uhttpd: create self-signed certificates with unique subjects

Add a partially random O= item to the certificate subject in order
to make the automatically generated certificates' subjects unique.

Firefox has problems when several self-signed certificates
with CA:true attribute and identical subjects have been
seen (and stored) by the browser. Reference to upstream bugs:
https://bugzilla.mozilla.org/show_bug.cgi?id=1147544
https://bugzilla.mozilla.org/show_bug.cgi?id=1056341
https://bugzilla.redhat.com/show_bug.cgi?id=1204670#c34

Certificates created by the OpenSSL one-liner fall into that category.

Avoid identical certificate subjects by including a new 'O=' item
with CommonName + a random part (8 chars). Example:
/CN=LEDE/O=LEDEb986be0b/L=Unknown/ST=Somewhere/C=ZZ

That ensures that the browser properly sees the accumulating
certificates as separate items and does not spend time
trying to form a trust chain from them.

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>

diff --git a/package/network/services/uhttpd/files/uhttpd.init b/package/network/services/uhttpd/files/uhttpd.init
index 35c1985cd2b124d43b285a65a256cc9408be1a60..a2dbcd2f93720af782d9518d800de63246401994 100755 (executable)
--- a/package/network/services/uhttpd/files/uhttpd.init
+++ b/package/network/services/uhttpd/files/uhttpd.init
@@ -46,12 +46,13 @@ generate_keys() {
 
        # Prefer px5g for certificate generation (existence evaluated last)
        local GENKEY_CMD=""
+       local UNIQUEID=$(dd if=/dev/urandom bs=1 count=4 | hexdump -e '1/1 "%02x"')
        [ -x "$OPENSSL_BIN" ] && GENKEY_CMD="$OPENSSL_BIN req -x509 -outform der -nodes"
        [ -x "$PX5G_BIN" ] && GENKEY_CMD="$PX5G_BIN selfsigned -der"
        [ -n "$GENKEY_CMD" ] && {
                $GENKEY_CMD \
                        -days ${days:-730} -newkey rsa:${bits:-2048} -keyout "${UHTTPD_KEY}.new" -out "${UHTTPD_CERT}.new" \
-                       -subj /C="${country:-DE}"/ST="${state:-Saxony}"/L="${location:-Leipzig}"/CN="${commonname:-Lede}"
+                       -subj /C="${country:-DE}"/ST="${state:-Saxony}"/L="${location:-Leipzig}"/O="${commonname:-Lede}$UNIQUEID"/CN="${commonname:-Lede}"
                sync
                mv "${UHTTPD_KEY}.new" "${UHTTPD_KEY}"
                mv "${UHTTPD_CERT}.new" "${UHTTPD_CERT}"