Add some hacky prototype express work to return a modified hello-world container

Figured some things out, but was mostly just piecing things together by hacking
on responses

.gitignore

@@ -1 +1,2 @@
 *.sw*
+node_modules/

index.js

@@ -0,0 +1,221 @@
+const crypto = require('crypto');
+const express = require('express');
+const fs = require('fs');
+const request = require('request');
+const winston = require('winston');
+
+const {chain}  = require('stream-chain');
+const {parser} = require('stream-json');
+const {streamValues} = require('stream-json/streamers/StreamValues');
+
+const app = express();
+const port = 9090;
+const imageConfig = 'sha256:b0b17eacf99071d7178bbf12d31a556bb3f05b429564c7fc4db33899d3eda85b';
+
+let alpineResponse = {
+  "manifests": [
+    {
+      "digest": "sha256:acd3ca9941a85e8ed16515bfc5328e4e2f8c128caa72959a58a127b7801ee01f",
+      "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
+      "platform": {
+        "architecture": "amd64",
+        "os": "linux"
+      },
+      "size": 528
+    },
+    {
+      "digest": "sha256:0489474da8ea22426ece86ace6c1c0026ab2fd3cdfbbd62b7e94650266c37d9a",
+      "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
+      "platform": {
+        "architecture": "arm",
+        "os": "linux",
+        "variant": "v6"
+      },
+      "size": 528
+    },
+    {
+      "digest": "sha256:1316a4e4b2361242457f4136cc409c38e8a48ffda76e4e1be31896006e5fc4a2",
+      "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
+      "platform": {
+        "architecture": "arm",
+        "os": "linux",
+        "variant": "v7"
+      },
+      "size": 528
+    },
+    {
+      "digest": "sha256:db7f3dcef3d586f7dd123f107c93d7911515a5991c4b9e51fa2a43e46335a43e",
+      "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
+      "platform": {
+        "architecture": "arm64",
+        "os": "linux",
+        "variant": "v8"
+      },
+      "size": 528
+    },
+    {
+      "digest": "sha256:499416c8a5bcb311d75e12fb4667886e32b43aaf11003be2a334cbe265e81ce4",
+      "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
+      "platform": {
+        "architecture": "386",
+        "os": "linux"
+      },
+      "size": 528
+    },
+    {
+      "digest": "sha256:5abbfe2915ad8c466bf6c9f33d03622cde0298c36cd88f55d16a3aa3d9c2c35e",
+      "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
+      "platform": {
+        "architecture": "ppc64le",
+        "os": "linux"
+      },
+      "size": 528
+    },
+    {
+      "digest": "sha256:43955d6857268cc948ae9b370b221091057de83c4962da0826f9a2bdc9bd6b44",
+      "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
+      "platform": {
+        "architecture": "s390x",
+        "os": "linux"
+      },
+      "size": 528
+    }
+  ],
+  "mediaType": "application/vnd.docker.distribution.manifest.list.v2+json",
+  "schemaVersion": 2
+}
+
+let alpineImage = {
+  "schemaVersion": 2,
+  "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
+  "config": {
+    "mediaType": "application/vnd.docker.container.image.v1+json",
+    "size": 1512,
+    "digest": "sha256:961769676411f082461f9ef46626dd7a2d1e2b2a38e6a44364bcbecf51e66dd4"
+  },
+  "layers": [
+    {
+      "mediaType": "application/vnd.docker.image.rootfs.diff.tar.gzip",
+      "size": 2789669,
+      "digest": "sha256:9d48c3bd43c520dc2784e868a780e976b207cbf493eaff8c6596eb871cbd9609"
+    }
+  ]
+}
+
+let response = {
+  "schemaVersion": 2,
+  "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
+  "config": {
+    "mediaType": "application/vnd.docker.container.image.v1+json",
+    "size": 1585,
+    "digest": imageConfig,
+  },
+  "layers": [
+    {
