Am Dienstag, den 17.03.2015, 10:01 +0100 schrieb Sebastien Ferre:
> Hi,
> 
> when trying to use gnutls for TLS-secured
> connections with ocamlnet, I encounter a
> problem with SRP functions.
> 
> When linking with package nettls-gnutls of
> ocamlnet, I get the following linking errors
> (excerpt here, full log at the end).
> 
> /local/ferre/.opam/system/lib/nettls-gnutls/libnettls-gnutls.a(nettls_gnutls_bindings_stubs.o): 
> In function `abs_gnutls_srp_client_credentials_t_finalize':
> /home/ferre/.opam/system/build/ocamlnet.4.0.2/src/nettls-gnutls/nettls_gnutls_bindings_stubs.c:1841: 
> undefined reference to `gnutls_srp_free_client_credentials'
> [...]
> 
> All undefined functions start with 'gnutls_srp_'. After
> some web search, I found that those functions are excluded
> in some Linux distributions (mine is a Fedora) because of
> patent issues.

I was unaware of this.

> Are those functions really necessary for TLS connections ?

For TLS connections secured by X.509 keys these are not needed. (TLS is
a wide area, and there are more cryptographic options than what you
typically find in e.g. web browsers. SRP is one of these options.)

> If not, is there a patch of the package 'nettls-gnutls' that
> avoids them ? If yes, is there a workaround ? Has anybody else
> encounter the same problem.

In the svn repo of ocamlnet I just marked the srp functions as optional
(https://godirepo.camlcity.org/svn/lib-ocamlnet2/trunk/). I don't know
whether this is sufficient or not, as I have no system for testing.

Gerd

> 
> My global objective is to provide a secure authentication
> for a Web application.
> 
> Thanks,
> ---
> Sébastien Ferré
> 
> ==============================================================
> /local/ferre/.opam/system/lib/nettls-gnutls/libnettls-gnutls.a(nettls_gnutls_bindings_stubs.o): 
> In function `abs_gnutls_srp_client_credentials_t_finalize':
> /home/ferre/.opam/system/build/ocamlnet.4.0.2/src/nettls-gnutls/nettls_gnutls_bindings_stubs.c:1841: 
> undefined reference to `gnutls_srp_free_client_credentials'
> /local/ferre/.opam/system/lib/nettls-gnutls/libnettls-gnutls.a(nettls_gnutls_bindings_stubs.o): 
> In function `abs_gnutls_srp_server_credentials_t_finalize':
> /home/ferre/.opam/system/build/ocamlnet.4.0.2/src/nettls-gnutls/nettls_gnutls_bindings_stubs.c:1770: 
> undefined reference to `gnutls_srp_free_server_credentials'
> /local/ferre/.opam/system/lib/nettls-gnutls/libnettls-gnutls.a(nettls_gnutls_bindings_stubs.o): 
> In function `net_gnutls_srp_allocate_client_credentials':
> /home/ferre/.opam/system/build/ocamlnet.4.0.2/src/nettls-gnutls/nettls_gnutls_bindings_stubs.c:5431: 
> undefined reference to `gnutls_srp_allocate_client_credentials'
> /local/ferre/.opam/system/lib/nettls-gnutls/libnettls-gnutls.a(nettls_gnutls_bindings_stubs.o): 
> In function `net_gnutls_srp_set_client_credentials':
> /home/ferre/.opam/system/build/ocamlnet.4.0.2/src/nettls-gnutls/nettls_gnutls_bindings_stubs.c:5446: 
> undefined reference to `gnutls_srp_set_client_credentials'
> /local/ferre/.opam/system/lib/nettls-gnutls/libnettls-gnutls.a(nettls_gnutls_bindings_stubs.o): 
> In function `net_gnutls_srp_allocate_server_credentials':
> /home/ferre/.opam/system/build/ocamlnet.4.0.2/src/nettls-gnutls/nettls_gnutls_bindings_stubs.c:5456: 
> undefined reference to `gnutls_srp_allocate_server_credentials'
> /local/ferre/.opam/system/lib/nettls-gnutls/libnettls-gnutls.a(nettls_gnutls_bindings_stubs.o): 
> In function `net_gnutls_srp_set_server_credentials_file':
> /home/ferre/.opam/system/build/ocamlnet.4.0.2/src/nettls-gnutls/nettls_gnutls_bindings_stubs.c:5471: 
> undefined reference to `gnutls_srp_set_server_credentials_file'
> /local/ferre/.opam/system/lib/nettls-gnutls/libnettls-gnutls.a(nettls_gnutls_bindings_stubs.o): 
> In function `net_gnutls_srp_server_get_username':
> /home/ferre/.opam/system/build/ocamlnet.4.0.2/src/nettls-gnutls/nettls_gnutls_bindings_stubs.c:5482: 
> undefined reference to `gnutls_srp_server_get_username'
> /local/ferre/.opam/system/lib/nettls-gnutls/libnettls-gnutls.a(nettls_gnutls_bindings_stubs.o): 
> In function `net_gnutls_srp_set_prime_bits':
> /home/ferre/.opam/system/build/ocamlnet.4.0.2/src/nettls-gnutls/nettls_gnutls_bindings_stubs.c:5493: 
> undefined reference to `gnutls_srp_set_prime_bits'
> /local/ferre/.opam/system/lib/nettls-gnutls/libnettls-gnutls.a(nettls_gnutls_bindings_stubs.o): 
> In function `net_gnutls_srp_verifier':
> /home/ferre/.opam/system/build/ocamlnet.4.0.2/src/nettls-gnutls/nettls_gnutls_bindings_stubs.c:5512: 
> undefined reference to `gnutls_srp_verifier'
> collect2: error: ld returned 1 exit status
> File "caml_startup", line 1:
> Error: Error during linking
> 
> 

-- 
------------------------------------------------------------
Gerd Stolpmann, Darmstadt, Germany    gerd@gerd-stolpmann.de
My OCaml site:          http://www.camlcity.org
Contact details:        http://www.camlcity.org/contact.html
Company homepage:       http://www.gerd-stolpmann.de
------------------------------------------------------------