- (djm) Big OpenBSD sync:

   - markus@cvs.openbsd.org  2000/09/30 10:27:44
     [log.c]
     allow loglevel debug
   - markus@cvs.openbsd.org  2000/10/03 11:59:57
     [packet.c]
     hmac->mac
   - markus@cvs.openbsd.org  2000/10/03 12:03:03
     [auth-krb4.c auth-passwd.c auth-rh-rsa.c auth-rhosts.c auth-rsa.c auth1.c]
     move fake-auth from auth1.c to individual auth methods, disables s/key in
     debug-msg
   - markus@cvs.openbsd.org  2000/10/03 12:16:48
     ssh.c
     do not resolve canonname, i have no idea why this was added oin ossh
   - markus@cvs.openbsd.org  2000/10/09 15:30:44
     ssh-keygen.1 ssh-keygen.c
     -X now reads private ssh.com DSA keys, too.
   - markus@cvs.openbsd.org  2000/10/09 15:32:34
     auth-options.c
     clear options on every call.
   - markus@cvs.openbsd.org  2000/10/09 15:51:00
     authfd.c authfd.h
     interop with ssh-agent2, from <res@shore.net>
   - markus@cvs.openbsd.org  2000/10/10 14:20:45
     compat.c
     use rexexp for version string matching
   - provos@cvs.openbsd.org  2000/10/10 22:02:18
     [kex.c kex.h myproposal.h ssh.h ssh2.h sshconnect2.c sshd.c dh.c dh.h]
     First rough implementation of the diffie-hellman group exchange.  The
     client can ask the server for bigger groups to perform the diffie-hellman
     in, thus increasing the attack complexity when using ciphers with longer
     keys.  University of Windsor provided network, T the company.
   - markus@cvs.openbsd.org  2000/10/11 13:59:52
     [auth-rsa.c auth2.c]
     clear auth options unless auth sucessfull
   - markus@cvs.openbsd.org  2000/10/11 14:00:27
     [auth-options.h]
     clear auth options unless auth sucessfull
   - markus@cvs.openbsd.org  2000/10/11 14:03:27
     [scp.1 scp.c]
     support 'scp -o' with help from mouring@pconline.com
   - markus@cvs.openbsd.org  2000/10/11 14:11:35
     [dh.c]
     Wall
   - markus@cvs.openbsd.org  2000/10/11 14:14:40
     [auth.h auth2.c readconf.c readconf.h readpass.c servconf.c servconf.h]
     [ssh.h sshconnect2.c sshd_config auth2-skey.c cli.c cli.h]
     add support for s/key (kbd-interactive) to ssh2, based on work by
     mkiernan@avantgo.com and me
   - markus@cvs.openbsd.org  2000/10/11 14:27:24
     [auth.c auth1.c auth2.c authfile.c cipher.c cipher.h kex.c kex.h]
     [myproposal.h packet.c readconf.c session.c ssh.c ssh.h sshconnect1.c]
     [sshconnect2.c sshd.c]
     new cipher framework
   - markus@cvs.openbsd.org  2000/10/11 14:45:21
     [cipher.c]
     remove DES
   - markus@cvs.openbsd.org  2000/10/12 03:59:20
     [cipher.c cipher.h sshconnect1.c sshconnect2.c sshd.c]
     enable DES in SSH-1 clients only
   - markus@cvs.openbsd.org  2000/10/12 08:21:13
     [kex.h packet.c]
     remove unused
   - markus@cvs.openbsd.org  2000/10/13 12:34:46
     [sshd.c]
     Kludge for F-Secure Macintosh < 1.0.2; appro@fy.chalmers.se
   - markus@cvs.openbsd.org  2000/10/13 12:59:15
     [cipher.c cipher.h myproposal.h  rijndael.c rijndael.h]
     rijndael/aes support
   - markus@cvs.openbsd.org  2000/10/13 13:10:54
     [sshd.8]
     more info about -V
   - markus@cvs.openbsd.org  2000/10/13 13:12:02
     [myproposal.h]
     prefer no compression

1 files changed, 396 insertions, 311 deletions

diff --git a/cipher.c b/cipher.c
index c7985a79c..226e4256a 100644
--- a/cipher.c
+++ b/cipher.c
@@ -35,14 +35,91 @@
  */
 
 #include "includes.h"
-RCSID("$OpenBSD: cipher.c,v 1.31 2000/09/12 00:38:32 deraadt Exp $");
+RCSID("$OpenBSD: cipher.c,v 1.35 2000/10/13 18:59:13 markus Exp $");
 
