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https://github.com/Divested-Mobile/DivestOS-Build.git
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83 lines
2.6 KiB
Diff
83 lines
2.6 KiB
Diff
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From 44c037827f0aeddbbbb323930fa3d09a7b4fffca Mon Sep 17 00:00:00 2001
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From: David Howells <dhowells@redhat.com>
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Date: Tue, 18 Apr 2017 15:31:07 +0100
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Subject: KEYS: Disallow keyrings beginning with '.' to be joined as session
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keyrings
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commit ee8f844e3c5a73b999edf733df1c529d6503ec2f upstream.
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This fixes CVE-2016-9604.
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Keyrings whose name begin with a '.' are special internal keyrings and so
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userspace isn't allowed to create keyrings by this name to prevent
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shadowing. However, the patch that added the guard didn't fix
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KEYCTL_JOIN_SESSION_KEYRING. Not only can that create dot-named keyrings,
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it can also subscribe to them as a session keyring if they grant SEARCH
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permission to the user.
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This, for example, allows a root process to set .builtin_trusted_keys as
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its session keyring, at which point it has full access because now the
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possessor permissions are added. This permits root to add extra public
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keys, thereby bypassing module verification.
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This also affects kexec and IMA.
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This can be tested by (as root):
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keyctl session .builtin_trusted_keys
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keyctl add user a a @s
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keyctl list @s
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which on my test box gives me:
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2 keys in keyring:
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180010936: ---lswrv 0 0 asymmetric: Build time autogenerated kernel key: ae3d4a31b82daa8e1a75b49dc2bba949fd992a05
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801382539: --alswrv 0 0 user: a
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Fix this by rejecting names beginning with a '.' in the keyctl.
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Signed-off-by: David Howells <dhowells@redhat.com>
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Acked-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
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cc: linux-ima-devel@lists.sourceforge.net
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Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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---
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security/keys/keyctl.c | 9 +++++++--
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1 file changed, 7 insertions(+), 2 deletions(-)
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diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
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index fee27fe..af86b35 100644
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--- a/security/keys/keyctl.c
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+++ b/security/keys/keyctl.c
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@@ -277,7 +277,8 @@ error:
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* Create and join an anonymous session keyring or join a named session
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* keyring, creating it if necessary. A named session keyring must have Search
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* permission for it to be joined. Session keyrings without this permit will
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- * be skipped over.
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+ * be skipped over. It is not permitted for userspace to create or join
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+ * keyrings whose name begin with a dot.
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*
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* If successful, the ID of the joined session keyring will be returned.
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*/
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@@ -294,12 +295,16 @@ long keyctl_join_session_keyring(const char __user *_name)
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ret = PTR_ERR(name);
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goto error;
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}
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+
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+ ret = -EPERM;
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+ if (name[0] == '.')
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+ goto error_name;
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}
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/* join the session */
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ret = join_session_keyring(name);
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+error_name:
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kfree(name);
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-
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error:
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return ret;
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}
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--
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cgit v1.1
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