Provided by: libssl-doc_3.0.5-2ubuntu1_all 
NAME
OSSL_HTTP_open, OSSL_HTTP_bio_cb_t, OSSL_HTTP_proxy_connect, OSSL_HTTP_set1_request,
OSSL_HTTP_exchange, OSSL_HTTP_get, OSSL_HTTP_transfer, OSSL_HTTP_close - HTTP client
high-level functions
SYNOPSIS
#include <openssl/http.h>
typedef BIO *(*OSSL_HTTP_bio_cb_t)(BIO *bio, void *arg,
int connect, int detail);
OSSL_HTTP_REQ_CTX *OSSL_HTTP_open(const char *server, const char *port,
const char *proxy, const char *no_proxy,
int use_ssl, BIO *bio, BIO *rbio,
OSSL_HTTP_bio_cb_t bio_update_fn, void *arg,
int buf_size, int overall_timeout);
int OSSL_HTTP_proxy_connect(BIO *bio, const char *server, const char *port,
const char *proxyuser, const char *proxypass,
int timeout, BIO *bio_err, const char *prog);
int OSSL_HTTP_set1_request(OSSL_HTTP_REQ_CTX *rctx, const char *path,
const STACK_OF(CONF_VALUE) *headers,
const char *content_type, BIO *req,
const char *expected_content_type, int expect_asn1,
size_t max_resp_len, int timeout, int keep_alive);
BIO *OSSL_HTTP_exchange(OSSL_HTTP_REQ_CTX *rctx, char **redirection_url);
BIO *OSSL_HTTP_get(const char *url, const char *proxy, const char *no_proxy,
BIO *bio, BIO *rbio,
OSSL_HTTP_bio_cb_t bio_update_fn, void *arg,
int buf_size, const STACK_OF(CONF_VALUE) *headers,
const char *expected_content_type, int expect_asn1,
size_t max_resp_len, int timeout);
BIO *OSSL_HTTP_transfer(OSSL_HTTP_REQ_CTX **prctx,
const char *server, const char *port,
const char *path, int use_ssl,
const char *proxy, const char *no_proxy,
BIO *bio, BIO *rbio,
OSSL_HTTP_bio_cb_t bio_update_fn, void *arg,
int buf_size, const STACK_OF(CONF_VALUE) *headers,
const char *content_type, BIO *req,
const char *expected_content_type, int expect_asn1,
size_t max_resp_len, int timeout, int keep_alive);
int OSSL_HTTP_close(OSSL_HTTP_REQ_CTX *rctx, int ok);
DESCRIPTION
OSSL_HTTP_open() initiates an HTTP session using the bio argument if not NULL, else by
connecting to a given server optionally via a proxy.
Typically the OpenSSL build supports sockets and the bio parameter is NULL. In this case
rbio must be NULL as well and the server must be non-NULL. The function creates a network
BIO internally using BIO_new_connect(3) for connecting to the given server and the
optionally given port, defaulting to 80 for HTTP or 443 for HTTPS. Then this internal BIO
is used for setting up a connection and for exchanging one or more request and response.
If bio is given and rbio is NULL then this bio is used instead. If both bio and rbio are
given (which may be memory BIOs for instance) then no explicit connection is set up, but
bio is used for writing requests and rbio for reading responses. As soon as the client
has flushed bio the server must be ready to provide a response or indicate a waiting
condition via rbio.
If bio is given, it is an error to provide proxy or no_proxy arguments, while server and
port arguments may be given to support diagnostic output. If bio is NULL the optional
proxy parameter can be used to set an HTTP(S) proxy to use (unless overridden by
"no_proxy" settings). If TLS is not used this defaults to the environment variable
"http_proxy" if set, else "HTTP_PROXY". If use_ssl != 0 it defaults to "https_proxy" if
set, else "HTTPS_PROXY". An empty proxy string "" forbids using a proxy. Else the format
is "[http[s]://][userinfo@]host[:port][/path][?query][#fragment]", where any userinfo,
path, query, and fragment given is ignored. The default proxy port number is 80, or 443
in case "https:" is given. The HTTP client functions connect via the given proxy unless
the server is found in the optional list no_proxy of proxy hostnames (if not NULL; default
is the environment variable "no_proxy" if set, else "NO_PROXY"). Proxying plain HTTP is
supported directly, while using a proxy for HTTPS connections requires a suitable callback
function such as OSSL_HTTP_proxy_connect(), described below.
