GET request with headers using cURL PHP - php

Question

I m trying to make a GET request with headers using cURL PHP. I am getting an empty response form the server. I would like to know if I have made this request correctly using cURL PHP.
// curl GET request with headers
$url = $sendMailURL;
$requestHeaders = array(
$hConLength_.':'.$conLengthValue,
$hConType_.':'.$conTypeValue,
$hHost_.':'.$conHostValue,
$hDate_.':'.$conAmzDateValue);
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_HTTPHEADER, $requestHeaders);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$output = curl_exec($ch);
if(curl_error($ch)){
echo 'curl error: '.curl_error($ch);
}else{
print_r($output);
}
print_r($requestHeaders):
Array ( [0] => Content-Length:207
[1] => Content-Type:application/x-www-form-urlencoded
[2] => Host:email.eu-west-1.amazonaws.com
[3] => X-amz-date:20180115T224433Z )

Answer 1

I'm positive that you have found your answer, but in case there are others who will probably want to figure out how to check the headers or want to go down the rabbit hole trying to figure out how SignatureV4 works.
You need to set curl_option CURLINFO_HEADER_OUT
I used following to set all the options in one go, but I don't see why you can't set them one by one.
$conf = [
\CURLOPT_CUSTOMREQUEST => $method, // method
\CURLOPT_URL => $url, // url
\CURLOPT_HTTPHEADER => $requestHeaders, // headers
\CURLOPT_RETURNTRANSFER => true,
\CURLOPT_HEADER => true,
\CURLOPT_CONNECTTIMEOUT => $timeout, // set to anything that fits
\CURLOPT_PROTOCOLS => CURLPROTO_HTTPS, // whatever is your protocol
\CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1, // normally 1.1
\CURLINFO_HEADER_OUT => 1, // this will cause request headers to show up
];
curl_setopt_array($this->curl, $conf);
After running your request and before closing curl you can check for your headers and response headers all together.
$result = curl_exec($this->curl);
$info = curl_getinfo($this->curl, CURLINFO_HEADER_OUT); // run after exec before close
var_dump($info);
curl_close($this->curl);
you don't have to specify CURLINFO_HEADER_OUT when calling curl_getinfo but it will show a lot more info which makes it a little harder to find what you are looking for.
Since you mentioned in comments that you are trying to make SignatureV4 for AWS and I had the same issue, a few notes:
Although http headers are not case sensitive, when calculating hash they should be in lowercase and also specified in authorization token in lower case too. to make it easier, I just included headers in both request and hash as lowercase
You don't need to hash all the headers, since you will need to mention which headers are included in hash, in the authorization token.
Someone at AWS thought it is cool to sort querystring items alphabetically before calculating hash, so if you are sending querystring, make sure tokens are sorted before hashing it e.g.
Engine=standard&LanguageCode=en-US // will work
LanguageCode=en-US&Engine=standard // will not work
The only two headers that need to be in hash are x-amz-date and host. (at least that was the case for Polly) and they need to look like this
host:service.region.amazonaws.com
x-amz-date:20210920T180242Z
authorization:AWS4-HMAC-SHA256 Credential=xxxxxxxxxxxxxxxxxxxx/20210920/region/service/aws4_request, SignedHeaders=host;x-amz-date, Signature=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx