1=pod
2
3=head1 NAME
4
5OSSL_HTTP_REQ_CTX,
6OSSL_HTTP_REQ_CTX_new,
7OSSL_HTTP_REQ_CTX_free,
8OSSL_HTTP_REQ_CTX_set_request_line,
9OSSL_HTTP_REQ_CTX_add1_header,
10OSSL_HTTP_REQ_CTX_set_expected,
11OSSL_HTTP_REQ_CTX_set1_req,
12OSSL_HTTP_REQ_CTX_nbio,
13OSSL_HTTP_REQ_CTX_nbio_d2i,
14OSSL_HTTP_REQ_CTX_exchange,
15OSSL_HTTP_REQ_CTX_get0_mem_bio,
16OSSL_HTTP_REQ_CTX_get_resp_len,
17OSSL_HTTP_REQ_CTX_set_max_response_length,
18OSSL_HTTP_is_alive
19- HTTP client low-level functions
20
21=head1 SYNOPSIS
22
23 #include <openssl/http.h>
24
25 typedef struct ossl_http_req_ctx_st OSSL_HTTP_REQ_CTX;
26
27 OSSL_HTTP_REQ_CTX *OSSL_HTTP_REQ_CTX_new(BIO *wbio, BIO *rbio, int buf_size);
28 void OSSL_HTTP_REQ_CTX_free(OSSL_HTTP_REQ_CTX *rctx);
29
30 int OSSL_HTTP_REQ_CTX_set_request_line(OSSL_HTTP_REQ_CTX *rctx, int method_POST,
31                                        const char *server, const char *port,
32                                        const char *path);
33 int OSSL_HTTP_REQ_CTX_add1_header(OSSL_HTTP_REQ_CTX *rctx,
34                                   const char *name, const char *value);
35
36 int OSSL_HTTP_REQ_CTX_set_expected(OSSL_HTTP_REQ_CTX *rctx,
37                                    const char *content_type, int asn1,
38                                    int timeout, int keep_alive);
39 int OSSL_HTTP_REQ_CTX_set1_req(OSSL_HTTP_REQ_CTX *rctx, const char *content_type,
40                                const ASN1_ITEM *it, const ASN1_VALUE *req);
41 int OSSL_HTTP_REQ_CTX_nbio(OSSL_HTTP_REQ_CTX *rctx);
42 int OSSL_HTTP_REQ_CTX_nbio_d2i(OSSL_HTTP_REQ_CTX *rctx,
43                                ASN1_VALUE **pval, const ASN1_ITEM *it);
44 BIO *OSSL_HTTP_REQ_CTX_exchange(OSSL_HTTP_REQ_CTX *rctx);
45
46 BIO *OSSL_HTTP_REQ_CTX_get0_mem_bio(const OSSL_HTTP_REQ_CTX *rctx);
47 size_t OSSL_HTTP_REQ_CTX_get_resp_len(const OSSL_HTTP_REQ_CTX *rctx);
48 void OSSL_HTTP_REQ_CTX_set_max_response_length(OSSL_HTTP_REQ_CTX *rctx,
49                                                unsigned long len);
50
51 int OSSL_HTTP_is_alive(const OSSL_HTTP_REQ_CTX *rctx);
52
53=head1 DESCRIPTION
54
55B<OSSL_HTTP_REQ_CTX> is a context structure for an HTTP request and response,
56used to collect all the necessary data to perform that request.
57
58This file documents low-level HTTP functions rarely used directly.  High-level
59HTTP client functions like L<OSSL_HTTP_get(3)> and L<OSSL_HTTP_transfer(3)>
60should be preferred.
61
62OSSL_HTTP_REQ_CTX_new() allocates a new HTTP request context structure,
63which gets populated with the B<BIO> to write/send the request to (I<wbio>),
64the B<BIO> to read/receive the response from (I<rbio>, which may be equal to
65I<wbio>), and the maximum expected response header line length I<buf_size>.
66A value <= 0 indicates that
67the B<OSSL_HTTP_DEFAULT_MAX_LINE_LEN> of 4KiB should be used.
68I<buf_size> is also used as the number of content bytes that are read at a time.
69The allocated context structure includes an internal memory B<BIO>,
70which collects the HTTP request header lines.
71
72OSSL_HTTP_REQ_CTX_free() frees up the HTTP request context I<rctx>.
73The I<rbio> is not free'd, I<wbio> will be free'd if I<free_wbio> is set.
74
75OSSL_HTTP_REQ_CTX_set_request_line() adds the HTTP request line to the context.
76The HTTP method is determined by I<method_POST>,
77which should be 1 to indicate C<POST> or 0 to indicate C<GET>.
78I<server> and I<port> may be set to indicate a proxy server and port
79that the request should go through, otherwise they should be left NULL.
