[jira] [Comment Edited] (GUACAMOLE-720) Build failure with GCC 9

["Michael Jumper (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/GUACAMOLE-720?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16753201#comment-16753201 ] 

Michael Jumper edited comment on GUACAMOLE-720 at 1/26/19 10:12 PM:
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Yep, the changes from GUACAMOLE-637 definitely should address this. We're replacing usage of {{strncpy()}} and {{strncat()}} with variants that are guaranteed to always null-terminate: {{guac_strlcpy()}} and {{guac_strlcat()}}.


was (Author: mike.jumper):
Yep, the changes from GUACAMOLE-637 definitely should address this. We're replacing usage of {{strncpy()}} and {{strncat()}} with variants that are guaranteed to always null-terminate: {{guac_strlcpy()}} and {{guac_strlcat}}.

> Build failure with GCC 9
> ------------------------
>
>                 Key: GUACAMOLE-720
>                 URL: https://issues.apache.org/jira/browse/GUACAMOLE-720
>             Project: Guacamole
>          Issue Type: Bug
>          Components: guacd
>    Affects Versions: 1.0.0
>            Reporter: Simone Caronni
>            Priority: Minor
>
> In particular GCC 9 complains about this code:
> {code}
> > BUILDSTDERR: In file included from /usr/include/string.h:494,
> > BUILDSTDERR:                  from /usr/include/winpr/collections.h:25,
> > BUILDSTDERR:                  from /usr/include/freerdp/types.h:80,
> > BUILDSTDERR:                  from /usr/include/freerdp/svc.h:24,
> > BUILDSTDERR:                  from /usr/include/freerdp/utils/svc_plugin.h:27,
> > BUILDSTDERR:                  from ./rdp_svc.h:25,
> > BUILDSTDERR:                  from guac_svc/svc_service.h:24,
> > BUILDSTDERR:                  from guac_svc/svc_service.c:22:
> > BUILDSTDERR: In function 'strncpy',
> > BUILDSTDERR:     inlined from 'VirtualChannelEntry' at guac_svc/svc_service.c:56:5:
> > BUILDSTDERR: /usr/include/bits/string_fortified.h:106:10: error: '__builtin_strncpy' output may be truncated copying 7 bytes from a string of length 7 [-Werror=stringop-truncation]
> > BUILDSTDERR:   106 |   return __builtin___strncpy_chk (__dest, __src, __len, __bos (__dest));
> > BUILDSTDERR:       |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > BUILDSTDERR: cc1: all warnings being treated as errors
> {code}
> Which stems from this code:
> {code}
> >   /* Init channel def */
> >     strncpy(svc_plugin->[plugin.channel_def.name|http://plugin.channel_def.name/], svc->name,
> >             GUAC_RDP_SVC_MAX_LENGTH);
> {code}
> The compiler is complaining because it can not prove the resulting string has a proper NUL terminator.  This can cause runtime faults and even  security issues.
> Most folks are fixing this by either NUL terminating the string after the call to strncpy .  However, in some cases the string is not guaranteed to be NUL terminated -- in those cases the "nonstring" attribute is more appropriate.  Note that using "nonstring" will cause the compiler to analyze use points and warn if you pass a "nonstring" variable to a routine that expects a properly terminated NUL string such as strlen.



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