 #include "ssh.h"
-#include "cipher.h"
 #include "xmalloc.h"
 
 #include <openssl/md5.h>
 
+
+/* no encryption */
+void
+none_setkey(CipherContext *cc, const u_char *key, u_int keylen)
+{
+}
+void
+none_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
+{
+}
+void
+none_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
+{
+        memcpy(dest, src, len);
+}
+
+/* DES */
+void
+des_ssh1_setkey(CipherContext *cc, const u_char *key, u_int keylen)
+{
+        static int dowarn = 1;
+        if (dowarn) {
+                error("Warning: use of DES is strongly discouraged "
+                    "due to cryptographic weaknesses");
+                dowarn = 0;
+        }
+        des_set_key((void *)key, cc->u.des.key);
+}
+void
+des_ssh1_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
+{
+        memset(cc->u.des.iv, 0, sizeof(cc->u.des.iv));
+}
+void
+des_ssh1_encrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
+{
+        des_ncbc_encrypt(src, dest, len, cc->u.des.key, &cc->u.des.iv,
+            DES_ENCRYPT);
+}
+void
+des_ssh1_decrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
+{
+        des_ncbc_encrypt(src, dest, len, cc->u.des.key, &cc->u.des.iv,
+            DES_DECRYPT);
+}
+
+/* 3DES */
+void
+des3_setkey(CipherContext *cc, const u_char *key, u_int keylen)
+{
+        des_set_key((void *) key, cc->u.des3.key1);
+        des_set_key((void *) (key+8), cc->u.des3.key2);
+        des_set_key((void *) (key+16), cc->u.des3.key3);
+}
+void
+des3_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
+{
+        memset(cc->u.des3.iv2, 0, sizeof(cc->u.des3.iv2));
+        memset(cc->u.des3.iv3, 0, sizeof(cc->u.des3.iv3));
+        if (iv == NULL)
+                return;
+        memcpy(cc->u.des3.iv3, (char *)iv, 8);
+}
+void
+des3_cbc_encrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
+{
+        des_ede3_cbc_encrypt(src, dest, len,
+            cc->u.des3.key1, cc->u.des3.key2, cc->u.des3.key3,
+            &cc->u.des3.iv3, DES_ENCRYPT);
+}
+void
+des3_cbc_decrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
+{
+        des_ede3_cbc_encrypt(src, dest, len,
+            cc->u.des3.key1, cc->u.des3.key2, cc->u.des3.key3,
+            &cc->u.des3.iv3, DES_DECRYPT);
+}
+
 /*
  * This is used by SSH1:
  *
@@ -58,48 +135,84 @@ RCSID("$OpenBSD: cipher.c,v 1.31 2000/09/12 00:38:32 deraadt Exp $");
  * choosing the X block.
  */
 void
-SSH_3CBC_ENCRYPT(des_key_schedule ks1,
-                 des_key_schedule ks2, des_cblock * iv2,
-                 des_key_schedule ks3, des_cblock * iv3,
-                 unsigned char *dest, unsigned char *src,
-                 unsigned int len)
+des3_ssh1_setkey(CipherContext *cc, const u_char *key, u_int keylen)
+{
+        des_set_key((void *) key, cc->u.des3.key1);
+        des_set_key((void *) (key+8), cc->u.des3.key2);
+        if (keylen <= 16)
+                des_set_key((void *) key, cc->u.des3.key3);
+        else
+                des_set_key((void *) (key+16), cc->u.des3.key3);
+}
+void
+des3_ssh1_encrypt(CipherContext *cc, u_char *dest, const u_char *src,
+    u_int len)
 {
         des_cblock iv1;
+        des_cblock *iv2 = &cc->u.des3.iv2;
+        des_cblock *iv3 = &cc->u.des3.iv3;
 
         memcpy(&iv1, iv2, 8);
 
-        des_cbc_encrypt(src, dest, len, ks1, &iv1, DES_ENCRYPT);
+        des_cbc_encrypt(src, dest, len, cc->u.des3.key1, &iv1, DES_ENCRYPT);
         memcpy(&iv1, dest + len - 8, 8);
 
-        des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_DECRYPT);
+        des_cbc_encrypt(dest, dest, len, cc->u.des3.key2, iv2, DES_DECRYPT);
         memcpy(iv2, &iv1, 8);   /* Note how iv1 == iv2 on entry and exit. */
 
