diff --git a/src/Composer/Util/Http/CurlDownloader.php b/src/Composer/Util/Http/CurlDownloader.php
index 7e12870c6..9ab716e58 100644
--- a/src/Composer/Util/Http/CurlDownloader.php
+++ b/src/Composer/Util/Http/CurlDownloader.php
@@ -41,6 +41,9 @@ class CurlDownloader
     private $authHelper;
     private $selectTimeout = 5.0;
     private $maxRedirects = 20;
+    /** @var ProxyManager */
+    private $proxyManager;
+    private $supportsSecureProxy;
     protected $multiErrors = array(
         CURLM_BAD_HANDLE      => array('CURLM_BAD_HANDLE', 'The passed-in handle is not a valid CURLM handle.'),
         CURLM_BAD_EASY_HANDLE => array('CURLM_BAD_EASY_HANDLE', "An easy handle was not good/valid. It could mean that it isn't an easy handle at all, or possibly that the handle already is in used by this or another multi handle."),
@@ -92,6 +95,11 @@ class CurlDownloader
         }
 
         $this->authHelper = new AuthHelper($io, $config);
+        $this->proxyManager = ProxyManager::getInstance();
+
+        $version = curl_version();
+        $features = $version['features'];
+        $this->supportsSecureProxy = defined('CURL_VERSION_HTTPS_PROXY') && ($features & CURL_VERSION_HTTPS_PROXY);
     }
 
     /**
@@ -176,7 +184,8 @@ class CurlDownloader
         }
 
         $options['http']['header'] = $this->authHelper->addAuthenticationHeader($options['http']['header'], $origin, $url);
-        $options = StreamContextFactory::initOptions($url, $options);
+        // Merge in headers - we don't get any proxy values
+        $options = StreamContextFactory::initOptions($url, $options, true);
 
         foreach (self::$options as $type => $curlOptions) {
             foreach ($curlOptions as $name => $curlOption) {
@@ -190,6 +199,25 @@ class CurlDownloader
             }
         }
 
+        // Always set CURLOPT_PROXY to enable/disable proxy handling
+        // Any proxy authorization is included in the proxy url
+        $proxy = $this->proxyManager->getProxyForRequest($url);
+        curl_setopt($curlHandle, CURLOPT_PROXY, $proxy->getUrl());
+
+        // Curl needs certificate locations for secure proxies.
+        // CURLOPT_PROXY_SSL_VERIFY_PEER/HOST are enabled by default
+        if ($proxy->isSecure()) {
+            if (!$this->supportsSecureProxy) {
+                throw new TransportException('Connecting to a secure proxy using curl is not supported on PHP versions below 7.3.0.');
+            }
+            if (!empty($options['ssl']['cafile'])) {
+                curl_setopt($curlHandle, CURLOPT_PROXY_CAINFO, $options['ssl']['cafile']);
+            }
+            if (!empty($options['ssl']['capath'])) {
+                curl_setopt($curlHandle, CURLOPT_PROXY_CAPATH, $options['ssl']['capath']);
+            }
+        }
+
         $progress = array_diff_key(curl_getinfo($curlHandle), self::$timeInfo);
 
         $this->jobs[(int) $curlHandle] = array(
@@ -206,7 +234,7 @@ class CurlDownloader
             'reject' => $reject,
         );
 
