<?xml version="1.0" encoding="utf-8"?>
<section xmlns="http://docbook.org/ns/docbook"
         xmlns:xlink="http://www.w3.org/1999/xlink"
         xmlns:xi="http://www.w3.org/2001/XInclude"
         version="5.0"
         xml:id="ssec-s3-substituter">

<title>Serving a Nix store via AWS S3 or S3-compatible Service</title>

<para>Nix has built-in support for storing and fetching store paths
from Amazon S3 and S3 compatible services. This uses the same
<emphasis>binary</emphasis> cache mechanism that Nix usually uses to
fetch prebuilt binaries from <uri>cache.nixos.org</uri>.</para>

<para>The following options can be specified as URL parameters to
the S3 URL:</para>

<variablelist>
  <varlistentry><term><literal>profile</literal></term>
  <listitem>
    <para>
      The name of the AWS configuration profile to use. By default
      Nix will use the <literal>default</literal> profile.
    </para>
  </listitem>
  </varlistentry>

  <varlistentry><term><literal>region</literal></term>
  <listitem>
    <para>
      The region of the S3 bucket. <literal>us–east-1</literal> by
      default.
    </para>

    <para>
      If your bucket is not in <literal>us–east-1</literal>, you
      should always explicitly specify the region parameter.
    </para>
  </listitem>
  </varlistentry>

  <varlistentry><term><literal>endpoint</literal></term>
  <listitem>
    <para>
      The URL to your S3-compatible service, for when not using
      Amazon S3. Do not specify this value if you're using Amazon
      S3.
    </para>
    <note><para>This endpoint must support HTTPS and will use
    path-based addressing instead of virtual host based
    addressing.</para></note>
  </listitem>
  </varlistentry>

  <varlistentry><term><literal>scheme</literal></term>
  <listitem>
    <para>
      The scheme used for S3 requests, <literal>https</literal>
      (default) or <literal>http</literal>.  This option allows you to
      disable HTTPS for binary caches which don't support it.
    </para>
    <note><para>HTTPS should be used if the cache might contain
    sensitive information.</para></note>
  </listitem>
  </varlistentry>
</variablelist>

<para>In this example we will use the bucket named
<literal>example-nix-cache</literal>.</para>

<section xml:id="ssec-s3-substituter-anonymous-reads">
  <title>Anonymous Reads to your S3-compatible binary cache</title>

  <para>If your binary cache is publicly accessible and does not
  require authentication, the simplest and easiest way to use Nix with
  your S3 compatible binary cache is to use the HTTP URL for that
  cache.</para>

  <para>For AWS S3 the binary cache URL for example bucket will be
  exactly <uri>https://example-nix-cache.s3.amazonaws.com</uri> or
  <uri>s3://example-nix-cache</uri>. For S3 compatible binary caches,
  consult that cache's documentation.</para>

  <para>Your bucket will need the following bucket policy:</para>

  <programlisting><![CDATA[
{
    "Id": "DirectReads",
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "AllowDirectReads",
            "Action": [
                "s3:GetObject",
                "s3:GetBucketLocation"
            ],
            "Effect": "Allow",
            "Resource": [
                "arn:aws:s3:::example-nix-cache",
                "arn:aws:s3:::example-nix-cache/*"
            ],
            "Principal": "*"
        }
    ]
}
]]></programlisting>
</section>

<section xml:id="ssec-s3-substituter-authenticated-reads">
  <title>Authenticated Reads to your S3 binary cache</title>

  <para>For AWS S3 the binary cache URL for example bucket will be
  exactly <uri>s3://example-nix-cache</uri>.</para>

  <para>Nix will use the <link
  xlink:href="https://docs.aws.amazon.com/sdk-for-cpp/v1/developer-guide/credentials.html">default
  credential provider chain</link> for authenticating requests to
  Amazon S3.</para>

  <para>Nix supports authenticated reads from Amazon S3 and S3
  compatible binary caches.</para>

  <para>Your bucket will need a bucket policy allowing the desired
  users to perform the <literal>s3:GetObject</literal> and
  <literal>s3:GetBucketLocation</literal> action on all objects in the
  bucket. The anonymous policy in <xref
  linkend="ssec-s3-substituter-anonymous-reads" /> can be updated to
  have a restricted <literal>Principal</literal> to support
  this.</para>
</section>


<section xml:id="ssec-s3-substituter-authenticated-writes">
  <title>Authenticated Writes to your S3-compatible binary cache</title>

  <para>Nix support fully supports writing to Amazon S3 and S3
  compatible buckets. The binary cache URL for our example bucket will
  be <uri>s3://example-nix-cache</uri>.</para>

  <para>Nix will use the <link
  xlink:href="https://docs.aws.amazon.com/sdk-for-cpp/v1/developer-guide/credentials.html">default
  credential provider chain</link> for authenticating requests to
  Amazon S3.</para>

  <para>Your account will need the following IAM policy to
  upload to the cache:</para>

  <programlisting><![CDATA[
{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "UploadToCache",
      "Effect": "Allow",
      "Action": [
        "s3:AbortMultipartUpload",
        "s3:GetBucketLocation",
        "s3:GetObject",
        "s3:ListBucket",
        "s3:ListBucketMultipartUploads",
        "s3:ListMultipartUploadParts",
        "s3:ListObjects",
        "s3:PutObject"
      ],
      "Resource": [
        "arn:aws:s3:::example-nix-cache",
        "arn:aws:s3:::example-nix-cache/*"
      ]
    }
  ]
}
]]></programlisting>


  <example><title>Uploading with a specific credential profile for Amazon S3</title>
    <para><command>nix copy --to 's3://example-nix-cache?profile=cache-upload&amp;region=eu-west-2' nixpkgs.hello</command></para>
  </example>

  <example><title>Uploading to an S3-Compatible Binary Cache</title>
    <para><command>nix copy --to 's3://example-nix-cache?profile=cache-upload&amp;scheme=https&amp;endpoint=minio.example.com' nixpkgs.hello</command></para>
  </example>
</section>
</section>
