[PATCH] namei: allow restricted O_CREAT of FIFOs and regular files

[PATCH] namei: allow restricted O_CREAT of FIFOs and regular files

[Loic]

Hello,

Please picked up this patch for linux 4.9 and 4.14 (linux 4.4 needs a small modification).
Indeed, this code will be beneficial to the GNU/Linux distributions that use a longterm kernel.

Compiled/tested without problem.

Thank.

[ Upstream commit 30aba6656f61ed44cba445a3c0d38b296fa9e8f5 ]

From: Salvatore Mesoraca <s.mesoraca16@gmail.com>
Date: Thu, 23 Aug 2018 17:00:35 -0700
Subject: namei: allow restricted O_CREAT of FIFOs and regular files

Disallows open of FIFOs or regular files not owned by the user in world
writable sticky directories, unless the owner is the same as that of the
directory or the file is opened without the O_CREAT flag.  The purpose
is to make data spoofing attacks harder.  This protection can be turned
on and off separately for FIFOs and regular files via sysctl, just like
the symlinks/hardlinks protection.  This patch is based on Openwall's
"HARDEN_FIFO" feature by Solar Designer.

This is a brief list of old vulnerabilities that could have been prevented
by this feature, some of them even allow for privilege escalation:

CVE-2000-1134
CVE-2007-3852
CVE-2008-0525
CVE-2009-0416
CVE-2011-4834
CVE-2015-1838
CVE-2015-7442
CVE-2016-7489

This list is not meant to be complete.  It's difficult to track down all
vulnerabilities of this kind because they were often reported without any
mention of this particular attack vector.  In fact, before
hardlinks/symlinks restrictions, fifos/regular files weren't the favorite
vehicle to exploit them.

[s.mesoraca16@gmail.com: fix bug reported by Dan Carpenter]
  Link: https://lkml.kernel.org/r/20180426081456.GA7060@mwanda
  Link: http://lkml.kernel.org/r/1524829819-11275-1-git-send-email-s.mesoraca16@gmail.com
[keescook@chromium.org: drop pr_warn_ratelimited() in favor of audit changes in the future]
[keescook@chromium.org: adjust commit subjet]
Link: http://lkml.kernel.org/r/20180416175918.GA13494@beast
Signed-off-by: Salvatore Mesoraca <s.mesoraca16@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Suggested-by: Solar Designer <solar@openwall.com>
Suggested-by: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 Documentation/sysctl/fs.txt | 36 ++++++++++++++++++++++++++++++
 fs/namei.c                  | 53 ++++++++++++++++++++++++++++++++++++++++++---
 include/linux/fs.h          |  2 ++
 kernel/sysctl.c             | 18 +++++++++++++++
 4 files changed, 106 insertions(+), 3 deletions(-)

diff --git a/Documentation/sysctl/fs.txt b/Documentation/sysctl/fs.txt
index 6c00c1e2743f..819caf8ca05f 100644
--- a/Documentation/sysctl/fs.txt
+++ b/Documentation/sysctl/fs.txt
@@ -34,7 +34,9 @@ Currently, these files are in /proc/sys/fs:
 - overflowgid
 - pipe-user-pages-hard
 - pipe-user-pages-soft
+- protected_fifos
 - protected_hardlinks
+- protected_regular
 - protected_symlinks
 - suid_dumpable
 - super-max
@@ -182,6 +184,24 @@ applied.
 
 ==============================================================
 
+protected_fifos:
+
+The intent of this protection is to avoid unintentional writes to
+an attacker-controlled FIFO, where a program expected to create a regular
+file.
+
+When set to "0", writing to FIFOs is unrestricted.
+
+When set to "1" don't allow O_CREAT open on FIFOs that we don't own
+in world writable sticky directories, unless they are owned by the
+owner of the directory.
+
+When set to "2" it also applies to group writable sticky directories.
+
+This protection is based on the restrictions in Openwall.
+
+==============================================================
+
 protected_hardlinks:
 
 A long-standing class of security issues is the hardlink-based
@@ -202,6 +222,22 @@ This protection is based on the restrictions in Openwall and grsecurity.
 
