initial commit

diff --git a/askpass.sh b/askpass.sh
new file mode 100755 (executable)
index 0000000..9304907
--- /dev/null
+++ b/askpass.sh
@@ -0,0 +1,68 @@
+#!/bin/bash
+
+# askpass.sh by Felix Kästner, GPL3
+
+
+# in $* there could be the prompt-message (from an invoking program like sudo)
+# delete any trailing space or colon and write it to stderr
+promptmsg="enter password:"
+[ "$*" != "" ] && promptmsg="${*% }"
+echo -en "$0: ${promptmsg%:}: " >&2
+
+pw=""
+stars=0
+cx='abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789' # chars that can be echoed as feedback for a keypress, there have been problems when using special chars
+
+while :
+do
+    # set IFS to newline and read a character
+    # -s silent, -r \ is taken literal, not as escape character, -n 1 only one char is read
+    IFS=$'\n' read -s -r -n 1 char
+    case "$char" in
+        "\7f")
+            # backspace was pressed
+            # deletes the last character from $pw and moves the cursor one char back, deleting this char, but don't delete more chars than available
+            pw="${pw%?}"
+            [ $stars -gt 0 ] && { ((stars--)); echo -en "\b \b" >&2; }
+        ;;
+        "\ 4")
+            # ctrl + d was pressed, this means abort/cancel
+            # delete all echoed characters, unset variables and exit
+            while [ $((stars--)) -gt 0 ]
+            do
+                echo -en "\b \b" >&2
+            done
+            
+            unset pw char stars rnd cx
+            echo "cancelled " >&2
+            exit 1
+        ;;
+        ?)
+            # add the char to pw and echo some chars as visual feedback
+            pw="$pw$char"
+            ((rnd = RANDOM % 3 + 1)) # bash specific
+            ((stars += rnd))
+            # echos $rnd much of the characters from $cx
+            while [ $((rnd--)) -gt 0 ]
+            do
+                echo -n "${cx:$(($RANDOM % ${#cx})):1}" >&2
+            done
+        ;;
+        "")
+            # no new character, so pw is completed
+            # delete the echoed characters
+            remain=$(($RANDOM % 4 + 6))
+            while [ $((stars--)) -gt $remain ]
+            do
+                echo -en "\b \b" >&2
+            done
+            break
+        ;;
+    esac
+done
+
+# write a newline to stderr and the password to stdout
+echo "" >&2
+echo "$pw"
+unset pw char stars rnd cx remain
+