1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
|
// SPDX-License-Identifier: GPL-2.0+
/*
* SSH message parser.
*
* Copyright (C) 2019-2022 Maximilian Luz <luzmaximilian@gmail.com>
*/
#include <linux/unaligned.h>
#include <linux/compiler.h>
#include <linux/device.h>
#include <linux/types.h>
#include <linux/surface_aggregator/serial_hub.h>
#include "ssh_parser.h"
/**
* sshp_validate_crc() - Validate a CRC in raw message data.
* @src: The span of data over which the CRC should be computed.
* @crc: The pointer to the expected u16 CRC value.
*
* Computes the CRC of the provided data span (@src), compares it to the CRC
* stored at the given address (@crc), and returns the result of this
* comparison, i.e. %true if equal. This function is intended to run on raw
* input/message data.
*
* Return: Returns %true if the computed CRC matches the stored CRC, %false
* otherwise.
*/
static bool sshp_validate_crc(const struct ssam_span *src, const u8 *crc)
{
u16 actual = ssh_crc(src->ptr, src->len);
u16 expected = get_unaligned_le16(crc);
return actual == expected;
}
/**
* sshp_starts_with_syn() - Check if the given data starts with SSH SYN bytes.
* @src: The data span to check the start of.
*/
static bool sshp_starts_with_syn(const struct ssam_span *src)
{
return src->len >= 2 && get_unaligned_le16(src->ptr) == SSH_MSG_SYN;
}
/**
* sshp_find_syn() - Find SSH SYN bytes in the given data span.
* @src: The data span to search in.
* @rem: The span (output) indicating the remaining data, starting with SSH
* SYN bytes, if found.
*
* Search for SSH SYN bytes in the given source span. If found, set the @rem
* span to the remaining data, starting with the first SYN bytes and capped by
* the source span length, and return %true. This function does not copy any
* data, but rather only sets pointers to the respective start addresses and
* length values.
*
* If no SSH SYN bytes could be found, set the @rem span to the zero-length
* span at the end of the source span and return %false.
*
* If partial SSH SYN bytes could be found at the end of the source span, set
* the @rem span to cover these partial SYN bytes, capped by the end of the
* source span, and return %false. This function should then be re-run once
* more data is available.
*
* Return: Returns %true if a complete SSH SYN sequence could be found,
* %false otherwise.
*/
bool sshp_find_syn(const struct ssam_span *src, struct ssam_span *rem)
{
size_t i;
for (i = 0; i < src->len - 1; i++) {
if (likely(get_unaligned_le16(src->ptr + i) == SSH_MSG_SYN)) {
rem->ptr = src->ptr + i;
rem->len = src->len - i;
return true;
}
}
if (unlikely(src->ptr[src->len - 1] == (SSH_MSG_SYN & 0xff))) {
rem->ptr = src->ptr + src->len - 1;
rem->len = 1;
return false;
}
rem->ptr = src->ptr + src->len;
rem->len = 0;
return false;
}
/**
* sshp_parse_frame() - Parse SSH frame.
* @dev: The device used for logging.
* @source: The source to parse from.
* @frame: The parsed frame (output).
* @payload: The parsed payload (output).
* @maxlen: The maximum supported message length.
*
* Parses and validates a SSH frame, including its payload, from the given
* source. Sets the provided @frame pointer to the start of the frame and
* writes the limits of the frame payload to the provided @payload span
* pointer.
*
* This function does not copy any data, but rather only validates the message
* data and sets pointers (and length values) to indicate the respective parts.
*
* If no complete SSH frame could be found, the frame pointer will be set to
* the %NULL pointer and the payload span will be set to the null span (start
* pointer %NULL, size zero).
*
* Return: Returns zero on success or if the frame is incomplete, %-ENOMSG if
* the start of the message is invalid, %-EBADMSG if any (frame-header or
* payload) CRC is invalid, or %-EMSGSIZE if the SSH message is bigger than
* the maximum message length specified in the @maxlen parameter.