 ==============================================================
 
+protected_regular:
+
+This protection is similar to protected_fifos, but it
+avoids writes to an attacker-controlled regular file, where a program
+expected to create one.
+
+When set to "0", writing to regular files is unrestricted.
+
+When set to "1" don't allow O_CREAT open on regular files that we
+don't own in world writable sticky directories, unless they are
+owned by the owner of the directory.
+
+When set to "2" it also applies to group writable sticky directories.
+
+==============================================================
+
 protected_symlinks:
 
 A long-standing class of security issues is the symlink-based
diff --git a/fs/namei.c b/fs/namei.c
index ae6aa9ae757c..0cab6494978c 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -887,6 +887,8 @@ static inline void put_link(struct nameidata *nd)
 
 int sysctl_protected_symlinks __read_mostly = 0;
 int sysctl_protected_hardlinks __read_mostly = 0;
+int sysctl_protected_fifos __read_mostly;
+int sysctl_protected_regular __read_mostly;
 
 /**
  * may_follow_link - Check symlink following for unsafe situations
@@ -1003,6 +1005,45 @@ static int may_linkat(struct path *link)
 	return -EPERM;
 }
 
+/**
+ * may_create_in_sticky - Check whether an O_CREAT open in a sticky directory
+ *			  should be allowed, or not, on files that already
+ *			  exist.
+ * @dir: the sticky parent directory
+ * @inode: the inode of the file to open
+ *
+ * Block an O_CREAT open of a FIFO (or a regular file) when:
+ *   - sysctl_protected_fifos (or sysctl_protected_regular) is enabled
+ *   - the file already exists
+ *   - we are in a sticky directory
+ *   - we don't own the file
+ *   - the owner of the directory doesn't own the file
+ *   - the directory is world writable
+ * If the sysctl_protected_fifos (or sysctl_protected_regular) is set to 2
+ * the directory doesn't have to be world writable: being group writable will
+ * be enough.
+ *
+ * Returns 0 if the open is allowed, -ve on error.
+ */
+static int may_create_in_sticky(struct dentry * const dir,
+				struct inode * const inode)
+{
+	if ((!sysctl_protected_fifos && S_ISFIFO(inode->i_mode)) ||
+	    (!sysctl_protected_regular && S_ISREG(inode->i_mode)) ||
+	    likely(!(dir->d_inode->i_mode & S_ISVTX)) ||
+	    uid_eq(inode->i_uid, dir->d_inode->i_uid) ||
+	    uid_eq(current_fsuid(), inode->i_uid))
+		return 0;
+
+	if (likely(dir->d_inode->i_mode & 0002) ||
+	    (dir->d_inode->i_mode & 0020 &&
+	     ((sysctl_protected_fifos >= 2 && S_ISFIFO(inode->i_mode)) ||
+	      (sysctl_protected_regular >= 2 && S_ISREG(inode->i_mode))))) {
+		return -EACCES;
+	}
+	return 0;
+}
+
 static __always_inline
 const char *get_link(struct nameidata *nd)
 {
@@ -3348,9 +3389,15 @@ finish_open:
 	if (error)
 		return error;
 	audit_inode(nd->name, nd->path.dentry, 0);
-	error = -EISDIR;
-	if ((open_flag & O_CREAT) && d_is_dir(nd->path.dentry))
-		goto out;
+	if (open_flag & O_CREAT) {
+		error = -EISDIR;
+		if (d_is_dir(nd->path.dentry))
+			goto out;
+		error = may_create_in_sticky(dir,
+					     d_backing_inode(nd->path.dentry));
+		if (unlikely(error))
+			goto out;
+	}
 	error = -ENOTDIR;
 	if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry))
 		goto out;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index e5710541183b..33322702c910 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -74,6 +74,8 @@ extern struct inodes_stat_t inodes_stat;
 extern int leases_enable, lease_break_time;
 extern int sysctl_protected_symlinks;
 extern int sysctl_protected_hardlinks;
+extern int sysctl_protected_fifos;
+extern int sysctl_protected_regular;
 
 typedef __kernel_rwf_t rwf_t;
 
