[Samba] Solaris interposer code for nsswitch.conf

[Wright, Tim (ANTS)]

Hi

there was a mail a while back on this list about using the LD_PRELOAD
feature on Solaris in order to override the location of nsswitch.conf for
smbd so only it would use winbindd. I did some digging and came up with the
code at the bottom of this mail ( I've overridden every file open call I
could find, but I think it's only the _open() call which is actually
necessary ). Initial testing seems to show it working ok - may be of use to
some people.

tim.

ps I'm not a C coder so this may not be the best in the world - if anyone
can do it better then please fix and post to the list.

/* 
 * Intercept open() call so that rather than using /etc/nsswitch.conf,
 * a different file can be used. Build as follows:
 * cc -o nsswitch_interposer.so -G -Jpic nsswitch_interposer.c
 * setenv LD_PRELOAD $cwd/nsswitch_interposer.so
 * run smbd
 *
 * Remove the printf statements in each function when using in earnest -
they are just there for debugging.
 */

#include <stdio.h>
#include <strings.h>
#include <dlfcn.h>

FILE* fopen(const char *fpath, const char *mode ){

	static FILE * (*func)(const char*, const char *);

	if(!func)
	 func = ( FILE * (*)(const char*, const char *))dlsym(RTLD_NEXT,
"fopen");

	if(strcmp(fpath,"/etc/nsswitch.conf")==0)
		fpath = "/etc/nsswitch_samba.conf";
		 
	printf("	calling fopen(%s, %s)\n", fpath, mode);
	return(func(fpath, mode));

}

FILE* fopen64(const char *fpath, const char *mode ){

	static FILE * (*func)(const char*, const char *);

	if(!func)
	 func = ( FILE * (*)(const char*, const char *))dlsym(RTLD_NEXT,
"fopen64");

	if(strcmp(fpath,"/etc/nsswitch.conf")==0)
		fpath = "/etc/nsswitch_samba.conf";
		 
	printf("	calling fopen64(%s, %s)\n", fpath, mode);
	return(func(fpath, mode));

}

int open(const char *path, int oflag ){

	static int (*func)(const char*, int);

	if(!func)
	 func = ( int (*)(const char*, int))dlsym(RTLD_NEXT, "open");

	if(strcmp(path,"/etc/nsswitch.conf")==0)
		path = "/etc/nsswitch_samba.conf";
		 
	printf("	calling open(%s, %d)\n", path, oflag);
	return(func(path, oflag));

}

int _open(const char *path, int oflag ){

        static int (*func)(const char*, int);

        if(!func)
         func = ( int (*)(const char*, int))dlsym(RTLD_NEXT, "_open");

        if(strcmp(path,"/etc/nsswitch.conf")==0)
                path = "/etc/nsswitch_samba.conf";

        printf("        calling _open(%s, %d)\n", path, oflag);
        return(func(path, oflag));

}


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