-        $usingProxy = !empty($options['http']['proxy']) ? ' using proxy ' . $options['http']['proxy'] : '';
+        $usingProxy = $proxy->getLastProxy(' using proxy (%s)');
         $ifModified = false !== stripos(implode(',', $options['http']['header']), 'if-modified-since:') ? ' if modified' : '';
         if ($attributes['redirects'] === 0) {
             $this->io->writeError('Downloading ' . Url::sanitize($url) . $usingProxy . $ifModified, true, IOInterface::DEBUG);
diff --git a/src/Composer/Util/Http/ProxyHelper.php b/src/Composer/Util/Http/ProxyHelper.php
new file mode 100644
index 000000000..2f03de735
--- /dev/null
+++ b/src/Composer/Util/Http/ProxyHelper.php
@@ -0,0 +1,179 @@
+<?php
+
+/*
+ * This file is part of Composer.
+ *
+ * (c) Nils Adermann <naderman@naderman.de>
+ *     Jordi Boggiano <j.boggiano@seld.be>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Composer\Util\Http;
+
+/**
+ * Proxy discovery and helper class
+ *
+ * @internal
+ * @author John Stevenson <john-stevenson@blueyonder.co.uk>
+ */
+class ProxyHelper
+{
+    /**
+     * Returns proxy environment values
+     *
+     * @throws \RuntimeException on malformed url
+     * @return array httpProxy, httpsProxy, noProxy values
+     */
+    public static function getProxyData()
+    {
+        $httpProxy = null;
+        $httpsProxy = null;
+
+        // Handle http_proxy/HTTP_PROXY on CLI only for security reasons
+        if (PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg') {
+            if ($env = self::getProxyEnv(array('http_proxy', 'HTTP_PROXY'), $name)) {
+                $httpProxy = self::checkProxy($env, $name);
+            }
+        }
+
+        // Prefer CGI_HTTP_PROXY if available
+        if ($env = self::getProxyEnv(array('CGI_HTTP_PROXY'), $name)) {
+            $httpProxy = self::checkProxy($env, $name);
+        }
+
+        // Handle https_proxy/HTTPS_PROXY
+        if ($env = self::getProxyEnv(array('https_proxy', 'HTTPS_PROXY'), $name)) {
+            $httpsProxy = self::checkProxy($env, $name);
+        } else {
+            $httpsProxy = $httpProxy;
+        }
+
+        // Handle no_proxy
+        $noProxy = self::getProxyEnv(array('no_proxy', 'NO_PROXY'), $name);
+
+        return array($httpProxy, $httpsProxy, $noProxy);
+    }
+
+    /**
+     * Returns http context options for the proxy url
+     *
+     * @param string $proxyUrl
+     * @return array
+     */
+    public static function getContextOptions($proxyUrl)
+    {
+        $proxy = parse_url($proxyUrl);
+
+        // Remove any authorization
+        $proxyUrl = self::formatParsedUrl($proxy, false);
+        $proxyUrl = str_replace(array('http://', 'https://'), array('tcp://', 'ssl://'), $proxyUrl);
+
+        $options['http']['proxy'] = $proxyUrl;
+
+        // Handle any authorization
+        if (isset($proxy['user'])) {
+            $auth = rawurldecode($proxy['user']);
+
+            if (isset($proxy['pass'])) {
+                $auth .= ':' . rawurldecode($proxy['pass']);
+            }
+            $auth = base64_encode($auth);
+            // Set header as a string
+            $options['http']['header'] = "Proxy-Authorization: Basic {$auth}";
+        }
+
+        return $options;
+    }
+
+    /**
+     * Sets/unsets request_fulluri value in http context options array
+     *
+     * @param string $requestUrl
+     * @param array $options Set by method
+     */
+    public static function setRequestFullUri($requestUrl, array &$options)
+    {
+        if ('http' === parse_url($requestUrl, PHP_URL_SCHEME)) {
+            $options['http']['request_fulluri'] = true;
+        } else {
+            unset($options['http']['request_fulluri']);
+        }
+    }
+
+    /**
+     * Searches $_SERVER for case-sensitive values
+     *
+     * @param array $names Names to search for
+     * @param mixed $name Name of any found value
+     * @return string|null The found value
+     */
+    private static function getProxyEnv(array $names, &$name)
+    {
+        foreach ($names as $name) {
+            if (!empty($_SERVER[$name])) {
+                return $_SERVER[$name];
+            }
+        }
+    }
+
+    /**
+     * Checks and formats a proxy url from the environment
+     *
+     * @param string $proxyUrl
+     * @param string $envName
+     * @throws \RuntimeException on malformed url
+     * @return string The formatted proxy url
+     */
+    private static function checkProxy($proxyUrl, $envName)
+    {
+        $error = sprintf('malformed %s url', $envName);
+        $proxy = parse_url($proxyUrl);
+
+        if (!isset($proxy['host'])) {
+            throw new \RuntimeException($error);
+        }
+
+        $proxyUrl = self::formatParsedUrl($proxy, true);
+
+        if (!parse_url($proxyUrl, PHP_URL_PORT)) {
+            throw new \RuntimeException($error);
+        }
+
+        return $proxyUrl;
+    }
+
+    /**
+     * Formats a url from its component parts
+     *
+     * @param array $proxy Values from parse_url
+     * @param bool $includeAuth Whether to include authorization values
+     * @return string The formatted value
+     */
+    private static function formatParsedUrl(array $proxy, $includeAuth)
+    {
+        $proxyUrl = isset($proxy['scheme']) ? strtolower($proxy['scheme']) . '://' : '';
+
+        if ($includeAuth && isset($proxy['user'])) {
+            $proxyUrl .= $proxy['user'];
+
+            if (isset($proxy['pass'])) {
+                $proxyUrl .= ':' . $proxy['pass'];
+            }
+            $proxyUrl .= '@';
+        }
+
+        $proxyUrl .= $proxy['host'];
+
+        if (isset($proxy['port'])) {
+            $proxyUrl .= ':' . $proxy['port'];
+        } elseif (strpos($proxyUrl, 'http://') === 0) {
+            $proxyUrl .= ':80';
+        } elseif (strpos($proxyUrl, 'https://') === 0) {
+            $proxyUrl .= ':443';
+        }
+
+        return $proxyUrl;
+    }
+}
diff --git a/src/Composer/Util/Http/ProxyManager.php b/src/Composer/Util/Http/ProxyManager.php
new file mode 100644
index 000000000..be8983771
--- /dev/null
+++ b/src/Composer/Util/Http/ProxyManager.php
@@ -0,0 +1,178 @@
+<?php
+
+/*
+ * This file is part of Composer.
+ *
+ * (c) Nils Adermann <naderman@naderman.de>
+ *     Jordi Boggiano <j.boggiano@seld.be>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Composer\Util\Http;
+
+use Composer\Downloader\TransportException;
+use Composer\Util\NoProxyPattern;
+use Composer\Util\Url;
+
+/**
+ * @internal
+ * @author John Stevenson <john-stevenson@blueyonder.co.uk>
+ */
+class ProxyManager
+{
+    private $error;
+    private $fullProxy;
+    private $safeProxy;