*/
int sshp_parse_frame(const struct device *dev, const struct ssam_span *source,
struct ssh_frame **frame, struct ssam_span *payload,
size_t maxlen)
{
struct ssam_span sf;
struct ssam_span sp;
/* Initialize output. */
*frame = NULL;
payload->ptr = NULL;
payload->len = 0;
if (!sshp_starts_with_syn(source)) {
dev_warn(dev, "rx: parser: invalid start of frame\n");
return -ENOMSG;
}
/* Check for minimum packet length. */
if (unlikely(source->len < SSH_MESSAGE_LENGTH(0))) {
dev_dbg(dev, "rx: parser: not enough data for frame\n");
return 0;
}
/* Pin down frame. */
sf.ptr = source->ptr + sizeof(u16);
sf.len = sizeof(struct ssh_frame);
/* Validate frame CRC. */
if (unlikely(!sshp_validate_crc(&sf, sf.ptr + sf.len))) {
dev_warn(dev, "rx: parser: invalid frame CRC\n");
return -EBADMSG;
}
/* Ensure packet does not exceed maximum length. */
sp.len = get_unaligned_le16(&((struct ssh_frame *)sf.ptr)->len);
if (unlikely(SSH_MESSAGE_LENGTH(sp.len) > maxlen)) {
dev_warn(dev, "rx: parser: frame too large: %llu bytes\n",
SSH_MESSAGE_LENGTH(sp.len));
return -EMSGSIZE;
}
/* Pin down payload. */
sp.ptr = sf.ptr + sf.len + sizeof(u16);
/* Check for frame + payload length. */
if (source->len < SSH_MESSAGE_LENGTH(sp.len)) {
dev_dbg(dev, "rx: parser: not enough data for payload\n");
return 0;
}
/* Validate payload CRC. */
if (unlikely(!sshp_validate_crc(&sp, sp.ptr + sp.len))) {
dev_warn(dev, "rx: parser: invalid payload CRC\n");
return -EBADMSG;
}
*frame = (struct ssh_frame *)sf.ptr;
*payload = sp;
dev_dbg(dev, "rx: parser: valid frame found (type: %#04x, len: %u)\n",
(*frame)->type, (*frame)->len);
return 0;
}
/**
* sshp_parse_command() - Parse SSH command frame payload.
* @dev: The device used for logging.
* @source: The source to parse from.
* @command: The parsed command (output).
* @command_data: The parsed command data/payload (output).
*
* Parses and validates a SSH command frame payload. Sets the @command pointer
* to the command header and the @command_data span to the command data (i.e.
* payload of the command). This will result in a zero-length span if the
* command does not have any associated data/payload. This function does not
* check the frame-payload-type field, which should be checked by the caller
* before calling this function.
*
* The @source parameter should be the complete frame payload, e.g. returned
* by the sshp_parse_frame() command.
*
* This function does not copy any data, but rather only validates the frame
* payload data and sets pointers (and length values) to indicate the
* respective parts.
*
* Return: Returns zero on success or %-ENOMSG if @source does not represent a
* valid command-type frame payload, i.e. is too short.
*/
int sshp_parse_command(const struct device *dev, const struct ssam_span *source,
struct ssh_command **command,
struct ssam_span *command_data)
{
/* Check for minimum length. */
if (unlikely(source->len < sizeof(struct ssh_command))) {
*command = NULL;
command_data->ptr = NULL;
command_data->len = 0;
dev_err(dev, "rx: parser: command payload is too short\n");
return -ENOMSG;
}
*command = (struct ssh_command *)source->ptr;
command_data->ptr = source->ptr + sizeof(struct ssh_command);
command_data->len = source->len - sizeof(struct ssh_command);
dev_dbg(dev, "rx: parser: valid command found (tc: %#04x, cid: %#04x)\n",
(*command)->tc, (*command)->cid);
return 0;
}
|