calipso: Set the calipso socket label to match the secattr.

CALIPSO is a hop-by-hop IPv6 option.  A lot of this patch is based on
the equivalent CISPO code.  The main difference is due to manipulating
the options in the hop-by-hop header.

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

1 files changed, 595 insertions, 0 deletions

diff --git a/net/ipv6/calipso.c b/net/ipv6/calipso.c
index d7df7a4bd32e..959db5268b38 100644
--- a/net/ipv6/calipso.c
+++ b/net/ipv6/calipso.c
@@ -44,6 +44,24 @@
 #include <linux/atomic.h>
 #include <linux/bug.h>
 #include <asm/unaligned.h>
+#include <linux/crc-ccitt.h>
+
+/* Maximium size of the calipso option including
+ * the two-byte TLV header.
+ */
+#define CALIPSO_OPT_LEN_MAX (2 + 252)
+
+/* Size of the minimum calipso option including
+ * the two-byte TLV header.
+ */
+#define CALIPSO_HDR_LEN (2 + 8)
+
+/* Maximium size of the calipso option including
+ * the two-byte TLV header and upto 3 bytes of
+ * leading pad and 7 bytes of trailing pad.
+ */
+#define CALIPSO_OPT_LEN_MAX_WITH_PAD (3 + CALIPSO_OPT_LEN_MAX + 7)
+
 
 /* List of available DOI definitions */
 static DEFINE_SPINLOCK(calipso_doi_list_lock);
@@ -297,6 +315,580 @@ doi_walk_return:
 	return ret_val;
 }
 
+/**
+ * calipso_map_cat_hton - Perform a category mapping from host to network
+ * @doi_def: the DOI definition
+ * @secattr: the security attributes
+ * @net_cat: the zero'd out category bitmap in network/CALIPSO format
+ * @net_cat_len: the length of the CALIPSO bitmap in bytes
+ *
+ * Description:
+ * Perform a label mapping to translate a local MLS category bitmap to the
+ * correct CALIPSO bitmap using the given DOI definition.  Returns the minimum
+ * size in bytes of the network bitmap on success, negative values otherwise.
+ *
+ */
+static int calipso_map_cat_hton(const struct calipso_doi *doi_def,
+				const struct netlbl_lsm_secattr *secattr,
+				unsigned char *net_cat,
+				u32 net_cat_len)
+{
+	int spot = -1;
+	u32 net_spot_max = 0;
+	u32 net_clen_bits = net_cat_len * 8;
+
+	for (;;) {
+		spot = netlbl_catmap_walk(secattr->attr.mls.cat,
+					  spot + 1);
+		if (spot < 0)
+			break;
+		if (spot >= net_clen_bits)
+			return -ENOSPC;
+		netlbl_bitmap_setbit(net_cat, spot, 1);
+
+		if (spot > net_spot_max)
+			net_spot_max = spot;
+	}
+
+	return (net_spot_max / 32 + 1) * 4;
+}
+
+/**
+ * calipso_map_cat_ntoh - Perform a category mapping from network to host
+ * @doi_def: the DOI definition
+ * @net_cat: the category bitmap in network/CALIPSO format
+ * @net_cat_len: the length of the CALIPSO bitmap in bytes
+ * @secattr: the security attributes
+ *
+ * Description:
+ * Perform a label mapping to translate a CALIPSO bitmap to the correct local
+ * MLS category bitmap using the given DOI definition.  Returns zero on
+ * success, negative values on failure.
+ *
+ */
+static int calipso_map_cat_ntoh(const struct calipso_doi *doi_def,
+				const unsigned char *net_cat,
+				u32 net_cat_len,
+				struct netlbl_lsm_secattr *secattr)
+{
+	int ret_val;
+	int spot = -1;
+	u32 net_clen_bits = net_cat_len * 8;
+
+	for (;;) {
+		spot = netlbl_bitmap_walk(net_cat,
+					  net_clen_bits,
+					  spot + 1,
+					  1);
+		if (spot < 0) {
+			if (spot == -2)
+				return -EFAULT;
+			return 0;
+		}
+
+		ret_val = netlbl_catmap_setbit(&secattr->attr.mls.cat,
+					       spot,
+					       GFP_ATOMIC);
+		if (ret_val != 0)
+			return ret_val;
+	}
+
+	return -EINVAL;
+}
+
+/**
+ * calipso_pad_write - Writes pad bytes in TLV format
+ * @buf: the buffer
+ * @offset: offset from start of buffer to write padding
+ * @count: number of pad bytes to write
+ *
+ * Description:
+ * Write @count bytes of TLV padding into @buffer starting at offset @offset.
