A patch for libresolv

A patch for libresolv

[H.J. Lu]

Hi,

There are many options in libresolve. However, there are no codes to
set them. Here is a patch to handle options for libresolve.


-- 
H.J. Lu (hjl@gnu.org)
--
Tue Oct  5 18:23:01 1999  H.J. Lu  <hjl@gnu.org>

	* resolv/res_init.c (o_mnemonic): New.
	(res_setoptions): Use it.

Index: resolv/res_init.c
===================================================================
RCS file: /work/cvs/gnu/glibc-2.1/resolv/res_init.c,v
retrieving revision 1.1.1.9
diff -u -p -r1.1.1.9 res_init.c
--- resolv/res_init.c	1999/05/05 01:35:31	1.1.1.9
+++ resolv/res_init.c	1999/10/06 01:21:05
@@ -111,6 +111,7 @@ static int netinfo_res_init __P((int *ha
 #endif
 
 static void res_setoptions __P((char *, char *)) internal_function;
+static u_long o_mnemonic __P((const char * mnemonic)) internal_function;
 
 #ifdef RESOLVSORT
 static const char sort_mask[] = "/&";
@@ -427,12 +428,66 @@ res_init()
 	return (0);
 }
 
+/*
+ * Return an option from a mnemonic.
+ */
+static u_long
+internal_function
+o_mnemonic (mnemonic)
+	const char * mnemonic;
+{
+	if (strncasecmp (mnemonic, "init", sizeof ("init") - 1) == 0)
+		return RES_INIT;
+	else if (strncasecmp (mnemonic, "debug",
+			      sizeof ("debug") - 1) == 0)
+		return RES_DEBUG;
+	else if (strncasecmp (mnemonic, "aaonly",
+			      sizeof ("aaonly") - 1) == 0)
+		return RES_AAONLY;
+	else if (strncasecmp (mnemonic, "usevc",
+			      sizeof ("usevc") - 1) == 0)
+		return RES_USEVC;
+	else if (strncasecmp (mnemonic, "primry",
+			      sizeof ("primry") - 1) == 0)
+		return RES_PRIMARY;
+	else if (strncasecmp (mnemonic, "igntc",
+			      sizeof ("igntc") - 1) == 0)
+		return RES_IGNTC;
+	else if (strncasecmp (mnemonic, "recurs",
+			      sizeof ("recurs") - 1) == 0)
+		return RES_RECURSE;
+	else if (strncasecmp (mnemonic, "defnam",
+			      sizeof ("defnam") - 1) == 0)
+		return RES_DEFNAMES;
+	else if (strncasecmp (mnemonic, "styopn",
+			      sizeof ("styopn") - 1) == 0)
+		return RES_STAYOPEN;
+	else if (strncasecmp (mnemonic, "dnsrch",
+			      sizeof ("dnsrch") - 1) == 0)
+		return RES_DNSRCH;
+	else if (strncasecmp (mnemonic, "insecure1",
+			      sizeof ("insecure1") - 1) == 0)
+		return RES_INSECURE1;
+	else if (strncasecmp (mnemonic, "insecure2",
+			      sizeof ("insecure2") - 1) == 0)
+		return RES_INSECURE2;
+	else if (strncasecmp (mnemonic, "noaliases",
+			      sizeof ("noaliases") - 1) == 0)
+		return RES_NOALIASES;
+	else if (strncasecmp (mnemonic, "inet6",
+			      sizeof ("inet6") - 1) == 0)
+		return RES_USE_INET6;
+	else
+		return ~0;
+}
+
 static void
 internal_function
 res_setoptions(options, source)
 	char *options, *source;
 {
 	char *cp = options;
+	u_long option;
 	int i;
 
 #ifdef DEBUG
@@ -464,8 +519,8 @@ res_setoptions(options, source)
 			}
 			printf(";;\tdebug\n");
 #endif
-		} else if (!strncmp(cp, "inet6", sizeof("inet6") - 1)) {
-			_res.options |= RES_USE_INET6;
+		} else if ((option = o_mnemonic (cp)) != ~0) {
+			_res.options |= option;
 		} else {
 			/* XXX - print a warning here? */
 		}

Re: A patch for libresolv

[Ulrich Drepper]

hjl@valinux.com (H.J. Lu) writes:

> There are many options in libresolve. However, there are no codes to
> set them. Here is a patch to handle options for libresolve.

Where is the existing practice for this?  We cannot simply invent this
because at least I don't understand the code completely.

Just a brief look already showed a problem.  The RES_IGNTC flag is
used in the bind 8 code internally (res_sendsigned.c).  It is
obviously not meant to be set by the user.  Probably this is correct
for the rest as well.

I'll compare the res_init code in glibc and in bind 8 and make
whatever changes this suggests.  But simply extending the option
format is not correct.

-- 
---------------.      drepper at gnu.org  ,-.   1325 Chesapeake Terrace
Ulrich Drepper  \    ,-------------------'   \  Sunnyvale, CA 94089 USA
Cygnus Solutions `--' drepper at cygnus.com   `------------------------

Re: A patch for libresolv

[H.J. Lu]

> 
> hjl@valinux.com (H.J. Lu) writes:
> 
> > There are many options in libresolve. However, there are no codes to
> > set them. Here is a patch to handle options for libresolve.
> 
> Where is the existing practice for this?  We cannot simply invent this
> because at least I don't understand the code completely.
> 
> Just a brief look already showed a problem.  The RES_IGNTC flag is
> used in the bind 8 code internally (res_sendsigned.c).  It is

Then take it out from my patch.