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 71ceb6c13c1a..cc02050fd0c4 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1807,6 +1807,24 @@ static struct ctl_table fs_table[] = {
 		.extra1		= &zero,
 		.extra2		= &one,
 	},
+	{
+		.procname	= "protected_fifos",
+		.data		= &sysctl_protected_fifos,
+		.maxlen		= sizeof(int),
+		.mode		= 0600,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &zero,
+		.extra2		= &two,
+	},
+	{
+		.procname	= "protected_regular",
+		.data		= &sysctl_protected_regular,
+		.maxlen		= sizeof(int),
+		.mode		= 0600,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= &zero,
+		.extra2		= &two,
+	},
 	{
 		.procname	= "suid_dumpable",
 		.data		= &suid_dumpable,
-- 
cgit 1.2-0.3.lf.el7

Re: [PATCH] namei: allow restricted O_CREAT of FIFOs and regular files

[Kees Cook]

On Tue, Oct 23, 2018 at 7:37 PM, Loic <hackurx@opensec.fr> wrote:
> Hello,
>
> Please picked up this patch for linux 4.9 and 4.14 (linux 4.4 needs a small modification).
> Indeed, this code will be beneficial to the GNU/Linux distributions that use a longterm kernel.

Thanks for doing these (and 4.4). It'll be nice to have this available.

