CVE-2018-19591: if_nametoindex: Fix descriptor for overlong name [BZ #23927]

We need to check the length of the string right before the strncpy call
to avoid reintroducing the compiler warning from bug 22442.

2018-11-27  Florian Weimer  <fweimer@redhat.com>

	[BZ #23927]
	CVE-2018-19591
	* sysdeps/unix/sysv/linux/if_index.c (__if_nametoindex): Close
	descriptor in case of ENODEV error.

On Nov 27 2018, Florian Weimer <fweimer@redhat.com> wrote:

> diff --git a/sysdeps/unix/sysv/linux/if_index.c b/sysdeps/unix/sysv/linux/if_index.c
> index e3d08982d9..3e999d6509 100644
> --- a/sysdeps/unix/sysv/linux/if_index.c
> +++ b/sysdeps/unix/sysv/linux/if_index.c
> @@ -45,6 +45,7 @@ __if_nametoindex (const char *ifname)
>  
>    if (strlen (ifname) >= IFNAMSIZ)
>      {
> +      __close_nocancel_nostatus (fd);
>        __set_errno (ENODEV);
>        return 0;
>      }

Just move it before the opensock call.

Andreas.

* Andreas Schwab:

> On Nov 27 2018, Florian Weimer <fweimer@redhat.com> wrote:
>
>> diff --git a/sysdeps/unix/sysv/linux/if_index.c b/sysdeps/unix/sysv/linux/if_index.c
>> index e3d08982d9..3e999d6509 100644
>> --- a/sysdeps/unix/sysv/linux/if_index.c
>> +++ b/sysdeps/unix/sysv/linux/if_index.c
>> @@ -45,6 +45,7 @@ __if_nametoindex (const char *ifname)
>>  
>>    if (strlen (ifname) >= IFNAMSIZ)
>>      {
>> +      __close_nocancel_nostatus (fd);
>>        __set_errno (ENODEV);
>>        return 0;
>>      }
>
> Just move it before the opensock call.

Like this?

2018-11-27  Florian Weimer  <fweimer@redhat.com>

	[BZ #23927]
	CVE-2018-19591
	* sysdeps/unix/sysv/linux/if_index.c (__if_nametoindex): Avoid
	descriptor leak in case of ENODEV error.

diff --git a/NEWS b/NEWS
index f488821af1..1098be1afb 100644
--- a/NEWS
+++ b/NEWS
@@ -57,7 +57,9 @@ Changes to build and runtime requirements:
 
 Security related changes:
 
-  [Add security related changes here]
+  CVE-2018-19591: A file descriptor leak in if_nametoindex can lead to a
+  denial of service due to resource exhaustion when processing getaddrinfo
+  calls with crafted host names.  Reported by Guido Vranken.
 
 The following bugs are resolved with this release:
 
diff --git a/sysdeps/unix/sysv/linux/if_index.c b/sysdeps/unix/sysv/linux/if_index.c
index e3d08982d9..782fc5e175 100644
--- a/sysdeps/unix/sysv/linux/if_index.c
+++ b/sysdeps/unix/sysv/linux/if_index.c
@@ -38,11 +38,6 @@ __if_nametoindex (const char *ifname)
   return 0;
 #else
   struct ifreq ifr;
-  int fd = __opensock ();
-
-  if (fd < 0)
-    return 0;
-
   if (strlen (ifname) >= IFNAMSIZ)
     {
       __set_errno (ENODEV);
@@ -50,6 +45,12 @@ __if_nametoindex (const char *ifname)
     }
 
   strncpy (ifr.ifr_name, ifname, sizeof (ifr.ifr_name));
+
+  int fd = __opensock ();
+
+  if (fd < 0)
+    return 0;
+
   if (__ioctl (fd, SIOCGIFINDEX, &ifr) < 0)
     {
       int saved_errno = errno;

Ok.

Andreas.

On Tue, Nov 27, 2018 at 9:13 AM Florian Weimer <fweimer@redhat.com> wrote:
>
> * Andreas Schwab:
>
> > On Nov 27 2018, Florian Weimer <fweimer@redhat.com> wrote:
> >
> >> diff --git a/sysdeps/unix/sysv/linux/if_index.c b/sysdeps/unix/sysv/linux/if_index.c
> >> index e3d08982d9..3e999d6509 100644
> >> --- a/sysdeps/unix/sysv/linux/if_index.c
> >> +++ b/sysdeps/unix/sysv/linux/if_index.c
> >> @@ -45,6 +45,7 @@ __if_nametoindex (const char *ifname)
> >>
> >>    if (strlen (ifname) >= IFNAMSIZ)
> >>      {
> >> +      __close_nocancel_nostatus (fd);
> >>        __set_errno (ENODEV);
> >>        return 0;
> >>      }
> >
> > Just move it before the opensock call.
>
> Like this?
>
> 2018-11-27  Florian Weimer  <fweimer@redhat.com>
>
>         [BZ #23927]
>         CVE-2018-19591
>         * sysdeps/unix/sysv/linux/if_index.c (__if_nametoindex): Avoid
>         descriptor leak in case of ENODEV error.
>
> diff --git a/NEWS b/NEWS
> index f488821af1..1098be1afb 100644
> --- a/NEWS
> +++ b/NEWS
> @@ -57,7 +57,9 @@ Changes to build and runtime requirements:
>
>  Security related changes:
>
> -  [Add security related changes here]
> +  CVE-2018-19591: A file descriptor leak in if_nametoindex can lead to a
> +  denial of service due to resource exhaustion when processing getaddrinfo
> +  calls with crafted host names.  Reported by Guido Vranken.
>
>  The following bugs are resolved with this release:
>
> diff --git a/sysdeps/unix/sysv/linux/if_index.c b/sysdeps/unix/sysv/linux/if_index.c
> index e3d08982d9..782fc5e175 100644
> --- a/sysdeps/unix/sysv/linux/if_index.c
> +++ b/sysdeps/unix/sysv/linux/if_index.c
> @@ -38,11 +38,6 @@ __if_nametoindex (const char *ifname)
>    return 0;
>  #else
>    struct ifreq ifr;
> -  int fd = __opensock ();
> -
> -  if (fd < 0)
> -    return 0;
> -
>    if (strlen (ifname) >= IFNAMSIZ)
>      {
>        __set_errno (ENODEV);
> @@ -50,6 +45,12 @@ __if_nametoindex (const char *ifname)
>      }
>
>    strncpy (ifr.ifr_name, ifname, sizeof (ifr.ifr_name));
> +
> +  int fd = __opensock ();
> +
> +  if (fd < 0)
> +    return 0;
> +
>    if (__ioctl (fd, SIOCGIFINDEX, &ifr) < 0)
>      {
>        int saved_errno = errno;

Thanks for the fix, is this going to be in master?
Can we take this patch as CVE fix?

* Victor Rodriguez:

> Thanks for the fix, is this going to be in master?
> Can we take this patch as CVE fix?

I've pushed this to master now.  There's going to be test cases later.

Thanks,
Florian