+    private $streams;
+    private $hasProxy;
+    private $info;
+    private $lastProxy;
+    /** @var NoProxyPattern */
+    private $noProxyHandler;
+
+    /** @var ProxyManager */
+    private static $instance;
+
+    private function __construct()
+    {
+        $this->fullProxy = $this->safeProxy = array(
+            'http' => null,
+            'https' => null,
+        );
+
+        $this->streams['http'] = $this->streams['https'] = array(
+            'options' => null,
+        );
+
+        $this->hasProxy = false;
+        $this->initProxyData();
+    }
+
+    /**
+     * @return ProxyManager     *
+     */
+    public static function getInstance()
+    {
+        if (!self::$instance) {
+            self::$instance = new self();
+        }
+
+        return self::$instance;
+    }
+
+    /**
+     * Clears the persistent instance
+     */
+    public static function reset()
+    {
+        self::$instance = null;
+    }
+
+    /**
+     * Returns a RequestProxy instance for the request url
+     *
+     * @param string $requestUrl
+     * @return RequestProxy
+     */
+    public function getProxyForRequest($requestUrl)
+    {
+        if ($this->error) {
+            throw new TransportException('Unable to use a proxy: '.$this->error);
+        }
+
+        $scheme = parse_url($requestUrl, PHP_URL_SCHEME) ?: 'http';
+        $proxyUrl = '';
+        $options = array();
+        $lastProxy = '';
+
+        if ($this->hasProxy && $this->fullProxy[$scheme]) {
+            if ($this->noProxy($requestUrl)) {
+                $lastProxy = 'excluded by no_proxy';
+            } else {
+                $proxyUrl = $this->fullProxy[$scheme];
+                $options = $this->streams[$scheme]['options'];
+                ProxyHelper::setRequestFullUri($requestUrl, $options);
+                $lastProxy = $this->safeProxy[$scheme];
+            }
+        }
+
+        return new RequestProxy($proxyUrl, $options, $lastProxy);
+    }
+
+    /**
+     * Returns true if a proxy is being used
+     *
+     * @param string|null $message Set to safe proxy values
+     * @return bool If false any error will be in $message
+     */
+    public function getStatus(&$message)
+    {
+        $message = $this->hasProxy ? $this->info : $this->error;
+        return $this->hasProxy;
+    }
+
+    /**
+     * Initializes proxy values from the environment
+     */
+    private function initProxyData()
+    {
+        try {
+            list($httpProxy, $httpsProxy, $noProxy) = ProxyHelper::getProxyData();
+        } catch (\RuntimeException $e) {
+            $this->error = $e->getMessage();
+            return;
+        }
+
+        $info = array();
+
+        if ($httpProxy) {
+            $info[] = $this->setData($httpProxy, 'http');
+        }
+        if ($httpsProxy) {
+            $info[] = $this->setData($httpsProxy, 'https');
+        }
+        if ($this->hasProxy) {
+            $this->info = implode(', ', $info);
+            if ($noProxy) {
+                $this->noProxyHandler = array(new NoProxyPattern($noProxy), 'test');
+            }
+        }
+    }
+
+    /**
+     * Sets initial data
+     *
+     * @param string $proxyUrl Proxy url
+     * @param string $scheme Environment variable scheme
+     */
+    private function setData($url, $scheme)
+    {
+        $safeProxy = Url::sanitize($url);
+        $this->fullProxy[$scheme] = $url;
+        $this->safeProxy[$scheme] = $safeProxy;
+        $this->streams[$scheme]['options'] = ProxyHelper::getContextOptions($url);
+        $this->hasProxy = true;
+
+        return sprintf('%s=%s', $scheme, $safeProxy);
+    }
+
+    /**
+     * Returns true if a url matches no_proxy value
+     *
+     * @param string $requestUrl
+     * @return bool
+     */
+    private function noProxy($requestUrl)
+    {
+        if ($this->noProxyHandler) {
+            if (call_user_func($this->noProxyHandler, $requestUrl)) {
+                $this->lastProxy = 'excluded by no_proxy';
+                return true;
+            }
+        }
+
+        return false;
+    }
+}
diff --git a/src/Composer/Util/Http/RequestProxy.php b/src/Composer/Util/Http/RequestProxy.php
new file mode 100644
index 000000000..44f0c27cc
--- /dev/null
+++ b/src/Composer/Util/Http/RequestProxy.php
@@ -0,0 +1,89 @@
+<?php
+
+/*
+ * This file is part of Composer.
+ *
+ * (c) Nils Adermann <naderman@naderman.de>
+ *     Jordi Boggiano <j.boggiano@seld.be>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Composer\Util\Http;
+
+use Composer\Util\Url;
+
+/**
+ * @internal
+ * @author John Stevenson <john-stevenson@blueyonder.co.uk>
+ */
+class RequestProxy
+{
+    private $contextOptions;
+    private $isSecure;
+    private $lastProxy;
+    private $safeUrl;
+    private $url;
+
+    /**
+     * @param string $url
+     * @param array $contextOptions
+     * @param string $lastProxy
+     */
+    public function __construct($url, array $contextOptions, $lastProxy)
+    {
+        $this->url = $url;
+        $this->contextOptions = $contextOptions;
+        $this->lastProxy = $lastProxy;
+        $this->safeUrl = Url::sanitize($url);
+        $this->isSecure = 0 === strpos($url, 'https://');
+    }
+
+    /**
+     * Returns an array of context options
+     *
+     * @return array
+     */
+    public function getContextOptions()
+    {
+        return $this->contextOptions;
+    }
+
+    /**
+     * Returns the safe proxy url from the last request
+     *
+     * @param string|null $format Output format specifier
+     * @return string Safe proxy, no proxy or empty
+     */
+    public function getLastProxy($format = '')
+    {
+        $result = '';
+        if ($this->lastProxy) {
+            $format = $format ?: '%s';
+            $result = sprintf($format, $this->lastProxy);
+        }
+
+        return $result;
+    }
+
+    /**
+     * Returns the proxy url
+     *
+     * @return string Proxy url or empty
+     */
+    public function getUrl()
+    {
+        return $this->url;
+    }
+
+    /**
+     * Returns true if this is a secure-proxy
+     *
+     * @return bool False if not secure or there is no proxy
+     */
+    public function isSecure()
+    {
+        return $this->isSecure;
+    }
+}
diff --git a/src/Composer/Util/RemoteFilesystem.php b/src/Composer/Util/RemoteFilesystem.php
index 03cd0cce8..c5e5eba53 100644
--- a/src/Composer/Util/RemoteFilesystem.php
+++ b/src/Composer/Util/RemoteFilesystem.php
@@ -18,6 +18,7 @@ use Composer\IO\IOInterface;
 use Composer\Downloader\TransportException;
 use Composer\CaBundle\CaBundle;
 use Composer\Util\Http\Response;
+use Composer\Util\Http\ProxyManager;
 