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

>
> Compiled/tested without problem.
>
> Thank.
>
> [ Upstream commit 30aba6656f61ed44cba445a3c0d38b296fa9e8f5 ]
>
> From: Salvatore Mesoraca <s.mesoraca16@gmail.com>
> Date: Thu, 23 Aug 2018 17:00:35 -0700
> Subject: namei: allow restricted O_CREAT of FIFOs and regular files
>
> Disallows open of FIFOs or regular files not owned by the user in world
> writable sticky directories, unless the owner is the same as that of the
> directory or the file is opened without the O_CREAT flag.  The purpose
> is to make data spoofing attacks harder.  This protection can be turned
> on and off separately for FIFOs and regular files via sysctl, just like
> the symlinks/hardlinks protection.  This patch is based on Openwall's
> "HARDEN_FIFO" feature by Solar Designer.
>
> This is a brief list of old vulnerabilities that could have been prevented
> by this feature, some of them even allow for privilege escalation:
>
> CVE-2000-1134
> CVE-2007-3852
> CVE-2008-0525
> CVE-2009-0416
> CVE-2011-4834
> CVE-2015-1838
> CVE-2015-7442
> CVE-2016-7489
>
> This list is not meant to be complete.  It's difficult to track down all
> vulnerabilities of this kind because they were often reported without any
> mention of this particular attack vector.  In fact, before
> hardlinks/symlinks restrictions, fifos/regular files weren't the favorite
> vehicle to exploit them.
>
> [s.mesoraca16@gmail.com: fix bug reported by Dan Carpenter]
>   Link: https://lkml.kernel.org/r/20180426081456.GA7060@mwanda
>   Link: http://lkml.kernel.org/r/1524829819-11275-1-git-send-email-s.mesoraca16@gmail.com
> [keescook@chromium.org: drop pr_warn_ratelimited() in favor of audit changes in the future]
> [keescook@chromium.org: adjust commit subjet]
> Link: http://lkml.kernel.org/r/20180416175918.GA13494@beast
> Signed-off-by: Salvatore Mesoraca <s.mesoraca16@gmail.com>
> Signed-off-by: Kees Cook <keescook@chromium.org>
> Suggested-by: Solar Designer <solar@openwall.com>
> Suggested-by: Kees Cook <keescook@chromium.org>
> Cc: Al Viro <viro@zeniv.linux.org.uk>
> Cc: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> ---
>  Documentation/sysctl/fs.txt | 36 ++++++++++++++++++++++++++++++
>  fs/namei.c                  | 53 ++++++++++++++++++++++++++++++++++++++++++---
>  include/linux/fs.h          |  2 ++
>  kernel/sysctl.c             | 18 +++++++++++++++
>  4 files changed, 106 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/sysctl/fs.txt b/Documentation/sysctl/fs.txt
> index 6c00c1e2743f..819caf8ca05f 100644
> --- a/Documentation/sysctl/fs.txt
> +++ b/Documentation/sysctl/fs.txt
> @@ -34,7 +34,9 @@ Currently, these files are in /proc/sys/fs:
>  - overflowgid
>  - pipe-user-pages-hard
>  - pipe-user-pages-soft
> +- protected_fifos
>  - protected_hardlinks
> +- protected_regular
>  - protected_symlinks
>  - suid_dumpable
>  - super-max
> @@ -182,6 +184,24 @@ applied.
>
>  ==============================================================
>
> +protected_fifos:
> +
> +The intent of this protection is to avoid unintentional writes to
> +an attacker-controlled FIFO, where a program expected to create a regular
> +file.
> +
> +When set to "0", writing to FIFOs is unrestricted.
> +
> +When set to "1" don't allow O_CREAT open on FIFOs that we don't own
> +in world writable sticky directories, unless they are owned by the
> +owner of the directory.
> +
> +When set to "2" it also applies to group writable sticky directories.
> +
> +This protection is based on the restrictions in Openwall.
> +
> +==============================================================
> +
>  protected_hardlinks:
>
>  A long-standing class of security issues is the hardlink-based
> @@ -202,6 +222,22 @@ This protection is based on the restrictions in Openwall and grsecurity.
>
>  ==============================================================
>
> +protected_regular:
> +
> +This protection is similar to protected_fifos, but it
> +avoids writes to an attacker-controlled regular file, where a program
> +expected to create one.
> +
> +When set to "0", writing to regular files is unrestricted.
> +
> +When set to "1" don't allow O_CREAT open on regular files that we
> +don't own in world writable sticky directories, unless they are
> +owned by the owner of the directory.
> +
> +When set to "2" it also applies to group writable sticky directories.
> +
> +==============================================================
> +
>  protected_symlinks:
>
>  A long-standing class of security issues is the symlink-based
> diff --git a/fs/namei.c b/fs/namei.c
> index ae6aa9ae757c..0cab6494978c 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -887,6 +887,8 @@ static inline void put_link(struct nameidata *nd)
>
>  int sysctl_protected_symlinks __read_mostly = 0;
>  int sysctl_protected_hardlinks __read_mostly = 0;
> +int sysctl_protected_fifos __read_mostly;
> +int sysctl_protected_regular __read_mostly;
>
>  /**
>   * may_follow_link - Check symlink following for unsafe situations
> @@ -1003,6 +1005,45 @@ static int may_linkat(struct path *link)
>         return -EPERM;
>  }
>
> +/**
> + * may_create_in_sticky - Check whether an O_CREAT open in a sticky directory
> + *                       should be allowed, or not, on files that already
> + *                       exist.
> + * @dir: the sticky parent directory
> + * @inode: the inode of the file to open
> + *
> + * Block an O_CREAT open of a FIFO (or a regular file) when:
> + *   - sysctl_protected_fifos (or sysctl_protected_regular) is enabled
> + *   - the file already exists
> + *   - we are in a sticky directory
> + *   - we don't own the file
> + *   - the owner of the directory doesn't own the file
> + *   - the directory is world writable
> + * If the sysctl_protected_fifos (or sysctl_protected_regular) is set to 2
> + * the directory doesn't have to be world writable: being group writable will
> + * be enough.
> + *
> + * Returns 0 if the open is allowed, -ve on error.
> + */
> +static int may_create_in_sticky(struct dentry * const dir,
> +                               struct inode * const inode)
> +{
> +       if ((!sysctl_protected_fifos && S_ISFIFO(inode->i_mode)) ||
> +           (!sysctl_protected_regular && S_ISREG(inode->i_mode)) ||
> +           likely(!(dir->d_inode->i_mode & S_ISVTX)) ||
> +           uid_eq(inode->i_uid, dir->d_inode->i_uid) ||
> +           uid_eq(current_fsuid(), inode->i_uid))
> +               return 0;
> +
> +       if (likely(dir->d_inode->i_mode & 0002) ||
> +           (dir->d_inode->i_mode & 0020 &&
> +            ((sysctl_protected_fifos >= 2 && S_ISFIFO(inode->i_mode)) ||
> +             (sysctl_protected_regular >= 2 && S_ISREG(inode->i_mode))))) {
> +               return -EACCES;
> +       }
> +       return 0;
> +}
> +
>  static __always_inline
>  const char *get_link(struct nameidata *nd)
>  {
> @@ -3348,9 +3389,15 @@ finish_open:
>         if (error)
>                 return error;
>         audit_inode(nd->name, nd->path.dentry, 0);
> -       error = -EISDIR;
> -       if ((open_flag & O_CREAT) && d_is_dir(nd->path.dentry))
> -               goto out;
> +       if (open_flag & O_CREAT) {
> +               error = -EISDIR;
> +               if (d_is_dir(nd->path.dentry))
> +                       goto out;
> +               error = may_create_in_sticky(dir,
> +                                            d_backing_inode(nd->path.dentry));
> +               if (unlikely(error))
> +                       goto out;
> +       }
>         error = -ENOTDIR;
>         if ((nd->flags & LOOKUP_DIRECTORY) && !d_can_lookup(nd->path.dentry))
>                 goto out;
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index e5710541183b..33322702c910 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -74,6 +74,8 @@ extern struct inodes_stat_t inodes_stat;
>  extern int leases_enable, lease_break_time;
>  extern int sysctl_protected_symlinks;
>  extern int sysctl_protected_hardlinks;
> +extern int sysctl_protected_fifos;
> +extern int sysctl_protected_regular;
>
>  typedef __kernel_rwf_t rwf_t;
>
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 71ceb6c13c1a..cc02050fd0c4 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -1807,6 +1807,24 @@ static struct ctl_table fs_table[] = {
>                 .extra1         = &zero,
>                 .extra2         = &one,
>         },
> +       {
> +               .procname       = "protected_fifos",
> +               .data           = &sysctl_protected_fifos,
> +               .maxlen         = sizeof(int),
> +               .mode           = 0600,
> +               .proc_handler   = proc_dointvec_minmax,
> +               .extra1         = &zero,
> +               .extra2         = &two,
> +       },
> +       {
> +               .procname       = "protected_regular",
> +               .data           = &sysctl_protected_regular,
> +               .maxlen         = sizeof(int),
> +               .mode           = 0600,
> +               .proc_handler   = proc_dointvec_minmax,
> +               .extra1         = &zero,
> +               .extra2         = &two,
> +       },
>         {
>                 .procname       = "suid_dumpable",
>                 .data           = &suid_dumpable,
> --
> cgit 1.2-0.3.lf.el7



