nhyatt/putty-source
1
0
Fork 0
mirror of https://git.tartarus.org/simon/putty.git synced 2025-07-06 22:12:47 -05:00
Code Issues Projects Releases Wiki Activity

Allow a cipher to specify encryption of the packet length.

Browse Source 
No cipher uses this facility yet, but one shortly will.
This commit is contained in:
Chris Staite
2015-06-07 12:51:24 +01:00
committed by Simon Tatham
parent 705f159255
commit 5d9a9a7bdf
6 changed files with 37 additions and 17 deletions
Download Patch File Download Diff File Expand all files Collapse all files

20
ssh.c
View File

@ -1649,7 +1649,7 @@ static struct Packet *ssh2_rdpkt(Ssh ssh, const unsigned char **data,
/*
* OpenSSH encrypt-then-MAC mode: the packet length is
* unencrypted.
* unencrypted, unless the cipher supports length encryption.
*/
for (st->i = st->len = 0; st->i < 4; st->i++) {
while ((*datalen) == 0)
@ -1657,7 +1657,16 @@ static struct Packet *ssh2_rdpkt(Ssh ssh, const unsigned char **data,
st->pktin->data[st->i] = *(*data)++;
(*datalen)--;
}
st->len = toint(GET_32BIT(st->pktin->data));
/* Cipher supports length decryption, so do it */
if (ssh->sccipher && (ssh->sccipher->flags & SSH_CIPHER_SEPARATE_LENGTH)) {
/* Keep the packet the same though, so the MAC passes */
unsigned char len[4];
memcpy(len, st->pktin->data, 4);
ssh->sccipher->decrypt_length(ssh->sc_cipher_ctx, len, 4, st->incoming_sequence);
st->len = toint(GET_32BIT(len));
} else {
st->len = toint(GET_32BIT(st->pktin->data));
}
/*
* _Completely_ silly lengths should be stomped on before they
@ -2277,6 +2286,13 @@ static int ssh2_pkt_construct(Ssh ssh, struct Packet *pkt)
for (i = 0; i < padding; i++)
pkt->data[pkt->length + i] = random_byte();
PUT_32BIT(pkt->data, pkt->length + padding - 4);
/* Encrypt length if the scheme requires it */
if (ssh->cscipher && (ssh->cscipher->flags & SSH_CIPHER_SEPARATE_LENGTH)) {
ssh->cscipher->encrypt_length(ssh->cs_cipher_ctx, pkt->data, 4,
ssh->v2_outgoing_sequence);
}
if (ssh->csmac && ssh->csmac_etm) {
/*
* OpenSSH-defined encrypt-then-MAC protocol.