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Documentation: tls: RSTify the ktls documentation
Convert the TLS doc to RST. Use C code blocks for the code samples, and mark hyperlinks. Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com> Acked-by: Dave Watson <davejwatson@fb.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -28,6 +28,7 @@ Contents:
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checksum-offloads
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segmentation-offloads
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scaling
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tls
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.. only:: subproject
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@ -1,3 +1,7 @@
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==========
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Kernel TLS
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==========
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Overview
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========
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@ -12,6 +16,8 @@ Creating a TLS connection
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First create a new TCP socket and set the TLS ULP.
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.. code-block:: c
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sock = socket(AF_INET, SOCK_STREAM, 0);
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setsockopt(sock, SOL_TCP, TCP_ULP, "tls", sizeof("tls"));
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@ -21,6 +27,8 @@ handshake is complete, we have all the parameters required to move the
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data-path to the kernel. There is a separate socket option for moving
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the transmit and the receive into the kernel.
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.. code-block:: c
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/* From linux/tls.h */
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struct tls_crypto_info {
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unsigned short version;
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@ -58,6 +66,8 @@ After setting the TLS_TX socket option all application data sent over this
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socket is encrypted using TLS and the parameters provided in the socket option.
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For example, we can send an encrypted hello world record as follows:
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.. code-block:: c
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const char *msg = "hello world\n";
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send(sock, msg, strlen(msg));
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@ -67,6 +77,8 @@ to the encrypted kernel send buffer if possible.
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The sendfile system call will send the file's data over TLS records of maximum
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length (2^14).
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.. code-block:: c
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file = open(filename, O_RDONLY);
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fstat(file, &stat);
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sendfile(sock, file, &offset, stat.st_size);
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@ -89,6 +101,8 @@ After setting the TLS_RX socket option, all recv family socket calls
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are decrypted using TLS parameters provided. A full TLS record must
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be received before decryption can happen.
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.. code-block:: c
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char buffer[16384];
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recv(sock, buffer, 16384);
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@ -97,12 +111,12 @@ large enough, and no additional allocations occur. If the userspace
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buffer is too small, data is decrypted in the kernel and copied to
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userspace.
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EINVAL is returned if the TLS version in the received message does not
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``EINVAL`` is returned if the TLS version in the received message does not
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match the version passed in setsockopt.
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EMSGSIZE is returned if the received message is too big.
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``EMSGSIZE`` is returned if the received message is too big.
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EBADMSG is returned if decryption failed for any other reason.
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``EBADMSG`` is returned if decryption failed for any other reason.
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Send TLS control messages
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-------------------------
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@ -113,9 +127,11 @@ These messages can be sent over the socket by providing the TLS record type
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via a CMSG. For example the following function sends @data of @length bytes
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using a record of type @record_type.
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/* send TLS control message using record_type */
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.. code-block:: c
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/* send TLS control message using record_type */
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static int klts_send_ctrl_message(int sock, unsigned char record_type,
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void *data, size_t length)
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void *data, size_t length)
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{
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struct msghdr msg = {0};
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int cmsg_len = sizeof(record_type);
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@ -151,6 +167,8 @@ type passed via cmsg. If no cmsg buffer is provided, an error is
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returned if a control message is received. Data messages may be
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received without a cmsg buffer set.
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.. code-block:: c
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char buffer[16384];
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char cmsg[CMSG_SPACE(sizeof(unsigned char))];
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struct msghdr msg = {0};
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@ -186,12 +204,10 @@ Integrating in to userspace TLS library
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At a high level, the kernel TLS ULP is a replacement for the record
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layer of a userspace TLS library.
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A patchset to OpenSSL to use ktls as the record layer is here:
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A patchset to OpenSSL to use ktls as the record layer is
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`here <https://github.com/Mellanox/openssl/commits/tls_rx2>`_.
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https://github.com/Mellanox/openssl/commits/tls_rx2
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An example of calling send directly after a handshake using
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gnutls. Since it doesn't implement a full record layer, control
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messages are not supported:
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https://github.com/ktls/af_ktls-tool/commits/RX
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`An example <https://github.com/ktls/af_ktls-tool/commits/RX>`_
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of calling send directly after a handshake using gnutls.
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Since it doesn't implement a full record layer, control
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messages are not supported.
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