Add osc(1df)

3 files changed, 110 insertions, 0 deletions

diff --git a/README.markdown b/README.markdown
index 586594a4..bce41cd0 100644
--- a/README.markdown
+++ b/README.markdown
@@ -483,6 +483,8 @@ Installed by the `install-bin` target:
 *   `mkmv(1df)` creates a directory and moves preceding arguments into it.
 *   `motd(1df)` shows the system MOTD.
 *   `onl(1df)` crunches input down to one printable line.
+*   `osc(1df)` implements a `netcat(1)`-like wrapper for `openssl(1)`'s
+    `s_client` subcommand.
 *   `pa(1df)` prints its arguments, one per line.
 *   `pp(1df)` prints the full path of each argument using `$PWD`.
 *   `pph(1df)` runs `pp(1df)` and includes a leading `$HOSTNAME:`.
diff --git a/bin/osc b/bin/osc
new file mode 100755
index 00000000..c1fe6ed0
--- /dev/null
+++ b/bin/osc
@@ -0,0 +1,86 @@
+#!/bin/sh
+# Sane and safe OpenSSL s_client(1ssl) connection
+self=osc 
+
+# Check we have openssl(1); we need to fail early lest we go setting up FIFOs
+# needlessly
+if ! command -v openssl >/dev/null 2>&1 ; then
+    printf >&2 '%s: openssl(1) not found in $PATH\n'
+    exit 1
+fi
+
+# Hostname is first argument; assume localhost if empty/unset
+host=${1:-localhost}
+# Service name or port is second argument; assume HTTPS if empty/unset
+serv=${2:-https}
+
+# Start building the command-line string
+set --
+## If we have rlwrap, use it, but don't complain if we don't
+if command -v rlwrap >/dev/null 2>&1 ; then
+    set -- "$@" rlwrap
+fi
+## The actual openssl(1ssl) and subcommand call
+set -- "$@" openssl s_client
+## No insecure SSL methods
+set -- "$@" -no_ssl2 -no_ssl3
+## Don't dump nonsense to terminal, and don't renegotiate on R or quit on Q
+set -- "$@" -quiet
+## But do cut the connection if I issue ^D, even though I just set -quiet
+set -- "$@" -no_ign_eof
+## Do verify the certificate chain and don't connect if we can't
+set -- "$@" -verify 5 -verify_return_error
+## We might add STARTTLS for the supported services:
+case $serv in
+    ftp|21)
+        set -- "$@" -starttls ftp
+        ;;
+    smtp|25)
+        set -- "$@" -starttls smtp
+        ;;
+    pop3|110)
+        set -- "$@" -starttls pop3
+        ;;
+    imap|143)
+        set -- "$@" -starttls imap
+        ;;
+esac
+## Finally, add the host and service to connect to
+set -- "$@" -connect "$host":"$serv"
+
+# Do the POSIX dance to kill child processes and clean up temp files even if
+# killed by a signal
+td= fil=
+cleanup() {
+    trap - EXIT "$1"
+    [ -n "$fil" ] && kill -TERM "$fil"
+    [ -n "$td" ] && rm -fr -- "$td"
+    if [ "$1" != EXIT ] ; then
+        kill -"$1" "$$"
+    fi
+}
+for sig in EXIT HUP INT TERM ; do
+    trap "cleanup $sig" "$sig"
+done
+ 
+# Create a temporary directory and a FIFO in it
+td=$(mktd "$self") || exit
+mkfifo -- "$td"/verify-filter || exit
+
+# Open a read-write file descriptor onto the FIFO
+exec 3<>"$td"/verify-filter || exit
+
+# Start a background filter process on the FIFO to get rid of the leading
+# verification output set to stderr; as soon as we find a single line that
+# doesn't look like that routine output, print all future lines to stderr as
+# normal
+awk '
+body{print;next}
+/^verify depth is [0-9]+$/{next}
+/^depth=[0-9]+ /{next}
+/^verify return:[0-9]+$/{next}
+{body=1;print}
+' <&3 >&2 & fil=$!
+
+# Start the process with the options we stacked up
+"$@" 2>&3
diff --git a/man/man1/osc.1df b/man/man1/osc.1df
new file mode 100644
index 00000000..9fb61dde
--- /dev/null
+++ b/man/man1/osc.1df
@@ -0,0 +1,22 @@
+.TH OSC 1df "February 2017" "Manual page for osc"
+.SH NAME
+.B osc
+\- netcat-like wrapper for openssl s_client
+.SH SYNOPSIS
+.B osc [HOST [SERVICE]]
+.SH DESCRIPTION
+.B osc
+runs openssl(1ssl)'s s_client subcommand with some options to make it behave a
+bit like netcat(1), quieting errors and even handling STARTTLS if it knows how,
+but still forcing correct verification of certificates and only connecting with
+TLS (not SSL).
+.P
+If rlwrap(1) is available, the client will be run within that to allow line
+editing.
+.P
+It's intended to be run as an interactive tool for cases where you want to
+focus more on debugging the data exchange with the actual server, and not
+debugging the OpenSSL negotiation itself. The author finds it handy for poking
+his STARTTLS SMTP mailserver.
+.SH AUTHOR
+Tom Ryder <tom@sanctum.geek.nz>