 /**
  * @internal
@@ -46,6 +47,7 @@ class RemoteFilesystem
     private $degradedMode = false;
     private $redirects;
     private $maxRedirects = 20;
+    private $proxyManager;
 
     /**
      * Constructor.
@@ -72,6 +74,7 @@ class RemoteFilesystem
         $this->options = array_replace_recursive($this->options, $options);
         $this->config = $config;
         $this->authHelper = isset($authHelper) ? $authHelper : new AuthHelper($io, $config);
+        $this->proxyManager = ProxyManager::getInstance();
     }
 
     /**
@@ -251,10 +254,10 @@ class RemoteFilesystem
 
         $ctx = StreamContextFactory::getContext($fileUrl, $options, array('notification' => array($this, 'callbackGet')));
 
-        $actualContextOptions = stream_context_get_options($ctx);
-        $usingProxy = !empty($actualContextOptions['http']['proxy']) ? ' using proxy ' . $actualContextOptions['http']['proxy'] : '';
+        $proxy = ProxyManager::getInstance()->getProxyForRequest($fileUrl);
+        $usingProxy = $proxy->getLastProxy(' using proxy (%s)');
         $this->io->writeError((strpos($origFileUrl, 'http') === 0 ? 'Downloading ' : 'Reading ') . Url::sanitize($origFileUrl) . $usingProxy, true, IOInterface::DEBUG);
-        unset($origFileUrl, $actualContextOptions);
+        unset($origFileUrl, $proxy, $usingProxy);
 
         // Check for secure HTTP, but allow insecure Packagist calls to $hashed providers as file integrity is verified with sha256
         if ((!preg_match('{^http://(repo\.)?packagist\.org/p/}', $fileUrl) || (false === strpos($fileUrl, '$') && false === strpos($fileUrl, '%24'))) && empty($degradedPackagist) && $this->config) {
diff --git a/src/Composer/Util/StreamContextFactory.php b/src/Composer/Util/StreamContextFactory.php
index d81119aff..e62bb7e52 100644
--- a/src/Composer/Util/StreamContextFactory.php
+++ b/src/Composer/Util/StreamContextFactory.php
@@ -15,6 +15,7 @@ namespace Composer\Util;
 use Composer\Composer;
 use Composer\CaBundle\CaBundle;
 use Composer\Downloader\TransportException;
+use Composer\Util\Http\ProxyManager;
 use Psr\Log\LoggerInterface;
 
 /**
@@ -57,10 +58,11 @@ final class StreamContextFactory
     /**
      * @param string $url
      * @param array $options
+     * @param bool $forCurl
      * @psalm-return array{http:{header: string[], proxy?: string, request_fulluri: bool}, ssl: array}
      * @return array formatted as a stream context array
      */
-    public static function initOptions($url, array $options)
+    public static function initOptions($url, array $options, $forCurl = false)
     {
         // Make sure the headers are in an array form
         if (!isset($options['http']['header'])) {
@@ -70,76 +72,26 @@ final class StreamContextFactory
             $options['http']['header'] = explode("\r\n", $options['http']['header']);
         }
 
