Question

I’m trying to parse the json signed_request you receive from Facebook in perl but need a little help!

($encoded_sig, $payload) = split('\.', $formdata{'signed_request'});
$sig  = decode_base64url($encoded_sig);
$data = decode_json(decode_base64url($payload));
%decoded = %{ decode_json(decode_base64url($payload)) };
$expected_sig = hmac_sha256($payload, $app_secret);

if ($expected_sig eq $sig) {
while (my ($key, $value) = each %decoded) { 
print "$key = $value\n<br>";
}
}

Each $value can either contain a string or a reference to another HASH (and some of those HASHs may contain another HASH), is there a better way to process this?

The script above returns:

algorithm = HMAC-SHA256
page = HASH(0x632b100) 
issued_at = 1323081670 
user = HASH(0x632b150) 

and the json received after decoding is:

{"algorithm":"HMAC-SHA256","issued_at":1323081670,"page":{"id":"192130540873448","liked":true,"admin":true},"user":{"country":"gb","locale":"en_GB","age":{"min":21}}}

Ideally would like to see a result of:

algorithm = HMAC-SHA256
page-id = 192130540873448
page-liked = true
page-admin = true
issued_at = 1323081670 
user-country = gb
user-locale = en_GB
user-age-min = 21 

Data structure will increase as upon an authorised user response from Facebook more data is provided.

Many thanks

Answer 1

To answer my own question 🙂

if ($expected_sig eq $sig) {
while (my ($key, $value) = each %decoded) { 
 if (ref($value) eq "HASH") {
 while ( my ($key2, $value2) = each(%{$value}) ) {
$mydata{"$key-$key2"}=$value2;
 if (ref($value2) eq "HASH") {
  while ( my ($key3, $value3) = each(%{$value2}) ) {
$mydata{"$key-$key2-$key3"}=$value3;
        print "$key-$key2-$key3 = $value3\n<br>";
}}
else
{
        print "$key-$key2 = $value2\n<br>";
}}}
else
{ 

$mydata{"$key"}=$value;
print "$key = $value\n<br>";
}}}

outputs:

algorithm = HMAC-SHA256 
page-admin = 1 
page-liked = 1 
page-id = 192130540873448   
issued_at = 1323081670    
user-country = gb 
user-locale = en_GB 
user-age-min = 21