2 .\" Copyright (c) 1998-2013 Dag-Erling Smørgrav
3 .\" Copyright (c) 2013 Michael Gmelin <freebsd@grem.de>
4 .\" All rights reserved.
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7 .\" modification, are permitted provided that the following conditions
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61 .Nd file transfer functions
69 .Fn fetchMakeURL "const char *scheme" "const char *host" "int port" "const char *doc" "const char *user" "const char *pwd"
71 .Fn fetchParseURL "const char *URL"
73 .Fn fetchFreeURL "struct url *u"
75 .Fn fetchXGetURL "const char *URL" "struct url_stat *us" "const char *flags"
77 .Fn fetchGetURL "const char *URL" "const char *flags"
79 .Fn fetchPutURL "const char *URL" "const char *flags"
81 .Fn fetchStatURL "const char *URL" "struct url_stat *us" "const char *flags"
83 .Fn fetchListURL "const char *URL" "const char *flags"
85 .Fn fetchXGet "struct url *u" "struct url_stat *us" "const char *flags"
87 .Fn fetchGet "struct url *u" "const char *flags"
89 .Fn fetchPut "struct url *u" "const char *flags"
91 .Fn fetchStat "struct url *u" "struct url_stat *us" "const char *flags"
93 .Fn fetchList "struct url *u" "const char *flags"
95 .Fn fetchXGetFile "struct url *u" "struct url_stat *us" "const char *flags"
97 .Fn fetchGetFile "struct url *u" "const char *flags"
99 .Fn fetchPutFile "struct url *u" "const char *flags"
101 .Fn fetchStatFile "struct url *u" "struct url_stat *us" "const char *flags"
103 .Fn fetchListFile "struct url *u" "const char *flags"
105 .Fn fetchXGetHTTP "struct url *u" "struct url_stat *us" "const char *flags"
107 .Fn fetchGetHTTP "struct url *u" "const char *flags"
109 .Fn fetchPutHTTP "struct url *u" "const char *flags"
111 .Fn fetchStatHTTP "struct url *u" "struct url_stat *us" "const char *flags"
113 .Fn fetchListHTTP "struct url *u" "const char *flags"
115 .Fn fetchXGetFTP "struct url *u" "struct url_stat *us" "const char *flags"
117 .Fn fetchGetFTP "struct url *u" "const char *flags"
119 .Fn fetchPutFTP "struct url *u" "const char *flags"
121 .Fn fetchStatFTP "struct url *u" "struct url_stat *us" "const char *flags"
123 .Fn fetchListFTP "struct url *u" "const char *flags"
125 These functions implement a high-level library for retrieving and
126 uploading files using Uniform Resource Locators (URLs).
129 takes a URL in the form of a null-terminated string and splits it into
130 its components function according to the Common Internet Scheme Syntax
132 A regular expression which produces this syntax is:
134 <scheme>:(//(<user>(:<pwd>)?@)?<host>(:<port>)?)?/(<document>)?
137 If the URL does not seem to begin with a scheme name, the following
140 ((<user>(:<pwd>)?@)?<host>(:<port>)?)?/(<document>)?
143 Note that some components of the URL are not necessarily relevant to
145 For instance, the file scheme only needs the <scheme> and <document>
151 return a pointer to a
153 structure, which is defined as follows in
156 #define URL_SCHEMELEN 16
157 #define URL_USERLEN 256
158 #define URL_PWDLEN 256
161 char scheme[URL_SCHEMELEN+1];
162 char user[URL_USERLEN+1];
163 char pwd[URL_PWDLEN+1];
164 char host[MAXHOSTNAMELEN+1];
175 field stores the time value for
176 .Li If-Modified-Since
179 The pointer returned by
183 should be freed using
190 constitute the recommended interface to the
193 They examine the URL passed to them to determine the transfer
194 method, and call the appropriate lower-level functions to perform the
197 also returns the remote document's metadata in the
199 structure pointed to by the
205 argument is a string of characters which specify transfer options.
207 meaning of the individual flags is scheme-dependent, and is detailed
208 in the appropriate section below.
211 attempts to obtain the requested document's metadata and fill in the
212 structure pointed to by its second argument.