-- 
Kees Cook

Re: [PATCH] namei: allow restricted O_CREAT of FIFOs and regular files

[Sasha Levin]

On Tue, Oct 30, 2018 at 01:28:36PM -0700, Kees Cook wrote:
>On Tue, Oct 23, 2018 at 7:37 PM, Loic <hackurx@opensec.fr> wrote:
>> Hello,
>>
>> Please picked up this patch for linux 4.9 and 4.14 (linux 4.4 needs a small modification).
>> Indeed, this code will be beneficial to the GNU/Linux distributions that use a longterm kernel.
>
>Thanks for doing these (and 4.4). It'll be nice to have this available.
>
>Reviewed-by: Kees Cook <keescook@chromium.org>

This is a hardening patch rather than something that addresses a known
issue, no? Why would it go into stable?

--
Thanks,
Sasha

Re: [PATCH] namei: allow restricted O_CREAT of FIFOs and regular files

[Kees Cook]

On Wed, Oct 31, 2018 at 8:00 AM, Sasha Levin <sashal@kernel.org> wrote:
> On Tue, Oct 30, 2018 at 01:28:36PM -0700, Kees Cook wrote:
>>
>> On Tue, Oct 23, 2018 at 7:37 PM, Loic <hackurx@opensec.fr> wrote:
>>>
>>> Hello,
>>>
>>> Please picked up this patch for linux 4.9 and 4.14 (linux 4.4 needs a
>>> small modification).
>>> Indeed, this code will be beneficial to the GNU/Linux distributions that
>>> use a longterm kernel.
>>
>>
>> Thanks for doing these (and 4.4). It'll be nice to have this available.
>>
>> Reviewed-by: Kees Cook <keescook@chromium.org>
>
>
> This is a hardening patch rather than something that addresses a known
> issue, no? Why would it go into stable?

