calipso: Allow the lsm to label the skbuff directly.

In some cases, the lsm needs to add the label to the skbuff directly.
A NF_INET_LOCAL_OUT IPv6 hook is added to selinux to match the IPv4
behaviour.  This allows selinux to label the skbuffs that it requires.

Signed-off-by: Huw Davies <huw@codeweavers.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

net/ipv6/calipso.c

@@ -62,6 +62,11 @@
  */
 #define CALIPSO_OPT_LEN_MAX_WITH_PAD (3 + CALIPSO_OPT_LEN_MAX + 7)
 
+ /* Maximium size of u32 aligned buffer required to hold calipso
+  * option.  Max of 3 initial pad bytes starting from buffer + 3.
+  * i.e. the worst case is when the previous tlv finishes on 4n + 3.
+  */
+#define CALIPSO_MAX_BUFFER (6 + CALIPSO_OPT_LEN_MAX)
 
 /* List of available DOI definitions */
 static DEFINE_SPINLOCK(calipso_doi_list_lock);
@@ -973,6 +978,162 @@ static void calipso_req_delattr(struct request_sock *req)
 	kfree(new);
 }
 
+/* skbuff functions.
+ */
+
+/**
+ * calipso_skbuff_optptr - Find the CALIPSO option in the packet
+ * @skb: the packet
+ *
+ * Description:
+ * Parse the packet's IP header looking for a CALIPSO option.  Returns a pointer
+ * to the start of the CALIPSO option on success, NULL if one if not found.
+ *
+ */
+static unsigned char *calipso_skbuff_optptr(const struct sk_buff *skb)
+{
+	const struct ipv6hdr *ip6_hdr = ipv6_hdr(skb);
+	int offset;
+
+	if (ip6_hdr->nexthdr != NEXTHDR_HOP)
+		return NULL;
+
+	offset = ipv6_find_tlv(skb, sizeof(*ip6_hdr), IPV6_TLV_CALIPSO);
+	if (offset >= 0)
+		return (unsigned char *)ip6_hdr + offset;
+
+	return NULL;
+}
+
+/**
+ * calipso_skbuff_setattr - Set the CALIPSO option on a packet
+ * @skb: the packet
+ * @doi_def: the CALIPSO DOI to use
+ * @secattr: the security attributes
+ *
+ * Description:
+ * Set the CALIPSO option on the given packet based on the security attributes.
+ * Returns a pointer to the IP header on success and NULL on failure.
+ *
+ */
+static int calipso_skbuff_setattr(struct sk_buff *skb,
+				  const struct calipso_doi *doi_def,
+				  const struct netlbl_lsm_secattr *secattr)
+{
+	int ret_val;
+	struct ipv6hdr *ip6_hdr;
+	struct ipv6_opt_hdr *hop;
+	unsigned char buf[CALIPSO_MAX_BUFFER];
+	int len_delta, new_end, pad;
+	unsigned int start, end;
+
+	ip6_hdr = ipv6_hdr(skb);
+	if (ip6_hdr->nexthdr == NEXTHDR_HOP) {
+		hop = (struct ipv6_opt_hdr *)(ip6_hdr + 1);
+		ret_val = calipso_opt_find(hop, &start, &end);
+		if (ret_val && ret_val != -ENOENT)
+			return ret_val;
+	} else {
+		start = 0;
+		end = 0;
+	}
+
+	memset(buf, 0, sizeof(buf));
+	ret_val = calipso_genopt(buf, start & 3, sizeof(buf), doi_def, secattr);
+	if (ret_val < 0)
+		return ret_val;
+
+	new_end = start + ret_val;
+	/* At this point new_end aligns to 4n, so (new_end & 4) pads to 8n */
+	pad = ((new_end & 4) + (end & 7)) & 7;
+	len_delta = new_end - (int)end + pad;
+	ret_val = skb_cow(skb, skb_headroom(skb) + len_delta);
+	if (ret_val < 0)
+		return ret_val;
+
+	if (len_delta) {
+		if (len_delta > 0)
+			skb_push(skb, len_delta);
+		else
+			skb_pull(skb, -len_delta);
+		memmove((char *)ip6_hdr - len_delta, ip6_hdr,
+			sizeof(*ip6_hdr) + start);
+		skb_reset_network_header(skb);
+		ip6_hdr = ipv6_hdr(skb);
+	}
+
+	hop = (struct ipv6_opt_hdr *)(ip6_hdr + 1);
+	if (start == 0) {
+		struct ipv6_opt_hdr *new_hop = (struct ipv6_opt_hdr *)buf;
+
+		new_hop->nexthdr = ip6_hdr->nexthdr;
+		new_hop->hdrlen = len_delta / 8 - 1;
+		ip6_hdr->nexthdr = NEXTHDR_HOP;
+	} else {
+		hop->hdrlen += len_delta / 8;
+	}
+	memcpy((char *)hop + start, buf + (start & 3), new_end - start);
+	calipso_pad_write((unsigned char *)hop, new_end, pad);
+
+	return 0;
+}
+
+/**
+ * calipso_skbuff_delattr - Delete any CALIPSO options from a packet
+ * @skb: the packet
+ *
+ * Description:
+ * Removes any and all CALIPSO options from the given packet.  Returns zero on
+ * success, negative values on failure.
+ *
+ */
+static int calipso_skbuff_delattr(struct sk_buff *skb)
+{
+	int ret_val;
+	struct ipv6hdr *ip6_hdr;
+	struct ipv6_opt_hdr *old_hop;
+	u32 old_hop_len, start = 0, end = 0, delta, size, pad;
+
+	if (!calipso_skbuff_optptr(skb))
+		return 0;
+
+	/* since we are changing the packet we should make a copy */
+	ret_val = skb_cow(skb, skb_headroom(skb));
+	if (ret_val < 0)
+		return ret_val;
+
+	ip6_hdr = ipv6_hdr(skb);
+	old_hop = (struct ipv6_opt_hdr *)(ip6_hdr + 1);
+	old_hop_len = ipv6_optlen(old_hop);
+
+	ret_val = calipso_opt_find(old_hop, &start, &end);
+	if (ret_val)
+		return ret_val;
+
+	if (start == sizeof(*old_hop) && end == old_hop_len) {
+		/* There's no other option in the header so we delete
+		 * the whole thing. */
+		delta = old_hop_len;
+		size = sizeof(*ip6_hdr);
+		ip6_hdr->nexthdr = old_hop->nexthdr;
+	} else {
+		delta = (end - start) & ~7;
+		if (delta)
+			old_hop->hdrlen -= delta / 8;
+		pad = (end - start) & 7;
+		size = sizeof(*ip6_hdr) + start + pad;
+		calipso_pad_write((unsigned char *)old_hop, start, pad);
+	}
+
+	if (delta) {
+		skb_pull(skb, delta);
+		memmove((char *)ip6_hdr + delta, ip6_hdr, size);
+		skb_reset_network_header(skb);
+	}
+
+	return 0;
+}
+
 static const struct netlbl_calipso_ops ops = {
 	.doi_add          = calipso_doi_add,
 	.doi_free         = calipso_doi_free,
@@ -985,6 +1146,10 @@ static const struct netlbl_calipso_ops ops = {
 	.sock_delattr     = calipso_sock_delattr,
 	.req_setattr      = calipso_req_setattr,
 	.req_delattr      = calipso_req_delattr,
+	.opt_getattr      = calipso_opt_getattr,
+	.skbuff_optptr    = calipso_skbuff_optptr,
+	.skbuff_setattr   = calipso_skbuff_setattr,
+	.skbuff_delattr   = calipso_skbuff_delattr,
 };
 
 /**