215 structure is defined as follows in
225 If the size could not be obtained from the server, the
228 If the modification time could not be obtained from the server, the
230 field is set to the epoch.
231 If the access time could not be obtained from the server, the
233 field is set to the modification time.
236 attempts to list the contents of the directory pointed to by the URL
238 If successful, it returns a malloced array of
243 structure is defined as follows in
248 struct url_stat stat;
252 The list is terminated by an entry with an empty name.
254 The pointer returned by
256 should be freed using
270 except that they expect a pre-parsed URL in the form of a pointer to
273 rather than a string.
280 functions return a pointer to a stream which can be used to read or
281 write data from or to the requested document, respectively.
283 although the implementation details of the individual access methods
284 vary, it can generally be assumed that a stream returned by one of the
288 functions is read-only, and that a stream returned by one of the
290 functions is write-only.
296 provide access to documents which are files in a locally mounted file
298 Only the <document> component of the URL is used.
303 do not accept any flags.
308 (append to file) flag.
309 If that flag is specified, the data written to
310 the stream returned by
312 will be appended to the previous contents of the file, instead of
319 implement the FTP protocol as described in RFC959.
323 (not passive) flag is specified, an active (rather than passive)
324 connection will be attempted.
328 flag is supported for compatibility with earlier versions where active
329 connections were the default.
330 It has precedence over the
332 flag, so if both are specified,
334 will use a passive connection.
338 (low) flag is specified, data sockets will be allocated in the low (or
339 default) port range instead of the high port range (see
344 (direct) flag is specified,
349 will use a direct connection even if a proxy server is defined.
351 If no user name or password is given, the
353 library will attempt an anonymous login, with user name "anonymous"
354 and password "anonymous@<hostname>".
361 functions implement the HTTP/1.1 protocol.
362 With a little luck, there is
363 even a chance that they comply with RFC2616 and RFC2617.
367 (direct) flag is specified,
372 will use a direct connection even if a proxy server is defined.
376 (if-modified-since) flag is specified, and
385 will send a conditional
386 .Li If-Modified-Since
387 HTTP header to only fetch the content if it is newer than
390 Since there seems to be no good way of implementing the HTTP PUT
391 method in a manner consistent with the rest of the
395 is currently unimplemented.
397 Based on HTTP SCHEME.
398 By default the peer is verified using the CA bundle located in
399 .Pa /etc/ssl/cert.pem .
400 The file may contain multiple CA certificates.
401 A common source of a current CA bundle is
402 .Pa \%security/ca_root_nss .
404 The CA bundle used for peer verification can be changed by setting the
405 environment variables
407 to point to a concatenated bundle of trusted certificates and
409 to point to a directory containing hashes of trusted CAs (see
412 A certificate revocation list (CRL) can be used by setting the
418 Peer verification can be disabled by setting the environment variable
419 .Ev SSL_NO_VERIFY_PEER .
420 Note that this also disables CRL checking.
422 By default the service identity is verified according to the rules
423 detailed in RFC6125 (also known as hostname verification).
424 This feature can be disabled by setting the environment variable
425 .Ev SSL_NO_VERIFY_HOSTNAME .
427 Client certificate based authentication is supported.
428 The environment variable
429 .Ev SSL_CLIENT_CERT_FILE
430 should be set to point to a file containing key and client certificate
431 to be used in PEM format. In case the key is stored in a separate
432 file, the environment variable
433 .Ev SSL_CLIENT_KEY_FILE
434 can be set to point to the key in PEM format.
435 In case the key uses a password, the user will be prompted on standard
441 allows TLSv1 and newer when negotiating the connecting with the remote
443 You can change this behavior by setting the
447 environment variables to allow SSLv2 and SSLv3, respectively, and
449 .Ev SSL_NO_TLS1_1 and
451 to disable TLS 1.0, 1.1 and 1.2 respectively.
453 Apart from setting the appropriate environment variables and
454 specifying the user name and password in the URL or the
456 the calling program has the option of defining an authentication
457 function with the following prototype:
460 .Fn myAuthMethod "struct url *u"
462 The callback function should fill in the
466 fields in the provided
468 and return 0 on success, or any other value to indicate failure.
