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Special Forums News, Links, Events and Announcements Complex Event Processing RSS News Proxy Caches are a Challenging Threat to Internet Security Post 302243384 by Linux Bot on Sunday 5th of October 2008 06:50:03 AM
Old 10-05-2008
Proxy Caches are a Challenging Threat to Internet Security

Tim Bass
10-05-2008 03:41 AM
Proxy caches, combined with poorly written session management code, can easily leads to serious security flaws similar to what we highlighted in A New Security Breach in Google Docs Revealed.

Web developers have no control over proxy caches in the Internet. However, developers do have control of the code they write and their admin teams have configuration control of their web servers. Developers must assume the worst case Internet scenario with aggressive Internet cache management policies that serve cached data for economic and performance reasons.

As a consequence, this fact-of-life on the Internet sometimes results in multiple web clients being sent the same Set-Cookie HTTP headers, for example.* Caching proxy servers should obtain a fresh cookie for the each new client request. Ideally, proxy caches should not cache session management cookies and distribute cached cookies to multiple clients. However, application developers cannot assume that proxy caches are well behaved, especially for applications where security and privacy are required.

Web developers cannot know whether their content is consumed directly or via a proxy cache. Developers also cannot assume that the HTTP responses will be delivered to the intended browser. Moreover, developers cannot be sure that the intended browser even receives the intended content.* For example, a session ID issued to a client gets used while it is valid or until abandoned and expired. If it is served and delivered in response to an unencrypted HTTP GET request, there's no guarantee it will be consumed by the intended web browser.

Ideally, SSL should be used on all web transactions that require confidentiality and privacy, including our recent Google Docs breach.* On the other hand, even SSL is not foolproof. For example, many web developers do not correctly set the “Encrypted Sessions Only” cookie property. These incorrectly configured “secure” servers will send HTTPS cookies in the open, unencrypted.

There be dragons …


Note: Reposted from the (ISC)2 blog.</p>

Source...
 

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CURLOPT_PROXY(3)					     curl_easy_setopt options						  CURLOPT_PROXY(3)

NAME
CURLOPT_PROXY - set proxy to use SYNOPSIS
#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PROXY, char *proxy); DESCRIPTION
Set the proxy to use for the upcoming request. The parameter should be a char * to a zero terminated string holding the host name or dotted numerical IP address. A numerical IPv6 address must be written within [brackets]. To specify port number in this string, append :[port] to the end of the host name. The proxy's port number may optionally be specified with the separate option CURLOPT_PROXYPORT(3). If not specified, libcurl will default to using port 1080 for proxies. The proxy string may be prefixed with [scheme]:// to specify which kind of proxy is used. http:// HTTP Proxy. Default when no scheme or proxy type is specified. https:// HTTPS Proxy. (Added in 7.52.0 for OpenSSL, GnuTLS and NSS) socks4:// SOCKS4 Proxy. socks4a:// SOCKS4a Proxy. Proxy resolves URL hostname. socks5:// SOCKS5 Proxy. socks5h:// SOCKS5 Proxy. Proxy resolves URL hostname. Without a scheme prefix, CURLOPT_PROXYTYPE(3) can be used to specify which kind of proxy the string identifies. When you tell the library to use a HTTP proxy, libcurl will transparently convert operations to HTTP even if you specify an FTP URL etc. This may have an impact on what other features of the library you can use, such as CURLOPT_QUOTE(3) and similar FTP specifics that don't work unless you tunnel through the HTTP proxy. Such tunneling is activated with CURLOPT_HTTPPROXYTUNNEL(3). libcurl respects the environment variables http_proxy, ftp_proxy, all_proxy etc, if any of those are set. The CURLOPT_PROXY(3) option does however override any possibly set environment variables. Setting the proxy string to "" (an empty string) will explicitly disable the use of a proxy, even if there is an environment variable set for it. A proxy host string can also include protocol scheme (http://) and embedded user + password. The application does not have to keep the string around after setting this option. DEFAULT
Default is NULL, meaning no proxy is used. When you set a host name to use, do not assume that there's any particular single port number used widely for proxies. Specify it! PROTOCOLS
All except file://. Note that some protocols don't do very well over proxy. EXAMPLE
TODO AVAILABILITY
Since 7.14.1 the proxy environment variable names can include the protocol scheme. Since 7.21.7 the proxy string supports the socks protocols as "schemes". Since 7.50.2, unsupported schemes in proxy strings cause libcurl to return error. RETURN VALUE
Returns CURLE_OK if proxies are supported, CURLE_UNKNOWN_OPTION if not, or CURLE_OUT_OF_MEMORY if there was insufficient heap space. SEE ALSO
CURLOPT_PROXYPORT(3), CURLOPT_HTTPPROXYTUNNEL(3), CURLOPT_PROXYTYPE(3) libcurl 7.54.0 February 06, 2017 CURLOPT_PROXY(3)
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