headers and security blurb added
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@ -413,8 +413,8 @@ HTTP POSTing
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The following example sets two simple text parts with plain textual contents,
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and then a file with binary contents and upload the whole thing.
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struct HttpPost *post=NULL;
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struct HttpPost *last=NULL;
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struct curl_httppost *post=NULL;
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struct curl_httppost *last=NULL;
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curl_formadd(&post, &last,
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CURLFORM_COPYNAME, "name",
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CURLFORM_COPYCONTENTS, "daniel", CURLFORM_END);
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@ -871,7 +871,25 @@ Cookies Without Chocolate Chips
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Headers Equal Fun
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[ use the header callback for HTTP, FTP etc ]
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Some protocols provide "headers", meta-data separated from the normal
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data. These headers are by default not included in the normal data stream,
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but you can make them appear in the data stream by setting CURLOPT_HEADER to
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TRUE.
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What might be even more useful, is libcurl's ability to separate the headers
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from the data and thus make the callbacks differ. You can for example set a
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different pointer to pass to the ordinary write callback by setting
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CURLOPT_WRITEHEADER.
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Or, you can set an entirely separate function to receive the headers, by
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using CURLOPT_HEADERFUNCTION.
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The headers are passed to the callback function one by one, and you can
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depend on that fact. It makes it easier for you to add custom header parsers
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etc.
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"Headers" for FTP transfers equal all the FTP server responses. They aren't
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actually true headers, but in this case we pretend they are! ;-)
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Post Transfer Information
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@ -881,7 +899,61 @@ Post Transfer Information
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Security Considerations
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[ ps output, netrc plain text, plain text protocols / base64 ]
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libcurl is in itself not insecure. If used the right way, you can use libcurl
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to transfer data pretty safely.
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There are of course many things to consider that may loosen up this
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situation:
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Command Lines
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If you use a command line tool (such as curl) that uses libcurl, and you
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give option to the tool on the command line those options can very likely
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get read by other users of your system when they use 'ps' or other tools
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to list currently running processes.
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To avoid this problem, never feed sensitive things to programs using
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command line options.
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.netrc
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.netrc is a pretty handy file/feature that allows you to login quickly and
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automaticly to frequently visited sites. The file contains passwords in
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clear text and is a real security risk. In some cases, your .netrc is also
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stored in a home directory that is NFS mounter or used on another network
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based file system, so the clear text password will fly through your
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network every time anyone reads that file!
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To avoid this problem, don't use .netrc files and never store passwords as
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plain text anywhere.
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Clear Text Passwords
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Many of the protocols libcurl supports send name and password unencrypted
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as clear text (HTTP Basic authentication, FTP, TELNET etc). It is very
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easy for anyone on your network or a network nearby yours, to just fire up
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a network analyzer tool and evesdrop on your passwords. Don't let the fact
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that HTTP uses base64 encoded passwords fool you. They may not look
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readable at a first glance, but they very easily "deciphered" by anyone
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within seconds.
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To avoid this problem, use protocols that don't let snoopers see your
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password: HTTPS, FTPS and FTP-kerberos are a few examples. HTTP Digest
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authentication allows this too, but isn't supported by libcurl as of this
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writing.
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Showing What You Do
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On a related issue, be aware that even in situations like when you have
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problems with libcurl and ask somone for help, everything you reveal in
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order to get best possible help might also impose certain security related
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risks. Host names, user names, paths, operating system specifics etc (not
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to mention passwords of course) may in fact be used by intruders to gain
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additional information of a potential target.
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To avoid this problem, you must of course use your common sense. Often,
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you can just edit out the senstive data or just rearch/replace your true
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information with faked data.
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SSL, Certificates and Other Tricks
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