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Diffstat (limited to 'src/protocol/internal/ssh_packet.c')
| -rw-r--r-- | src/protocol/internal/ssh_packet.c | 142 |
1 files changed, 142 insertions, 0 deletions
diff --git a/src/protocol/internal/ssh_packet.c b/src/protocol/internal/ssh_packet.c new file mode 100644 index 0000000..6aad6d9 --- /dev/null +++ b/src/protocol/internal/ssh_packet.c @@ -0,0 +1,142 @@ +/* + * ssh_packet.c: SSH packet maker + * Copyright (C) 2018 Iru Cai <mytbk920423@gmail.com> + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#include "ssh_packet.h" +#include "crc32.h" +#include "ssh_error.h" + +//============================================================================== +// +// SSH1 Packet Structure: +// -------------------------------------------------------------------------- +// | length | padding | type | data | crc32 | +// -------------------------------------------------------------------------- +// | uint32 | 1-7bytes | uchar | | 4bytes| +// -------------------------------------------------------------------------- +// encrypt = padding + type + data + crc32 +// length = type + data + crc32 +// +//============================================================================== +void make_ssh1_packet(buffer *orig_data, buffer *data_to_send, + SSH_CIPHER *cipher) +{ + int len, padding_len; + uint32_t padding[2]; + uint8_t *data = buffer_data(orig_data); + size_t data_len = buffer_len(orig_data); + + len = data_len + 4; //CRC32 + padding_len = 8 - (len % 8); + padding[0] = rand(); + padding[1] = rand(); + + buffer_clear(data_to_send); + buffer_append_be32(data_to_send, len); + buffer_append(data_to_send, (const uint8_t *)padding, padding_len); + buffer_append(data_to_send, data, data_len); + buffer_append_be32(data_to_send, + ssh_crc32(buffer_data(data_to_send) + 4, + buffer_len(data_to_send) - 4)); + + if (cipher->started) { + cipher->crypt(cipher, buffer_data(data_to_send) + 4, + buffer_data(data_to_send) + 4, + buffer_len(data_to_send) - 4); + } +} + +//============================================================================== +// SSH2 Packet Structure: +// uint32 packet_length +// byte padding_length +// byte[n1] payload; n1 = packet_length - padding_length - 1 +// byte[n2] random padding; n2 = padding_length +// byte[m] mac (Message Authentication Code - MAC); m = mac_length +//============================================================================== +int make_ssh2_packet(buffer *orig_data, buffer *data_to_send, + SSH_CIPHER *cipher, SSH_MAC *mac, bool is_mac_, + uint32_t *seq) +{ + // 1. compute the padding length for padding. + int non_padding_len = 4 + 1 + buffer_len(orig_data); + + int padding_block_len = 8; + if (cipher->started && cipher->blkSize > padding_block_len) + padding_block_len = cipher->blkSize; + + int padding_len = + padding_block_len - (non_padding_len % padding_block_len); + if (padding_len < 4) + padding_len += padding_block_len; + + // 2. renew the output buffer. + int total_len = non_padding_len + padding_len; + if (is_mac_) + total_len += mac->dgstSize; + + buffer_clear(data_to_send); + + // 3. Fill the output buffer. + int packet_len = 1 + buffer_len(orig_data) + padding_len; + + buffer_append_be32(data_to_send, packet_len); + buffer_append_byte(data_to_send, padding_len); + buffer_append(data_to_send, buffer_data(orig_data), + buffer_len(orig_data)); + + uint32_t padding[8]; /* padding at most 256 bits */ + for (int i = 0; i < 8; i++) + padding[i] = rand(); + buffer_append(data_to_send, (const uint8_t *)padding, padding_len); + + // 4. Add MAC on the entire unencrypted packet, + // including two length fields, 'payload' and 'random padding'. + if (is_mac_) { + const unsigned char *packet = buffer_data(data_to_send); + int len = buffer_len(data_to_send); + + uint8_t digest[MAX_DGSTLEN]; + + buffer mbuffer; + buffer_init(&mbuffer); + buffer_append_be32(&mbuffer, *seq); + buffer_append(&mbuffer, packet, len); + mac->getmac(mac, buffer_data(&mbuffer), buffer_len(&mbuffer), + digest); + buffer_deinit(&mbuffer); + + buffer_append(data_to_send, digest, mac->dgstSize); + } + + if (cipher->started) { + // as RFC 4253: + // When encryption is in effect, the packet length, padding + // length, payload, and padding fields of each packet MUST be encrypted + // with the given algorithm. + + uint8_t *data = buffer_data(data_to_send); + int len = buffer_len(data_to_send) - mac->dgstSize; + + if (cipher->crypt(cipher, data, data, len) != 1) + return -ECRYPT; + } + + *seq = *seq + 1; + return 0; +} |