470 To register the authentication callback, simply set
473 The callback will be used whenever a site requires authentication and
474 the appropriate environment variables are not set.
476 This interface is experimental and may be subject to change.
479 returns a pointer to a
481 containing the individual components of the URL.
483 unable to allocate memory, or the URL is syntactically incorrect,
485 returns a NULL pointer.
489 functions return 0 on success and -1 on failure.
491 All other functions return a stream pointer which may be used to
492 access the requested document, or NULL if an error occurred.
494 The following error codes are defined in
497 .It Bq Er FETCH_ABORT
500 Authentication failed
503 .It Bq Er FETCH_EXISTS
508 Informational response
509 .It Bq Er FETCH_MEMORY
511 .It Bq Er FETCH_MOVED
513 .It Bq Er FETCH_NETWORK
517 .It Bq Er FETCH_PROTO
519 .It Bq Er FETCH_RESOLV
521 .It Bq Er FETCH_SERVER
525 .It Bq Er FETCH_TIMEOUT
527 .It Bq Er FETCH_UNAVAIL
528 File is not available
529 .It Bq Er FETCH_UNKNOWN
535 The accompanying error message includes a protocol-specific error code
536 and message, e.g.\& "File is not available (404 Not Found)"
538 .Bl -tag -width ".Ev FETCH_BIND_ADDRESS"
539 .It Ev FETCH_BIND_ADDRESS
540 Specifies a hostname or IP address to which sockets used for outgoing
541 connections will be bound.
543 Default FTP login if none was provided in the URL.
544 .It Ev FTP_PASSIVE_MODE
547 forces the FTP code to use active mode.
548 If set to any other value, forces passive mode even if the application
549 requested active mode.
551 Default FTP password if the remote server requests one and none was
554 URL of the proxy to use for FTP requests.
555 The document part is ignored.
556 FTP and HTTP proxies are supported; if no scheme is specified, FTP is
558 If the proxy is an FTP proxy,
562 as user name to the proxy, where
564 is the real user name, and
566 is the name of the FTP server.
568 If this variable is set to an empty string, no proxy will be used for
569 FTP requests, even if the
577 Specifies the value of the
579 header for HTTP requests.
586 Specifies HTTP authorization parameters as a colon-separated list of
588 The first and second item are the authorization scheme and realm
589 respectively; further items are scheme-dependent.
594 authorization methods are supported.
596 Both methods require two parameters: the user name and
597 password, in that order.
599 This variable is only used if the server requires authorization and
600 no user name or password was specified in the URL.
602 URL of the proxy to use for HTTP requests.
603 The document part is ignored.
604 Only HTTP proxies are supported for HTTP requests.
605 If no port number is specified, the default is 3128.
607 Note that this proxy will also be used for FTP documents, unless the
614 .It Ev HTTP_PROXY_AUTH
615 Specifies authorization parameters for the HTTP proxy in the same
620 This variable is used if and only if connected to an HTTP proxy, and
621 is ignored if a user and/or a password were specified in the proxy
624 Specifies the referrer URL to use for HTTP requests.
627 the document URL will be used as referrer URL.
628 .It Ev HTTP_USER_AGENT
629 Specifies the User-Agent string to use for HTTP requests.
630 This can be useful when working with HTTP origin or proxy servers that
631 differentiate between user agents.
632 If defined but empty, no User-Agent header is sent.
634 Specifies a file to use instead of
636 to look up login names and passwords for FTP sites.
639 for a description of the file format.
640 This feature is experimental.
642 Either a single asterisk, which disables the use of proxies
643 altogether, or a comma- or whitespace-separated list of hosts for
644 which proxies should not be used.
649 .It Ev SSL_ALLOW_SSL2
650 Allow SSL version 2 when negotiating the connection (not recommended).
651 .It Ev SSL_ALLOW_SSL3
652 Allow SSL version 3 when negotiating the connection (not recommended).
653 .It Ev SSL_CA_CERT_FILE
654 CA certificate bundle containing trusted CA certificates.
656 .Pa /etc/ssl/cert.pem .
