmation
echo_tty ''
if [ ! "$confirmation" = "$passphrase" ]; then
passphrase=''
echo_tty ''
echo_tty -n 'Passphrases do not match; try again: '
echo_tty -n 'Passphrases do not match.'
continue
fi
[ -t 0 ] && stty echo
if [ -z "$passphrase" ]; then
if [ -n "$ENABLENOPASS" ]; then
echo_tty -n \
'You did not specify a passphrase. Your keys will not be encrypted.
Only do this if you are confident that your keys are stored in a secure location.
Do you want to continue? [y/N]: '
read -r response
if [ "${response#[Yy]}" = "$response" ]; then
continue
else
NOPASS='y'
echo_tty 'No password set, keys will not be encrypted'
fi
else
echo_tty \
'Passphrases cannot be empty unless the keyfile
is stored separately from the chroot using -k.'
continue
fi
fi
confirmation=''
done
[ -t 0 ] && stty echo
echo_tty ''
}

# Mount each chroot
Expand Down Expand Up @@ -186,63 +208,112 @@ for NAME in "$@"; do
echo 'done' 1>&2

# Create key file
wrappedkey="`mktemp`"
wrappedfnek="`mktemp`"
addtrap "rm -f '$wrappedkey' '$wrappedfnek'"
echo -n "$key
if [ -z "$NOPASS" ]; then
wrappedkey="`mktemp`"
wrappedfnek="`mktemp`"
addtrap "rm -f '$wrappedkey' '$wrappedfnek'"
echo -n "$key
$passphrase" | ecryptfs-wrap-passphrase "$wrappedkey" -
echo -n "$fnek
echo -n "$fnek
$passphrase" | ecryptfs-wrap-passphrase "$wrappedfnek" -
unset key fnek
echo | cat - "$wrappedkey" "$wrappedfnek" > "$KEYFILE"
unset key fnek
echo | cat - "$wrappedkey" "$wrappedfnek" > "$KEYFILE"
else
echo -n "
$PAD$key$PAD$fnek" > "$KEYFILE"
NOENC=$NOPASS
fi
if [ ! -f "$CHROOTSRC/.ecryptfs" ]; then
echo "$KEYFILE" > "$CHROOTSRC/.ecryptfs"
fi
elif [ ! -f "$KEYFILE" ]; then
error 1 "Unable to find encryption key file $KEYFILE"
else
echo_tty -n "Enter encryption passphrase for $NAME: "
[ -t 0 ] && stty -echo
if [ -z "$passphrase" ]; then
read -r passphrase
fi
[ -t 0 ] && stty echo
echo_tty ''

wrappedkey="`mktemp`"
wrappedfnek="`mktemp`"
addtrap "rm -f '$wrappedkey' '$wrappedfnek'"

# Extract wrapped keys from keyfile
tail -c 160 "$KEYFILE" | head -c 80 > "$wrappedkey"
tail -c 80 "$KEYFILE" > "$wrappedfnek"
PAD1="`tail -n+2 "$KEYFILE" | head -c 16`"

if [ "$PAD1" = "$PAD" ]; then
NOENC='y'
contents="`tail -n+2 "$KEYFILE"`"
key="${contents#${PAD}}"
key="${key%%${PAD}*}"
fnek="${contents##*${PAD}}"
else
# Extract wrapped keys from keyfile
tail -c 160 "$KEYFILE" | head -c 80 > "$wrappedkey"
tail -c 80 "$KEYFILE" > "$wrappedfnek"

while [ -z "$passphrase" ]; do
echo_tty -n "Enter encryption passphrase for $NAME: "
[ -t 0 ] && stty -echo
read -r passphrase
[ -t 0 ] && stty echo
echo_tty ''
done
fi

# Change the passphrase if requested
if [ "${ENCRYPT:-0}" -ge 2 ]; then
oldpassphrase="$passphrase"
passphrase="$CROUTON_NEW_PASSPHRASE"
promptNewPassphrase

echo "Applying passphrase change" 1>&2
echo -n "$oldpassphrase

if [ -z "$NOENC" -a -z "$NOPASS" ]; then
# Re-wrap alreay encrypted passphrase
echo -n "$oldpassphrase
$passphrase" | ecryptfs-rewrap-passphrase "$wrappedkey" -
echo -n "$oldpassphrase
echo -n "$oldpassphrase
$passphrase" | ecryptfs-rewrap-passphrase "$wrappedfnek" -
echo | cat - "$wrappedkey" "$wrappedfnek" > "$KEYFILE"
echo | cat - "$wrappedkey" "$wrappedfnek" > "$KEYFILE"
elif [ -n "$NOENC" -a -z "$NOPASS" ]; then
# Wrap previously unwrapped pasphrase
echo -n "$key
$passphrase" | ecryptfs-wrap-passphrase "$wrappedkey" -
echo -n "$fnek
$passphrase" | ecryptfs-wrap-passphrase "$wrappedfnek" -
echo | cat - "$wrappedkey" "$wrappedfnek" > "$KEYFILE"
unset key fnek
elif [ -z "$NOENC" -a -n "$NOPASS" ]; then
# Unwrap previously wrapped passphrase
key="`echo -n "$oldpassphrase" \
| ecryptfs-unwrap-passphrase "$wrappedkey" - 2>/dev/null`"
fnek="`echo -n "$oldpassphrase" \
| ecryptfs-unwrap-passphrase "$wrappedfnek" - 2>/dev/null`"
echo -n "
$PAD$key$PAD$fnek" > "$KEYFILE"
elif [ -n "$NOENC" -a -n "$NOPASS" ]; then
#Do nothing
echo 'Applying double-ROT13 encryption to keys.. :)' 1>&2
fi

NOENC=$NOPASS
unset oldpassphrase
fi
fi

# Add keys to keychain and extract
keysig="`echo -n "$passphrase" \
| ecryptfs-unwrap-passphrase "$wrappedkey" - 2>/dev/null \
| ecryptfs-add-passphrase - 2>/dev/null \
| sed -n 's/.*\[\([0-9a-zA-Z]*\)\].*/\1/p'`"
fneksig="`echo -n "$passphrase" \
| ecryptfs-unwrap-passphrase "$wrappedfnek" - 2>/dev/null \
| ecryptfs-add-passphrase - 2>/dev/null \
| sed -n 's/.*\[\([0-9a-zA-Z]*\)\].*/\1/p'`"
if [ -n "$NOENC" ]; then
keysig="`echo -n "$key" \
| ecryptfs-add-passphrase - 2>/dev/null \
| sed -n 's/.*\[\([0-9a-zA-Z]*\)\].*/\1/p'`"
fneksig="`echo -n "$fnek" \
| ecryptfs-add-passphrase - 2>/dev/null \
| sed -n 's/.*\[\([0-9a-zA-Z]*\)\].*/\1/p'`"
else
keysig="`echo -n "$passphrase" \
| ecryptfs-unwrap-passphrase "$wrappedkey" - 2>/dev/null \
| ecryptfs-add-passphrase - 2>/dev/null \
| sed -n 's/.*\[\([0-9a-zA-Z]*\)\].*/\1/p'`"
fneksig="`echo -n "$passphrase" \
| ecryptfs-unwrap-passphrase "$wrappedfnek" - 2>/dev/null \
| ecryptfs-add-passphrase - 2>/dev/null \
| sed -n 's/.*\[\([0-9a-zA-Z]*\)\].*/\1/p'`"
fi

if [ -z "$keysig" -o -z "$fneksig" ]; then
error 1 "Failed to decrypt $NAME."
fi
Expand Down