Getting different base64 encoding while porting to PHP from C#

Question

I don't know C# and I must port a small function into PHP. I broke down all the code into a simple example showing the issue.

Here is the C# portion where a sha1 hash is being base64 encoded:

HMACSHA1 hmacTest = new HMACSHA1();
hmacTest.Key = Convert.FromBase64String(identity);

byte[] sha1 = hmacTest.ComputeHash(new byte[]{0, 0, 0, 0, 86, 107, 192, 162, 99, 111, 110, 102});

Console.WriteLine(string.Concat(sha1.Select(b => b.ToString("x2"))));
Console.WriteLine(Convert.ToBase64String(sha1, Base64FormattingOptions.None));
// sha1: 02628928a3a2ab831a769f2fd64a3bae4036265f
// encoded: AmKJKKOiq4Madp8v1ko7rkA2Jl8=

Here is the PHP portion showing a different result, though the sha1 matches

$key = base64_decode($identity);
$data = call_user_func_array("pack", array_merge(array("C*"), array(0, 0, 0, 0, 86, 107, 192, 162, 99, 111, 110, 102)));

$sha1 = hash_hmac('sha1', $data, $key);

var_dump($sha1, base64_encode($sha1));
// sha1: 02628928a3a2ab831a769f2fd64a3bae4036265f
// encoded: MDI2Mjg5MjhhM2EyYWI4MzFhNzY5ZjJmZDY0YTNiYWU0MDM2MjY1Zg==

I must modify the PHP portion to match. I'm thinking it's an encoding issue. Or possibly that in C# ToBase64String is not being passed a string version of the sha1. How would I replicate this in PHP if that is why it's different?

TLJ · Accepted Answer · 2015-12-12 22:21:02Z

3

In your C# code sha1 is a byte array but in your PHP code I think your sha1 is a string

So Give this snippet a try:

$sha1 = hash_hmac('sha1', $data, $key,TRUE);

with the 4th param you'll get raw binary instead of string.

answered Dec 12, 2015 at 22:21

TLJ

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2 Comments

Justin Carlson Over a year ago

Oh my, that was so easy. Forgot all about the 4th param. Thank you so much.

Web-Beest Over a year ago

Thank you for this! I found this answer after 4 hours of digging around and Googleing.. I had a similar problem which drove me bananas :)

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