-        // Handle HTTP_PROXY/http_proxy on CLI only for security reasons
-        if ((PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg') && (!empty($_SERVER['HTTP_PROXY']) || !empty($_SERVER['http_proxy']))) {
-            $proxy = parse_url(!empty($_SERVER['http_proxy']) ? $_SERVER['http_proxy'] : $_SERVER['HTTP_PROXY']);
-        }
-
-        // Prefer CGI_HTTP_PROXY if available
-        if (!empty($_SERVER['CGI_HTTP_PROXY'])) {
-            $proxy = parse_url($_SERVER['CGI_HTTP_PROXY']);
-        }
-
-        // Override with HTTPS proxy if present and URL is https
-        if (preg_match('{^https://}i', $url) && (!empty($_SERVER['HTTPS_PROXY']) || !empty($_SERVER['https_proxy']))) {
-            $proxy = parse_url(!empty($_SERVER['https_proxy']) ? $_SERVER['https_proxy'] : $_SERVER['HTTPS_PROXY']);
-        }
-
-        // Remove proxy if URL matches no_proxy directive
-        if (!empty($_SERVER['NO_PROXY']) || !empty($_SERVER['no_proxy']) && parse_url($url, PHP_URL_HOST)) {
-            $pattern = new NoProxyPattern(!empty($_SERVER['no_proxy']) ? $_SERVER['no_proxy'] : $_SERVER['NO_PROXY']);
-            if ($pattern->test($url)) {
-                unset($proxy);
-            }
-        }
-
-        if (!empty($proxy)) {
-            $proxyURL = isset($proxy['scheme']) ? $proxy['scheme'] . '://' : '';
-            $proxyURL .= isset($proxy['host']) ? $proxy['host'] : '';
-
-            if (isset($proxy['port'])) {
-                $proxyURL .= ":" . $proxy['port'];
-            } elseif (strpos($proxyURL, 'http://') === 0) {
-                $proxyURL .= ":80";
-            } elseif (strpos($proxyURL, 'https://') === 0) {
-                $proxyURL .= ":443";
-            }
-
-            // http(s):// is not supported in proxy
-            $proxyURL = str_replace(array('http://', 'https://'), array('tcp://', 'ssl://'), $proxyURL);
-
-            if (0 === strpos($proxyURL, 'ssl:') && !extension_loaded('openssl')) {
-                throw new \RuntimeException('You must enable the openssl extension to use a proxy over https');
-            }
-
-            $options['http']['proxy'] = $proxyURL;
-
-            // enabled request_fulluri unless it is explicitly disabled
-            switch (parse_url($url, PHP_URL_SCHEME)) {
-                case 'http': // default request_fulluri to true for HTTP
-                    $reqFullUriEnv = getenv('HTTP_PROXY_REQUEST_FULLURI');
-                    if ($reqFullUriEnv === false || $reqFullUriEnv === '' || (strtolower($reqFullUriEnv) !== 'false' && (bool) $reqFullUriEnv)) {
-                        $options['http']['request_fulluri'] = true;
-                    }
-                    break;
-                case 'https': // default request_fulluri to false for HTTPS
-                    $reqFullUriEnv = getenv('HTTPS_PROXY_REQUEST_FULLURI');
-                    if (strtolower($reqFullUriEnv) !== 'false' && (bool) $reqFullUriEnv) {
-                        $options['http']['request_fulluri'] = true;
-                    }
-                    break;
-            }
-
-            // handle proxy auth if present
-            if (isset($proxy['user'])) {
-                $auth = rawurldecode($proxy['user']);
-                if (isset($proxy['pass'])) {
-                    $auth .= ':' . rawurldecode($proxy['pass']);
+        // Add stream proxy options if there is a proxy
+        if (!$forCurl) {
+            $proxy = ProxyManager::getInstance()->getProxyForRequest($url);
+            if ($proxy->isSecure()) {
+                if (!extension_loaded('openssl')) {
+                    throw new TransportException('You must enable the openssl extension to use a proxy over https.');
+                }
+                if (0 === strpos($url, 'https://')) {
+                    throw new TransportException('PHP does not support https requests to a secure proxy.');
                 }
-                $auth = base64_encode($auth);
-
-                $options['http']['header'][] = "Proxy-Authorization: Basic {$auth}";
             }
+
+            $proxyOptions = $proxy->getContextOptions();
+
+            // Header will be a Proxy-Authorization string or not set
+            if (isset($proxyOptions['http']['header'])) {
+                $options['http']['header'][] = $proxyOptions['http']['header'];
+                unset($proxyOptions['http']['header']);
+            }
+            $options = array_replace_recursive($options, $proxyOptions);
         }
 
         if (defined('HHVM_VERSION')) {
@@ -148,7 +100,7 @@ final class StreamContextFactory
             $phpVersion = 'PHP ' . PHP_MAJOR_VERSION . '.' . PHP_MINOR_VERSION . '.' . PHP_RELEASE_VERSION;
         }
 
