[cifs-utils PATCH] cifs.upcall: trim even more capabilities

[cifs-utils PATCH] cifs.upcall: trim even more capabilities

[Jeff Layton]

We really only need CAP_DAC_READ_SEARCH, not CAP_DAC_OVERRIDE, and
only when we are going to probe the environ file.

Also, fix the non-libcap-ng trim_capabilities prototype.

Signed-off-by: Jeff Layton <jlayton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>
---
 cifs.upcall.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/cifs.upcall.c b/cifs.upcall.c
index 6d9c427b7032..dae58b919408 100644
--- a/cifs.upcall.c
+++ b/cifs.upcall.c
@@ -70,22 +70,21 @@ typedef enum _sectype {
 
 #ifdef HAVE_LIBCAP_NG
 static int
-trim_capabilities(bool need_ptrace)
+trim_capabilities(bool need_environ)
 {
 	capng_clear(CAPNG_SELECT_BOTH);
 
-	/*
-	 * Need PTRACE and DAC_OVERRIDE for environment scraping, SETGID to
-	 * change gid and grouplist, and SETUID to change uid.
-	 */
+	/* SETUID and SETGID to change uid, gid, and grouplist */
 	if (capng_updatev(CAPNG_ADD, CAPNG_PERMITTED|CAPNG_EFFECTIVE,
-			CAP_SETUID, CAP_SETGID, CAP_DAC_OVERRIDE, -1)) {
+			CAP_SETUID, CAP_SETGID, -1)) {
 		syslog(LOG_ERR, "%s: Unable to update capability set: %m\n", __func__);
 		return 1;
 	}
 
-	if (need_ptrace &&
-	    capng_update(CAPNG_ADD, CAPNG_PERMITTED|CAPNG_EFFECTIVE, CAP_SYS_PTRACE)) {
+	 /* Need PTRACE and DAC_OVERRIDE for environment scraping */
+	if (need_environ &&
+	    capng_updatev(CAPNG_ADD, CAPNG_PERMITTED|CAPNG_EFFECTIVE,
+			CAP_SYS_PTRACE, CAP_DAC_READ_SEARCH, -1)) {
 		syslog(LOG_ERR, "%s: Unable to update capability set: %m\n", __func__);
 		return 1;
 	}
@@ -109,7 +108,7 @@ drop_all_capabilities(void)
 }
 #else /* HAVE_LIBCAP_NG */
 static int
-trim_capabilities(void)
+trim_capabilities(bool unused)
 {
 	return 0;
 }
-- 
2.9.3

Re: [cifs-utils PATCH] cifs.upcall: trim even more capabilities

[Simo Sorce]

Reviewed-by: Simo Sorce <simo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

On Thu, 2017-02-16 at 09:59 -0500, Jeff Layton wrote:
> We really only need CAP_DAC_READ_SEARCH, not CAP_DAC_OVERRIDE, and
> only when we are going to probe the environ file.
> 
> Also, fix the non-libcap-ng trim_capabilities prototype.
> 
> Signed-off-by: Jeff Layton <jlayton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>
> ---
>  cifs.upcall.c | 17 ++++++++---------
>  1 file changed, 8 insertions(+), 9 deletions(-)
> 
> diff --git a/cifs.upcall.c b/cifs.upcall.c
> index 6d9c427b7032..dae58b919408 100644
> --- a/cifs.upcall.c
> +++ b/cifs.upcall.c
> @@ -70,22 +70,21 @@ typedef enum _sectype {
>  
>  #ifdef HAVE_LIBCAP_NG
>  static int
> -trim_capabilities(bool need_ptrace)
> +trim_capabilities(bool need_environ)
>  {
>  	capng_clear(CAPNG_SELECT_BOTH);
>  
> -	/*
> -	 * Need PTRACE and DAC_OVERRIDE for environment scraping, SETGID to
> -	 * change gid and grouplist, and SETUID to change uid.
> -	 */
> +	/* SETUID and SETGID to change uid, gid, and grouplist */
>  	if (capng_updatev(CAPNG_ADD, CAPNG_PERMITTED|CAPNG_EFFECTIVE,
> -			CAP_SETUID, CAP_SETGID, CAP_DAC_OVERRIDE, -1)) {
> +			CAP_SETUID, CAP_SETGID, -1)) {
>  		syslog(LOG_ERR, "%s: Unable to update capability set: %m\n", __func__);
>  		return 1;
>  	}
>  
> -	if (need_ptrace &&
> -	    capng_update(CAPNG_ADD, CAPNG_PERMITTED|CAPNG_EFFECTIVE, CAP_SYS_PTRACE)) {
> +	 /* Need PTRACE and DAC_OVERRIDE for environment scraping */
> +	if (need_environ &&
> +	    capng_updatev(CAPNG_ADD, CAPNG_PERMITTED|CAPNG_EFFECTIVE,
> +			CAP_SYS_PTRACE, CAP_DAC_READ_SEARCH, -1)) {
>  		syslog(LOG_ERR, "%s: Unable to update capability set: %m\n", __func__);
>  		return 1;
>  	}
> @@ -109,7 +108,7 @@ drop_all_capabilities(void)
>  }
>  #else /* HAVE_LIBCAP_NG */
>  static int
> -trim_capabilities(void)
> +trim_capabilities(bool unused)
>  {
>  	return 0;
>  }


