Digests using OpenSSL. Shell and perl editions,

Here's a small snippet that allows one to generate a digest.
Short of it: Perl

my $key_string = read_file("secretkey.pem");
my $key = Crypt::OpenSSL::RSA->new_private_key($key_string);
my $filestring = read_file("somefile");
$key->use_md5_hash();
my $signature = $key->sign($filestring);
print encode_base64($signature)."\n";

Short of it: shell

openssl dgst -md5 -sign secretkey.pem  <  somefile |base64 | tee somefile.sig_from_shell
cat somefile.sig_from_shell | base64 -d > somefile.sig_from_shell.raw
openssl dgst -md5 -verify public.pem  -signature somefile.sig_from_perl.raw <  somefile

In it's goriness:

Quick and dirty parallel ssh

Occasionally,  you may want to scp or run a job across many hosts.. Well there's parallel-[scp|ssh] for you.

However, if you are constrained or are out of time to install this wonderful tool, xargs might just save your day. So here goes my simple one/two liner. Say we want to scp /etc/passwd to a local dir, then we'll need to:

• Give a unique name to the file to be copied over.

$ mkdir /tmp/bah/results -p && cd /tmp/bah

$ cat hosts | xargs -n 1 -P 50 -IH  ssh -i ~/.ssh/key.pem user@H 'cp /etc/passwd /tmp/passwd.`hostname` && echo `hostname` ok'
a.b.c.d ok
.....

• Copy it over:)

 $ cat hosts | xargs -n 1 -P 50 -IH  scp  -i ~/.ssh/key.pem  user@H:/tmp/passwd.* results/
passwd.a.b.c.d                                                                    100% 1155     1.1KB/s   00:01
....

Total time is 9 seconds for 60 hosts... Not bad..

real    0m9.654s
user    0m2.120s
sys    0m0.276s

sh-4.2$ ls results/|wc
     60      60    1486

fgrep if you don't need regexes

I did know that fgrep was faster but I didn't know by how much!

So looking up a set of values (say IP address) from somefilesource in a bunch of logs (300 files with ~ 500k lines)

$ wc -l Some*
 3840 SomeFilesource

fgrep:

$ time fgrep  -hf SomeFilesource *log* > Wantedlogs
real 0m0.952s
user 0m0.890s
sys 0m0.030s

grep:

time grep -f  SomeFilesource *log* > Wantedlogs
real 33m45.601s
user 33m39.150s
sys 0m0.350s

That is quite a speed up. From now on it's fgrep by default... Now if I need to see whether the --mmap optimization speeds up subsequent [f]greps.

Read a snippet of a file using vim

:0r ! sed -n 1,22p .procmailrc

• Don't insert a newline prior to the read (0)
• Read
• Use sed to get an address range of a file

And there was much celebration

Dirt cheap steganography

This steg module is based on code, ideas and images from http://blog.wolfram.com/2010/07/08/doing-spy-stuff-with-mathematica/ .
It requires numpy & matplotlib but can be reworked to depend on pypng instead of matplotlib

Sample usage

$ python2.7 simple_decode.py --help

Usage:

Hide/Unhide info in images as described in this post:

http://blog.wolfram.com/2010/07/08/doing-spy-stuff-with-mathematica/

usage: simple_decode.py [options]

Options:

-h, --help show this help message and exit

-v DEBUG, --verbose=DEBUG

Debug. Higher integers increases verbosity

-e ENCODED_FILE, --encoded_file=ENCODED_FILE

Encoded PNG file to work with. Default is

steg_chicken_secret.png

-d DATA_FILE, --data_file=DATA_FILE

File with decoded data or with data to encode.

Example decode of data hidden in the wolfram blog images

$ python2.7 simple_decode.py -e steg_chicken_secret.png -d chicken.txt
$ cat chicken.txt ;echo

This is a secret message.



$ python2.7 simple_decode.py -e alice.png -d alice.txt

$ file alice.txt

alice.txt: UTF-8 Unicode English text, with very long lines, with no line terminators



$ python2.7 simple_decode.py -e finalImage.png -d data.jpg

$ file data.jpg

data.jpg: JPEG image data, JFIF standard 1.01, comment: "Created by Wolfram Mathematica "

RPKI tools

An ISC implementation of the RPKI drafts can be found here http://www.rpki.net/.
Since all objects published in RPKI repository are in ASN1, dumpasn1 can be used to quickly peek at the objects. Here's an example.

Sample asn1 dump

RPKI Products: ROA

Current described by this draft, Route Origin Authorizations (ROAs) associate an AS number and a list prefixes in an object which is then CMS signed by a the owner of the prefixes. By generating a ROA, the owner of the prefix is stating that the as number in the ROA is allowed to originate the prefixes listed in the ROA. Third parties can then fetch ROAs, verify their cms signature and then use validation rules as per http://tools.ietf.org/wg/sidr/draft-ietf-sidr-roa-validation/. ROAs encapsulate end entity certificates within them. A sample ROA is shown below.

Sample ROA