-        if (extension_loaded('curl')) {
+        if ($forCurl) {
             $curl = curl_version();
             $httpVersion = 'curl '.$curl['version'];
         } else {
diff --git a/tests/Composer/Test/Util/Http/ProxyHelperTest.php b/tests/Composer/Test/Util/Http/ProxyHelperTest.php
new file mode 100644
index 000000000..2b31fb470
--- /dev/null
+++ b/tests/Composer/Test/Util/Http/ProxyHelperTest.php
@@ -0,0 +1,190 @@
+<?php
+
+/*
+ * This file is part of Composer.
+ *
+ * (c) Nils Adermann <naderman@naderman.de>
+ *     Jordi Boggiano <j.boggiano@seld.be>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Composer\Test\Util\Http;
+
+use Composer\Util\Http\ProxyHelper;
+use Composer\Test\TestCase;
+
+class ProxyHelperTest extends TestCase
+{
+    protected function setUp()
+    {
+        unset(
+            $_SERVER['HTTP_PROXY'],
+            $_SERVER['http_proxy'],
+            $_SERVER['HTTPS_PROXY'],
+            $_SERVER['https_proxy'],
+            $_SERVER['NO_PROXY'],
+            $_SERVER['no_proxy'],
+            $_SERVER['CGI_HTTP_PROXY']
+        );
+    }
+
+    protected function tearDown()
+    {
+        unset(
+            $_SERVER['HTTP_PROXY'],
+            $_SERVER['http_proxy'],
+            $_SERVER['HTTPS_PROXY'],
+            $_SERVER['https_proxy'],
+            $_SERVER['NO_PROXY'],
+            $_SERVER['no_proxy'],
+            $_SERVER['CGI_HTTP_PROXY']
+        );
+    }
+
+    /**
+     * @dataProvider dataMalformed
+     */
+    public function testThrowsOnMalformedUrl($url)
+    {
+        $_SERVER['http_proxy'] = $url;
+
+        $this->setExpectedException('RuntimeException');
+        ProxyHelper::getProxyData();
+    }
+
+    public function dataMalformed()
+    {
+        return array(
+            'no-host' => array('localhost'),
+            'no-port' => array('scheme://localhost'),
+        );
+    }
+
+    /**
+     * @dataProvider dataFormatting
+     */
+    public function testUrlFormatting($url, $expected)
+    {
+        $_SERVER['http_proxy'] = $url;
+
+        list($httpProxy, $httpsProxy, $noProxy) = ProxyHelper::getProxyData();
+        $this->assertSame($expected, $httpProxy);
+    }
+
+    public function dataFormatting()
+    {
+        // url, expected
+        return array(
+            'lowercases-scheme' => array('HTTP://proxy.com:8888', 'http://proxy.com:8888'),
+            'adds-http-port'    => array('http://proxy.com', 'http://proxy.com:80'),
+            'adds-https-port'   => array('https://proxy.com', 'https://proxy.com:443'),
+        );
+    }
+
+    /**
+     * @dataProvider dataCaseOverrides
+     */
+    public function testLowercaseOverridesUppercase(array $server, $expected, $index)
+    {
+        $_SERVER = array_merge($_SERVER, $server);
+
+        $list = ProxyHelper::getProxyData();
+        $this->assertSame($expected, $list[$index]);
+    }
+
+    public function dataCaseOverrides()
+    {
+        // server, expected, list index
+        return array(
+            array(array('HTTP_PROXY' => 'http://upper.com', 'http_proxy' => 'http://lower.com'), 'http://lower.com:80', 0),
+            array(array('HTTPS_PROXY' => 'http://upper.com', 'https_proxy' => 'http://lower.com'), 'http://lower.com:80', 1),
+            array(array('NO_PROXY' => 'upper.com', 'no_proxy' => 'lower.com'), 'lower.com', 2),
+        );
+    }
+
+    /**
+     * @dataProvider dataCGIOverrides
+     */
+    public function testCGIUpperCaseOverridesHttp(array $server, $expected, $index)
+    {
+        $_SERVER = array_merge($_SERVER, $server);
+
+        $list = ProxyHelper::getProxyData();
+        $this->assertSame($expected, $list[$index]);
+    }
+
+    public function dataCGIOverrides()
+    {
+         // server, expected, list index
+        return array(
+            array(array('http_proxy' => 'http://http.com', 'CGI_HTTP_PROXY' => 'http://cgi.com'), 'http://cgi.com:80', 0),
+            array(array('http_proxy' => 'http://http.com', 'cgi_http_proxy' => 'http://cgi.com'), 'http://http.com:80', 0),
+        );
+    }
+
+    public function testNoHttpsProxyUsesHttpProxy()
+    {
+        $_SERVER['http_proxy'] = 'http://http.com';
+
+        list($httpProxy, $httpsProxy, $noProxy) = ProxyHelper::getProxyData();
+        $this->assertSame('http://http.com:80', $httpsProxy);
+    }
+
+    public function testNoHttpProxyDoesNotUseHttpsProxy()
+    {
+        $_SERVER['https_proxy'] = 'http://https.com';
+
+        list($httpProxy, $httpsProxy, $noProxy) = ProxyHelper::getProxyData();
+        $this->assertSame(null, $httpProxy);
+    }
+
+    /**
+     * @dataProvider dataContextOptions
+     */
+    public function testGetContextOptions($url, $expected)
+    {
+        $this->assertEquals($expected, ProxyHelper::getContextOptions($url));
+    }
+
+    public function dataContextOptions()
+    {
+        // url, expected
+        return array(
+            array('http://proxy.com', array('http' => array(
+                'proxy' => 'tcp://proxy.com:80',
+            ))),
+            array('https://proxy.com', array('http' => array(
+                'proxy' => 'ssl://proxy.com:443',
+            ))),
+            array('http://user:p%40ss@proxy.com', array('http' => array(
+                'proxy' => 'tcp://proxy.com:80',
+                'header' => 'Proxy-Authorization: Basic dXNlcjpwQHNz',
+            ))),
+        );
+    }
+
+    /**
+     * @dataProvider dataRequestFullUri
+     */
+    public function testSetRequestFullUri($requestUrl, $expected)
+    {
+        $options = array();
+        ProxyHelper::setRequestFullUri($requestUrl, $options);
+
+        $this->assertEquals($expected, $options);
+    }
+
+    public function dataRequestFullUri()
+    {
+        $options = array('http' => array('request_fulluri' => true));
+
+        // $requestUrl, expected
+        return array(
+            'http'      => array('http://repo.org', $options),
+            'https'     => array('https://repo.org', array()),
+            'no-scheme' => array('repo.org', array()),
+        );
+    }
+}
diff --git a/tests/Composer/Test/Util/Http/ProxyManagerTest.php b/tests/Composer/Test/Util/Http/ProxyManagerTest.php
new file mode 100644
index 000000000..e4eb54a46
--- /dev/null
+++ b/tests/Composer/Test/Util/Http/ProxyManagerTest.php
@@ -0,0 +1,167 @@
+<?php
+
+/*
+ * This file is part of Composer.
+ *
+ * (c) Nils Adermann <naderman@naderman.de>
+ *     Jordi Boggiano <j.boggiano@seld.be>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Composer\Test\Util\Http;
+
+use Composer\Util\Http\ProxyHelper;
+use Composer\Util\Http\ProxyManager;
+use Composer\Test\TestCase;
+
+class ProxyManagerTest extends TestCase
+{
+    protected function setUp()
+    {
+        unset(
+            $_SERVER['HTTP_PROXY'],
+            $_SERVER['http_proxy'],
+            $_SERVER['HTTPS_PROXY'],