-- 
Simo Sorce * Red Hat, Inc * New York

Re: [cifs-utils PATCH] cifs.upcall: trim even more capabilities

[Pavel Shilovsky]

2017-02-16 6:59 GMT-08:00 Jeff Layton <jlayton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>:
> We really only need CAP_DAC_READ_SEARCH, not CAP_DAC_OVERRIDE, and
> only when we are going to probe the environ file.
>
> Also, fix the non-libcap-ng trim_capabilities prototype.
>
> Signed-off-by: Jeff Layton <jlayton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>
> ---
>  cifs.upcall.c | 17 ++++++++---------
>  1 file changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/cifs.upcall.c b/cifs.upcall.c
> index 6d9c427b7032..dae58b919408 100644
> --- a/cifs.upcall.c
> +++ b/cifs.upcall.c
> @@ -70,22 +70,21 @@ typedef enum _sectype {
>
>  #ifdef HAVE_LIBCAP_NG
>  static int
> -trim_capabilities(bool need_ptrace)
> +trim_capabilities(bool need_environ)
>  {
>         capng_clear(CAPNG_SELECT_BOTH);
>
> -       /*
> -        * Need PTRACE and DAC_OVERRIDE for environment scraping, SETGID to
> -        * change gid and grouplist, and SETUID to change uid.
> -        */
> +       /* SETUID and SETGID to change uid, gid, and grouplist */
>         if (capng_updatev(CAPNG_ADD, CAPNG_PERMITTED|CAPNG_EFFECTIVE,
> -                       CAP_SETUID, CAP_SETGID, CAP_DAC_OVERRIDE, -1)) {
> +                       CAP_SETUID, CAP_SETGID, -1)) {
>                 syslog(LOG_ERR, "%s: Unable to update capability set: %m\n", __func__);
>                 return 1;
>         }
>
> -       if (need_ptrace &&
> -           capng_update(CAPNG_ADD, CAPNG_PERMITTED|CAPNG_EFFECTIVE, CAP_SYS_PTRACE)) {
> +        /* Need PTRACE and DAC_OVERRIDE for environment scraping */

It seems that the comment above doesn't reflect the proposed change.
Should it be DAC_READ_SEARCH instead?

> +       if (need_environ &&
> +           capng_updatev(CAPNG_ADD, CAPNG_PERMITTED|CAPNG_EFFECTIVE,
> +                       CAP_SYS_PTRACE, CAP_DAC_READ_SEARCH, -1)) {
>                 syslog(LOG_ERR, "%s: Unable to update capability set: %m\n", __func__);
>                 return 1;
>         }
> @@ -109,7 +108,7 @@ drop_all_capabilities(void)
>  }
>  #else /* HAVE_LIBCAP_NG */
>  static int
> -trim_capabilities(void)
> +trim_capabilities(bool unused)
>  {
>         return 0;
>  }
> --
> 2.9.3
>
> --
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-- 
Best regards,
Pavel Shilovsky

Re: [cifs-utils PATCH] cifs.upcall: trim even more capabilities

[Jeff Layton]

On Thu, 2017-02-16 at 09:28 -0800, Pavel Shilovsky wrote:
> 2017-02-16 6:59 GMT-08:00 Jeff Layton <jlayton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>:
> > We really only need CAP_DAC_READ_SEARCH, not CAP_DAC_OVERRIDE, and
> > only when we are going to probe the environ file.
> > 
> > Also, fix the non-libcap-ng trim_capabilities prototype.
> > 
> > Signed-off-by: Jeff Layton <jlayton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>
> > ---
> >  cifs.upcall.c | 17 ++++++++---------
> >  1 file changed, 8 insertions(+), 9 deletions(-)
> > 
> > diff --git a/cifs.upcall.c b/cifs.upcall.c
> > index 6d9c427b7032..dae58b919408 100644
> > --- a/cifs.upcall.c
> > +++ b/cifs.upcall.c
> > @@ -70,22 +70,21 @@ typedef enum _sectype {
> > 
> >  #ifdef HAVE_LIBCAP_NG
> >  static int
> > -trim_capabilities(bool need_ptrace)
> > +trim_capabilities(bool need_environ)
> >  {
> >         capng_clear(CAPNG_SELECT_BOTH);
> > 
> > -       /*
> > -        * Need PTRACE and DAC_OVERRIDE for environment scraping, SETGID to
> > -        * change gid and grouplist, and SETUID to change uid.
> > -        */
> > +       /* SETUID and SETGID to change uid, gid, and grouplist */
> >         if (capng_updatev(CAPNG_ADD, CAPNG_PERMITTED|CAPNG_EFFECTIVE,
> > -                       CAP_SETUID, CAP_SETGID, CAP_DAC_OVERRIDE, -1)) {
> > +                       CAP_SETUID, CAP_SETGID, -1)) {
> >                 syslog(LOG_ERR, "%s: Unable to update capability set: %m\n", __func__);
> >                 return 1;
> >         }
> > 
> > -       if (need_ptrace &&
> > -           capng_update(CAPNG_ADD, CAPNG_PERMITTED|CAPNG_EFFECTIVE, CAP_SYS_PTRACE)) {
> > +        /* Need PTRACE and DAC_OVERRIDE for environment scraping */
> 
> It seems that the comment above doesn't reflect the proposed change.
> Should it be DAC_READ_SEARCH instead?
> 

Yes! It should and it's fixed in the version in the tree.

Thanks,
-- 
Jeff Layton <jlayton-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>