> obviously not meant to be set by the user.  Probably this is correct
> for the rest as well.
> 
> I'll compare the res_init code in glibc and in bind 8 and make
> whatever changes this suggests.  But simply extending the option
> format is not correct.
> 

There are many RES_XXXXX macros but they are not settable by users.
I have a need to set RES_INSECURE1/RES_INSECURE2. I don't want to
recompile glibc to do it. 


-- 
H.J. Lu (hjl@gnu.org)

Re: A patch for libresolv

[Ulrich Drepper]

hjl@valinux.com (H.J. Lu) writes:

> Then take it out from my patch.

So I go through your patch and correct the problems?  There is
something wrong with this...

> There are many RES_XXXXX macros but they are not settable by users.
> I have a need to set RES_INSECURE1/RES_INSECURE2. I don't want to
> recompile glibc to do it. 

Identify exactly which flags you need and I will try to find out how
they are supposed to be used.

-- 
---------------.      drepper at gnu.org  ,-.   1325 Chesapeake Terrace
Ulrich Drepper  \    ,-------------------'   \  Sunnyvale, CA 94089 USA
Cygnus Solutions `--' drepper at cygnus.com   `------------------------

Re: A patch for libresolv

[H.J. Lu]

> 
> > There are many RES_XXXXX macros but they are not settable by users.
> > I have a need to set RES_INSECURE1/RES_INSECURE2. I don't want to
> > recompile glibc to do it. 
> 
> Identify exactly which flags you need and I will try to find out how
> they are supposed to be used.
> 

I need to be able to set RES_INSECURE1/RES_INSECURE2 in
/etc/resolv.conf and via an environment variable.

Thanks.


-- 
H.J. Lu (hjl@gnu.org)

Re: A patch for libresolv

[Geoff Keating]

> Date: Mon, 11 Oct 1999 15:11:15 -0700 (PDT)
> Cc: libc-hacker@sourceware.cygnus.com (GNU C Library)
> From: hjl@valinux.com (H.J. Lu)

> I need to be able to set RES_INSECURE1/RES_INSECURE2 in
> /etc/resolv.conf and via an environment variable.

You've considered the security issues involved in this, and you're
sure it's OK to put it in everyone's glibc?

-- 
Geoffrey Keating <geoffk@cygnus.com>

Re: A patch for libresolv

[H.J. Lu]

> 
> > Date: Mon, 11 Oct 1999 15:11:15 -0700 (PDT)
> > Cc: libc-hacker@sourceware.cygnus.com (GNU C Library)
> > From: hjl@valinux.com (H.J. Lu)
> 
> > I need to be able to set RES_INSECURE1/RES_INSECURE2 in
> > /etc/resolv.conf and via an environment variable.
> 
> You've considered the security issues involved in this, and you're
> sure it's OK to put it in everyone's glibc?
> 

They are off by default. You have to turn them on by hand in
/etc/resolv.conf or via an environment variable. They are a few
sites on the Internet which rerquires them. I'd like to be able
to do

# RES_OPTS=insecure2 foobar

What is the problem with that? Are you suggesting we should check

# rm -rf /dev

now?


-- 
H.J. Lu (hjl@gnu.org)

Re: A patch for libresolv

[Geoff Keating]

> Date: Mon, 11 Oct 1999 17:26:42 -0700 (PDT)
> Cc: libc-hacker@sourceware.cygnus.com (GNU C Library)
> From: hjl@valinux.com (H.J. Lu)

> They are off by default. You have to turn them on by hand in
> /etc/resolv.conf or via an environment variable. They are a few
> sites on the Internet which rerquires them. I'd like to be able
> to do
> 
> # RES_OPTS=insecure2 foobar
> 
> What is the problem with that? Are you suggesting we should check
> 
> # rm -rf /dev
> 
> now?

So your proposed patch checks for getuid() == 0?

-- 
Geoffrey Keating <geoffk@cygnus.com>

Re: A patch for libresolv

[H.J. Lu]

> 
> > Date: Mon, 11 Oct 1999 17:26:42 -0700 (PDT)
> > Cc: libc-hacker@sourceware.cygnus.com (GNU C Library)
> > From: hjl@valinux.com (H.J. Lu)
> 
> > They are off by default. You have to turn them on by hand in
> > /etc/resolv.conf or via an environment variable. They are a few
> > sites on the Internet which rerquires them. I'd like to be able
> > to do
> > 
> > # RES_OPTS=insecure2 foobar
> > 
> > What is the problem with that? Are you suggesting we should check
> > 
> > # rm -rf /dev
> > 
> > now?
> 
> So your proposed patch checks for getuid() == 0?
> 

RES_OPTIONS is called with __secure_getenv so that it is not a problem.
However, all those options, including RES_IGNTC, are set/cleared in
dig/host/nslookup in bind 8. Right now my patch will only affect root
if those options are turned on in /etc/resolv.conf. If anyone can
change /etc/resolv.conf on your machine, my patch is the last thing 
you want to worry about.


-- 
H.J. Lu (hjl@gnu.org)