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Fix some DLL hell: use dladdr() to find plugin dir

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Normally one would dlopen() a shared object's basename, not its absolute
path.  However, lib/krb5/plugin.c, in an effort to be zero-conf-ish,
wants to readdir() to find plugins to load, and in the process it ends
up defeating the RTLD's search-the-caller's-rpath.

This commit partially addresses this by allowing the use of $ORIGIN in
plugin_dir values and using them for the default (except on OS X).

This allows multiple Heimdal versions installed on the same host, but
with different plugin ABIs, to co-exist.  A step forward for doing make
check on hosts where Heimdal is installed.

For now we hardcode $ORIGIN/../lib/plugin/krb5 (linux, Solaris, *BSD),
or $ORIGIN (Windows; for assemblies objects need to be in the same
directory) and we eval $ORIGIN by using dladdr() (Linux, Solaris) or
GetModuleHandleEx() (Win32, via a dladdr() wrapper in libroken) to find
the path to libkrb5 whose dirname to use as $ORIGIN.  For Windows,
because we need the plugins to be in the same directory as libkrb5, we
require a prefix on plugin DLLs ("plugin_krb5_") to distinguish them
from other objects.

We should add a special token to mean "look in $ORIGIN, sure, but
dlopen() the plugin basenames only (so the RTLD can search the rpath)".
This commit is contained in:
Nicolas Williams
2013-09-04 22:23:13 -05:00
parent 3e0fd6449e
commit 3e74e2e3bb
7 changed files with 110 additions and 4 deletions
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49
lib/krb5/plugin.c
View File

@@ -219,6 +219,38 @@ plug_dealloc(void *ptr)
dlclose(p->dsohandle);
}
static char *
resolve_origin(const char *di)
{
#ifdef HAVE_DLADDR
Dl_info dl_info;
const char *dname;
char *path, *p;
#endif
if (strncmp(di, "$ORIGIN/", sizeof("$ORIGIN/") - 1) &&
strcmp(di, "$ORIGIN"))
return strdup(di);
#ifndef HAVE_DLADDR
return strdup(LIBDIR "/plugin/krb5");
#else
di += sizeof("$ORIGIN") - 1;
if (dladdr(_krb5_load_plugins, &dl_info) == 0)
return strdup(LIBDIR "/plugin/krb5");
dname = dl_info.dli_fname;
p = strrchr(dname, '/');
if (p)
*p = '\0';
if (asprintf(&path, "%s%s", dname, di) == -1)
return NULL;
return path;
#endif
}
/**
* Load plugins (new system) for the given module @name (typicall
@@ -239,6 +271,7 @@ _krb5_load_plugins(krb5_context context, const char *name, const char **paths)
struct dirent *entry;
krb5_error_code ret;
const char **di;
char *dirname = NULL;
DIR *d;
HEIMDAL_MUTEX_lock(&plugin_mutex);
@@ -264,7 +297,11 @@ _krb5_load_plugins(krb5_context context, const char *name, const char **paths)
heim_release(s);
for (di = paths; *di != NULL; di++) {
d = opendir(*di);
free(dirname);
dirname = resolve_origin(*di);
if (dirname == NULL)
continue;
d = opendir(dirname);
if (d == NULL)
continue;
rk_cloexec_dir(d);
@@ -279,16 +316,21 @@ _krb5_load_plugins(krb5_context context, const char *name, const char **paths)
if (n[0] == '.' && (n[1] == '\0' || (n[1] == '.' && n[2] == '\0')))
continue;
#ifdef _WIN32
if (strncmp(n, "plugin_krb5_", sizeof("plugin_krb5_") - 1))
continue;
#endif
ret = 0;
#ifdef __APPLE__
{ /* support loading bundles on MacOS */
size_t len = strlen(n);
if (len > 7 && strcmp(&n[len - 7], ".bundle") == 0)
ret = asprintf(&path, "%s/%s/Contents/MacOS/%.*s", *di, n, (int)(len - 7), n);
ret = asprintf(&path, "%s/%s/Contents/MacOS/%.*s", dirname, n, (int)(len - 7), n);
}
#endif
if (ret < 0 || path == NULL)
ret = asprintf(&path, "%s/%s", *di, n);
ret = asprintf(&path, "%s/%s", dirname, n);
if (ret < 0 || path == NULL)
continue;
@@ -318,6 +360,7 @@ _krb5_load_plugins(krb5_context context, const char *name, const char **paths)
}
closedir(d);
}
free(dirname);
HEIMDAL_MUTEX_unlock(&plugin_mutex);
heim_release(module);
#endif /* HAVE_DLOPEN */