80I<path> is the HTTP request path; if left NULL, C</> is used.
81
82OSSL_HTTP_REQ_CTX_add1_header() adds header I<name> with value I<value> to the
83context I<rctx>. It can be called more than once to add multiple header lines.
84For example, to add a C<Host> header for C<example.com> you would call:
85
86 OSSL_HTTP_REQ_CTX_add1_header(ctx, "Host", "example.com");
87
88OSSL_HTTP_REQ_CTX_set_expected() optionally sets in I<rctx> some expectations
89of the HTTP client on the response.
90Due to the structure of an HTTP request, if the I<keep_alive> argument is
91nonzero the function must be used before calling OSSL_HTTP_REQ_CTX_set1_req().
92If the I<content_type> parameter
93is not NULL then the client will check that the given content type string
94is included in the HTTP header of the response and return an error if not.
95If the I<asn1> parameter is nonzero a structure in ASN.1 encoding will be
96expected as the response content and input streaming is disabled.  This means
97that an ASN.1 sequence header is required, its length field is checked, and
98OSSL_HTTP_REQ_CTX_get0_mem_bio() should be used to get the buffered response.
99Otherwise (by default) any input format is allowed without length checks.
100In this case the BIO given as I<rbio> argument to OSSL_HTTP_REQ_CTX_new() should
101be used directly to read the response contents, which may support streaming.
102If the I<timeout> parameter is > 0 this indicates the maximum number of seconds
103the subsequent HTTP transfer (sending the request and receiving a response)
104is allowed to take.
105I<timeout> == 0 enables waiting indefinitely, i.e., no timeout can occur.
106This is the default.
107I<timeout> < 0 takes over any value set via the I<overall_timeout> argument of
108L<OSSL_HTTP_open(3)> with the default being 0, which means no timeout.
109If the I<keep_alive> parameter is 0, which is the default, the connection is not
110kept open after receiving a response. This is the default behavior for HTTP 1.0.
111If the value is 1 or 2 then a persistent connection is requested.
112If the value is 2 then a persistent connection is required,
113i.e., an error occurs in case the server does not grant it.
114
115OSSL_HTTP_REQ_CTX_set1_req() finalizes the HTTP request context.
116It is needed if the I<method_POST> parameter in the
117OSSL_HTTP_REQ_CTX_set_request_line() call was 1
118and an ASN.1-encoded request should be sent.
119It must also be used when requesting "keep-alive",
120even if a GET request is going to be sent, in which case I<req> must be NULL.
121Unless I<req> is NULL, the function adds the DER encoding of I<req> using
122the ASN.1 template I<it> to do the encoding (which does not support streaming).
123The HTTP header C<Content-Length> is filled out with the length of the request.
124I<content_type> must be NULL if I<req> is NULL.
125If I<content_type> isn't NULL,
126the HTTP header C<Content-Type> is also added with the given string value.
127The header lines are added to the internal memory B<BIO> for the request header.
128
129OSSL_HTTP_REQ_CTX_nbio() attempts to send the request prepared in I<rctx>
130and to gather the response via HTTP, using the I<wbio> and I<rbio>
131that were given when calling OSSL_HTTP_REQ_CTX_new().
132The function may need to be called again if its result is -1, which indicates
133L<BIO_should_retry(3)>.  In such a case it is advisable to sleep a little in
134between, using L<BIO_wait(3)> on the read BIO to prevent a busy loop.
135
136OSSL_HTTP_REQ_CTX_nbio_d2i() is like OSSL_HTTP_REQ_CTX_nbio() but on success
137in addition parses the response, which must be a DER-encoded ASN.1 structure,
138using the ASN.1 template I<it> and places the result in I<*pval>.
139
140OSSL_HTTP_REQ_CTX_exchange() calls OSSL_HTTP_REQ_CTX_nbio() as often as needed
141in order to exchange a request and response or until a timeout is reached.
142On success it returns a pointer to the BIO that can be used to read the result.
143If an ASN.1-encoded response was expected, this is the BIO
144returned by OSSL_HTTP_REQ_CTX_get0_mem_bio() when called after the exchange.
145This memory BIO does not support streaming.
146Otherwise the returned BIO is the I<rbio> given to OSSL_HTTP_REQ_CTX_new(),
147which may support streaming.
148When this BIO is returned, it has been read past the end of the response header,
149such that the actual response body can be read from it.
150The returned BIO pointer MUST NOT be freed by the caller.
151
152OSSL_HTTP_REQ_CTX_get0_mem_bio() returns the internal memory B<BIO>.
153Before the HTTP request is sent, this could be used to adapt its header lines.
154I<Use with caution!>
155After receiving a response via HTTP, the BIO represents the current state of
156reading the response header. If the response was expected to be ASN.1 encoded,
157its contents can be read via this BIO, which does not support streaming.