+      "mediaType": "application/vnd.docker.image.rootfs.diff.tar.gzip",
+      "size": 977,
+      "digest": "sha256:1b930d010525941c1d56ec53b97bd057a67ae1865eebf042686d2a2d18271ced"
+    },
+    {
+      "mediaType": "application/vnd.docker.image.rootfs.diff.tar.gzip",
+      "size": 5808040,
+      "digest": "sha256:cf98438b1781c2be1fde41967959140379c715b75a85723501d0bca82f215a76"
+    }
+  ]
+};
+
+
+/*
+ * The specific manifests route we must override
+ */
+app.get('/v2/:org/:image/manifests/:digest', (req, res) => {
+  console.log(req.originalUrl);
+  const checksum = crypto.createHash('sha256').update(JSON.stringify(response), 'utf8').digest('hex');
+  res.set('Docker-Content-Digest', `sha256:${checksum}`);
+
+  /*
+   * If we don't explicitly set the content type here, the client will think
+   * that we're sending back a v1 manifest schema and complain about a "missing
+   * signature key"
+   */
+  res.set('Content-Type', 'application/vnd.docker.distribution.manifest.v2+json');
+  res.send(response);
+});
+
+/*
+ * Serve up a custom blob if we've got one!
+ */
+app.get('/v2/:org/:image/blobs/:sha', (req, res) => {
+  console.log(`Hitting ${req.originalUrl}`);
+
+  if (req.params.sha == 'sha256:cf98438b1781c2be1fde41967959140379c715b75a85723501d0bca82f215a76') {
+    /*
+     * Requesting our custom blob layer itself
+     */
+    const filename = 'layer.tar.gz';
+    console.log('hitting our custom blob');
+    fs.createReadStream(filename).pipe(res);
+  } else if (req.params.sha == imageConfig) {
+    /*
+     * Requesting our image configuration
+     */
+    console.log('hitting our image configuration')
+    let image = '';
+    /*
+     * We need to modify the diff_ids of the image configuration to include the
+     * checksum of the gunzipped version of our custom layer
+     *
+     * https://medium.com/@saschagrunert/demystifying-containers-part-iii-container-images-244865de6fef
+     *
+     */
+
+    const upstreamBlob = 'sha256:fce289e99eb9bca977dae136fbe2a82b6b7d4c372474c9235adc1741675f587e'
+    request({
+      url: `https://registry-1.docker.io/v2/library/hello-world/blobs/${upstreamBlob}`,
+      method: req.method,
+      headers: {
+        'Authorization' : req.get('Authorization'),
+      },
+    })
+      .on('response', (response) => {
+        console.log(`Hitting upstream gave a ${response.statusCode}`);
+      })
+      .on('data', (chunk) => {
+        image += chunk;
+      })
+      .on('end', () => {
+        image = JSON.parse(image);
+        image.rootfs.diff_ids.push(
+          'sha256:5f9da7cc9d8d83c96245ac27854466f6ed89fbfade5dd8a4f307861bfb72d1b8',
+        );
+        console.log(image.rootfs);
+        const checksum = crypto.createHash('sha256').update(JSON.stringify(image), 'utf8').digest('hex');
+        console.log(JSON.stringify(image));
+        console.log(`Sending content with a checksum of ${checksum}`);
+        console.log(`Client is expecting ${req.params.sha}`);
+        res.send(image);
+      });
+  } else {
+    console.log(`Piping blob upstream for ${req.originalUrl}`);
+    request({
+      url: `https://registry-1.docker.io${req.originalUrl}`,
+      method: req.method,
+      headers: {
+        'Authorization' : req.get('Authorization'),
+      },
+    }).pipe(res);
+  }
+});
+
+/*
+ * Pass all v2 API requests on to the upstream Docker registry
+ */
+app.get('/v2/*', (req, res) => {
+  console.log(`Piping request through for ${req.originalUrl}`);
+  request({
+    url: `https://registry-1.docker.io${req.originalUrl}`,
+    method: req.method,
+  }).pipe(res);
+});
+
+app.listen(port, () => console.log(`Example app listening on port ${port}!`))