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Message-ID: <20240416152913.1527166-3-omosnace@redhat.com>
Date: Tue, 16 Apr 2024 17:29:13 +0200
From: Ondrej Mosnacek <omosnace@...hat.com>
To: Paul Moore <paul@...l-moore.com>
Cc: netdev@...r.kernel.org,
linux-security-module@...r.kernel.org
Subject: [PATCH 2/2] cipso: make cipso_v4_skbuff_delattr() fully remove the CIPSO options
As the comment in this function says, the code currently just clears the
CIPSO part with IPOPT_NOP, rather than removing it completely and
trimming the packet. This is inconsistent with the other
cipso_v4_*_delattr() functions and with CALIPSO (IPv6).
Implement the proper option removal to make it consistent and producing
more optimal IP packets when there are CIPSO options set.
Signed-off-by: Ondrej Mosnacek <omosnace@...hat.com>
---
net/ipv4/cipso_ipv4.c | 89 ++++++++++++++++++++++++++++---------------
1 file changed, 59 insertions(+), 30 deletions(-)
diff --git a/net/ipv4/cipso_ipv4.c b/net/ipv4/cipso_ipv4.c
index 75b5e3c35f9bf..c08c6d0262ba8 100644
--- a/net/ipv4/cipso_ipv4.c
+++ b/net/ipv4/cipso_ipv4.c
@@ -1810,6 +1810,34 @@ static int cipso_v4_genopt(unsigned char *buf, u32 buf_len,
return CIPSO_V4_HDR_LEN + ret_val;
}
+static int cipso_v4_get_actual_opt_len(const unsigned char *data, int len)
+{
+ int iter = 0, optlen = 0;
+
+ /* determining the new total option length is tricky because of
+ * the padding necessary, the only thing i can think to do at
+ * this point is walk the options one-by-one, skipping the
+ * padding at the end to determine the actual option size and
+ * from there we can determine the new total option length
+ */
+ while (iter < len) {
+ if (data[iter] == IPOPT_END) {
+ break;
+ } else if (data[iter] == IPOPT_NOP) {
+ iter++;
+ } else {
+ if (WARN_ON(data[iter + 1] < 2))
+ iter += 2;
+ else
+ iter += data[iter + 1];
+ optlen = iter;
+ }
+ }
+ if (WARN_ON(optlen > len))
+ optlen = len;
+ return optlen;
+}
+
/**
* cipso_v4_sock_setattr - Add a CIPSO option to a socket
* @sk: the socket
@@ -1985,7 +2013,6 @@ static int cipso_v4_delopt(struct ip_options_rcu __rcu **opt_ptr)
u8 cipso_len;
u8 cipso_off;
unsigned char *cipso_ptr;
- int iter;
int optlen_new;
cipso_off = opt->opt.cipso - sizeof(struct iphdr);
@@ -2005,28 +2032,8 @@ static int cipso_v4_delopt(struct ip_options_rcu __rcu **opt_ptr)
memmove(cipso_ptr, cipso_ptr + cipso_len,
opt->opt.optlen - cipso_off - cipso_len);
- /* determining the new total option length is tricky because of
- * the padding necessary, the only thing i can think to do at
- * this point is walk the options one-by-one, skipping the
- * padding at the end to determine the actual option size and
- * from there we can determine the new total option length */
- iter = 0;
- optlen_new = 0;
- while (iter < opt->opt.optlen) {
- if (opt->opt.__data[iter] == IPOPT_END) {
- break;
- } else if (opt->opt.__data[iter] == IPOPT_NOP) {
- iter++;
- } else {
- if (WARN_ON(opt->opt.__data[iter + 1] < 2))
- iter += 2;
- else
- iter += opt->opt.__data[iter + 1];
- optlen_new = iter;
- }
- }
- if (WARN_ON(optlen_new > opt->opt.optlen))
- optlen_new = opt->opt.optlen;
+ optlen_new = cipso_v4_get_actual_opt_len(opt->opt.__data,
+ opt->opt.optlen);
hdr_delta = opt->opt.optlen;
opt->opt.optlen = (optlen_new + 3) & ~3;
hdr_delta -= opt->opt.optlen;
@@ -2246,7 +2253,8 @@ int cipso_v4_skbuff_setattr(struct sk_buff *skb,
*/
int cipso_v4_skbuff_delattr(struct sk_buff *skb)
{
- int ret_val;
+ int ret_val, cipso_len, hdr_len_actual, new_hdr_len_actual, new_hdr_len,
+ hdr_len_delta;
struct iphdr *iph;
struct ip_options *opt = &IPCB(skb)->opt;
unsigned char *cipso_ptr;
@@ -2259,16 +2267,37 @@ int cipso_v4_skbuff_delattr(struct sk_buff *skb)
if (ret_val < 0)
return ret_val;
- /* the easiest thing to do is just replace the cipso option with noop
- * options since we don't change the size of the packet, although we
- * still need to recalculate the checksum */
-
iph = ip_hdr(skb);
cipso_ptr = (unsigned char *)iph + opt->cipso;
- memset(cipso_ptr, IPOPT_NOOP, cipso_ptr[1]);
+ cipso_len = cipso_ptr[1];
+
+ hdr_len_actual = sizeof(struct iphdr) +
+ cipso_v4_get_actual_opt_len((unsigned char *)(iph + 1),
+ opt->optlen);
+ new_hdr_len_actual = hdr_len_actual - cipso_len;
+ new_hdr_len = (new_hdr_len_actual + 3) & ~3;
+ hdr_len_delta = (iph->ihl << 2) - new_hdr_len;
+
+ /* 1. shift any options after CIPSO to the left */
+ memmove(cipso_ptr, cipso_ptr + cipso_len,
+ new_hdr_len_actual - opt->cipso);
+ /* 2. move the whole IP header to its new place */
+ memmove((unsigned char *)iph + hdr_len_delta, iph, new_hdr_len_actual);
+ /* 3. adjust the skb layout */
+ skb_pull(skb, hdr_len_delta);
+ skb_reset_network_header(skb);
+ iph = ip_hdr(skb);
+ /* 4. re-fill new padding with IPOPT_END (may now be longer) */
+ memset((unsigned char *)iph + new_hdr_len_actual, IPOPT_END,
+ new_hdr_len - new_hdr_len_actual);
+
+ opt->optlen -= hdr_len_delta;
opt->cipso = 0;
opt->is_changed = 1;
-
+ if (hdr_len_delta != 0) {
+ iph->ihl = new_hdr_len >> 2;
+ iph_set_totlen(iph, skb->len);
+ }
ip_send_check(iph);
return 0;
--
2.44.0
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