-        des_cbc_encrypt(dest, dest, len, ks3, iv3, DES_ENCRYPT);
+        des_cbc_encrypt(dest, dest, len, cc->u.des3.key3, iv3, DES_ENCRYPT);
         memcpy(iv3, dest + len - 8, 8);
 }
-
 void
-SSH_3CBC_DECRYPT(des_key_schedule ks1,
-                 des_key_schedule ks2, des_cblock * iv2,
-                 des_key_schedule ks3, des_cblock * iv3,
-                 unsigned char *dest, unsigned char *src,
-                 unsigned int len)
+des3_ssh1_decrypt(CipherContext *cc, u_char *dest, const u_char *src,
+    u_int len)
 {
         des_cblock iv1;
+        des_cblock *iv2 = &cc->u.des3.iv2;
+        des_cblock *iv3 = &cc->u.des3.iv3;
 
         memcpy(&iv1, iv2, 8);
 
-        des_cbc_encrypt(src, dest, len, ks3, iv3, DES_DECRYPT);
+        des_cbc_encrypt(src, dest, len, cc->u.des3.key3, iv3, DES_DECRYPT);
         memcpy(iv3, src + len - 8, 8);
 
-        des_cbc_encrypt(dest, dest, len, ks2, iv2, DES_ENCRYPT);
+        des_cbc_encrypt(dest, dest, len, cc->u.des3.key2, iv2, DES_ENCRYPT);
         memcpy(iv2, dest + len - 8, 8);
 
-        des_cbc_encrypt(dest, dest, len, ks1, &iv1, DES_DECRYPT);
+        des_cbc_encrypt(dest, dest, len, cc->u.des3.key1, &iv1, DES_DECRYPT);
         /* memcpy(&iv1, iv2, 8); */
         /* Note how iv1 == iv2 on entry and exit. */
 }
 
+/* Blowfish */
+void
+blowfish_setkey(CipherContext *cc, const u_char *key, u_int keylen)
+{
+        BF_set_key(&cc->u.bf.key, keylen, (unsigned char *)key);
+}
+void
+blowfish_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
+{
+        if (iv == NULL)
+                memset(cc->u.bf.iv, 0, 8);
+        else
+                memcpy(cc->u.bf.iv, (char *)iv, 8);
+}
+void
+blowfish_cbc_encrypt(CipherContext *cc, u_char *dest, const u_char *src,
+     u_int len)
+{
+        BF_cbc_encrypt((void *)src, dest, len, &cc->u.bf.key, cc->u.bf.iv,
+            BF_ENCRYPT);
+}
+void
+blowfish_cbc_decrypt(CipherContext *cc, u_char *dest, const u_char *src,
+     u_int len)
+{
+        BF_cbc_encrypt((void *)src, dest, len, &cc->u.bf.key, cc->u.bf.iv,
+            BF_DECRYPT);
+}
+
 /*
  * SSH1 uses a variation on Blowfish, all bytes must be swapped before
  * and after encryption/decryption. Thus the swap_bytes stuff (yuk).
@@ -130,88 +243,255 @@ swap_bytes(const unsigned char *src, unsigned char *dst_, int n)
         }
 }
 
-/*
- * Names of all encryption algorithms.
- * These must match the numbers defined in cipher.h.
- */
-static char *cipher_names[] =
-{
-        "none",
-        "idea",
-        "des",
-        "3des",
-        "tss",
-        "rc4",          /* Alleged RC4 */
-        "blowfish",
-        "reserved",
-        "blowfish-cbc",
-        "3des-cbc",
-        "arcfour",
-        "cast128-cbc"
-};
+void
+blowfish_ssh1_encrypt(CipherContext *cc, u_char *dest, const u_char *src,
+    u_int len)
+{
+        swap_bytes(src, dest, len);
+        BF_cbc_encrypt((void *)dest, dest, len, &cc->u.bf.key, cc->u.bf.iv,
+            BF_ENCRYPT);
+        swap_bytes(dest, dest, len);
+}
+void
+blowfish_ssh1_decrypt(CipherContext *cc, u_char *dest, const u_char *src,
+    u_int len)
+{
+        swap_bytes(src, dest, len);
+        BF_cbc_encrypt((void *)dest, dest, len, &cc->u.bf.key, cc->u.bf.iv,
+            BF_DECRYPT);
+        swap_bytes(dest, dest, len);
+}
 
-/*
- * Returns a bit mask indicating which ciphers are supported by this
- * implementation.  The bit mask has the corresponding bit set of each
- * supported cipher.
- */
+/* alleged rc4 */
+void
+arcfour_setkey(CipherContext *cc, const u_char *key, u_int keylen)
+{
+        RC4_set_key(&cc->u.rc4, keylen, (u_char *)key);
+}
+void
+arcfour_crypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
+{
+        RC4(&cc->u.rc4, len, (u_char *)src, dest);
+}
 