657 .It Ev SSL_CA_CERT_PATH
658 Path containing trusted CA hashes.
659 .It Ev SSL_CLIENT_CERT_FILE
660 PEM encoded client certificate/key which will be used in
661 client certificate authentication.
662 .It Ev SSL_CLIENT_KEY_FILE
663 PEM encoded client key in case key and client certificate
664 are stored separately.
666 File containing certificate revocation list.
668 Do not allow TLS version 1.0 when negotiating the connection.
670 Do not allow TLS version 1.1 when negotiating the connection.
672 Do not allow TLS version 1.2 when negotiating the connection.
673 .It Ev SSL_NO_VERIFY_HOSTNAME
674 If set, do not verify that the hostname matches the subject of the
675 certificate presented by the server.
676 .It Ev SSL_NO_VERIFY_PEER
677 If set, do not verify the peer certificate against trusted CAs.
680 To access a proxy server on
681 .Pa proxy.example.com
684 environment variable in a manner similar to this:
686 .Dl HTTP_PROXY=http://proxy.example.com:8080
688 If the proxy server requires authentication, there are
689 two options available for passing the authentication data.
690 The first method is by using the proxy URL:
692 .Dl HTTP_PROXY=http://<user>:<pwd>@proxy.example.com:8080
694 The second method is by using the
696 environment variable:
697 .Bd -literal -offset indent
698 HTTP_PROXY=http://proxy.example.com:8080
699 HTTP_PROXY_AUTH=basic:*:<user>:<pwd>
702 To disable the use of a proxy for an HTTP server running on the local
706 .Bd -literal -offset indent
707 NO_PROXY=localhost,127.0.0.1
710 Access HTTPS website without any certificate verification whatsoever:
711 .Bd -literal -offset indent
713 SSL_NO_VERIFY_HOSTNAME=1
716 Access HTTPS website using client certificate based authentication
718 .Bd -literal -offset indent
719 SSL_CLIENT_CERT_FILE=/path/to/client.pem
720 SSL_CA_CERT_FILE=/path/to/myca.pem
730 .%B File Transfer Protocol
738 .%T How to Use Anonymous FTP
746 .%T Uniform Resource Locators (URL)
758 .%B Hypertext Transfer Protocol -- HTTP/1.1
770 .%B HTTP Authentication: Basic and Digest Access Authentication
776 library first appeared in
782 library was mostly written by
783 .An Dag-Erling Sm\(/orgrav Aq des@FreeBSD.org
784 with numerous suggestions and contributions from
785 .An Jordan K. Hubbard Aq jkh@FreeBSD.org ,
786 .An Eugene Skepner Aq eu@qub.com ,
787 .An Hajimu Umemoto Aq ume@FreeBSD.org ,
788 .An Henry Whincup Aq henry@techiebod.com ,
789 .An Jukka A. Ukkonen Aq jau@iki.fi ,
790 .An Jean-Fran\(,cois Dockes Aq jf@dockes.org ,
791 .An Michael Gmelin Aq freebsd@grem.de
793 It replaces the older
796 .An Poul-Henning Kamp Aq phk@FreeBSD.org
798 .An Jordan K. Hubbard Aq jkh@FreeBSD.org .
800 This manual page was written by
801 .An Dag-Erling Sm\(/orgrav Aq des@FreeBSD.org
803 .An Michael Gmelin Aq freebsd@grem.de .
805 Some parts of the library are not yet implemented.
811 and FTP proxy support.
813 There is no way to select a proxy at run-time other than setting the
817 environment variables as appropriate.
820 does not understand or obey 305 (Use Proxy) replies.
822 Error numbers are unique only within a certain context; the error
823 codes used for FTP and HTTP overlap, as do those used for resolver and
825 For instance, error code 202 means "Command not
826 implemented, superfluous at this site" in an FTP context and
827 "Accepted" in an HTTP context.
830 does not check that the result of an MDTM command is a valid date.
832 In case password protected keys are used for client certificate based
833 authentication the user is prompted for the password on each and every
836 The man page is incomplete, poorly written and produces badly
839 The error reporting mechanism is unsatisfactory.
841 Some parts of the code are not fully reentrant.