+ * @count should be less than 8 - see RFC 4942.
+ *
+ */
+static int calipso_pad_write(unsigned char *buf, unsigned int offset,
+			     unsigned int count)
+{
+	if (WARN_ON_ONCE(count >= 8))
+		return -EINVAL;
+
+	switch (count) {
+	case 0:
+		break;
+	case 1:
+		buf[offset] = IPV6_TLV_PAD1;
+		break;
+	default:
+		buf[offset] = IPV6_TLV_PADN;
+		buf[offset + 1] = count - 2;
+		if (count > 2)
+			memset(buf + offset + 2, 0, count - 2);
+		break;
+	}
+	return 0;
+}
+
+/**
+ * calipso_genopt - Generate a CALIPSO option
+ * @buf: the option buffer
+ * @start: offset from which to write
+ * @buf_len: the size of opt_buf
+ * @doi_def: the CALIPSO DOI to use
+ * @secattr: the security attributes
+ *
+ * Description:
+ * Generate a CALIPSO option using the DOI definition and security attributes
+ * passed to the function. This also generates upto three bytes of leading
+ * padding that ensures that the option is 4n + 2 aligned.  It returns the
+ * number of bytes written (including any initial padding).
+ */
+static int calipso_genopt(unsigned char *buf, u32 start, u32 buf_len,
+			  const struct calipso_doi *doi_def,
+			  const struct netlbl_lsm_secattr *secattr)
+{
+	int ret_val;
+	u32 len, pad;
+	u16 crc;
+	static const unsigned char padding[4] = {2, 1, 0, 3};
+	unsigned char *calipso;
+
+	/* CALIPSO has 4n + 2 alignment */
+	pad = padding[start & 3];
+	if (buf_len <= start + pad + CALIPSO_HDR_LEN)
+		return -ENOSPC;
+
+	if ((secattr->flags & NETLBL_SECATTR_MLS_LVL) == 0)
+		return -EPERM;
+
+	len = CALIPSO_HDR_LEN;
+
+	if (secattr->flags & NETLBL_SECATTR_MLS_CAT) {
+		ret_val = calipso_map_cat_hton(doi_def,
+					       secattr,
+					       buf + start + pad + len,
+					       buf_len - start - pad - len);
+		if (ret_val < 0)
+			return ret_val;
+		len += ret_val;
+	}
+
+	calipso_pad_write(buf, start, pad);
+	calipso = buf + start + pad;
+
+	calipso[0] = IPV6_TLV_CALIPSO;
+	calipso[1] = len - 2;
+	*(__be32 *)(calipso + 2) = htonl(doi_def->doi);
+	calipso[6] = (len - CALIPSO_HDR_LEN) / 4;
+	calipso[7] = secattr->attr.mls.lvl,
+	crc = ~crc_ccitt(0xffff, calipso, len);
+	calipso[8] = crc & 0xff;
+	calipso[9] = (crc >> 8) & 0xff;
+	return pad + len;
+}
+
+/* Hop-by-hop hdr helper functions
+ */
+
+/**
+ * calipso_opt_update - Replaces socket's hop options with a new set
+ * @sk: the socket
+ * @hop: new hop options
+ *
+ * Description:
+ * Replaces @sk's hop options with @hop.  @hop may be NULL to leave
+ * the socket with no hop options.
+ *
+ */
+static int calipso_opt_update(struct sock *sk, struct ipv6_opt_hdr *hop)
+{
+	struct ipv6_txoptions *old = txopt_get(inet6_sk(sk)), *txopts;
+
+	txopts = ipv6_renew_options_kern(sk, old, IPV6_HOPOPTS,
+					 hop, hop ? ipv6_optlen(hop) : 0);
+	txopt_put(old);
+	if (IS_ERR(txopts))
+		return PTR_ERR(txopts);
+
+	txopts = ipv6_update_options(sk, txopts);
+	if (txopts) {
+		atomic_sub(txopts->tot_len, &sk->sk_omem_alloc);
+		txopt_put(txopts);
+	}
+
+	return 0;
+}
+
+/**
+ * calipso_tlv_len - Returns the length of the TLV
+ * @opt: the option header
+ * @offset: offset of the TLV within the header
+ *
+ * Description:
+ * Returns the length of the TLV option at offset @offset within
+ * the option header @opt.  Checks that the entire TLV fits inside
+ * the option header, returns a negative value if this is not the case.
