HMAC SHA1 + base64

[rtweed]

I'm nearly there on this but having a mental block - I'm sure what I
need to do is possible with the available libraries in node but
there's a step I can't figure out, and wonder if anyone else can help.

I'm trying to perform the signing necessary for Amazon SimpleDB. This
involves creating an HMACSHA1 digest from the data and a secret key,
and then Base64 encoding the result.

I've installed hashlib and node-base64. I can get the HMACSHA1
digest, but it returns the result as a hex string, eg

var key = "1234567" ;
var data = "hello world" ;
var hash = hashlib.hmac_sha1(data, key);

hash = 73a8e6a0d7966cf3257cbe3c5a6ec7cf06a7cda4

What I need to create is the Base64 result of the binary value
represented by this hex string. So I need to be able to get the
result:

c6jmoNeWbPMlfL48Wm7HzwanzaQ=

So, in other words, I can't just pass the value of hash into
base64.encode (that would give me
NzNhOGU2YTBkNzk2NmNmMzI1N2NiZTNjNWE2ZWM3Y2YwNmE3Y2RhNA==)

What's the intermediate step I need to get the right result?

Many thanks!

Rob

[rtweed]

I'll answer my own post!

Turned out I didn't need anything but node.js itself - just use the
crypto module:

var crypto = require("crypto");

sys.puts("Node.js HMACSHA1 test");

var key = "1234567" ;
var data = "hello world" ;

var hmac = crypto.createHmac("sha1", key);
var hash2 = hmac.update(data);
var digest = hmac.digest(encoding="base64");
sys.puts("digest=" + digest);

Out pops
digest=c6jmoNeWbPMlfL48Wm7HzwanzaQ=

Rob

[Jorge]

hash= "73a8e6a0d7966cf3257cbe3c5a6ec7cf06a7cda4";
if (hash.length % 2) hash= "0"+ hash;
btoa(hash.replace(/[a-f0-9][a-f0-9]/g, function (c, i) { return String.fromCharCode(parseInt(c, 16)) }));
-> "c6jmoNeWbPMlfL48Wm7HzwanzaQ="

--
Jorge.

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[Jorge]

D'oh

[Micheil Smith]

I should note that you also had the following:

var digest = hmac.digest(encoding="base64");

It should have been:

var digest = hmac.digest("base64");

Was it written like this in the documentation? If so, this needs to be fixed.

Yours,
Micheil Smith
--
BrandedCode.com

[tjholowaychuk]

I think he is writing it pythonic..-ish lol for some reason, and
creating a global instead

> >> For more options, visit this group athttp://groups.google.com/group/nodejs?hl=en.

[rtweed]

Yes I used the documentation at http://nodejs.org/api.html

I quote:

hash.digest(encoding='binary')
Calculates the digest of all of the passed data to be hashed. The
encoding can be 'hex', 'binary' or 'base64'.

> >> For more options, visit this group athttp://groups.google.com/group/nodejs?hl=en.

[rtweed]

No I RTFM

[rtweed]

In fact I now realise that the documentation is written so that it
tells you what the default values of parameters are, so yes I was
being somewhat dumb, especially since I work in Javascript most of my
time! In my defence:

1) The documentation does not make that clear (more examples would
help clarify that). I suspect this aspect of the documentation may
confuse others.

2) I was trying to get this working quickly last night and didn't want
to plough through copious amounts of documentation in detail. So I
just took what I read at face value , did some cut and pasting and.
woohoo it just worked :-) Now, in the cold light of morning, what I
used does look pretty daft :-)

To be honest the documentation on the crypto module is pretty,
well....cryptic. Some examples would definitely help, but then that's
true of many of the modules and I know how much time and effort it
takes to write examples. However most developers, from my experience,
work from examples first and then follow-up by consulting the
documentation which then makes perfect sense.

Anyway the bottom line is I now have the critical piece I needed for
my project in place. The rest should hopefully be pretty
straightforward.



On 27 Sep, 08:12, rtweed <rob.tw...@gmail.com> wrote:
> Yes I used the documentation athttp://nodejs.org/api.html

[Micheil Smith]

Okay, that's on the todo list to work on then. No harm done.

– Micheil Smith