---
c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
SPDX-License-Identifier: curl
Title: CURLOPT_AWS_SIGV4
Section: 3
Source: libcurl
See-also:
  - CURLOPT_HEADEROPT (3)
  - CURLOPT_HTTPAUTH (3)
  - CURLOPT_HTTPHEADER (3)
  - CURLOPT_PROXYAUTH (3)
Protocol:
  - HTTP
Added-in: 7.75.0
---

# NAME

CURLOPT_AWS_SIGV4 - V4 signature

# SYNOPSIS

~~~c
#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) to CURLAUTH_AWS_SIGV4. Calling
CURLOPT_HTTPAUTH(3) 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.

Setting CURLOPT_HTTPAUTH(3) with the CURLAUTH_AWS_SIGV4 bit set is the same as
setting this option with a **"aws:amz"** parameter.

# DEFAULT

NULL

# %PROTOCOLS%

# EXAMPLE

~~~c
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);
  }
}
~~~

# NOTES

This option overrides the other auth types you might have set in
CURLOPT_HTTPAUTH(3) 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). 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".

# %AVAILABILITY%

# RETURN VALUE

Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.