-unsigned int
-cipher_mask1()
+/* CAST */
+void
+cast_setkey(CipherContext *cc, const u_char *key, u_int keylen)
 {
-        unsigned int mask = 0;
-        mask |= 1 << SSH_CIPHER_3DES;           /* Mandatory */
-        mask |= 1 << SSH_CIPHER_BLOWFISH;
-        return mask;
+        CAST_set_key(&cc->u.cast.key, keylen, (unsigned char *) key);
+}
+void
+cast_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
+{
+        if (iv == NULL) 
+                fatal("no IV for %s.", cc->cipher->name);
+        memcpy(cc->u.cast.iv, (char *)iv, 8);
+}
+void
+cast_cbc_encrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
+{
+        CAST_cbc_encrypt(src, dest, len, &cc->u.cast.key, cc->u.cast.iv,
+            CAST_ENCRYPT);
+}
+void
+cast_cbc_decrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
+{
+        CAST_cbc_encrypt(src, dest, len, &cc->u.cast.key, cc->u.cast.iv,
+            CAST_DECRYPT);
+}
+
+/* RIJNDAEL */
+
+#define RIJNDAEL_BLOCKSIZE 16
+void
+rijndael_setkey(CipherContext *cc, const u_char *key, u_int keylen)
+{
+        rijndael_set_key(&cc->u.rijndael.enc, (u4byte *)key, 8*keylen, 1);
+        rijndael_set_key(&cc->u.rijndael.dec, (u4byte *)key, 8*keylen, 0);
+}
+void
+rijndael_setiv(CipherContext *cc, const u_char *iv, u_int ivlen)
+{
+        if (iv == NULL) 
+                fatal("no IV for %s.", cc->cipher->name);
+        memcpy((u_char *)cc->u.rijndael.iv, iv, RIJNDAEL_BLOCKSIZE);
 }
+void
+rijndael_cbc_encrypt(CipherContext *cc, u_char *dest, const u_char *src,
+    u_int len)
+{
+        rijndael_ctx *ctx = &cc->u.rijndael.enc;
+        u4byte *iv = cc->u.rijndael.iv;
+        u4byte in[4];
+        u4byte *cprev, *cnow, *plain;
+        int i, blocks = len / RIJNDAEL_BLOCKSIZE;
+        if (len == 0)
+                return;
+        if (len % RIJNDAEL_BLOCKSIZE)
+                fatal("rijndael_cbc_encrypt: bad len %d", len);
+        cnow  = (u4byte*) dest;
+        plain = (u4byte*) src;
+        cprev = iv;
+        for(i = 0; i < blocks; i++, plain+=4, cnow+=4) {
+                in[0] = plain[0] ^ cprev[0];
+                in[1] = plain[1] ^ cprev[1];
+                in[2] = plain[2] ^ cprev[2];
+                in[3] = plain[3] ^ cprev[3];
+                rijndael_encrypt(ctx, in, cnow);
+                cprev = cnow;
+        }
+        memcpy(iv, cprev, RIJNDAEL_BLOCKSIZE);
+}
+
+void
+rijndael_cbc_decrypt(CipherContext *cc, u_char *dest, const u_char *src,
+    u_int len)
+{
+        rijndael_ctx *ctx = &cc->u.rijndael.dec;
+        u4byte *iv = cc->u.rijndael.iv;
+        u4byte ivsaved[4];
+        u4byte *cnow =  (u4byte*) (src+len-RIJNDAEL_BLOCKSIZE);
+        u4byte *plain = (u4byte*) (dest+len-RIJNDAEL_BLOCKSIZE);
+        u4byte *ivp;
+        int i, blocks = len / RIJNDAEL_BLOCKSIZE;
+        if (len == 0)
+                return;
+        if (len % RIJNDAEL_BLOCKSIZE)
+                fatal("rijndael_cbc_decrypt: bad len %d", len);
+        memcpy(ivsaved, cnow, RIJNDAEL_BLOCKSIZE);
+        for(i = blocks; i > 0; i--, cnow-=4, plain-=4) {
+                rijndael_decrypt(ctx, cnow, plain);
+                ivp =  (i == 1) ? iv : cnow-4;
+                plain[0] ^= ivp[0];
+                plain[1] ^= ivp[1];
+                plain[2] ^= ivp[2];
+                plain[3] ^= ivp[3];
+        }
+        memcpy(iv, ivsaved, RIJNDAEL_BLOCKSIZE);
+}
+
+Cipher ciphers[] = {
+        { "none",
+                SSH_CIPHER_NONE, 8, 0,
