---
name: "CURLOPT_AWS_SIGV4"
section: "3"
platform: "macos"
package: "curl"
version: "166.0.0.0.1"
release: "macOS 26.5"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/CURLOPT_AWS_SIGV4"
---

# CURLOPT\_AWS\_SIGV4(3)

V4 signature

## NAME

CURLOPT\_AWS\_SIGV4 - V4 signature

## SYNOPSIS

```
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_AWS_SIGV4, char *param);
```

## DESCRIPTION

Provides AWS V4 signature authentication on HTTP(S) header.

Pass a char pointer that is the collection of specific arguments are used for creating outgoing authentication headers. The format of the *param* option is:

- provider1\[:provider2\[:region\[:service\]\]\]

  - provider1, provider2

  The providers arguments are used for generating some authentication parameters such as "Algorithm", "date", "request type" and "signed headers".

- region

  The argument is a geographic area of a resources collection. It is extracted from the hostname specified in the URL if omitted.

- service

  The argument is a function provided by a cloud. It is extracted from the hostname specified in the URL if omitted.

  NOTE: This call set *[CURLOPT\_HTTPAUTH(3)](/CURLOPT_HTTPAUTH/3.md)* to CURLAUTH\_AWS\_SIGV4. Calling *[CURLOPT\_HTTPAUTH(3)](/CURLOPT_HTTPAUTH/3.md)* with CURLAUTH\_AWS\_SIGV4 is the same as calling this with **"aws:amz"** in parameter.

  Example with "Test:Try", when curl uses the algorithm, it generates **"TEST-HMAC-SHA256"** for "Algorithm", **"x-try-date"** and **"X-Try-Date"** for "date", **"test4\_request"** for "request type", **"SignedHeaders=content-type;host;x-try-date"** for "signed headers"

  If you use just "test", instead of "test:try", test is used for every generated string.

## DEFAULT

By default, the value of this parameter is NULL. Calling *[CURLOPT\_HTTPAUTH(3)](/CURLOPT_HTTPAUTH/3.md)* with CURLAUTH\_AWS\_SIGV4 is the same as calling this with **"aws:amz"** in parameter.

## PROTOCOLS

HTTP

## EXAMPLE

```
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL,
                    "https://service.region.example.com/uri");
    curl_easy_setopt(curl, CURLOPT_AWS_SIGV4, "provider1:provider2");
    /* service and region can also be set in CURLOPT_AWS_SIGV4 */
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/uri");
    curl_easy_setopt(curl, CURLOPT_AWS_SIGV4,
                     "provider1:provider2:region:service");
    curl_easy_setopt(curl, CURLOPT_USERPWD, "MY_ACCESS_KEY:MY_SECRET_KEY");
    curl_easy_perform(curl);
  }
}
```

## AVAILABILITY

Added in 7.75.0

## RETURN VALUE

Returns CURLE\_OK if the option is supported, and CURLE\_UNKNOWN\_OPTION if not.

## NOTES

This option overrides the other auth types you might have set in *[CURLOPT\_HTTPAUTH(3)](/CURLOPT_HTTPAUTH/3.md)* which should be highlighted as this makes this auth method special. This method cannot be combined with other auth types.

A sha256 checksum of the request payload is used as input to the signature calculation. For POST requests, this is a checksum of the provided *[CURLOPT\_POSTFIELDS(3)](/CURLOPT_POSTFIELDS/3.md)*. Otherwise, it is the checksum of an empty buffer. For requests like PUT, you can provide your own checksum in an HTTP header named **x-provider2-content-sha256**.

For **aws:s3**, a **x-amz-content-sha256** header is added to every request if not already present. For s3 requests with unknown payload, this header takes the special value "UNSIGNED-PAYLOAD".

## SEE ALSO

[**CURLOPT\_HEADEROPT**(3)](/CURLOPT_HEADEROPT/3.md), [**CURLOPT\_HTTPAUTH**(3)](/CURLOPT_HTTPAUTH/3.md), [**CURLOPT\_HTTPHEADER**(3)](/CURLOPT_HTTPHEADER/3.md), [**CURLOPT\_PROXYAUTH**(3)](/CURLOPT_PROXYAUTH/3.md)