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https://github.com/Divested-Mobile/DivestOS-Build.git
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74 lines
2.9 KiB
Diff
74 lines
2.9 KiB
Diff
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From 20e1db19db5d6b9e4e83021595eab0dc8f107bef Mon Sep 17 00:00:00 2001
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From: Pablo Neira Ayuso <pablo@netfilter.org>
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Date: Thu, 23 Aug 2012 02:09:11 +0000
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Subject: netlink: fix possible spoofing from non-root processes
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Non-root user-space processes can send Netlink messages to other
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processes that are well-known for being subscribed to Netlink
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asynchronous notifications. This allows ilegitimate non-root
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process to send forged messages to Netlink subscribers.
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The userspace process usually verifies the legitimate origin in
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two ways:
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a) Socket credentials. If UID != 0, then the message comes from
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some ilegitimate process and the message needs to be dropped.
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b) Netlink portID. In general, portID == 0 means that the origin
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of the messages comes from the kernel. Thus, discarding any
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message not coming from the kernel.
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However, ctnetlink sets the portID in event messages that has
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been triggered by some user-space process, eg. conntrack utility.
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So other processes subscribed to ctnetlink events, eg. conntrackd,
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know that the event was triggered by some user-space action.
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Neither of the two ways to discard ilegitimate messages coming
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from non-root processes can help for ctnetlink.
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This patch adds capability validation in case that dst_pid is set
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in netlink_sendmsg(). This approach is aggressive since existing
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applications using any Netlink bus to deliver messages between
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two user-space processes will break. Note that the exception is
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NETLINK_USERSOCK, since it is reserved for netlink-to-netlink
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userspace communication.
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Still, if anyone wants that his Netlink bus allows netlink-to-netlink
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userspace, then they can set NL_NONROOT_SEND. However, by default,
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I don't think it makes sense to allow to use NETLINK_ROUTE to
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communicate two processes that are sending no matter what information
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that is not related to link/neighbouring/routing. They should be using
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NETLINK_USERSOCK instead for that.
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Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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---
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net/netlink/af_netlink.c | 4 +++-
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1 file changed, 3 insertions(+), 1 deletion(-)
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diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
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index 1445d73..5270238 100644
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--- a/net/netlink/af_netlink.c
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+++ b/net/netlink/af_netlink.c
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@@ -1373,7 +1373,8 @@ static int netlink_sendmsg(struct kiocb *kiocb, struct socket *sock,
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dst_pid = addr->nl_pid;
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dst_group = ffs(addr->nl_groups);
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err = -EPERM;
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- if (dst_group && !netlink_capable(sock, NL_NONROOT_SEND))
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+ if ((dst_group || dst_pid) &&
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+ !netlink_capable(sock, NL_NONROOT_SEND))
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goto out;
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} else {
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dst_pid = nlk->dst_pid;
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@@ -2147,6 +2148,7 @@ static void __init netlink_add_usersock_entry(void)
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rcu_assign_pointer(nl_table[NETLINK_USERSOCK].listeners, listeners);
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nl_table[NETLINK_USERSOCK].module = THIS_MODULE;
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nl_table[NETLINK_USERSOCK].registered = 1;
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+ nl_table[NETLINK_USERSOCK].nl_nonroot = NL_NONROOT_SEND;
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netlink_table_ungrab();
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}
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--
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cgit v1.1
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