+            $_SERVER['https_proxy'],
+            $_SERVER['NO_PROXY'],
+            $_SERVER['no_proxy'],
+            $_SERVER['CGI_HTTP_PROXY']
+        );
+        ProxyManager::reset();
+    }
+
+    protected function tearDown()
+    {
+        unset(
+            $_SERVER['HTTP_PROXY'],
+            $_SERVER['http_proxy'],
+            $_SERVER['HTTPS_PROXY'],
+            $_SERVER['https_proxy'],
+            $_SERVER['NO_PROXY'],
+            $_SERVER['no_proxy'],
+            $_SERVER['CGI_HTTP_PROXY']
+        );
+        ProxyManager::reset();
+    }
+
+    public function testInstantiation()
+    {
+        $originalInstance = ProxyManager::getInstance();
+        $this->assertInstanceOf('Composer\Util\Http\ProxyManager', $originalInstance);
+
+        $sameInstance = ProxyManager::getInstance();
+        $this->assertTrue($originalInstance === $sameInstance);
+
+        ProxyManager::reset();
+        $newInstance = ProxyManager::getInstance();
+        $this->assertFalse($sameInstance === $newInstance);
+    }
+
+    public function testGetProxyForRequestThrowsOnBadProxyUrl()
+    {
+        $_SERVER['http_proxy'] = 'localhost';
+        $proxyManager = ProxyManager::getInstance();
+        $this->setExpectedException('Composer\Downloader\TransportException');
+        $proxyManager->getProxyForRequest('http://example.com');
+    }
+
+    /**
+     * @dataProvider dataRequest
+     */
+    public function testGetProxyForRequest($server, $url, $expectedUrl, $expectedOptions, $expectedSecure, $expectedMessage)
+    {
+        $_SERVER = array_merge($_SERVER, $server);
+        $proxyManager = ProxyManager::getInstance();
+
+        $proxy = $proxyManager->getProxyForRequest($url);
+        $this->assertInstanceOf('Composer\Util\Http\RequestProxy', $proxy);
+
+        $this->assertSame($expectedUrl, $proxy->getUrl());
+        $this->assertSame($expectedOptions, $proxy->getContextOptions());
+        $this->assertSame($expectedSecure, $proxy->isSecure());
+
+        $message = $proxy->getLastProxy();
+
+        if ($expectedMessage) {
+            $condition = stripos($message, $expectedMessage) !== false;
+        } else {
+            $condition = $expectedMessage === $message;
+        }
+
+        $this->assertTrue($condition, 'lastProxy check');
+    }
+
+    public function dataRequest()
+    {
+        $server = array(
+            'http_proxy' => 'http://user:p%40ss@proxy.com',
+            'https_proxy' => 'https://proxy.com:443',
+            'no_proxy' => 'other.repo.org',
+        );
+
+        // server, url, expectedUrl, expectedOptions, expectedSecure, expectedMessage
+        return array(
+            array(array(), 'http://repo.org', '', array(), false, ''),
+            array($server, 'http://repo.org', 'http://user:p%40ss@proxy.com:80',
+                array('http' => array(
+                    'proxy' => 'tcp://proxy.com:80',
+                    'header' => 'Proxy-Authorization: Basic dXNlcjpwQHNz',
+                    'request_fulluri' => true,
+                    )
+                ),
+                false,
+                'http://user:***@proxy.com:80',
+            ),
+            array(
+                $server, 'https://repo.org', 'https://proxy.com:443',
+                array('http' => array(
+                    'proxy' => 'ssl://proxy.com:443',
+                    )
+                ),
+                true,
+                'https://proxy.com:443',
+            ),
+            array($server, 'https://other.repo.org', '', array(), false, 'no_proxy'),
+        );
+    }
+
+    /**
+     * @dataProvider dataStatus
+     */
+    public function testGetStatus($server, $expectedStatus, $expectedMessage)
+    {
+        $_SERVER = array_merge($_SERVER, $server);
+        $proxyManager = ProxyManager::getInstance();
+        $status = $proxyManager->getStatus($message);
+
+        $this->assertSame($expectedStatus, $status);
+
+        if ($expectedMessage) {
+            $condition = stripos($message, $expectedMessage) !== false;
+        } else {
+            $condition = $expectedMessage === $message;
+        }
+        $this->assertTrue($condition, 'message check');
+    }
+
+    public function dataStatus()
+    {
+        // server, expectedStatus, expectedMessage
+        return array(
+            array(array(), false, null),
+            array(array('http_proxy' => 'localhost'), false, 'malformed'),
+            array(
+                array('http_proxy' => 'http://user:p%40ss@proxy.com:80'),
+                true,
+                'http=http://user:***@proxy.com:80'
+            ),
+            array(
+                array('http_proxy' => 'proxy.com:80', 'https_proxy' => 'proxy.com:80'),
+                true,
+                'http=proxy.com:80, https=proxy.com:80'
+            ),
+        );
+    }
+}
diff --git a/tests/Composer/Test/Util/Http/RequestProxyTest.php b/tests/Composer/Test/Util/Http/RequestProxyTest.php
new file mode 100644
index 000000000..f87002515
--- /dev/null
+++ b/tests/Composer/Test/Util/Http/RequestProxyTest.php
@@ -0,0 +1,61 @@
+<?php
+
+/*
+ * This file is part of Composer.
+ *
+ * (c) Nils Adermann <naderman@naderman.de>
+ *     Jordi Boggiano <j.boggiano@seld.be>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Composer\Test\Util\Http;
+
+use Composer\Util\Http\RequestProxy;
+use Composer\Test\TestCase;
+
+class RequestProxyTest extends TestCase
+{
+    /**
+     * @dataProvider dataSecure
+     */
+    public function testIsSecure($url, $expectedSecure)
+    {
+        $proxy = new RequestProxy($url, array(), '');
+
+        $this->assertSame($expectedSecure, $proxy->isSecure());
+    }
+
+    public function dataSecure()
+    {
+        // url, secure
+        return array(
+            'basic'     => array('http://proxy.com:80', false),
+            'secure'    => array('https://proxy.com:443', true),
+            'none'      => array('', false),
+        );
+    }
+
+    /**
+     * @dataProvider dataLastProxy
+     */
+    public function testGetLastProxyFormat($url, $format, $expected)
+    {
+        $proxy = new RequestProxy($url, array(), $url);
+
+        $message = $proxy->getLastProxy($format);
+        $this->assertSame($expected, $message);
+    }
+
+    public function dataLastProxy()
+    {
+        $format = 'proxy (%s)';
+
+        // url, format, expected
+        return array(
+            array('', $format, ''),
+            array('http://proxy.com:80', $format, 'proxy (http://proxy.com:80)'),
+        );
+    }
+}
diff --git a/tests/Composer/Test/Util/StreamContextFactoryTest.php b/tests/Composer/Test/Util/StreamContextFactoryTest.php
index 973ff3254..80423a825 100644
--- a/tests/Composer/Test/Util/StreamContextFactoryTest.php
+++ b/tests/Composer/Test/Util/StreamContextFactoryTest.php
@@ -12,6 +12,7 @@
 