+                none_setkey, none_setiv,
+                none_crypt, none_crypt },
+        { "des",
+                SSH_CIPHER_DES, 8, 8,
+                des_ssh1_setkey, des_ssh1_setiv,
+                des_ssh1_encrypt, des_ssh1_decrypt },
+        { "3des",
+                SSH_CIPHER_3DES, 8, 16,
+                des3_ssh1_setkey, des3_setiv,
+                des3_ssh1_encrypt, des3_ssh1_decrypt },
+        { "blowfish",
+                SSH_CIPHER_BLOWFISH, 8, 16,
+                blowfish_setkey, blowfish_setiv,
+                blowfish_ssh1_encrypt, blowfish_ssh1_decrypt },
+
+        { "3des-cbc",
+                SSH_CIPHER_SSH2, 8, 24,
+                des3_setkey, des3_setiv,
+                des3_cbc_encrypt, des3_cbc_decrypt },
+        { "blowfish-cbc",
+                SSH_CIPHER_SSH2, 8, 16,
+                blowfish_setkey, blowfish_setiv,
+                blowfish_cbc_encrypt, blowfish_cbc_decrypt },
+        { "cast128-cbc",
+                SSH_CIPHER_SSH2, 8, 16,
+                cast_setkey, cast_setiv,
+                cast_cbc_encrypt, cast_cbc_decrypt },
+        { "arcfour",
+                SSH_CIPHER_SSH2, 8, 16,
+                arcfour_setkey, none_setiv,
+                arcfour_crypt, arcfour_crypt },
+        { "aes128-cbc",
+                SSH_CIPHER_SSH2, 16, 16,
+                rijndael_setkey, rijndael_setiv,
+                rijndael_cbc_encrypt, rijndael_cbc_decrypt },
+        { "aes192-cbc",
+                SSH_CIPHER_SSH2, 16, 24,
+                rijndael_setkey, rijndael_setiv,
+                rijndael_cbc_encrypt, rijndael_cbc_decrypt },
+        { "aes256-cbc",
+                SSH_CIPHER_SSH2, 16, 32,
+                rijndael_setkey, rijndael_setiv,
+                rijndael_cbc_encrypt, rijndael_cbc_decrypt },
+        { "rijndael128-cbc",
+                SSH_CIPHER_SSH2, 16, 16,
+                rijndael_setkey, rijndael_setiv,
+                rijndael_cbc_encrypt, rijndael_cbc_decrypt },
+        { "rijndael192-cbc",
+                SSH_CIPHER_SSH2, 16, 24,
+                rijndael_setkey, rijndael_setiv,
+                rijndael_cbc_encrypt, rijndael_cbc_decrypt },
+        { "rijndael256-cbc",
+                SSH_CIPHER_SSH2, 16, 32,
+                rijndael_setkey, rijndael_setiv,
+                rijndael_cbc_encrypt, rijndael_cbc_decrypt },
+        { "rijndael-cbc@lysator.liu.se",
+                SSH_CIPHER_SSH2, 16, 32,
+                rijndael_setkey, rijndael_setiv,
+                rijndael_cbc_encrypt, rijndael_cbc_decrypt },
+        { NULL, SSH_CIPHER_ILLEGAL, 0, 0, NULL, NULL, NULL, NULL }
+};
+
+/*--*/
+
 unsigned int
-cipher_mask2()
+cipher_mask_ssh1(int client)
 {
         unsigned int mask = 0;
-        mask |= 1 << SSH_CIPHER_BLOWFISH_CBC;
-        mask |= 1 << SSH_CIPHER_3DES_CBC;
-        mask |= 1 << SSH_CIPHER_ARCFOUR;
-        mask |= 1 << SSH_CIPHER_CAST128_CBC;
+        mask |= 1 << SSH_CIPHER_3DES;           /* Mandatory */
+        mask |= 1 << SSH_CIPHER_BLOWFISH;
+        if (client) {
+                mask |= 1 << SSH_CIPHER_DES;
+        }
         return mask;
 }
-unsigned int
-cipher_mask()
+
+Cipher *
+cipher_by_name(const char *name)
 {
-        return cipher_mask1() | cipher_mask2();
+        Cipher *c;
+        for (c = ciphers; c->name != NULL; c++)
+                if (strcasecmp(c->name, name) == 0)
+                        return c;
+        return NULL;
 }
 
