summaryrefslogtreecommitdiffstats
path: root/Documentation/networking/tls.rst
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2019-05-31 06:11:22 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2019-05-31 06:11:22 +0200
commit036e34310931e64ce4f1edead435708cd517db10 (patch)
tree7bd50541ef391bf0699b5d016a7a6fd697a5fdfa /Documentation/networking/tls.rst
parentMerge tag 'arm64-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/arm6... (diff)
parentnet: correct zerocopy refcnt with udp MSG_MORE (diff)
downloadlinux-036e34310931e64ce4f1edead435708cd517db10.tar.xz
linux-036e34310931e64ce4f1edead435708cd517db10.zip
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
Pull networking fixes from David Miller: 1) Fix OOPS during nf_tables rule dump, from Florian Westphal. 2) Use after free in ip_vs_in, from Yue Haibing. 3) Fix various kTLS bugs (NULL deref during device removal resync, netdev notification ignoring, etc.) From Jakub Kicinski. 4) Fix ipv6 redirects with VRF, from David Ahern. 5) Memory leak fix in igmpv3_del_delrec(), from Eric Dumazet. 6) Missing memory allocation failure check in ip6_ra_control(), from Gen Zhang. And likewise fix ip_ra_control(). 7) TX clean budget logic error in aquantia, from Igor Russkikh. 8) SKB leak in llc_build_and_send_ui_pkt(), from Eric Dumazet. 9) Double frees in mlx5, from Parav Pandit. 10) Fix lost MAC address in r8169 during PCI D3, from Heiner Kallweit. 11) Fix botched register access in mvpp2, from Antoine Tenart. 12) Use after free in napi_gro_frags(), from Eric Dumazet. * git://git.kernel.org/pub/scm/linux/kernel/git/davem/net: (89 commits) net: correct zerocopy refcnt with udp MSG_MORE ethtool: Check for vlan etype or vlan tci when parsing flow_rule net: don't clear sock->sk early to avoid trouble in strparser net-gro: fix use-after-free read in napi_gro_frags() net: dsa: tag_8021q: Create a stable binary format net: dsa: tag_8021q: Change order of rx_vid setup net: mvpp2: fix bad MVPP2_TXQ_SCHED_TOKEN_CNTR_REG queue value ipv4: tcp_input: fix stack out of bounds when parsing TCP options. mlxsw: spectrum: Prevent force of 56G mlxsw: spectrum_acl: Avoid warning after identical rules insertion net: dsa: mv88e6xxx: fix handling of upper half of STATS_TYPE_PORT r8169: fix MAC address being lost in PCI D3 net: core: support XDP generic on stacked devices. netvsc: unshare skb in VF rx handler udp: Avoid post-GRO UDP checksum recalculation net: phy: dp83867: Set up RGMII TX delay net: phy: dp83867: do not call config_init twice net: phy: dp83867: increase SGMII autoneg timer duration net: phy: dp83867: fix speed 10 in sgmii mode net: phy: marvell10g: report if the PHY fails to boot firmware ...
Diffstat (limited to 'Documentation/networking/tls.rst')
-rw-r--r--Documentation/networking/tls.rst215
1 files changed, 215 insertions, 0 deletions
diff --git a/Documentation/networking/tls.rst b/Documentation/networking/tls.rst
new file mode 100644
index 000000000000..5bcbf75e2025
--- /dev/null
+++ b/Documentation/networking/tls.rst
@@ -0,0 +1,215 @@
+.. _kernel_tls:
+
+==========
+Kernel TLS
+==========
+
+Overview
+========
+
+Transport Layer Security (TLS) is a Upper Layer Protocol (ULP) that runs over
+TCP. TLS provides end-to-end data integrity and confidentiality.
+
+User interface
+==============
+
+Creating a TLS connection
+-------------------------
+
+First create a new TCP socket and set the TLS ULP.
+
+.. code-block:: c
+
+ sock = socket(AF_INET, SOCK_STREAM, 0);
+ setsockopt(sock, SOL_TCP, TCP_ULP, "tls", sizeof("tls"));
+
+Setting the TLS ULP allows us to set/get TLS socket options. Currently
+only the symmetric encryption is handled in the kernel. After the TLS
+handshake is complete, we have all the parameters required to move the
+data-path to the kernel. There is a separate socket option for moving
+the transmit and the receive into the kernel.
+
+.. code-block:: c
+
+ /* From linux/tls.h */
+ struct tls_crypto_info {
+ unsigned short version;
+ unsigned short cipher_type;
+ };
+
+ struct tls12_crypto_info_aes_gcm_128 {
+ struct tls_crypto_info info;
+ unsigned char iv[TLS_CIPHER_AES_GCM_128_IV_SIZE];
+ unsigned char key[TLS_CIPHER_AES_GCM_128_KEY_SIZE];
+ unsigned char salt[TLS_CIPHER_AES_GCM_128_SALT_SIZE];
+ unsigned char rec_seq[TLS_CIPHER_AES_GCM_128_REC_SEQ_SIZE];
+ };
+
+
+ struct tls12_crypto_info_aes_gcm_128 crypto_info;
+
+ crypto_info.info.version = TLS_1_2_VERSION;
+ crypto_info.info.cipher_type = TLS_CIPHER_AES_GCM_128;
+ memcpy(crypto_info.iv, iv_write, TLS_CIPHER_AES_GCM_128_IV_SIZE);
+ memcpy(crypto_info.rec_seq, seq_number_write,
+ TLS_CIPHER_AES_GCM_128_REC_SEQ_SIZE);
+ memcpy(crypto_info.key, cipher_key_write, TLS_CIPHER_AES_GCM_128_KEY_SIZE);
+ memcpy(crypto_info.salt, implicit_iv_write, TLS_CIPHER_AES_GCM_128_SALT_SIZE);
+
+ setsockopt(sock, SOL_TLS, TLS_TX, &crypto_info, sizeof(crypto_info));
+
+Transmit and receive are set separately, but the setup is the same, using either
+TLS_TX or TLS_RX.
