doc/man3/OSSL_HTTP_transfer.pod

   1 =pod
   2
   3 =head1 NAME
   4
   5 OSSL_HTTP_open,
   6 OSSL_HTTP_bio_cb_t,
   7 OSSL_HTTP_proxy_connect,
   8 OSSL_HTTP_set1_request,
   9 OSSL_HTTP_exchange,
  10 OSSL_HTTP_get,
  11 OSSL_HTTP_transfer,
  12 OSSL_HTTP_close
  13 -  HTTP client high-level functions
  14
  15 =head1 SYNOPSIS
  16
  17  #include <openssl/http.h>
  18
  19  typedef BIO *(*OSSL_HTTP_bio_cb_t)(BIO *bio, void *arg,
  20                                     int connect, int detail);
  21  OSSL_HTTP_REQ_CTX *OSSL_HTTP_open(const char *server, const char *port,
  22                                    const char *proxy, const char *no_proxy,
  23                                    int use_ssl, BIO *bio, BIO *rbio,
  24                                    OSSL_HTTP_bio_cb_t bio_update_fn, void *arg,
  25                                    int buf_size, int overall_timeout);
  26  int OSSL_HTTP_proxy_connect(BIO *bio, const char *server, const char *port,
  27                              const char *proxyuser, const char *proxypass,
  28                              int timeout, BIO *bio_err, const char *prog);
  29  int OSSL_HTTP_set1_request(OSSL_HTTP_REQ_CTX *rctx, const char *path,
  30                             const STACK_OF(CONF_VALUE) *headers,
  31                             const char *content_type, BIO *req,
  32                             const char *expected_content_type, int expect_asn1,
  33                             size_t max_resp_len, int timeout, int keep_alive);
  34  BIO *OSSL_HTTP_exchange(OSSL_HTTP_REQ_CTX *rctx, char **redirection_url);
  35  BIO *OSSL_HTTP_get(const char *url, const char *proxy, const char *no_proxy,
  36                     BIO *bio, BIO *rbio,
  37                     OSSL_HTTP_bio_cb_t bio_update_fn, void *arg,
  38                     int buf_size, const STACK_OF(CONF_VALUE) *headers,
  39                     const char *expected_content_type, int expect_asn1,
  40                     size_t max_resp_len, int timeout);
  41  BIO *OSSL_HTTP_transfer(OSSL_HTTP_REQ_CTX **prctx,
  42                          const char *server, const char *port,
  43                          const char *path, int use_ssl,
  44                          const char *proxy, const char *no_proxy,
  45                          BIO *bio, BIO *rbio,
  46                          OSSL_HTTP_bio_cb_t bio_update_fn, void *arg,
  47                          int buf_size, const STACK_OF(CONF_VALUE) *headers,
  48                          const char *content_type, BIO *req,
  49                          const char *expected_content_type, int expect_asn1,
  50                          size_t max_resp_len, int timeout, int keep_alive);
  51  int OSSL_HTTP_close(OSSL_HTTP_REQ_CTX *rctx, int ok);
  52
  53 =head1 DESCRIPTION
  54
  55 OSSL_HTTP_open() initiates an HTTP session using the I<bio> argument if not
  56 NULL, else by connecting to a given I<server> optionally via a I<proxy>.
  57
  58 Typically the OpenSSL build supports sockets and the I<bio> parameter is NULL.
  59 In this case I<rbio> must be NULL as well and the I<server> must be non-NULL.
  60 The function creates a network BIO internally using L<BIO_new_connect(3)>
  61 for connecting to the given server and the optionally given I<port>,
  62 defaulting to 80 for HTTP or 443 for HTTPS.
  63 Then this internal BIO is used for setting up a connection
  64 and for exchanging one or more request and response.
  65 If I<bio> is given and I<rbio> is NULL then this I<bio> is used instead.
  66 If both I<bio> and I<rbio> are given (which may be memory BIOs for instance)
  67 then no explicit connection is set up, but
  68 I<bio> is used for writing requests and I<rbio> for reading responses.
  69 As soon as the client has flushed I<bio> the server must be ready to provide
  70 a response or indicate a waiting condition via I<rbio>.
  71
  72 If I<bio> is given, it is an error to provide I<proxy> or I<no_proxy> arguments,
  73 while I<server> and I<port> arguments may be given to support diagnostic output.