If use_ssl is nonzero a TLS connection is requested and the bio_update_fn parameter must
be provided.
The parameter bio_update_fn, which is optional if use_ssl is 0, may be used to modify the
connection BIO used by the HTTP client, but cannot be used when both bio and rbio are
given. bio_update_fn is a BIO connect/disconnect callback function with prototype
BIO *(*OSSL_HTTP_bio_cb_t)(BIO *bio, void *arg, int connect, int detail)
The callback function may modify the BIO provided in the bio argument, whereby it may make
use of a custom defined argument arg, which may for instance point to an SSL_CTX
structure. During connection establishment, just after calling BIO_do_connect_retry(),
the callback function is invoked with the connect argument being 1 and detail being 1 if
use_ssl is nonzero (i.e., HTTPS is requested), else 0. On disconnect connect is 0 and
detail is 1 if no error occurred, else 0. For instance, on connect the callback may push
an SSL BIO to implement HTTPS; after disconnect it may do some diagnostic output and pop
and free the SSL BIO.
The callback function must return either the potentially modified BIO bio. or NULL to
indicate failure, in which case it should not modify the BIO.
Here is a simple example that supports TLS connections (but not via a proxy):
BIO *http_tls_cb(BIO *bio, void *arg, int connect, int detail)
{
if (connect && detail) { /* connecting with TLS */
SSL_CTX *ctx = (SSL_CTX *)arg;
BIO *sbio = BIO_new_ssl(ctx, 1);
bio = sbio != NULL ? BIO_push(sbio, bio) : NULL;
} else if (!connect) { /* disconnecting */
BIO *hbio;
if (!detail) { /* an error has occurred */
/* optionally add diagnostics here */
}
BIO_ssl_shutdown(bio);
hbio = BIO_pop(bio);
BIO_free(bio); /* SSL BIO */
bio = hbio;
}
return bio;
}
After disconnect the modified BIO will be deallocated using BIO_free_all().
The buf_size parameter specifies the response header maximum line length. A value <= 0
means that the OSSL_HTTP_DEFAULT_MAX_LINE_LEN (4KiB) is used. buf_size is also used as
the number of content bytes that are read at a time.
If the overall_timeout parameter is > 0 this indicates the maximum number of seconds the
overall HTTP transfer (i.e., connection setup if needed, sending requests, and receiving
responses) is allowed to take until completion. A value <= 0 enables waiting
indefinitely, i.e., no timeout.
OSSL_HTTP_proxy_connect() may be used by an above BIO connect callback function to set up
an SSL/TLS connection via an HTTPS proxy. It promotes the given BIO bio representing a
connection pre-established with a TLS proxy using the HTTP CONNECT method, optionally
using proxy client credentials proxyuser and proxypass, to connect with TLS protection
ultimately to server and port. If the port argument is NULL or the empty string it
defaults to "443". If the timeout parameter is > 0 this indicates the maximum number of
seconds the connection setup is allowed to take. A value <= 0 enables waiting
indefinitely, i.e., no timeout. Since this function is typically called by applications
such as openssl-s_client(1) it uses the bio_err and prog parameters (unless NULL) to print
additional diagnostic information in a user-oriented way.
OSSL_HTTP_set1_request() sets up in rctx the request header and content data and
expectations on the response using the following parameters. If <rctx> indicates using a
proxy for HTTP (but not HTTPS), the server hostname (and optionally port) needs to be
placed in the header and thus must be present. If path is NULL it defaults to "/". If
req is NULL the HTTP GET method will be used to send the request else HTTP POST with the
contents of req and optional content_type, where the length of the data in req does not
need to be determined in advance: the BIO will be read on-the-fly while sending the
request, which supports streaming. The optional list headers may contain additional
custom HTTP header lines. If the parameter expected_content_type is not NULL then the
client will check that the given content type string is included in the HTTP header of the
response and return an error if not. If the expect_asn1 parameter is nonzero, a structure
in ASN.1 encoding will be expected as response content. The max_resp_len parameter
specifies the maximum allowed response content length, where the value 0 indicates no
limit. If the timeout parameter is > 0 this indicates the maximum number of seconds the
subsequent HTTP transfer (sending the request and receiving a response) is allowed to
take. A value of 0 enables waiting indefinitely, i.e., no timeout. A value < 0 indicates
that the overall_timeout parameter value given when opening the HTTP transfer will be used
instead. If keep_alive is 0 the connection is not kept open after receiving a response,
which is the default behavior for HTTP 1.0. If the value is 1 or 2 then a persistent
connection is requested. If the value is 2 then a persistent connection is required,
i.e., an error occurs in case the server does not grant it.
