mirror of https://gitee.com/openkylin/linux.git
136 lines
4.8 KiB
Plaintext
136 lines
4.8 KiB
Plaintext
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.
|
|
|
|
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.
|
|
|
|
/* 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));
|
|
|
|
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:
|
|
|
|
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).
|
|
|
|
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.
|
|
|
|
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.
|
|
|
|
/* 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.
|
|
|
|
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/tls-openssl
|
|
|
|
An example of calling send directly after a handshake using
|
|
gnutls. Since it doesn't implement a full record layer, control
|
|
messages are not supported:
|
|
|
|
https://github.com/Mellanox/tls-af_ktls_tool
|