  74 If I<bio> is NULL the optional I<proxy> parameter can be used to set an
  75 HTTP(S) proxy to use (unless overridden by "no_proxy" settings).
  76 If TLS is not used this defaults to the environment variable C<http_proxy>
  77 if set, else C<HTTP_PROXY>.
  78 If I<use_ssl> != 0 it defaults to C<https_proxy> if set, else C<HTTPS_PROXY>.
  79 An empty proxy string C<""> forbids using a proxy.
  80 Else the format is
  81 C<[http[s]://][userinfo@]host[:port][/path][?query][#fragment]>,
  82 where any userinfo, path, query, and fragment given is ignored.
  83 The default proxy port number is 80, or 443 in case "https:" is given.
  84 The HTTP client functions connect via the given proxy unless the I<server>
  85 is found in the optional list I<no_proxy> of proxy hostnames (if not NULL;
  86 default is the environment variable C<no_proxy> if set, else C<NO_PROXY>).
  87 Proxying plain HTTP is supported directly,
  88 while using a proxy for HTTPS connections requires a suitable callback function
  89 such as OSSL_HTTP_proxy_connect(), described below.
  90
  91 If I<use_ssl> is nonzero a TLS connection is requested
  92 and the I<bio_update_fn> parameter must be provided.
  93
  94 The parameter I<bio_update_fn>, which is optional if I<use_ssl> is 0,
  95 may be used to modify the connection BIO used by the HTTP client,
  96 but cannot be used when both I<bio> and I<rbio> are given.
  97 I<bio_update_fn> is a BIO connect/disconnect callback function with prototype
  98
  99  BIO *(*OSSL_HTTP_bio_cb_t)(BIO *bio, void *arg, int connect, int detail)
 100
 101 The callback function may modify the BIO provided in the I<bio> argument,
 102 whereby it may make use of a custom defined argument I<arg>,
 103 which may for instance point to an B<SSL_CTX> structure.
 104 During connection establishment, just after calling BIO_do_connect_retry(), the
 105 callback function is invoked with the I<connect> argument being 1 and
 106 I<detail> being 1 if I<use_ssl> is nonzero (i.e., HTTPS is requested), else 0.
 107 On disconnect I<connect> is 0 and I<detail> is 1 if no error occurred, else 0.
 108 For instance, on connect the callback may push an SSL BIO to implement HTTPS;
 109 after disconnect it may do some diagnostic output and pop and free the SSL BIO.
 110
 111 The callback function must return either the potentially modified BIO I<bio>.
 112 or NULL to indicate failure, in which case it should not modify the BIO.
 113
 114 Here is a simple example that supports TLS connections (but not via a proxy):
 115
 116  BIO *http_tls_cb(BIO *bio, void *arg, int connect, int detail)
 117  {
 118      if (connect && detail) { /* connecting with TLS */
 119          SSL_CTX *ctx = (SSL_CTX *)arg;
 120          BIO *sbio = BIO_new_ssl(ctx, 1);
 121
 122          bio = sbio != NULL ? BIO_push(sbio, bio) : NULL;
 123      } else if (!connect) { /* disconnecting */
 124          BIO *hbio;
 125
 126          if (!detail) { /* an error has occurred */
 127              /* optionally add diagnostics here */
 128          }
 129          BIO_ssl_shutdown(bio);
 130          hbio = BIO_pop(bio);
 131          BIO_free(bio); /* SSL BIO */
 132          bio = hbio;
 133      }
 134      return bio;
 135  }
 136
 137 After disconnect the modified BIO will be deallocated using BIO_free_all().
 138
 139 The I<buf_size> parameter specifies the response header maximum line length.
 140 A value <= 0 means that the B<OSSL_HTTP_DEFAULT_MAX_LINE_LEN> (4KiB) is used.
 141 I<buf_size> is also used as the number of content bytes that are read at a time.
 142
 143 If the I<overall_timeout> parameter is > 0 this indicates the maximum number of
 144 seconds the overall HTTP transfer (i.e., connection setup if needed,
 145 sending requests, and receiving responses) is allowed to take until completion.
 146 A value <= 0 enables waiting indefinitely, i.e., no timeout.
 147
 148 OSSL_HTTP_proxy_connect() may be used by an above BIO connect callback function
 149 to set up an SSL/TLS connection via an HTTPS proxy.