OSSL_HTTP_exchange() exchanges any form of HTTP request and response as specified by rctx,
which must include both connection and request data, typically set up using
OSSL_HTTP_open() and OSSL_HTTP_set1_request(). It implements the core of the functions
described below. If the HTTP method is GET and redirection_url is not NULL the latter
pointer is used to provide any new location that the server may return with HTTP code 301
(MOVED_PERMANENTLY) or 302 (FOUND). In this case the function returns NULL and the caller
is responsible for deallocating the URL with OPENSSL_free(3). If the response header
contains one or more "Content-Length" header lines and/or an ASN.1-encoded response is
expected, which should include a total length, the length indications received are checked
for consistency and for not exceeding any given maximum response length. If an
ASN.1-encoded response is expected, the function returns on success the contents buffered
in a memory BIO, which does not support streaming. Otherwise it returns directly the read
BIO that holds the response contents, which allows a response of indefinite length and may
support streaming. The caller is responsible for freeing the BIO pointer obtained.
OSSL_HTTP_get() uses HTTP GET to obtain data from bio if non-NULL, else from the server
contained in the url, and returns it as a BIO. It supports redirection via HTTP status
code 301 or 302. It is meant for transfers with a single round trip, so does not support
persistent connections. If bio is non-NULL, any host and port components in the url are
not used for connecting but the hostname is used, as usual, for the "Host" header. Any
userinfo and fragment components in the url are ignored. Any query component is handled
as part of the path component. If the scheme component of the url is "https" a TLS
connection is requested and the bio_update_fn, as described for OSSL_HTTP_open(), must be
provided. Also the remaining parameters are interpreted as described for OSSL_HTTP_open()
and OSSL_HTTP_set1_request(), respectively. The caller is responsible for freeing the BIO
pointer obtained.
OSSL_HTTP_transfer() exchanges an HTTP request and response over a connection managed via
prctx without supporting redirection. It combines OSSL_HTTP_open(),
OSSL_HTTP_set1_request(), OSSL_HTTP_exchange(), and OSSL_HTTP_close(). If prctx is not
NULL it reuses any open connection represented by a non-NULL *prctx. It keeps the
connection open if a persistent connection is requested or required and this was granted
by the server, else it closes the connection and assigns NULL to *prctx. The remaining
parameters are interpreted as described for OSSL_HTTP_open() and OSSL_HTTP_set1_request(),
respectively. The caller is responsible for freeing the BIO pointer obtained.
OSSL_HTTP_close() closes the connection and releases rctx. The ok parameter is passed to
any BIO update function given during setup as described above for OSSL_HTTP_open(). It
must be 1 if no error occurred during the HTTP transfer and 0 otherwise.
NOTES
The names of the environment variables used by this implementation: "http_proxy",
"HTTP_PROXY", "https_proxy", "HTTPS_PROXY", "no_proxy", and "NO_PROXY", have been chosen
for maximal compatibility with other HTTP client implementations such as wget, curl, and
git.
RETURN VALUES
OSSL_HTTP_open() returns on success a OSSL_HTTP_REQ_CTX, else NULL.
OSSL_HTTP_proxy_connect() and OSSL_HTTP_set1_request() return 1 on success, 0 on error.
On success, OSSL_HTTP_exchange(), OSSL_HTTP_get(), and OSSL_HTTP_transfer() return a
memory BIO that buffers all the data received if an ASN.1-encoded response is expected,
otherwise a BIO that may support streaming. The BIO must be freed by the caller. On
failure, they return NULL. Failure conditions include connection/transfer timeout, parse
errors, etc. The caller is responsible for freeing the BIO pointer obtained.
OSSL_HTTP_close() returns 0 if anything went wrong while disconnecting, else 1.
SEE ALSO
OSSL_HTTP_parse_url(3), BIO_new_connect(3), ASN1_item_i2d_mem_bio(3),
ASN1_item_d2i_bio(3), OSSL_HTTP_is_alive(3)
HISTORY
All the functions described here were added in OpenSSL 3.0.
COPYRIGHT
Copyright 2019-2021 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use this file except
in compliance with the License. You can obtain a copy in the file LICENSE in the source
distribution or at <https://www.openssl.org/source/license.html>.