 namespace Composer\Test\Util;
 
+use Composer\Util\Http\ProxyManager;
 use Composer\Util\StreamContextFactory;
 use Composer\Test\TestCase;
 
@@ -20,11 +21,13 @@ class StreamContextFactoryTest extends TestCase
     protected function setUp()
     {
         unset($_SERVER['HTTP_PROXY'], $_SERVER['http_proxy'], $_SERVER['HTTPS_PROXY'], $_SERVER['https_proxy'], $_SERVER['NO_PROXY'], $_SERVER['no_proxy']);
+        ProxyManager::reset();
     }
 
     protected function tearDown()
     {
         unset($_SERVER['HTTP_PROXY'], $_SERVER['http_proxy'], $_SERVER['HTTPS_PROXY'], $_SERVER['https_proxy'], $_SERVER['NO_PROXY'], $_SERVER['no_proxy']);
+        ProxyManager::reset();
     }
 
     /**
@@ -147,16 +150,9 @@ class StreamContextFactoryTest extends TestCase
         $_SERVER['http_proxy'] = 'http://username:password@proxyserver.net';
         $_SERVER['https_proxy'] = 'https://woopproxy.net';
 
+        // Pointless test replaced by ProxyHelperTest.php
+        $this->setExpectedException('Composer\Downloader\TransportException');
         $context = StreamContextFactory::getContext('https://example.org', array('http' => array('method' => 'GET', 'header' => 'User-Agent: foo')));
-        $options = stream_context_get_options($context);
-
-        $this->assertEquals(array('http' => array(
-            'proxy' => 'ssl://woopproxy.net:443',
-            'method' => 'GET',
-            'max_redirects' => 20,
-            'follow_location' => 1,
-            'header' => array('User-Agent: foo'),
-        )), $options);
     }
 
     /**
@@ -182,7 +178,7 @@ class StreamContextFactoryTest extends TestCase
                 StreamContextFactory::getContext('http://example.org');
                 $this->fail();
             } catch (\RuntimeException $e) {
-                $this->assertInstanceOf('RuntimeException', $e);
+                $this->assertInstanceOf('Composer\Downloader\TransportException', $e);
             }
         }
     }
@@ -216,4 +212,26 @@ class StreamContextFactoryTest extends TestCase
         $ctxoptions = stream_context_get_options($context);
         $this->assertEquals(end($expectedOptions['http']['header']), end($ctxoptions['http']['header']));
     }
+
+    public function testInitOptionsDoesIncludeProxyAuthHeaders()
+    {
+        $_SERVER['http_proxy'] = 'http://username:password@proxyserver.net:3128/';
+
+        $options = array();
+        $options = StreamContextFactory::initOptions('https://example.org', $options);
+        $headers = implode(' ', $options['http']['header']);
+
+        $this->assertTrue(false !== stripos($headers, 'Proxy-Authorization'));
+    }
+
+    public function testInitOptionsForCurlDoesNotIncludeProxyAuthHeaders()
+    {
+        $_SERVER['http_proxy'] = 'http://username:password@proxyserver.net:3128/';
+
+        $options = array();
+        $options = StreamContextFactory::initOptions('https://example.org', $options, true);
+        $headers = implode(' ', $options['http']['header']);
+
+        $this->assertFalse(stripos($headers, 'Proxy-Authorization'));
+    }
 }