Correct. Greg has stated that he'd take backported hardening patches
if there was someone to support them. (If Loic can't commit to that, I
can.)

-Kees

-- 
Kees Cook

Re: [PATCH] namei: allow restricted O_CREAT of FIFOs and regular files

[Loic]

Le 2018-10-31 17:27, Kees Cook a écrit :
> On Wed, Oct 31, 2018 at 8:00 AM, Sasha Levin <sashal@kernel.org> wrote:
>> On Tue, Oct 30, 2018 at 01:28:36PM -0700, Kees Cook wrote:
>>> 
>>> On Tue, Oct 23, 2018 at 7:37 PM, Loic <hackurx@opensec.fr> wrote:
>>>> 
>>>> Hello,
>>>> 
>>>> Please picked up this patch for linux 4.9 and 4.14 (linux 4.4 needs 
>>>> a
>>>> small modification).
>>>> Indeed, this code will be beneficial to the GNU/Linux distributions 
>>>> that
>>>> use a longterm kernel.
>>> 
>>> 
>>> Thanks for doing these (and 4.4). It'll be nice to have this 
>>> available.
>>> 
>>> Reviewed-by: Kees Cook <keescook@chromium.org>

But it's a pleasure. Yes, because enterprise Linux distributions need 
more hardening options available and they only use long-term kernels.

>> This is a hardening patch rather than something that addresses a known
>> issue, no? Why would it go into stable?
> 
> Correct. Greg has stated that he'd take backported hardening patches
> if there was someone to support them. (If Loic can't commit to that, I
> can.)
> 
> -Kees

Just a "Cc:" tag for me because i only suggest picked up this patch for 
stable.

As you may have seen, I am interested by picked up patchs in stable but 
I'm new here and I prefer that my suggestions and my backports be 
validated by experimented developers so as not to bother Greg with my 
startup errors ^^

So yes thanks :)

-- 
Best regards,

Loic

Re: [PATCH] namei: allow restricted O_CREAT of FIFOs and regular files

[Sasha Levin]

On Tue, Oct 23, 2018 at 08:37:39PM +0200, Loic wrote:
>Hello,
>
>Please picked up this patch for linux 4.9 and 4.14 (linux 4.4 needs a small modification).
>Indeed, this code will be beneficial to the GNU/Linux distributions that use a longterm kernel.
>
>Compiled/tested without problem.
>
>Thank.
>
>[ Upstream commit 30aba6656f61ed44cba445a3c0d38b296fa9e8f5 ]
>
>From: Salvatore Mesoraca <s.mesoraca16@gmail.com>
>Date: Thu, 23 Aug 2018 17:00:35 -0700
>Subject: namei: allow restricted O_CREAT of FIFOs and regular files
>
>Disallows open of FIFOs or regular files not owned by the user in world
>writable sticky directories, unless the owner is the same as that of the
>directory or the file is opened without the O_CREAT flag.  The purpose
>is to make data spoofing attacks harder.  This protection can be turned
>on and off separately for FIFOs and regular files via sysctl, just like
>the symlinks/hardlinks protection.  This patch is based on Openwall's
>"HARDEN_FIFO" feature by Solar Designer.
>
>This is a brief list of old vulnerabilities that could have been prevented
>by this feature, some of them even allow for privilege escalation:
>
>CVE-2000-1134
>CVE-2007-3852
>CVE-2008-0525
>CVE-2009-0416
>CVE-2011-4834
>CVE-2015-1838
>CVE-2015-7442
>CVE-2016-7489
>
>This list is not meant to be complete.  It's difficult to track down all
>vulnerabilities of this kind because they were often reported without any
>mention of this particular attack vector.  In fact, before
>hardlinks/symlinks restrictions, fifos/regular files weren't the favorite
>vehicle to exploit them.
>
>[s.mesoraca16@gmail.com: fix bug reported by Dan Carpenter]
>  Link: https://lkml.kernel.org/r/20180426081456.GA7060@mwanda
>  Link: http://lkml.kernel.org/r/1524829819-11275-1-git-send-email-s.mesoraca16@gmail.com
>[keescook@chromium.org: drop pr_warn_ratelimited() in favor of audit changes in the future]
>[keescook@chromium.org: adjust commit subjet]
>Link: http://lkml.kernel.org/r/20180416175918.GA13494@beast
>Signed-off-by: Salvatore Mesoraca <s.mesoraca16@gmail.com>
>Signed-off-by: Kees Cook <keescook@chromium.org>
>Suggested-by: Solar Designer <solar@openwall.com>
>Suggested-by: Kees Cook <keescook@chromium.org>
>Cc: Al Viro <viro@zeniv.linux.org.uk>
>Cc: Dan Carpenter <dan.carpenter@oracle.com>
>Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
>Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Loic, could you please sign off on this one? You did so for the other
but not this.

