Merge pull request #9 from uniquelyparticular/feature/mustache-token-replacement

Feature/mustache token replacement

Author: agrohs

README.md

@@ -11,18 +11,51 @@ Built with [Micro](https://github.com/zeit/micro)! 🤩
 Create a `.env` at the project root with the following credentials:
 
 ```dosini
-PROXY_PREFIX=proxy
 PROXY_REFERER_WHITELIST=localhost,*.zendesk.com,*.myshopify.com,*.now.sh
 PROXY_DESTINATION_WHITELIST=api.stripe.com,api.goshippo.com,api.shipengine.com,api.moltin.com,*.myshopify.com,*.salesforce.com,*.demandware.net
 ```
 
-`PROXY_PREFIX` is optional and will default to `'proxy'` but is used in the URI patterns to determine where to find the encoded uri to proxy request to (ie. `https://12345678.ngrok.io/<<<PROXY_PREFIX>>>/https%3A%2F%2Fapi.somethingsecure.com%2Fadmin%2Fcustomers.json`)
-
 `PROXY_REFERER_WHITELIST` is a comma separated list of patterns to match against the incoming requests 'Referer' header (ex. `localhost,*.myawesomesite.com,*.now.sh`)
 _(and yes, 'REFERER' is intentionally misspelled to match the http header! 😉)_
 
 `PROXY_DESTINATION_WHITELIST` is a comma separated list of patterns to match against the URI you are proxying requests to. (ex. `api.somethingsecure.com,*.somotherapi.com`)
 
+_Optional Additional Parameters_
+const proxyReplacePrefix = process.env.PROXY*REPLACE || 'PROXY_REPLACE*'
+const proxyReplaceMatchPrefix = process.env.PROXY_REPLACE_MATCH || 'setting'
+
+```dosini
+PROXY_PREFIX=proxy
+PROXY_REPLACE_MATCH=setting
+PROXY_REPLACE=PROXY_REPLACE_
+```
+
+`PROXY_PREFIX` will default to `'proxy'` and is used in the URI patterns to determine where to find the encoded uri to proxy request to (ie. `https://12345678.ngrok.io/<<<PROXY_PREFIX>>>/https%3A%2F%2Fapi.somethingsecure.com%2Fadmin%2Fcustomers.json`)
+
+`PROXY_REPLACE_MATCH` will default to `'setting'` and used within HTTP_HEADERS sent to the proxy to support Mustache like syntax `{{<<PROXY_REPLACE_MATCH>>.something_secure}}` to replace `something_secure` with a value found in your `process.env` (preceeded by your `PROXY_REPLACE` prefix)
+
+`PROXY_REPLACE` will default to `'PROXY_REPLACE_'` and is the prefix used to look for other keys in your `process.env` that it will then use to override matched HTTP_HEADER values with
+
+_Example_
+
+```dosini
+PROXY_REPLACE_MATCH=setting
+PROXY_REPLACE=PROXY_REPLACE_
+PROXY_REPLACE_SOMETHING_SECURE=1XXXXXxxxxxXXXXXxxxxxXXXXXxxxxx1
+```
+
+Which will then take something like the following HTTP_HEADER sent to the proxy:
+
+```dosini
+{ 'X-Shopify-Access-Token', '{{setting.something_secure}}' }
+```
+
+And before the request is proxied to the destination will inject your `process.env` value to send along in the proxied request:
+
+```dosini
+{ 'X-Shopify-Access-Token', '1XXXXXxxxxxXXXXXxxxxxXXXXXxxxxx1' }
+```
+
 ## 📦 Package
 
 Run the following command to build the app

direct.js

@@ -0,0 +1,29 @@
+const { filterByPrefix, mustachReplace } = require('./src/utils')
+
+process.on('unhandledRejection', (reason, p) => {
+  console.error(
+    'Promise unhandledRejection: ',
+    p,
+    ', reason:',
+    JSON.stringify(reason)
+  )
+})
+
+process.env.PROXY_REPLACE_FOO = 'very-secret-23234-324234-234'
+
+class Direct {
+  static async run() {
+    const secureHeader = 'asdas {{settings.foo}} sadsad'
+    console.log('secureHeader', secureHeader)
+    const replacements = filterByPrefix(process.env, 'PROXY_REPLACE_')
+    console.log('replacements', replacements)
+    const header = mustachReplace(secureHeader, replacements, 'setting')
+    console.log('header', header)
+  }
+}
+
+module.exports = Direct
+
+if (require.main === module) {
+  Direct.run()
+}