-/* Returns the name of the cipher. */
-
-const char *
-cipher_name(int cipher)
+Cipher *
+cipher_by_number(int id)
 {
-        if (cipher < 0 || cipher >= sizeof(cipher_names) / sizeof(cipher_names[0]) ||
-            cipher_names[cipher] == NULL)
-                fatal("cipher_name: bad cipher name: %d", cipher);
-        return cipher_names[cipher];
+        Cipher *c;
+        for (c = ciphers; c->name != NULL; c++)
+                if (c->number == id)
+                        return c;
+        return NULL;
 }
 
-/* Returns 1 if the name of the ciphers are valid. */
-
 #define CIPHER_SEP      ","
 int
 ciphers_valid(const char *names)
 {
+        Cipher *c;
         char *ciphers, *cp;
         char *p;
-        int i;
 
         if (names == NULL || strcmp(names, "") == 0)
                 return 0;
         ciphers = cp = xstrdup(names);
-        for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0'; 
+        for ((p = strsep(&cp, CIPHER_SEP)); p && *p != '\0';
              (p = strsep(&cp, CIPHER_SEP))) {
-                i = cipher_number(p);
-                if (i == -1 || !(cipher_mask2() & (1 << i))) {
+                c = cipher_by_name(p);
+                if (c == NULL || c->number != SSH_CIPHER_SSH2) {
+                        debug("bad cipher %s [%s]", p, names);
                         xfree(ciphers);
                         return 0;
+                } else {
+                        debug("cipher ok: %s [%s]", p, names);
                 }
         }
+        debug("ciphers ok: [%s]", names);
         xfree(ciphers);
         return 1;
 }
@@ -224,14 +504,49 @@ ciphers_valid(const char *names)
 int
 cipher_number(const char *name)
 {
-        int i;
+        Cipher *c;
         if (name == NULL)
                 return -1;
-        for (i = 0; i < sizeof(cipher_names) / sizeof(cipher_names[0]); i++)
-                if (strcmp(cipher_names[i], name) == 0 &&
-                    (cipher_mask() & (1 << i)))
-                        return i;
-        return -1;
+        c = cipher_by_name(name);
+        return (c==NULL) ? -1 : c->number;
+}
+
+char *
+cipher_name(int id)
+{
+        Cipher *c = cipher_by_number(id);
+        return (c==NULL) ? "<unknown>" : c->name;
+}
+
+void
+cipher_init(CipherContext *cc, Cipher *cipher,
+    const u_char *key, u_int keylen, const u_char *iv, u_int ivlen)
+{
+        if (keylen < cipher->key_len)
+                fatal("cipher_init: key length %d is insufficient for %s.",
+                    keylen, cipher->name);
+        if (iv != NULL && ivlen < cipher->block_size)
+                fatal("cipher_init: iv length %d is insufficient for %s.",
+                    ivlen, cipher->name);
+        cc->cipher = cipher;
+        cipher->setkey(cc, key, keylen);
+        cipher->setiv(cc, iv, ivlen);
+}
+
+void
+cipher_encrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
+{
+        if (len % cc->cipher->block_size)
+                fatal("cipher_encrypt: bad plaintext length %d", len);
+        cc->cipher->encrypt(cc, dest, src, len);
+}
+
+void
+cipher_decrypt(CipherContext *cc, u_char *dest, const u_char *src, u_int len)
+{
+        if (len % cc->cipher->block_size)
+                fatal("cipher_decrypt: bad ciphertext length %d", len);
+        cc->cipher->decrypt(cc, dest, src, len);
 }
 
 /*
@@ -240,248 +555,18 @@ cipher_number(const char *name)
  */
 
 void
-cipher_set_key_string(CipherContext *context, int cipher, const char *passphrase)
+cipher_set_key_string(CipherContext *cc, Cipher *cipher,
+    const char *passphrase)
 {
         MD5_CTX md;
         unsigned char digest[16];
 
         MD5_Init(&md);
-        MD5_Update(&md, (const unsigned char *) passphrase, strlen(passphrase));
+        MD5_Update(&md, (const u_char *)passphrase, strlen(passphrase));
         MD5_Final(digest, &md);
 
