Re: Function behaves differently when libssh is compiled statically

[Jakub Jelen <jjelen@xxxxxxxxxx>]

On 2/1/21 2:31 PM, Anderson Sasaki wrote:
> ----- Original Message -----
> > From: "petergeorgenm" <petergeorgenm@xxxxxxxxxxxxxx>
> > To: libssh@xxxxxxxxxx
> > Sent: Monday, February 1, 2021 2:04:18 PM
> > Subject: Function behaves differently when libssh is compiled statically
> >
> > I wrote a simple connection setup following the tutorial:
> > //main.c
> > #pragma comment(lib, "user32")
> > #pragma comment(lib, "Advapi32")
> > #pragma comment(lib, "Shell32")
> > #pragma comment(lib, "Ws2_32")
> >
> > #include <stdio.h>
> > #include <libssh/sftp.h>
> > #include <sys/stat.h>
> > #include <fcntl.h>
> >
> > int main(void){
> > int ret_c=0;
> > int rc;
> > int port=22;
> > ssh_session the_session=ssh_new();
> > if(the_session==NULL) {printf("1\n"); return -1;}
> >
> > ssh_options_set(the_session, SSH_OPTIONS_HOST, "user@1.2.3.4");
> > ssh_options_set(the_session, SSH_OPTIONS_PORT, &port);
> >
> > rc=ssh_connect(the_session);
> > if(rc !=SSH_OK) {
> > ssh_free(the_session);
> > printf("2, %d\n", rc);
> > getchar();
> > } else {
> > printf("success\n");
> > getchar();
> > }
> >
> > ssh_disconnect(the_session);
> > ssh_free(the_session);
> > return 0;
> > }
> >
> > I used vcpkg to install both static and dynamic versions of libssh, they
> > reside as follows respectively:
> > C:\Users\User\vcpkg\installed\x86-windows-static\
> > C:\Users\User\vcpkg\installed\x86-windows\
> > If I compile the previous code dynamically with:
> > cl /I C:\Users\User\vcpkg\installed\x86-windows\include main.c /link
> > C:\Users\User\vcpkg\installed\x86-windows\lib\* /SUBSYSTEM:CONSOLE
> > and then run, the output I see is:
> > success
> >
> > If I compile it statically with:
> > cl /D LIBSSH_STATIC /I
> > C:\Users\User\vcpkg\installed\x86-windows-static\include main.c /link
> > C:\Users\User\vcpkg\installed\x86-windows-static\lib\* /SUBSYSTEM:CONSOLE
> > and then run, the output I see is:
> > 2, -1
> >
> > Both versions compile and link without any errors. I also tried to use putty
> > to ssh to user@1.2.3.4 and it works fine.
> > Please tell me if I need to provide any more debugging information, or if any
> > information isn't clear.
>
> Hello,
>
> Could you please try to call ssh_init() before calling any other function from libssh (and ssh_finalize() at the end)?
> When using dynamic linking this will be a no-op.
>
> This is a requirement when statically linked. It is mentioned in Chapter 8 of the tutorial and in the API documentation. I'm sorry that this is not better documented.

I believe this was already discussed, but would it be possible to add 
some more noisy safeguard? At this moment, it is inside of ssh_connect() 
setting error quite visibly:

https://gitlab.com/libssh/libssh-mirror/-/blob/master/src/client.c#L512

At this moment, to read the error, one needs to use ssh_get_error() (I 
see it properly documented in the tutorial), but I am wondering if we 
could add this error earlier (even ssh_new?) or add normal 
fprintf(stderr, ...) as this is is quite huge programming issue and is 
most likely something that will be really captured in development 
environment. Even better would be some build-time check, but I do not 
think it is simply possible.

Regards,
--
Jakub Jelen
Senior Software Engineer
Crypto Team, Security Engineering
Red Hat, Inc.