+
+Sending TLS application data
+----------------------------
+
+After setting the TLS_TX socket option all application data sent over this
+socket is encrypted using TLS and the parameters provided in the socket option.
+For example, we can send an encrypted hello world record as follows:
+
+.. code-block:: c
+
+ const char *msg = "hello world\n";
+ send(sock, msg, strlen(msg));
+
+send() data is directly encrypted from the userspace buffer provided
+to the encrypted kernel send buffer if possible.
+
+The sendfile system call will send the file's data over TLS records of maximum
+length (2^14).
+
+.. code-block:: c
+
+ file = open(filename, O_RDONLY);
+ fstat(file, &stat);
+ sendfile(sock, file, &offset, stat.st_size);
+
+TLS records are created and sent after each send() call, unless
+MSG_MORE is passed. MSG_MORE will delay creation of a record until
+MSG_MORE is not passed, or the maximum record size is reached.
+
+The kernel will need to allocate a buffer for the encrypted data.
+This buffer is allocated at the time send() is called, such that
+either the entire send() call will return -ENOMEM (or block waiting
+for memory), or the encryption will always succeed. If send() returns
+-ENOMEM and some data was left on the socket buffer from a previous
+call using MSG_MORE, the MSG_MORE data is left on the socket buffer.
+
+Receiving TLS application data
+------------------------------
+
+After setting the TLS_RX socket option, all recv family socket calls
+are decrypted using TLS parameters provided. A full TLS record must
+be received before decryption can happen.
+
+.. code-block:: c
+
+ char buffer[16384];
+ recv(sock, buffer, 16384);
+
+Received data is decrypted directly in to the user buffer if it is
+large enough, and no additional allocations occur. If the userspace
+buffer is too small, data is decrypted in the kernel and copied to
+userspace.
+
+``EINVAL`` is returned if the TLS version in the received message does not
+match the version passed in setsockopt.
+
+``EMSGSIZE`` is returned if the received message is too big.
+
+``EBADMSG`` is returned if decryption failed for any other reason.
+
+Send TLS control messages
+-------------------------
+
+Other than application data, TLS has control messages such as alert
+messages (record type 21) and handshake messages (record type 22), etc.
+These messages can be sent over the socket by providing the TLS record type
+via a CMSG. For example the following function sends @data of @length bytes
+using a record of type @record_type.
+
+.. code-block:: c
+
+ /* send TLS control message using record_type */
+ static int klts_send_ctrl_message(int sock, unsigned char record_type,
+ void *data, size_t length)
+ {
+ struct msghdr msg = {0};
+ int cmsg_len = sizeof(record_type);
+ struct cmsghdr *cmsg;
+ char buf[CMSG_SPACE(cmsg_len)];
+ struct iovec msg_iov; /* Vector of data to send/receive into. */
+
+ msg.msg_control = buf;
+ msg.msg_controllen = sizeof(buf);
+ cmsg = CMSG_FIRSTHDR(&msg);
+ cmsg->cmsg_level = SOL_TLS;
+ cmsg->cmsg_type = TLS_SET_RECORD_TYPE;
+ cmsg->cmsg_len = CMSG_LEN(cmsg_len);
+ *CMSG_DATA(cmsg) = record_type;
+ msg.msg_controllen = cmsg->cmsg_len;
+
+ msg_iov.iov_base = data;
+ msg_iov.iov_len = length;
+ msg.msg_iov = &msg_iov;
+ msg.msg_iovlen = 1;
+
+ return sendmsg(sock, &msg, 0);
+ }
+
+Control message data should be provided unencrypted, and will be
+encrypted by the kernel.
+
+Receiving TLS control messages
+------------------------------
+
+TLS control messages are passed in the userspace buffer, with message
+type passed via cmsg. If no cmsg buffer is provided, an error is
+returned if a control message is received. Data messages may be
+received without a cmsg buffer set.
+
+.. code-block:: c
+
+ char buffer[16384];
+ char cmsg[CMSG_SPACE(sizeof(unsigned char))];
+ struct msghdr msg = {0};
+ msg.msg_control = cmsg;
+ msg.msg_controllen = sizeof(cmsg);
+
+ struct iovec msg_iov;
+ msg_iov.iov_base = buffer;
+ msg_iov.iov_len = 16384;
+
+ msg.msg_iov = &msg_iov;
+ msg.msg_iovlen = 1;
+
+ int ret = recvmsg(sock, &msg, 0 /* flags */);
+
+ struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
+ if (cmsg->cmsg_level == SOL_TLS &&
+ cmsg->cmsg_type == TLS_GET_RECORD_TYPE) {
+ int record_type = *((unsigned char *)CMSG_DATA(cmsg));
+ // Do something with record_type, and control message data in
+ // buffer.
+ //
+ // Note that record_type may be == to application data (23).
+ } else {
+ // Buffer contains application data.
+ }
+
+recv will never return data from mixed types of TLS records.
+
+Integrating in to userspace TLS library
+---------------------------------------
+
+At a high level, the kernel TLS ULP is a replacement for the record
+layer of a userspace TLS library.
+
+A patchset to OpenSSL to use ktls as the record layer is
+`here <https://github.com/Mellanox/openssl/commits/tls_rx2>`_.
+
+`An example <https://github.com/ktls/af_ktls-tool/commits/RX>`_
+of calling send directly after a handshake using gnutls.
+Since it doesn't implement a full record layer, control
+messages are not supported.