+ */
+static int calipso_tlv_len(struct ipv6_opt_hdr *opt, unsigned int offset)
+{
+	unsigned char *tlv = (unsigned char *)opt;
+	unsigned int opt_len = ipv6_optlen(opt), tlv_len;
+
+	if (offset < sizeof(*opt) || offset >= opt_len)
+		return -EINVAL;
+	if (tlv[offset] == IPV6_TLV_PAD1)
+		return 1;
+	if (offset + 1 >= opt_len)
+		return -EINVAL;
+	tlv_len = tlv[offset + 1] + 2;
+	if (offset + tlv_len > opt_len)
+		return -EINVAL;
+	return tlv_len;
+}
+
+/**
+ * calipso_opt_find - Finds the CALIPSO option in an IPv6 hop options header
+ * @hop: the hop options header
+ * @start: on return holds the offset of any leading padding
+ * @end: on return holds the offset of the first non-pad TLV after CALIPSO
+ *
+ * Description:
+ * Finds the space occupied by a CALIPSO option (including any leading and
+ * trailing padding).
+ *
+ * If a CALIPSO option exists set @start and @end to the
+ * offsets within @hop of the start of padding before the first
+ * CALIPSO option and the end of padding after the first CALIPSO
+ * option.  In this case the function returns 0.
+ *
+ * In the absence of a CALIPSO option, @start and @end will be
+ * set to the start and end of any trailing padding in the header.
+ * This is useful when appending a new option, as the caller may want
+ * to overwrite some of this padding.  In this case the function will
+ * return -ENOENT.
+ */
+static int calipso_opt_find(struct ipv6_opt_hdr *hop, unsigned int *start,
+			    unsigned int *end)
+{
+	int ret_val = -ENOENT, tlv_len;
+	unsigned int opt_len, offset, offset_s = 0, offset_e = 0;
+	unsigned char *opt = (unsigned char *)hop;
+
+	opt_len = ipv6_optlen(hop);
+	offset = sizeof(*hop);
+
+	while (offset < opt_len) {
+		tlv_len = calipso_tlv_len(hop, offset);
+		if (tlv_len < 0)
+			return tlv_len;
+
+		switch (opt[offset]) {
+		case IPV6_TLV_PAD1:
+		case IPV6_TLV_PADN:
+			if (offset_e)
+				offset_e = offset;
+			break;
+		case IPV6_TLV_CALIPSO:
+			ret_val = 0;
+			offset_e = offset;
+			break;
+		default:
+			if (offset_e == 0)
+				offset_s = offset;
+			else
+				goto out;
+		}
+		offset += tlv_len;
+	}
+
+out:
+	if (offset_s)
+		*start = offset_s + calipso_tlv_len(hop, offset_s);
+	else
+		*start = sizeof(*hop);
+	if (offset_e)
+		*end = offset_e + calipso_tlv_len(hop, offset_e);
+	else
+		*end = opt_len;
+
+	return ret_val;
+}
+
+/**
+ * calipso_opt_insert - Inserts a CALIPSO option into an IPv6 hop opt hdr
+ * @hop: the original hop options header
+ * @doi_def: the CALIPSO DOI to use
+ * @secattr: the specific security attributes of the socket
+ *
+ * Description:
+ * Creates a new hop options header based on @hop with a
+ * CALIPSO option added to it.  If @hop already contains a CALIPSO
+ * option this is overwritten, otherwise the new option is appended
+ * after any existing options.  If @hop is NULL then the new header
+ * will contain just the CALIPSO option and any needed padding.