-        cipher_set_key(context, cipher, digest, 16);
+        cipher_init(cc, cipher, digest, 16, NULL, 0);
 
         memset(digest, 0, sizeof(digest));
         memset(&md, 0, sizeof(md));
 }
-
-/* Selects the cipher to use and sets the key. */
-
-void
-cipher_set_key(CipherContext *context, int cipher, const unsigned char *key,
-    int keylen)
-{
-        unsigned char padded[32];
-
-        /* Set cipher type. */
-        context->type = cipher;
-
-        /* Get 32 bytes of key data.  Pad if necessary.  (So that code
-           below does not need to worry about key size). */
-        memset(padded, 0, sizeof(padded));
-        memcpy(padded, key, keylen < sizeof(padded) ? keylen : sizeof(padded));
-
-        /* Initialize the initialization vector. */
-        switch (cipher) {
-        case SSH_CIPHER_NONE:
-                /*
-                 * Has to stay for authfile saving of private key with no
-                 * passphrase
-                 */
-                break;
-
-        case SSH_CIPHER_3DES:
-                /*
-                 * Note: the least significant bit of each byte of key is
-                 * parity, and must be ignored by the implementation.  16
-                 * bytes of key are used (first and last keys are the same).
-                 */
-                if (keylen < 16)
-                        error("Key length %d is insufficient for 3DES.", keylen);
-                des_set_key((void *) padded, context->u.des3.key1);
-                des_set_key((void *) (padded + 8), context->u.des3.key2);
-                if (keylen <= 16)
-                        des_set_key((void *) padded, context->u.des3.key3);
-                else
-                        des_set_key((void *) (padded + 16), context->u.des3.key3);
-                memset(context->u.des3.iv2, 0, sizeof(context->u.des3.iv2));
-                memset(context->u.des3.iv3, 0, sizeof(context->u.des3.iv3));
-                break;
-
-        case SSH_CIPHER_BLOWFISH:
-                if (keylen < 16)
-                        error("Key length %d is insufficient for blowfish.", keylen);
-                BF_set_key(&context->u.bf.key, keylen, padded);
-                memset(context->u.bf.iv, 0, 8);
-                break;
-
-        case SSH_CIPHER_3DES_CBC:
-        case SSH_CIPHER_BLOWFISH_CBC:
-        case SSH_CIPHER_ARCFOUR:
-        case SSH_CIPHER_CAST128_CBC:
-                fatal("cipher_set_key: illegal cipher: %s", cipher_name(cipher));
-                break;
-
-        default:
-                fatal("cipher_set_key: unknown cipher: %s", cipher_name(cipher));
-        }
-        memset(padded, 0, sizeof(padded));
-}
-
-void
-cipher_set_key_iv(CipherContext * context, int cipher,
-    const unsigned char *key, int keylen,
-    const unsigned char *iv, int ivlen)
-{
-        /* Set cipher type. */
-        context->type = cipher;
-
-        /* Initialize the initialization vector. */
-        switch (cipher) {
-        case SSH_CIPHER_NONE:
-                break;
-
-        case SSH_CIPHER_3DES:
-        case SSH_CIPHER_BLOWFISH:
-                fatal("cipher_set_key_iv: illegal cipher: %s", cipher_name(cipher));
-                break;
-
-        case SSH_CIPHER_3DES_CBC:
-                if (keylen < 24)
-                        error("Key length %d is insufficient for 3des-cbc.", keylen);
-                des_set_key((void *) key, context->u.des3.key1);
-                des_set_key((void *) (key+8), context->u.des3.key2);
-                des_set_key((void *) (key+16), context->u.des3.key3);
-                if (ivlen < 8)
-                        error("IV length %d is insufficient for 3des-cbc.", ivlen);
-                memcpy(context->u.des3.iv3, (char *)iv, 8);
-                break;
-
-        case SSH_CIPHER_BLOWFISH_CBC:
-                if (keylen < 16)
-                        error("Key length %d is insufficient for blowfish.", keylen);
-                if (ivlen < 8)
-                        error("IV length %d is insufficient for blowfish.", ivlen);
-                BF_set_key(&context->u.bf.key, keylen, (unsigned char *)key);
-                memcpy(context->u.bf.iv, (char *)iv, 8);
-                break;
-
-        case SSH_CIPHER_ARCFOUR:
-                if (keylen < 16)
-                        error("Key length %d is insufficient for arcfour.", keylen);
-                RC4_set_key(&context->u.rc4, keylen, (unsigned char *)key);
-                break;
-
-        case SSH_CIPHER_CAST128_CBC:
