[jira] [Created] (DISPATCH-1009) _qd_policy_link_user_name_subst can return an unterminated string

["Alan Conway (JIRA)" <ji...@apache.org>]

Alan Conway created DISPATCH-1009:
-------------------------------------

             Summary: _qd_policy_link_user_name_subst can return an unterminated string
                 Key: DISPATCH-1009
                 URL: https://issues.apache.org/jira/browse/DISPATCH-1009
             Project: Qpid Dispatch
          Issue Type: Bug
          Components: Policy Engine
    Affects Versions: 1.0.1
            Reporter: Alan Conway
            Assignee: Chuck Rolke


On fedora 28 the gcc 8.1.1 compiler gives this warning-as-error:

/home/aconway/dispatch/src/policy.c: In function '_qd_policy_link_user_name_subst':
/home/aconway/dispatch/src/policy.c:541:9: error: 'strncpy' output may be truncated copying between 0 and 8 bytes from a string of length 7 [-Werror=stringop-truncation]
         strncpy(obuf, duser, copysize);
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

 

The error is correct: the function is using strncpy to copy a string into a space that may be too small for it, resulting in an un-terminated string.

I fixed some similar issues already but I'm confused by what's going on here: it looks like we are searching for the uname parameter and replacing it with "${user}" which seems backwards.

The function would be simpler and clearer if it used snprintf rather than successive strncpy, i.e.

    n = snprintf(obuf, osize, "%s%s%s", leading, duser, trailing);

but the problem of properly handling the error if the resulting string is too big for obuf remains.



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