usergen: Remove dependency against xxd(1)

xxd(1) is closely related to vim(1), might not be available under
some POSIX systems.

1 files changed, 15 insertions, 5 deletions

diff --git a/usergen b/usergen
index bc29e83..0052107 100755
--- a/usergen
+++ b/usergen
@@ -7,6 +7,16 @@ usage()
     echo "$0 <dir>"
 }
 
+to_hex()
+{
+    od -An -t x1 | tr -d ' '
+}
+
+to_bin()
+{
+    sed -e 's,\([0-9a-f]\{2\}\),\\\\\\x\1,g' | xargs printf
+}
+
 if [ $# != 1 ]; then
     usage >&2
     exit 1
@@ -44,17 +54,17 @@ echo "Quota, in MiB (leave empty for unlimited quota):" >&2
 read -r QUOTA
 QUOTA="$(printf '%d' "$QUOTA")"
 
-PWD=$(printf '%s' "$PWD" | xxd -p | tr -d '\n')
-SALT=$(openssl rand 32 | xxd -p | tr -d '\n')
-KEY=$(openssl rand 32 | xxd -p | tr -d '\n')
-PWD=$(printf '%s%s' $SALT "$PWD")
+PWD=$(printf '%s' "$PWD" | to_hex)
+SALT=$(openssl rand -hex 32)
+KEY=$(openssl rand -hex 32)
+PWD=$(printf '%s%s' "$SALT" "$PWD")
 
 ROUNDS=1000
 
 for i in $(seq $ROUNDS)
 do
     printf "\r%d/$ROUNDS" $i >&2
-    PWD=$(printf '%s' "$PWD" | xxd -p -r | sha256sum | cut -d' ' -f1)
+    PWD=$(printf '%s' "$PWD" | to_bin | sha256sum | cut -d' ' -f1)
 done
 
 echo >&2