158The returned BIO pointer must not be freed by the caller.
159
160OSSL_HTTP_REQ_CTX_get_resp_len() returns the size of the response contents
161in I<rctx> if provided by the server as <Content-Length> header field, else 0.
162
163OSSL_HTTP_REQ_CTX_set_max_response_length() sets the maximum allowed
164response content length for I<rctx> to I<len>. If not set or I<len> is 0
165then the B<OSSL_HTTP_DEFAULT_MAX_RESP_LEN> is used, which currently is 100 KiB.
166If the C<Content-Length> header is present and exceeds this value or
167the content is an ASN.1 encoded structure with a length exceeding this value
168or both length indications are present but disagree then an error occurs.
169
170OSSL_HTTP_is_alive() can be used to query if the HTTP connection
171given by I<rctx> is still alive, i.e., has not been closed.
172It returns 0 if I<rctx> is NULL.
173
174If the client application requested or required a persistent connection
175and this was granted by the server, it can keep I<rctx> as long as it wants
176to send further requests and OSSL_HTTP_is_alive() returns nonzero,
177else it should call I<OSSL_HTTP_REQ_CTX_free(rctx)> or L<OSSL_HTTP_close(3)>.
178In case the client application keeps I<rctx> but the connection then dies
179for any reason at the server side, it will notice this obtaining an
180I/O error when trying to send the next request via I<rctx>.
181
182=head1 WARNINGS
183
184The server's response may be unexpected if the hostname that was used to
185create the I<wbio>, any C<Host> header, and the host specified in the
186request URL do not match.
187
188Many of these functions must be called in a certain order.
189
190First, the HTTP request context must be allocated:
191OSSL_HTTP_REQ_CTX_new().
192
193Then, the HTTP request must be prepared with request data:
194
195=over 4
196
197=item 1.
198
199Calling OSSL_HTTP_REQ_CTX_set_request_line().
200
201=item 2.
202
203Adding extra header lines with OSSL_HTTP_REQ_CTX_add1_header().
204This is optional and may be done multiple times with different names.
205
206=item 3.
207
208Finalize the request using OSSL_HTTP_REQ_CTX_set1_req().
209This may be omitted if the GET method is used and "keep-alive" is not requested.
210
211=back
212
213When the request context is fully prepared, the HTTP exchange may be performed
214with OSSL_HTTP_REQ_CTX_nbio() or OSSL_HTTP_REQ_CTX_exchange().
215
216=head1 RETURN VALUES
217
218OSSL_HTTP_REQ_CTX_new() returns a pointer to a B<OSSL_HTTP_REQ_CTX>, or NULL
219on error.
220
221OSSL_HTTP_REQ_CTX_free() and OSSL_HTTP_REQ_CTX_set_max_response_length()
222do not return values.
223
224OSSL_HTTP_REQ_CTX_set_request_line(), OSSL_HTTP_REQ_CTX_add1_header(),
225OSSL_HTTP_REQ_CTX_set1_req(), and OSSL_HTTP_REQ_CTX_set_expected()
226return 1 for success and 0 for failure.
227
228OSSL_HTTP_REQ_CTX_nbio() and OSSL_HTTP_REQ_CTX_nbio_d2i()
229return 1 for success, 0 on error or redirection, -1 if retry is needed.
230
231OSSL_HTTP_REQ_CTX_exchange() and OSSL_HTTP_REQ_CTX_get0_mem_bio()
232return a pointer to a B<BIO> on success as described above or NULL on failure.
233The returned BIO must not be freed by the caller.
234
235OSSL_HTTP_REQ_CTX_get_resp_len() returns the size of the response contents
236or 0 if not available or an error occurred.
237
238OSSL_HTTP_is_alive() returns 1 if its argument is non-NULL
239and the client requested a persistent connection
240and the server did not disagree on keeping the connection open, else 0.
241
242=head1 SEE ALSO
243
244L<BIO_should_retry(3)>,
245L<BIO_wait(3)>,
246L<ASN1_item_d2i_bio(3)>,
247L<ASN1_item_i2d_mem_bio(3)>,
248L<OSSL_HTTP_open(3)>,
249L<OSSL_HTTP_get(3)>,
250L<OSSL_HTTP_transfer(3)>,
251L<OSSL_HTTP_close(3)>
252
253=head1 HISTORY
254
255The functions described here were added in OpenSSL 3.0.
256
257=head1 COPYRIGHT
258
259Copyright 2015-2023 The OpenSSL Project Authors. All Rights Reserved.
260
261Licensed under the Apache License 2.0 (the "License").  You may not use
262this file except in compliance with the License.  You can obtain a copy
263in the file LICENSE in the source distribution or at
264L<https://www.openssl.org/source/license.html>.
265
266=cut
267