зеркало из https://github.com/github/putty.git
Now that we've got at least some SDCTR modes working (and aes256-ctr is our
default preferred cipher), add code to inject SSH_MSG_IGNOREs to randomise the IV when using CBC-mode ciphers. Each cipher has a flag to indicate whether it needs this workaround, and the SSH packet output maze has gained some extra complexity to implement it. [originally from svn r5659]
This commit is contained in:
Ben Harris
Родитель
b28330fc35
Коммит
f2b0335c48
35
ssh.c
35
ssh.c
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@ -1797,8 +1797,19 @@ static int ssh2_pkt_construct(Ssh ssh, struct Packet *pkt)
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* ssh2_pkt_send() or ssh2_pkt_defer() either go straight to one of
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* these or get queued, and then when the queue is later emptied
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* the packets are all passed to defer_noqueue().
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*
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* When using a CBC-mode cipher, it's necessary to ensure that an
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* attacker can't provide data to be encrypted using an IV that they
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* know. We ensure this by prefixing each packet that might contain
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* user data with an SSH_MSG_IGNORE. This is done using the deferral
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* mechanism, so in this case send_noqueue() ends up redirecting to
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* defer_noqueue(). If you don't like this inefficiency, don't use
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* CBC.
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*/
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static void ssh2_pkt_defer_noqueue(Ssh, struct Packet *, int);
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static void ssh_pkt_defersend(Ssh);
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/*
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* Send an SSH-2 packet immediately, without queuing or deferring.
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*/
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@ -1806,6 +1817,12 @@ static void ssh2_pkt_send_noqueue(Ssh ssh, struct Packet *pkt)
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{
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int len;
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int backlog;
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if (ssh->cscipher != NULL && (ssh->cscipher->flags & SSH_CIPHER_IS_CBC)) {
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/* We need to send two packets, so use the deferral mechanism. */
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ssh2_pkt_defer_noqueue(ssh, pkt, FALSE);
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ssh_pkt_defersend(ssh);
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return;
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}
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len = ssh2_pkt_construct(ssh, pkt);
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backlog = sk_write(ssh->s, (char *)pkt->data, len);
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if (backlog > SSH_MAX_BACKLOG)
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@ -1823,9 +1840,19 @@ static void ssh2_pkt_send_noqueue(Ssh ssh, struct Packet *pkt)
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/*
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* Defer an SSH-2 packet.
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*/
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static void ssh2_pkt_defer_noqueue(Ssh ssh, struct Packet *pkt)
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static void ssh2_pkt_defer_noqueue(Ssh ssh, struct Packet *pkt, int noignore)
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{
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int len = ssh2_pkt_construct(ssh, pkt);
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int len;
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if (ssh->cscipher != NULL && (ssh->cscipher->flags & SSH_CIPHER_IS_CBC) &&
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ssh->deferred_len == 0 && !noignore) {
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/*
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* Interpose an SSH_MSG_IGNORE to ensure that user data don't
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* get encrypted with a known IV.
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*/
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struct Packet *ipkt = ssh2_pkt_init(SSH2_MSG_IGNORE);
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ssh2_pkt_defer_noqueue(ssh, ipkt, TRUE);
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}
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len = ssh2_pkt_construct(ssh, pkt);
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if (ssh->deferred_len + len > ssh->deferred_size) {
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ssh->deferred_size = ssh->deferred_len + len + 128;
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ssh->deferred_send_data = sresize(ssh->deferred_send_data,
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@ -1875,7 +1902,7 @@ static void ssh2_pkt_defer(Ssh ssh, struct Packet *pkt)
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if (ssh->queueing)
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ssh2_pkt_queue(ssh, pkt);
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else
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ssh2_pkt_defer_noqueue(ssh, pkt);
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ssh2_pkt_defer_noqueue(ssh, pkt, FALSE);
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}
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#endif
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@ -1923,7 +1950,7 @@ static void ssh2_pkt_queuesend(Ssh ssh)
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assert(!ssh->queueing);
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for (i = 0; i < ssh->queuelen; i++)
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ssh2_pkt_defer_noqueue(ssh, ssh->queue[i]);
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ssh2_pkt_defer_noqueue(ssh, ssh->queue[i], FALSE);
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ssh->queuelen = 0;
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ssh_pkt_defersend(ssh);
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2
ssh.h
2
ssh.h
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@ -154,6 +154,8 @@ struct ssh2_cipher {
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char *name;
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int blksize;
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int keylen;
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unsigned int flags;
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#define SSH_CIPHER_IS_CBC 1
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char *text_name;
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};
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14
sshaes.c
14
sshaes.c
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@ -1173,49 +1173,49 @@ static const struct ssh2_cipher ssh_aes128_ctr = {
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aes_make_context, aes_free_context, aes_iv, aes128_key,
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aes_ssh2_sdctr, aes_ssh2_sdctr,
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"aes128-ctr",
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16, 128, "AES-128 SDCTR"
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16, 128, 0, "AES-128 SDCTR"
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};
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static const struct ssh2_cipher ssh_aes192_ctr = {
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aes_make_context, aes_free_context, aes_iv, aes192_key,
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aes_ssh2_sdctr, aes_ssh2_sdctr,
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"aes192-ctr",
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16, 192, "AES-192 SDCTR"
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16, 192, 0, "AES-192 SDCTR"
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};
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static const struct ssh2_cipher ssh_aes256_ctr = {