+ *
+ */
+static struct ipv6_opt_hdr *
+calipso_opt_insert(struct ipv6_opt_hdr *hop,
+		   const struct calipso_doi *doi_def,
+		   const struct netlbl_lsm_secattr *secattr)
+{
+	unsigned int start, end, buf_len, pad, hop_len;
+	struct ipv6_opt_hdr *new;
+	int ret_val;
+
+	if (hop) {
+		hop_len = ipv6_optlen(hop);
+		ret_val = calipso_opt_find(hop, &start, &end);
+		if (ret_val && ret_val != -ENOENT)
+			return ERR_PTR(ret_val);
+	} else {
+		hop_len = 0;
+		start = sizeof(*hop);
+		end = 0;
+	}
+
+	buf_len = hop_len + start - end + CALIPSO_OPT_LEN_MAX_WITH_PAD;
+	new = kzalloc(buf_len, GFP_ATOMIC);
+	if (!new)
+		return ERR_PTR(-ENOMEM);
+
+	if (start > sizeof(*hop))
+		memcpy(new, hop, start);
+	ret_val = calipso_genopt((unsigned char *)new, start, buf_len, doi_def,
+				 secattr);
+	if (ret_val < 0)
+		return ERR_PTR(ret_val);
+
+	buf_len = start + ret_val;
+	/* At this point buf_len aligns to 4n, so (buf_len & 4) pads to 8n */
+	pad = ((buf_len & 4) + (end & 7)) & 7;
+	calipso_pad_write((unsigned char *)new, buf_len, pad);
+	buf_len += pad;
+
+	if (end != hop_len) {
+		memcpy((char *)new + buf_len, (char *)hop + end, hop_len - end);
+		buf_len += hop_len - end;
+	}
+	new->nexthdr = 0;
+	new->hdrlen = buf_len / 8 - 1;
+
+	return new;
+}
+
+/**
+ * calipso_opt_del - Removes the CALIPSO option from an option header
+ * @hop: the original header
+ * @new: the new header
+ *
+ * Description:
+ * Creates a new header based on @hop without any CALIPSO option.  If @hop
+ * doesn't contain a CALIPSO option it returns -ENOENT.  If @hop contains
+ * no other non-padding options, it returns zero with @new set to NULL.
+ * Otherwise it returns zero, creates a new header without the CALIPSO
+ * option (and removing as much padding as possible) and returns with
+ * @new set to that header.
+ *
+ */
+static int calipso_opt_del(struct ipv6_opt_hdr *hop,
+			   struct ipv6_opt_hdr **new)
+{
+	int ret_val;
+	unsigned int start, end, delta, pad, hop_len;
+
+	ret_val = calipso_opt_find(hop, &start, &end);
+	if (ret_val)
+		return ret_val;
+
+	hop_len = ipv6_optlen(hop);
+	if (start == sizeof(*hop) && end == hop_len) {
+		/* There's no other option in the header so return NULL */
+		*new = NULL;
+		return 0;
+	}
+
+	delta = (end - start) & ~7;
+	*new = kzalloc(hop_len - delta, GFP_ATOMIC);
+	if (!*new)
+		return -ENOMEM;
+
+	memcpy(*new, hop, start);
+	(*new)->hdrlen -= delta / 8;
+	pad = (end - start) & 7;
+	calipso_pad_write((unsigned char *)*new, start, pad);
+	if (end != hop_len)
+		memcpy((char *)*new + start + pad, (char *)hop + end,
+		       hop_len - end);
+
+	return 0;
+}
+
+/**
+ * calipso_opt_getattr - Get the security attributes from a memory block
+ * @calipso: the CALIPSO option
+ * @secattr: the security attributes
+ *
+ * Description:
+ * Inspect @calipso and return the security attributes in @secattr.
+ * Returns zero on success and negative values on failure.
+ *
+ */
+static int calipso_opt_getattr(const unsigned char *calipso,
+			       struct netlbl_lsm_secattr *secattr)
+{
+	int ret_val = -ENOMSG;
+	u32 doi, len = calipso[1], cat_len = calipso[6] * 4;
+	struct calipso_doi *doi_def;
+
+	if (cat_len + 8 > len)
+		return -EINVAL;
+
+	doi = get_unaligned_be32(calipso + 2);
+	rcu_read_lock();
+	doi_def = calipso_doi_search(doi);
+	if (!doi_def)
+		goto getattr_return;
+
+	secattr->attr.mls.lvl = calipso[7];
+	secattr->flags |= NETLBL_SECATTR_MLS_LVL;
+
+	if (cat_len) {
+		ret_val = calipso_map_cat_ntoh(doi_def,
+					       calipso + 10,
+					       cat_len,
+					       secattr);
+		if (ret_val != 0) {
+			netlbl_catmap_free(secattr->attr.mls.cat);
+			goto getattr_return;
+		}
+
+		secattr->flags |= NETLBL_SECATTR_MLS_CAT;
+	}
+
+	secattr->type = NETLBL_NLTYPE_CALIPSO;
+
+getattr_return:
+	rcu_read_unlock();
+	return ret_val;
+}
+
+/* sock functions.
