OpenSSL 3 HTTP client C++ example?

[David von Oheimb]

Hi again Beni,

On Wed, 2022-06-22 at 08:29 +0200, Benedikt Hallinger wrote:
> Hi David and thank you for your advice and example.

my pleasure.
I was about to send a slightly improved version of my example code
regarding the use of proxies and the expected content type - see
attached
and an extended sample invocation (of course, adapt "myproxy" as
needed):

https_proxy=myproxy ./http_client https://example.com && echo ok


> I tried to compile it, run onto errors tough.
> I just put the file into my openssl source tree, which is on commit:
> commit 9e86b3815719d29f7bde2294403f97c42ce82a16 (HEAD, 
> origin/openssl-3.0)

I've just tried myself using that commit (and default configuration)
and as expected everything works fine.

> $ gcc http_client.c -Iinclude -L. -lcrypto -lssl -o http_client
> /usr/bin/ld: ./libssl.a(libssl-lib-ssl_cert.o): in function 
> `add_uris_recursive':
> ssl_cert.c:(.text+0x116): undefined reference to `OSSL_STORE_open'
> /usr/bin/ld: ssl_cert.c:(.text+0x134): undefined reference to 
> `OSSL_STORE_eof'
> [...]

This issue is pretty surely unrelated to the example code itself
but most likely due to some general build issue you have, such as some
inconsistency with pre-installed OpenSSL versions.
Sorry that I do not have the time to provide further aid on such general
build issues.

 David

> 
> Am 2022-06-21 22:52, schrieb David von Oheimb:
> > Hallo Beni,
> > 
> > good that you ask.
> > 
> > Using the new HTTP client API with TLS (possibly via a proxy) indeed
> > is not easy so far.
> > I'm going to improve this by adding some high-level helper functions
> > and extending the docs.
> > 
> > A good starting point when looking for examples is, as usual, the
> > application code in apps/.
> > In this case, there is some pretty useful code in apps/lib/apps.c,
> > but it turns out that the adaptation of app_http_get_asn1() and
> > app_http_tls_cb()
> > 
> > for receiving plain text (rather than ASN.1 encoded data) from the
> > server
> > is not straightforward because OSSL_HTTP_get() may close the SSL
> > read
> > BIO prematurely.
> > Also the behavior of non-blocking BIOs makes things a little more
> > tricky than expected.
> > Meanwhile I got it working - see the example attached.
> > 
> > Example build and usage:
> > 
> > gcc http_client.c -Iinclude -L. -lcrypto -lssl -o http_client
> > 
> > ./http_client https://httpbin.org/ && echo ok
> > 
> > Regards,
> >  David
> > 
> > On 20.06.22 10:54, Benedikt Hallinger wrote:
> > 
> > > Hi there,
> > > I currently try to get my hands dirty with C++ and  the new HTTPs
> > > client
> > > introduced with OpenSSL 3.
> > > However I struggle to get started. My goal is to open a https
> > > secured
> > > website and download its contents into a std::string for further
> > > parsing.
> > > 
> > > Does someone on the list know of a small basic example?
> > > I imagine that I'm not the first person implementing a HTTPs
> > > website
> > > 
> > > connector with OpenSSL 3.
> > > 
> > > Thank you for your support,
> > > Beni
> 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mta.openssl.org/pipermail/openssl-users/attachments/20220622/dc0ba44c/attachment-0001.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: http_client.c
Type: text/x-csrc
Size: 5562 bytes
Desc: not available
URL: <https://mta.openssl.org/pipermail/openssl-users/attachments/20220622/dc0ba44c/attachment-0001.c>