--- /dev/null
+#!/bin/sh
+#
+# A posix sh CGI script (yeah, that's right) to update the daily
+# code for CharmBypass. This is not useful to you unless you
+# host CharmBypass on a public web server and are insane.
+#
+
+# Fail on the first error.
+set -e
+
+# The CGI spec says that the current working directory SHOULD be set
+# to the directory containing the script. Well, that's not always what
+# happens. It's true in apache...
+INDEX_HTML=$(pwd)/../index.html
+
+# But not in python's server.http
+[ -f "${INDEX_HTML}" ] || INDEX_HTML=$(pwd)/index.html
+
+
+# Die with an error. The first argument, an HTTP status code, is
+# returned as the Status. The second argument, an error message, is
+# printed after setting the Content-type to text/plain. Finally, we
+# cease execution.
+die() {
+ echo "Status: ${1}"
+ echo "Content-type: text/plain"
+ echo ""
+ echo "${2}"
+ exit 1
+}
+
+# Redirect to the given URL; return a 302 status, and send the
+# necessary location header.
+redirect() {
+ echo "Status: 302"
+ echo "Location: ${1}"
+ echo ""
+ exit
+}
+
+# Parse and return the daily code from the index.html file.
+# This relies on "implementation details" within the HTML;
+# namely, the field name and its value must appear next
+# to each other on the same line.
+parse_code() {
+ sed -n \
+ -e 's/.*name="code" value="\([A-Za-z0-9]\{2\}\)".*/\1/p' \
+ "${INDEX_HTML}" \
+ | head -n 1
+}
+
+# Update (replace) the daily code in the index.html file. The first
+# argument is the new code to use. This relies on "implementation
+# details" within the HTML; namely, the field name and its value must
+# appear next to each other on the same line.
+update_code() {
+ _new_code="${1}"
+ _find='name="code" value="[a-zA-Z0-9]\{0,2\}"'
+ _replace="name=\"code\" value=\"${_new_code}\""
+ _tmp=$(mktemp)
+
+ # The "-i" flag to sed isn't POSIX, and worse, it tries to use a
+ # temp file in CWD. We don't want to make the parent directory
+ # writable because then this script is writable.
+ sed -e "s/${_find}/${_replace}/g" "${INDEX_HTML}" > "${_tmp}"
+
+ # mv would also recreate the file here, so cp/rm instead.
+ cp "${_tmp}" "${INDEX_HTML}"
+ rm "${_tmp}"
+}
+
+# Display the "update code" form and exit.
+display_code_form() {
+ echo "Content-type: text/html"
+ echo ""
+
+ cat <<-EOF
+ <!doctype html>
+ <html lang="en-US">
+ <head>
+ <meta charset="utf-8">
+ <meta name="viewport"
+ content="width=device-width, initial-scale=1" />
+
+ <title>
+ CharmBypass: got that transit equity
+ </title>
+ </head>
+
+ <body>
+ <form method="post">
+ <label for="code">Today's code:</label>
+ <input id="code"
+ name="code" value="${1}"
+ type="text"
+ size="2"
+ minlength="2"
+ maxlength="2"
+ pattern="[a-zA-Z0-9]*" />
+ <br /><br />
+ <input type="submit" value="Update it" />
+ <form>
+ </body>
+ </html>
+EOF
+ exit
+}
+
+# If this isn't a POST request, it should be a "normal" page hit,
+# i.e. a GET request with no querystring parameters. If there are
+# parameters, we ignore them, and display the "update code" form
+# anyway.
+if [ "${REQUEST_METHOD}" != "POST" ]; then
+ # Parse the code before we start displaying the form
+ # so that we can throw a 500 error if it fails.
+ _old_code=$(parse_code) || die 500 "failed to parse the existing code"
+ display_code_form "${_old_code}"
+fi
+
+# Since display_code_form() exits, the only way we can get
+# here is if this is a POST request. And in that case, we
+# should have some data... At least, CONTENT_LENGTH will
+# be a number.
+if [ -n "${CONTENT_LENGTH}" -a "${CONTENT_LENGTH}" -gt 0 ]; then
+ POST_DATA=$(dd bs=1 count="${CONTENT_LENGTH}" 2>/dev/null)
+
+ # Sanity check the form data. To prevent mistakes, it's not possible
+ # to "erase" the code that somebody else entered. If it's wrong, who
+ # cares? Erasing it would make it random... i.e. still wrong.
+ case "${POST_DATA}" in
+ "code="[A-Za-z0-9][A-Za-z0-9])
+ CODE=$(echo "${POST_DATA}" | cut -d= -f2)
+ update_code "${CODE}" || die 500 "failed to update the code"
+ redirect "/"
+ ;;
+ *)
+ # If the form data isn't exactly what we expect,
+ # fail ASAP.
+ die 400 "bad request"
+ ;;
+ esac
+fi
projects / charm-bypass.git / commitdiff