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aes_make_context, aes_free_context, aes_iv, aes256_key,
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aes_ssh2_sdctr, aes_ssh2_sdctr,
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"aes256-ctr",
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16, 256, "AES-256 SDCTR"
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16, 256, 0, "AES-256 SDCTR"
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};
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static const struct ssh2_cipher ssh_aes128 = {
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aes_make_context, aes_free_context, aes_iv, aes128_key,
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aes_ssh2_encrypt_blk, aes_ssh2_decrypt_blk,
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"aes128-cbc",
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16, 128, "AES-128 CBC"
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16, 128, SSH_CIPHER_IS_CBC, "AES-128 CBC"
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};
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static const struct ssh2_cipher ssh_aes192 = {
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aes_make_context, aes_free_context, aes_iv, aes192_key,
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aes_ssh2_encrypt_blk, aes_ssh2_decrypt_blk,
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"aes192-cbc",
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16, 192, "AES-192 CBC"
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16, 192, SSH_CIPHER_IS_CBC, "AES-192 CBC"
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};
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static const struct ssh2_cipher ssh_aes256 = {
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aes_make_context, aes_free_context, aes_iv, aes256_key,
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aes_ssh2_encrypt_blk, aes_ssh2_decrypt_blk,
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"aes256-cbc",
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16, 256, "AES-256 CBC"
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16, 256, SSH_CIPHER_IS_CBC, "AES-256 CBC"
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};
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static const struct ssh2_cipher ssh_rijndael_lysator = {
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aes_make_context, aes_free_context, aes_iv, aes256_key,
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aes_ssh2_encrypt_blk, aes_ssh2_decrypt_blk,
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"rijndael-cbc@lysator.liu.se",
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16, 256, "AES-256 CBC"
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16, 256, SSH_CIPHER_IS_CBC, "AES-256 CBC"
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};
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static const struct ssh2_cipher *const aes_list[] = {
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@ -102,14 +102,14 @@ const struct ssh2_cipher ssh_arcfour128_ssh2 = {
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arcfour_make_context, arcfour_free_context, arcfour_iv, arcfour128_key,
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arcfour_block, arcfour_block,
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"arcfour128-draft-00@putty.projects.tartarus.org",
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1, 128, "Arcfour-128"
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1, 128, 0, "Arcfour-128"
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};
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const struct ssh2_cipher ssh_arcfour256_ssh2 = {
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arcfour_make_context, arcfour_free_context, arcfour_iv, arcfour256_key,
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arcfour_block, arcfour_block,
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"arcfour256-draft-00@putty.projects.tartarus.org",
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1, 256, "Arcfour-256"
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1, 256, 0, "Arcfour-256"
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};
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static const struct ssh2_cipher *const arcfour_list[] = {
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@ -573,7 +573,7 @@ static const struct ssh2_cipher ssh_blowfish_ssh2 = {
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blowfish_make_context, blowfish_free_context, blowfish_iv, blowfish_key,
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blowfish_ssh2_encrypt_blk, blowfish_ssh2_decrypt_blk,
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"blowfish-cbc",
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8, 128, "Blowfish-128 CBC"
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8, 128, SSH_CIPHER_IS_CBC, "Blowfish-128 CBC"
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};
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#ifdef ENABLE_BLOWFISH_SSH2_CTR
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@ -581,7 +581,7 @@ static const struct ssh2_cipher ssh_blowfish_ssh2_ctr = {
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blowfish_make_context, blowfish_free_context, blowfish_iv, blowfish256_key,
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blowfish_ssh2_sdctr, blowfish_ssh2_sdctr,
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"blowfish-ctr",
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8, 256, "Blowfish-256 SDCTR"
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8, 256, 0, "Blowfish-256 SDCTR"
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};
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#endif
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8
sshdes.c
8
sshdes.c
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@ -965,7 +965,7 @@ static const struct ssh2_cipher ssh_3des_ssh2 = {
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des3_make_context, des3_free_context, des3_iv, des3_key,
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des3_ssh2_encrypt_blk, des3_ssh2_decrypt_blk,
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"3des-cbc",
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8, 168, "triple-DES CBC"
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8, 168, SSH_CIPHER_IS_CBC, "triple-DES CBC"
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};
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#ifdef ENABLE_3DES_SSH2_CTR
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@ -973,7 +973,7 @@ static const struct ssh2_cipher ssh_3des_ssh2_ctr = {
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des3_make_context, des3_free_context, des3_iv, des3_key,
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des3_ssh2_sdctr, des3_ssh2_sdctr,
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"3des-ctr",
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8, 168, "triple-DES SDCTR"
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8, 168, 0, "triple-DES SDCTR"
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};
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#endif
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@ -989,14 +989,14 @@ static const struct ssh2_cipher ssh_des_ssh2 = {
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des_make_context, des3_free_context, des3_iv, des_key,
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des_ssh2_encrypt_blk, des_ssh2_decrypt_blk,
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"des-cbc",
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8, 56, "single-DES CBC"
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8, 56, SSH_CIPHER_IS_CBC, "single-DES CBC"
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};
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static const struct ssh2_cipher ssh_des_sshcom_ssh2 = {
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des_make_context, des3_free_context, des3_iv, des_key,
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des_ssh2_encrypt_blk, des_ssh2_decrypt_blk,
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"des-cbc@ssh.com",
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8, 56, "single-DES CBC"
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8, 56, SSH_CIPHER_IS_CBC, "single-DES CBC"
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};
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/*
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