AWS Signature Version 4 Signing Library for Elixir
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README.md

AWSAuth

A small library used to sign AWS request urls using AWS Signature Version 4.

Takes some inspiration from the Simplex Library.

Does both URL and Authorization Header signing.

AWSAuth.sign_url(access_key, secret_key, http_method, url, region, service, headers \\ Map.new)

access_key: Your AWS Access key

secret_key: Your AWS secret key

http_method: "GET","POST","PUT","DELETE", etc

url: The AWS url you want to sign

region: The AWS name for the region you want to access (i.e. us-east-1). Check here for the region names

service: The AWS service you are trying to access (i.e. s3). Check the url above for names as well.

headers (optional): The headers that will be used in the request. Used for signing the request. For signing, host is the only one required unless using any other x-amx-* headers. If host is present here, it will override using the host in the url to attempt signing. If only the host is needed, then you don't have to supply it and the host from the url will be used.

In most cases, you would probably call it like this (examples using the example access key and secret from AWS):

signed_request = AWSAuth.sign_url("AKIAIOSFODNN7EXAMPLE", "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY",
  "GET",
  "https://examplebucket.s3.amazonaws.com/test.txt",
  "us-east-1",
  "s3")
"https://examplebucket.s3.amazonaws.com/test.txt?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIAIOSFODNN7EXAMPLE%2F20141219%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20141219T153739Z&X-Amz-Expires=86400&X-Amz-Signature=89d9f702dc8fb4fad2fd75bf07fc8468d60634f13234dd17e63835ed1fc324cd&X-Amz-SignedHeaders=host"

Or if you need to supply headers for signing, like this:

signed_request = AWSAuth.sign_url("AKIAIOSFODNN7EXAMPLE", "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY",
  "GET",
  "https://examplebucket.s3.amazonaws.com/test.txt",
  "us-east-1",
  "s3",
  Map.new |> Map.put("x-amz-header","value"))
"https://examplebucket.s3.amazonaws.com/test.txt?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIAIOSFODNN7EXAMPLE%2F20141219%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20141219T153646Z&X-Amz-Expires=86400&X-Amz-Signature=b05688cc482398bf2d6ff4068560b85b310a6bb24c5d21711b7099ab5e3df510&X-Amz-SignedHeaders=host,x-amx-header"

Using the example from AWS (http://docs.aws.amazon.com/AmazonS3/latest/API/sigv4-query-string-auth.html)

signed_request = AWSAuth.sign_url("AKIAIOSFODNN7EXAMPLE", "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY",
  "GET",
  "https://examplebucket.s3.amazonaws.com/test.txt",
  "us-east-1",
  "s3",
  Map.new,
  ~N[2013-05-24 00:00:00])
"https://examplebucket.s3.amazonaws.com/test.txt?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIAIOSFODNN7EXAMPLE%2F20130524%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20130524T000000Z&X-Amz-Expires=86400&X-Amz-Signature=aeeed9bbccd4d02ee5c0109b86d86835f995330da4c265957d157751f604d404&X-Amz-SignedHeaders=host"

AWSAuth.sign_authorization_header(access_key, secret_key, http_method, url, region, service, headers \\ Map.new, payload \\ "")

access_key: Your AWS Access key

secret_key: Your AWS secret key

http_method: "GET","POST","PUT","DELETE", etc

url: The AWS url you want to sign

region: The AWS name for the region you want to access (i.e. us-east-1). Check here for the region names

service: The AWS service you are trying to access (i.e. s3). Check the url above for names as well.

headers (optional. defaults to Map.new): The headers that will be used in the request. Used for signing the request. For signing, host is the only one required unless using any other x-amx-* headers. If host is present here, it will override using the host in the url to attempt signing. Same goes for the x-amz-content-sha256 headers If only the host and x-amz-content-sha256 headers are needed, then you don't have to supply it and the host from the url will be used and the payload will be hashed to get the x-amz-content-sha256 header.

payload (optional. defaults to ""): The contents of the payload if there is one.

headers = Map.new
|> Map.put("Date", "Fri, 24 May 2013 00:00:00 GMT")
|> Map.put("x-amz-storage-class", "REDUCED_REDUNDANCY")
|> Map.put("x-amz-date", "20130524T000000Z")

signed_request = AWSAuth.sign_authorization_header("AKIAIOSFODNN7EXAMPLE", "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY",
  "PUT",
  "https://examplebucket.s3.amazonaws.com/test$file.text",
  "us-east-1",
  "s3",
  headers,
  "Welcome to Amazon S3.")
"AWS4-HMAC-SHA256 Credential=AKIAIOSFODNN7EXAMPLE/20141220/us-east-1/s3/aws4_request,SignedHeaders=date;host;x-amz-content-sha256;x-amz-date;x-amz-storage-class,Signature=dddba55b1ae5cd9233e9dc8e43a0daf6e2e120bec86294b1d80d802cab8af258"

Using the example from AWS (http://docs.aws.amazon.com/AmazonS3/latest/API/sig-v4-header-based-auth.html)

headers = Map.new
|> Map.put("Date", "Fri, 24 May 2013 00:00:00 GMT")
|> Map.put("x-amz-storage-class", "REDUCED_REDUNDANCY")
|> Map.put("x-amz-date", "20130524T000000Z")

signed_request = AWSAuth.sign_authorization_header("AKIAIOSFODNN7EXAMPLE", "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY",
  "PUT",
  "https://examplebucket.s3.amazonaws.com/test$file.text",
  "us-east-1",
  "s3",
  headers,
  "Welcome to Amazon S3.",
  ~N[2013-05-24 00:00:00])
"AWS4-HMAC-SHA256 Credential=AKIAIOSFODNN7EXAMPLE/20130524/us-east-1/s3/aws4_request,SignedHeaders=date;host;x-amz-content-sha256;x-amz-date;x-amz-storage-class,Signature=98ad721746da40c64f1a55b78f14c238d841ea1380cd77a1b5971af0ece108bd"