aboutsummaryrefslogtreecommitdiffstats
path: root/src
diff options
context:
space:
mode:
authorGuilhem Moulin <guilhem@fripost.org>2014-01-23 02:18:40 +0100
committerGuilhem Moulin <guilhem@fripost.org>2015-06-07 04:27:57 +0200
commitba40cbca9650e1ddaa8357c21b5de31cc376c481 (patch)
tree292c6f88b870eee95d229c52a42b74655bc7ae2e /src
parentef60bfefc79b00a41ca3a8e9388d3cf3ff46068e (diff)
Ensure urandom entropy is of cryptographic quality.
The non-blocking PRNG /dev/urandom doesn't block if it has been seeded enough, sadly (e.g., if the entropy pool is empty). Reading a few bytes from the *blocking* should ensure that "the kernel RNG has [...] reach full entropy at least once, which guarantees cryptographic quality of the rest of the /dev/urandom stream." -- Tor bug #10676 https://trac.torproject.org/projects/tor/ticket/10676 See also urandom(4).
Diffstat (limited to 'src')
-rw-r--r--src/fripost-partman-udeb/base.sh45
-rw-r--r--src/fripost-partman-udeb/debian/templates8
-rwxr-xr-xsrc/fripost-postinst-udeb/finish-install.d/07fripost1
3 files changed, 54 insertions, 0 deletions
diff --git a/src/fripost-partman-udeb/base.sh b/src/fripost-partman-udeb/base.sh
index c23dcc1..b6770f8 100644
--- a/src/fripost-partman-udeb/base.sh
+++ b/src/fripost-partman-udeb/base.sh
@@ -52,6 +52,49 @@ wait_for_device() {
[ -b "$device" ] || fatal "Error: $device not found!"
}
+# The non-blocking PRNG /dev/urandom doesn't block if it has been seeded
+# enough, sadly (e.g., if the entropy pool is empty). Reading a few
+# bytes from the *blocking* should ensure that "the kernel RNG has [...]
+# reach full entropy at least once, which guarantees cryptographic
+# quality of the rest of the /dev/urandom stream." -- Tor bug #10676.
+# See also urandom(4). (XXX It's possible that the debian installer
+# does that already.)
+seed_urandom() {
+ local seed=/var/run/random-seed fifo n records dir
+ local poolfile=/proc/sys/kernel/random/poolsize bytes=512
+
+ if [ -f "$seed" ]; then
+ log "/dev/urandom has already been seeded since start-up"
+ return
+ fi
+
+ [ -r $poolfile ] && bytes=$(cat $poolfile)
+ log "Seeding /dev/urandom with $bytes bytes from /dev/random"
+ db_subst fripost/seed_urandom_progress_title BYTES $bytes
+ db_progress START 0 $bytes fripost/seed_urandom_progress_title
+ db_progress INFO fripost/seed_urandom_progress_info
+
+ fifo=$(mktemp -u)
+ /bin/mknod "$fifo" p || exit 1
+ trap 'kill $pid' EXIT
+ /bin/dd if=/dev/random bs=1 count=$bytes of=/dev/null 2> "$fifo" & pid=$!
+ heartbeat $pid USR1 &
+
+ local n records dir
+ while read -u 7 n records dir; do
+ [ "$records" = records -a "$dir" = out ] && db_progress SET ${n%+*}
+ done 7< "$fifo"
+ db_progress SET $bytes; sleep 0.25
+
+ rm -f "$fifo"
+ trap '' EXIT
+
+ db_progress STOP
+ db_unregister fripost/seed_urandom_progress_title
+ db_unregister fripost/seed_urandom_progress_info
+ touch "$seed"
+}
+
##############################################################################
# Wipe the disk (unless d-i's 'fripost/wipe-device' is 'none')
@@ -69,6 +112,7 @@ fripost_wipe() {
fi
source="/dev/$RET"
+ [ "$source" != /dev/urandom ] || seed_urandom
log "Want to wipe $device using source $source"
[ -b "$device" -a -d "$blockdir" -a -c "$source" ] || \
fatal "Invalid device $device or source $source"
@@ -211,6 +255,7 @@ fripost_encrypt() {
keyfile=$(mktemp) || exit 1
log "Encryting device $device and sets up a mapping $name"
+ seed_urandom
db_input high fripost/encryption-password || true
db_go
diff --git a/src/fripost-partman-udeb/debian/templates b/src/fripost-partman-udeb/debian/templates
index 2088e19..4f4d177 100644
--- a/src/fripost-partman-udeb/debian/templates
+++ b/src/fripost-partman-udeb/debian/templates
@@ -1,3 +1,11 @@
+Template: fripost/seed_urandom_progress_title
+Type: text
+Description: Seeding /dev/urandom with ${BYTES} bytes from /dev/random
+
+Template: fripost/seed_urandom_progress_info
+Type: text
+Description: This may take a while
+
Template: debian-installer/fripost-partman/title
Type: text
Description: Partition disks using a shell script
diff --git a/src/fripost-postinst-udeb/finish-install.d/07fripost b/src/fripost-postinst-udeb/finish-install.d/07fripost
index c00e617..5a7cd73 100755
--- a/src/fripost-postinst-udeb/finish-install.d/07fripost
+++ b/src/fripost-postinst-udeb/finish-install.d/07fripost
@@ -24,6 +24,7 @@ set -ue
. /lib/fripost-partman/base.sh
import=/cdrom/include
+seed_urandom
# Update the information below the progress bar. Also, log the argument.
progress() {