-                if (keylen < 16)
-                        error("Key length %d is insufficient for cast128.", keylen);
-                if (ivlen < 8)
-                        error("IV length %d is insufficient for cast128.", ivlen);
-                CAST_set_key(&context->u.cast.key, keylen, (unsigned char *) key);
-                memcpy(context->u.cast.iv, (char *)iv, 8);
-                break;
-
-        default:
-                fatal("cipher_set_key: unknown cipher: %s", cipher_name(cipher));
-        }
-}
-
-/* Encrypts data using the cipher. */
-
-void
-cipher_encrypt(CipherContext *context, unsigned char *dest,
-               const unsigned char *src, unsigned int len)
-{
-        if ((len & 7) != 0)
-                fatal("cipher_encrypt: bad plaintext length %d", len);
-
-        switch (context->type) {
-        case SSH_CIPHER_NONE:
-                memcpy(dest, src, len);
-                break;
-
-        case SSH_CIPHER_3DES:
-                SSH_3CBC_ENCRYPT(context->u.des3.key1,
-                                 context->u.des3.key2, &context->u.des3.iv2,
-                                 context->u.des3.key3, &context->u.des3.iv3,
-                                 dest, (unsigned char *) src, len);
-                break;
-
-        case SSH_CIPHER_BLOWFISH:
-                swap_bytes(src, dest, len);
-                BF_cbc_encrypt(dest, dest, len,
-                               &context->u.bf.key, context->u.bf.iv,
-                               BF_ENCRYPT);
-                swap_bytes(dest, dest, len);
-                break;
-
-        case SSH_CIPHER_BLOWFISH_CBC:
-                BF_cbc_encrypt((void *)src, dest, len,
-                               &context->u.bf.key, context->u.bf.iv,
-                               BF_ENCRYPT);
-                break;
-
-        case SSH_CIPHER_3DES_CBC:
-                des_ede3_cbc_encrypt(src, dest, len,
-                    context->u.des3.key1, context->u.des3.key2,
-                    context->u.des3.key3, &context->u.des3.iv3, DES_ENCRYPT);
-                break;
-
-        case SSH_CIPHER_ARCFOUR:
-                RC4(&context->u.rc4, len, (unsigned char *)src, dest);
-                break;
-
-        case SSH_CIPHER_CAST128_CBC:
-                CAST_cbc_encrypt(src, dest, len,
-                    &context->u.cast.key, context->u.cast.iv, CAST_ENCRYPT);
-                break;
-
-        default:
-                fatal("cipher_encrypt: unknown cipher: %s", cipher_name(context->type));
-        }
-}
-
-/* Decrypts data using the cipher. */
-
-void
-cipher_decrypt(CipherContext *context, unsigned char *dest,
-               const unsigned char *src, unsigned int len)
-{
-        if ((len & 7) != 0)
-                fatal("cipher_decrypt: bad ciphertext length %d", len);
-
-        switch (context->type) {
-        case SSH_CIPHER_NONE:
-                memcpy(dest, src, len);
-                break;
-
-        case SSH_CIPHER_3DES:
-                SSH_3CBC_DECRYPT(context->u.des3.key1,
-                                 context->u.des3.key2, &context->u.des3.iv2,
-                                 context->u.des3.key3, &context->u.des3.iv3,
-                                 dest, (unsigned char *) src, len);
-                break;
-
-        case SSH_CIPHER_BLOWFISH:
-                swap_bytes(src, dest, len);
-                BF_cbc_encrypt((void *) dest, dest, len,
-                               &context->u.bf.key, context->u.bf.iv,
-                               BF_DECRYPT);
-                swap_bytes(dest, dest, len);
-                break;
-
-        case SSH_CIPHER_BLOWFISH_CBC:
-                BF_cbc_encrypt((void *) src, dest, len,
-                               &context->u.bf.key, context->u.bf.iv,
-                               BF_DECRYPT);
-                break;
-
-        case SSH_CIPHER_3DES_CBC:
-                des_ede3_cbc_encrypt(src, dest, len,
-                    context->u.des3.key1, context->u.des3.key2,
-                    context->u.des3.key3, &context->u.des3.iv3, DES_DECRYPT);
-                break;
-
-        case SSH_CIPHER_ARCFOUR:
-                RC4(&context->u.rc4, len, (unsigned char *)src, dest);
-                break;
-
-        case SSH_CIPHER_CAST128_CBC:
-                CAST_cbc_encrypt(src, dest, len,
-                    &context->u.cast.key, context->u.cast.iv, CAST_DECRYPT);
-                break;
-
-        default:
-                fatal("cipher_decrypt: unknown cipher: %s", cipher_name(context->type));
-        }
-}