 150 It promotes the given BIO I<bio> representing a connection
 151 pre-established with a TLS proxy using the HTTP CONNECT method,
 152 optionally using proxy client credentials I<proxyuser> and I<proxypass>,
 153 to connect with TLS protection ultimately to I<server> and I<port>.
 154 If the I<port> argument is NULL or the empty string it defaults to "443".
 155 If the I<timeout> parameter is > 0 this indicates the maximum number of
 156 seconds the connection setup is allowed to take.
 157 A value <= 0 enables waiting indefinitely, i.e., no timeout.
 158 Since this function is typically called by applications such as
 159 L<openssl-s_client(1)> it uses the I<bio_err> and I<prog> parameters (unless
 160 NULL) to print additional diagnostic information in a user-oriented way.
 161
 162 OSSL_HTTP_set1_request() sets up in I<rctx> the request header and content data
 163 and expectations on the response using the following parameters.
 164 If <rctx> indicates using a proxy for HTTP (but not HTTPS), the server host
 165 (and optionally port) needs to be placed in the header; thus it must be present
 166 in I<rctx>.
 167 For backward compatibility, the server (and optional port) may also be given in
 168 the I<path> argument beginning with C<http://> (thus giving an absoluteURI).
 169 If I<path> is NULL it defaults to "/".
 170 If I<req> is NULL the HTTP GET method will be used to send the request
 171 else HTTP POST with the contents of I<req> and optional I<content_type>, where
 172 the length of the data in I<req> does not need to be determined in advance: the
 173 BIO will be read on-the-fly while sending the request, which supports streaming.
 174 The optional list I<headers> may contain additional custom HTTP header lines.
 175
 176 If the I<expected_content_type> argument is not NULL,
 177 the client will check that the specified content-type string
 178 is included in the HTTP header of the response and return an error if not.
 179 In the content-type header line the specified string should be present either
 180 as a whole, or in case the specified string does not include a C<;> character,
 181 it is sufficient that the specified string appears as a prefix
 182 in the header line, followed by a C<;> character and any further text.
 183 For instance, if I<expected_content_type> specifies C<text/html>,
 184 this is matched by C<text/html>, C<text/html; charset=UTF-8>, etc.
 185
 186 If the I<expect_asn1> parameter is nonzero,
 187 a structure in ASN.1 encoding will be expected as response content.
 188 The I<max_resp_len> parameter specifies the maximum allowed
 189 response content length, where the value 0 indicates no limit.
 190 If the I<timeout> parameter is > 0 this indicates the maximum number of seconds
 191 the subsequent HTTP transfer (sending the request and receiving a response)
 192 is allowed to take.
 193 A value of 0 enables waiting indefinitely, i.e., no timeout.
 194 A value < 0 indicates that the I<overall_timeout> parameter value given
 195 when opening the HTTP transfer will be used instead.
 196 If I<keep_alive> is 0 the connection is not kept open
 197 after receiving a response, which is the default behavior for HTTP 1.0.
 198 If the value is 1 or 2 then a persistent connection is requested.
 199 If the value is 2 then a persistent connection is required,
 200 i.e., an error occurs in case the server does not grant it.
 201
 202 OSSL_HTTP_exchange() exchanges any form of HTTP request and response
 203 as specified by I<rctx>, which must include both connection and request data,
 204 typically set up using OSSL_HTTP_open() and OSSL_HTTP_set1_request().
 205 It implements the core of the functions described below.
 206 If the HTTP method is GET and I<redirection_url>
 207 is not NULL the latter pointer is used to provide any new location that
 208 the server may return with HTTP code 301 (MOVED_PERMANENTLY) or 302 (FOUND).
 209 In this case the function returns NULL and the caller is
 210 responsible for deallocating the URL with L<OPENSSL_free(3)>.
 211 If the response header contains one or more "Content-Length" header lines and/or
 212 an ASN.1-encoded response is expected, which should include a total length,
 213 the length indications received are checked for consistency
 214 and for not exceeding any given maximum response length.
 215 If an ASN.1-encoded response is expected, the function returns on success
 216 the contents buffered in a memory BIO, which does not support streaming.
 217 Otherwise it returns directly the read BIO that holds the response contents,
 218 which allows a response of indefinite length and may support streaming.
 219 The caller is responsible for freeing the BIO pointer obtained.
 220
 221 OSSL_HTTP_get() uses HTTP GET to obtain data from I<bio> if non-NULL,
 222 else from the server contained in the I<url>, and returns it as a BIO.