now.json

@@ -5,7 +5,9 @@
     "NODE_ENV": "production",
     "PROXY_PREFIX": "@demo-proxy-prefix",
     "PROXY_REFERER_WHITELIST": "@demo-proxy-referer-whitelist",
-    "PROXY_DESTINATION_WHITELIST": "@demo-proxy-destination-whitelist"
+    "PROXY_DESTINATION_WHITELIST": "@demo-proxy-destination-whitelist",
+    "PROXY_REPLACE_GATEWAY_PK": "@particular-gateway-pk",
+    "PROXY_REPLACE_GATEWAY_SK": "@particular-gateway-sk"
   },
   "routes": [{ "src": "/(.*)", "dest": "/src" }],
   "builds": [

src/index.js

@@ -5,6 +5,7 @@ const { URL } = require('whatwg-url')
 const UrlPattern = require('url-pattern')
 const cors = require('micro-cors')()
 const fetch = require('node-fetch')
+const { filterByPrefix, mustachReplace } = require('./utils')
 
 const _toJSON = error => {
   return !error
@@ -74,24 +75,39 @@ const destinationWhiteList = toRegexArray(
   process.env.PROXY_DESTINATION_WHITELIST
 )
 const proxyPrefix = process.env.PROXY_PREFIX || 'proxy'
-// console.log('process.env.PROXY_PREFIX', process.env.PROXY_PREFIX)
+const proxyReplacePrefix = process.env.PROXY_REPLACE || 'PROXY_REPLACE_'
+const proxyReplaceMatchPrefix = process.env.PROXY_REPLACE_MATCH || 'setting'
+// console.log('process.env.PROXY_PREFIX', proxyPrefix)
+// console.log('process.env.PROXY_REPLACE', proxyReplacePrefix)
+// console.log('process.env.PROXY_REPLACE_MATCH', proxyReplaceMatchPrefix)
+const envReplacements = filterByPrefix(process.env, proxyReplacePrefix)
+// console.log('envReplacements', envReplacements)
+
+const filterValue = input => {
+  return mustachReplace(input, envReplacements, proxyReplaceMatchPrefix)
+}
 
 const requestHeaders = headers => {
-  console.log('requestHeaders, headers', headers)
   const {
     host,
     referer,
     origin,
     'x-requested-with': requestedWith,
-    ...filteredHeaders
+    ...filteringHeaders
   } = headers
+
+  const filteredHeaders = Object.keys(filteringHeaders).reduce((obj, key) => {
+    obj[key] = filterValue(filteringHeaders[key])
+    return obj
+  }, {})
+
   const defaultHeaders = {
     'x-forwarded-by': `${name}-${version}`,
     'x-forwarded-origin': origin,
     'x-forwarded-referer': referer
   }
   const modifiedHeaders = { ...filteredHeaders, ...defaultHeaders }
-  // console.log('requestHeaders, modifiedHeaders', modifiedHeaders)
+  console.log('requestHeaders, modifiedHeaders', modifiedHeaders)
   return modifiedHeaders
 }
 

src/utils.js

@@ -0,0 +1,35 @@
+module.exports = {
+  filterByPrefix(input, ...matchPrefixes) {
+    return Object.keys(input)
+      .filter(key => {
+        // return only objects within input who's keys start with any envPrefix
+        let matched = false
+        matchPrefixes.forEach(prefix => {
+          matched = matched || key.startsWith(prefix)
+        })
+        return matched
+      })
+      .reduce((obj, rawKey) => {
+        // remove any envPrefix that object startswith
+        let key = rawKey
+        matchPrefixes.forEach(prefix => {
+          key = key.startsWith(prefix) ? key.replace(prefix, '') : key
+        })
+        obj[key] = input[rawKey]
+        return obj
+      }, {})
+  },
+
+  mustachReplace(input, replacements, ...mustachPrefixes) {
+    // will search for input containing {{mustachePrefix.XYZ}}
+    return input.replace(/{{((.*?)\.(.*?))}}/g, (match, ...groups) => {
+      if (mustachPrefixes.includes(groups[1])) {
+        return groups[2] !== 'undefined'
+          ? replacements[groups[2].toUpperCase()] || match
+          : match
+      } else {
+        return match
+      }
+    })
+  }
+}