Updated: 2022/Sep/29
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OSSL_HTTP_transfer(3) OpenSSL OSSL_HTTP_transfer(3)
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
LIBRARY
libcrypto, -lcrypto
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
host (and optionally port) needs to be placed in the header; thus it
must be present in rctx. For backward compatibility, the server (and
optional port) may also be given in the path argument beginning with
"http://" (thus giving an absoluteURI). 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 2019-2023 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>.
3.0.12 2023-10-25 OSSL_HTTP_transfer(3)