 223 It supports redirection via HTTP status code 301 or 302.  It is meant for
 224 transfers with a single round trip, so does not support persistent connections.
 225 If I<bio> is non-NULL, any host and port components in the I<url> are not used
 226 for connecting but the hostname is used, as usual, for the C<Host> header.
 227 Any userinfo and fragment components in the I<url> are ignored.
 228 Any query component is handled as part of the path component.
 229 If the scheme component of the I<url> is C<https> a TLS connection is requested
 230 and the I<bio_update_fn>, as described for OSSL_HTTP_open(), must be provided.
 231 Also the remaining parameters are interpreted as described for OSSL_HTTP_open()
 232 and OSSL_HTTP_set1_request(), respectively.
 233 The caller is responsible for freeing the BIO pointer obtained.
 234
 235 OSSL_HTTP_transfer() exchanges an HTTP request and response
 236 over a connection managed via I<prctx> without supporting redirection.
 237 It combines OSSL_HTTP_open(), OSSL_HTTP_set1_request(), OSSL_HTTP_exchange(),
 238 and OSSL_HTTP_close().
 239 If I<prctx> is not NULL it reuses any open connection represented by a non-NULL
 240 I<*prctx>.  It keeps the connection open if a persistent connection is requested
 241 or required and this was granted by the server, else it closes the connection
 242 and assigns NULL to I<*prctx>.
 243 The remaining parameters are interpreted as described for OSSL_HTTP_open()
 244 and OSSL_HTTP_set1_request(), respectively.
 245 The caller is responsible for freeing the BIO pointer obtained.
 246
 247 OSSL_HTTP_close() closes the connection and releases I<rctx>.
 248 The I<ok> parameter is passed to any BIO update function
 249 given during setup as described above for OSSL_HTTP_open().
 250 It must be 1 if no error occurred during the HTTP transfer and 0 otherwise.
 251
 252 =head1 NOTES
 253
 254 The names of the environment variables used by this implementation:
 255 C<http_proxy>, C<HTTP_PROXY>, C<https_proxy>, C<HTTPS_PROXY>, C<no_proxy>, and
 256 C<NO_PROXY>, have been chosen for maximal compatibility with
 257 other HTTP client implementations such as wget, curl, and git.
 258
 259 When built with tracing enabled, OSSL_HTTP_transfer() and all functions using it
 260 may be traced using B<OSSL_TRACE_CATEGORY_HTTP>.
 261 See also L<OSSL_trace_enabled(3)> and L<openssl(1)/ENVIRONMENT>.
 262
 263 =head1 RETURN VALUES
 264
 265 OSSL_HTTP_open() returns on success a B<OSSL_HTTP_REQ_CTX>, else NULL.
 266
 267 OSSL_HTTP_proxy_connect() and OSSL_HTTP_set1_request()
 268 return 1 on success, 0 on error.
 269
 270 On success, OSSL_HTTP_exchange(), OSSL_HTTP_get(), and OSSL_HTTP_transfer()
 271 return a memory BIO that buffers all the data received if an ASN.1-encoded
 272 response is expected, otherwise a BIO that may support streaming.
 273 The BIO must be freed by the caller.
 274 On failure, they return NULL.
 275 Failure conditions include connection/transfer timeout, parse errors, etc.
 276 The caller is responsible for freeing the BIO pointer obtained.
 277
 278 OSSL_HTTP_close() returns 0 if anything went wrong while disconnecting, else 1.
 279
 280 =head1 SEE ALSO
 281
 282 L<OSSL_HTTP_parse_url(3)>, L<BIO_new_connect(3)>,
 283 L<ASN1_item_i2d_mem_bio(3)>, L<ASN1_item_d2i_bio(3)>,
 284 L<OSSL_HTTP_is_alive(3)>,
 285 L<OSSL_trace_enabled(3)>
 286
 287 =head1 HISTORY
 288
 289 All the functions described here were added in OpenSSL 3.0.
 290
 291 =head1 COPYRIGHT
 292
 293 Copyright 2019-2023 The OpenSSL Project Authors. All Rights Reserved.
 294
 295 Licensed under the Apache License 2.0 (the "License").  You may not use
 296 this file except in compliance with the License.  You can obtain a copy
 297 in the file LICENSE in the source distribution or at
 298 L<https://www.openssl.org/source/license.html>.
 299
 300 =cut