+ */
+
+/**
+ * calipso_sock_getattr - Get the security attributes from a sock
+ * @sk: the sock
+ * @secattr: the security attributes
+ *
+ * Description:
+ * Query @sk to see if there is a CALIPSO option attached to the sock and if
+ * there is return the CALIPSO security attributes in @secattr.  This function
+ * requires that @sk be locked, or privately held, but it does not do any
+ * locking itself.  Returns zero on success and negative values on failure.
+ *
+ */
+static int calipso_sock_getattr(struct sock *sk,
+				struct netlbl_lsm_secattr *secattr)
+{
+	struct ipv6_opt_hdr *hop;
+	int opt_len, len, ret_val = -ENOMSG, offset;
+	unsigned char *opt;
+	struct ipv6_txoptions *txopts = txopt_get(inet6_sk(sk));
+
+	if (!txopts || !txopts->hopopt)
+		goto done;
+
+	hop = txopts->hopopt;
+	opt = (unsigned char *)hop;
+	opt_len = ipv6_optlen(hop);
+	offset = sizeof(*hop);
+	while (offset < opt_len) {
+		len = calipso_tlv_len(hop, offset);
+		if (len < 0) {
+			ret_val = len;
+			goto done;
+		}
+		switch (opt[offset]) {
+		case IPV6_TLV_CALIPSO:
+			if (len < CALIPSO_HDR_LEN)
+				ret_val = -EINVAL;
+			else
+				ret_val = calipso_opt_getattr(&opt[offset],
+							      secattr);
+			goto done;
+		default:
+			offset += len;
+			break;
+		}
+	}
+done:
+	txopt_put(txopts);
+	return ret_val;
+}
+
+/**
+ * calipso_sock_setattr - Add a CALIPSO option to a socket
+ * @sk: the socket
+ * @doi_def: the CALIPSO DOI to use
+ * @secattr: the specific security attributes of the socket
+ *
+ * Description:
+ * Set the CALIPSO option on the given socket using the DOI definition and
+ * security attributes passed to the function.  This function requires
+ * exclusive access to @sk, which means it either needs to be in the
+ * process of being created or locked.  Returns zero on success and negative
+ * values on failure.
+ *
+ */
+static int calipso_sock_setattr(struct sock *sk,
+				const struct calipso_doi *doi_def,
+				const struct netlbl_lsm_secattr *secattr)
+{
+	int ret_val;
+	struct ipv6_opt_hdr *old, *new;
+	struct ipv6_txoptions *txopts = txopt_get(inet6_sk(sk));
+
+	old = NULL;
+	if (txopts)
+		old = txopts->hopopt;
+
+	new = calipso_opt_insert(old, doi_def, secattr);
+	txopt_put(txopts);
+	if (IS_ERR(new))
+		return PTR_ERR(new);
+
+	ret_val = calipso_opt_update(sk, new);
+
+	kfree(new);
+	return ret_val;
+}
+
+/**
+ * calipso_sock_delattr - Delete the CALIPSO option from a socket
+ * @sk: the socket
+ *
+ * Description:
+ * Removes the CALIPSO option from a socket, if present.
+ *
+ */
+static void calipso_sock_delattr(struct sock *sk)
+{
+	struct ipv6_opt_hdr *new_hop;
+	struct ipv6_txoptions *txopts = txopt_get(inet6_sk(sk));
+
+	if (!txopts || !txopts->hopopt)
+		goto done;
+
+	if (calipso_opt_del(txopts->hopopt, &new_hop))
+		goto done;
+
+	calipso_opt_update(sk, new_hop);
+	kfree(new_hop);
+
+done:
+	txopt_put(txopts);
+}
+
 static const struct netlbl_calipso_ops ops = {
 	.doi_add          = calipso_doi_add,
 	.doi_free         = calipso_doi_free,
@@ -304,6 +896,9 @@ static const struct netlbl_calipso_ops ops = {
 	.doi_getdef       = calipso_doi_getdef,
 	.doi_putdef       = calipso_doi_putdef,
 	.doi_walk         = calipso_doi_walk,
+	.sock_getattr     = calipso_sock_getattr,
+	.sock_setattr     = calipso_sock_setattr,
+	.sock_delattr     = calipso_sock_delattr,
 };
 
 /**