_sasl_locate_entry() in Cyrus SASL's lib/dlopen.c assumes a leading underscore is needed for calls to dlsym()

[steven-michaud (Steven Michaud)]

I've installed cyrus-sasl2 @2.1.27_2+kerberos on macOS 11.2.3 and have been using it with postfix @3.5.9_0+dovecot_sasl+pcre+sasl+tls and dovecot @2.3.11.3_2. Sending mail with STARTTLS and the SASL PLAIN mechanism simply didn't work. I've spent the last several days debugging the problem, and now I've found the cause.

Here's a fragment of code from _sasl_locate_entry():

#if defined(DLSYM_NEEDS_UNDERSCORE)

(defined(OpenBSD) && !defined(ELF))

snprintf(adj_entryname, sizeof adj_entryname, "_%s", entryname);

#endif

*entry_point = NULL; *entry_point = dlsym(library, adj_entryname); if (*entry_point == NULL) {

#if 0 /* This message appears to confuse people */

_sasl_log(NULL, SASL_LOG_DEBUG,

"unable to get entry point %s: %s", adj_entryname, dlerror());

#endif

return SASL_FAIL;

}

By means of various tests, and by looking at libsasl2.3.dylib in a disassembler, I've found that (in your distro) this code is behaving as if DLSYM_NEEDS_UNDERSCORE is defined. Of course it shouldn't be. I don't know why. The sasl_cv_dlsym_adds_uscore test in configure.ac looks like it should work. Could your cyrus_sasl2 distro have been compiled on something other than a Mac? In other words, might it have been cross-compiled on some other kind of system (e.g. Linux)?

Every time I try to send mail via STARTTLS and the SASL PLAIN mechanism, I get the error message "No worthy mechs found". Postfix is correctly set up -- the same setup works fine on other machines which use Cyrus SASL from other providers (like Apple). The reason is that my connection's list of mechanisms (sasl_client_conn_t.mech_list) only includes the "EXTERNAL" mechanism. sasl_client_add_plugin() is only ever called on this mechanism. The reason it isn't called on all the others (including the PLAIN mechanism) is that _sasl_locate_entry() (called from _sasl_plugin_load()) always fails, because it always adds an underscore in front of entryname.

[steven-michaud (Steven Michaud)]

HookCase hook library I tested with