--
Thanks,
Sasha

Re: [PATCH] namei: allow restricted O_CREAT of FIFOs and regular files

[Sasha Levin]

On Thu, Nov 15, 2018 at 12:05:49PM -0500, Sasha Levin wrote:
>On Tue, Oct 23, 2018 at 08:37:39PM +0200, Loic wrote:
>>Hello,
>>
>>Please picked up this patch for linux 4.9 and 4.14 (linux 4.4 needs a small modification).
>>Indeed, this code will be beneficial to the GNU/Linux distributions that use a longterm kernel.
>>
>>Compiled/tested without problem.
>>
>>Thank.
>>
>>[ Upstream commit 30aba6656f61ed44cba445a3c0d38b296fa9e8f5 ]
>>
>>From: Salvatore Mesoraca <s.mesoraca16@gmail.com>
>>Date: Thu, 23 Aug 2018 17:00:35 -0700
>>Subject: namei: allow restricted O_CREAT of FIFOs and regular files
>>
>>Disallows open of FIFOs or regular files not owned by the user in world
>>writable sticky directories, unless the owner is the same as that of the
>>directory or the file is opened without the O_CREAT flag.  The purpose
>>is to make data spoofing attacks harder.  This protection can be turned
>>on and off separately for FIFOs and regular files via sysctl, just like
>>the symlinks/hardlinks protection.  This patch is based on Openwall's
>>"HARDEN_FIFO" feature by Solar Designer.
>>
>>This is a brief list of old vulnerabilities that could have been prevented
>>by this feature, some of them even allow for privilege escalation:
>>
>>CVE-2000-1134
>>CVE-2007-3852
>>CVE-2008-0525
>>CVE-2009-0416
>>CVE-2011-4834
>>CVE-2015-1838
>>CVE-2015-7442
>>CVE-2016-7489
>>
>>This list is not meant to be complete.  It's difficult to track down all
>>vulnerabilities of this kind because they were often reported without any
>>mention of this particular attack vector.  In fact, before
>>hardlinks/symlinks restrictions, fifos/regular files weren't the favorite
>>vehicle to exploit them.
>>
>>[s.mesoraca16@gmail.com: fix bug reported by Dan Carpenter]
>> Link: https://lkml.kernel.org/r/20180426081456.GA7060@mwanda
>> Link: http://lkml.kernel.org/r/1524829819-11275-1-git-send-email-s.mesoraca16@gmail.com
>>[keescook@chromium.org: drop pr_warn_ratelimited() in favor of audit changes in the future]
>>[keescook@chromium.org: adjust commit subjet]
>>Link: http://lkml.kernel.org/r/20180416175918.GA13494@beast
>>Signed-off-by: Salvatore Mesoraca <s.mesoraca16@gmail.com>
>>Signed-off-by: Kees Cook <keescook@chromium.org>
>>Suggested-by: Solar Designer <solar@openwall.com>
>>Suggested-by: Kees Cook <keescook@chromium.org>
>>Cc: Al Viro <viro@zeniv.linux.org.uk>
>>Cc: Dan Carpenter <dan.carpenter@oracle.com>
>>Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
>>Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
>
>Loic, could you please sign off on this one? You did so for the other
>but not this.

