---
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.

The application does not have to keep the string around after setting this
option.

Using this option multiple times makes the last set string override the
previous ones. Set it to NULL to disable its use again.

# 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

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error occurred, see
libcurl-errors(3).