Actually, you only Cc'ed yourself on the other one, you'd need to sign
off on both of them. It's fine doing it as a reply for each commit, no
need to respin the patch.

--
Thanks,
Sasha

Re: [PATCH] namei: allow restricted O_CREAT of FIFOs and regular files

[Loic]

Le 2018-11-15 18:05, Sasha Levin a écrit :
> On Tue, Oct 23, 2018 at 08:37:39PM +0200, Loic wrote:
>> Hello,
>> 
>> Please picked up this patch for linux 4.9 and 4.14 (linux 4.4 needs a 
>> small modification).
>> Indeed, this code will be beneficial to the GNU/Linux distributions 
>> that use a longterm kernel.
>> 
>> Compiled/tested without problem.
>> 
>> Thank.
>> 
>> [ Upstream commit 30aba6656f61ed44cba445a3c0d38b296fa9e8f5 ]
>> 
>> From: Salvatore Mesoraca <s.mesoraca16@gmail.com>
>> Date: Thu, 23 Aug 2018 17:00:35 -0700
>> Subject: namei: allow restricted O_CREAT of FIFOs and regular files
>> 
>> Disallows open of FIFOs or regular files not owned by the user in 
>> world
>> writable sticky directories, unless the owner is the same as that of 
>> the
>> directory or the file is opened without the O_CREAT flag.  The purpose
>> is to make data spoofing attacks harder.  This protection can be 
>> turned
>> on and off separately for FIFOs and regular files via sysctl, just 
>> like
>> the symlinks/hardlinks protection.  This patch is based on Openwall's
>> "HARDEN_FIFO" feature by Solar Designer.
>> 
>> This is a brief list of old vulnerabilities that could have been 
>> prevented
>> by this feature, some of them even allow for privilege escalation:
>> 
>> CVE-2000-1134
>> CVE-2007-3852
>> CVE-2008-0525
>> CVE-2009-0416
>> CVE-2011-4834
>> CVE-2015-1838
>> CVE-2015-7442
>> CVE-2016-7489
>> 
>> This list is not meant to be complete.  It's difficult to track down 
>> all
>> vulnerabilities of this kind because they were often reported without 
>> any
>> mention of this particular attack vector.  In fact, before
>> hardlinks/symlinks restrictions, fifos/regular files weren't the 
>> favorite
>> vehicle to exploit them.
>> 
>> [s.mesoraca16@gmail.com: fix bug reported by Dan Carpenter]
>>  Link: https://lkml.kernel.org/r/20180426081456.GA7060@mwanda
>>  Link: 
>> http://lkml.kernel.org/r/1524829819-11275-1-git-send-email-s.mesoraca16@gmail.com
>> [keescook@chromium.org: drop pr_warn_ratelimited() in favor of audit 
>> changes in the future]
>> [keescook@chromium.org: adjust commit subjet]
>> Link: http://lkml.kernel.org/r/20180416175918.GA13494@beast
>> Signed-off-by: Salvatore Mesoraca <s.mesoraca16@gmail.com>
>> Signed-off-by: Kees Cook <keescook@chromium.org>
>> Suggested-by: Solar Designer <solar@openwall.com>
>> Suggested-by: Kees Cook <keescook@chromium.org>
>> Cc: Al Viro <viro@zeniv.linux.org.uk>
>> Cc: Dan Carpenter <dan.carpenter@oracle.com>
>> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
>> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> 
> Loic, could you please sign off on this one? You did so for the other
> but not this.

Of course if you need it.

Signed-off-by: Loic Fr. <hackurx@opensec.fr>

> --
> Thanks,
> Sasha

Thanks to you too

Best regards,

Loic

Re: [PATCH] namei: allow restricted O_CREAT of FIFOs and regular files

[Greg KH]

On Tue, Oct 23, 2018 at 08:37:39PM +0200, Loic wrote:
> Hello,
> 
> Please picked up this patch for linux 4.9 and 4.14 (linux 4.4 needs a small modification).
> Indeed, this code will be beneficial to the GNU/Linux distributions that use a longterm kernel.
> 
> Compiled/tested without problem.

I've applied this now, and did the 4.4 backport as well.

thanks,

greg k-h