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5b30e6f7a6
Similarly to 'utils', I've moved all the stuff in the crypto build-time library into a source directory of its own, and while I'm at it, split up the monolithic sshauxcrypt.c into its various unrelated parts. This is also an opportunity to remove the annoying 'ssh' prefix from the front of the file names, and give several of them less cryptic names.
142 lines
3.5 KiB
C
142 lines
3.5 KiB
C
/*
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* Arcfour (RC4) implementation for PuTTY.
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*
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* Coded from Schneier.
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*/
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#include <assert.h>
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#include "ssh.h"
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typedef struct {
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unsigned char i, j, s[256];
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ssh_cipher ciph;
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} ArcfourContext;
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static void arcfour_block(void *handle, void *vblk, int len)
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{
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unsigned char *blk = (unsigned char *)vblk;
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ArcfourContext *ctx = (ArcfourContext *)handle;
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unsigned k;
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unsigned char tmp, i, j, *s;
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s = ctx->s;
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i = ctx->i; j = ctx->j;
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for (k = 0; (int)k < len; k++) {
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i = (i + 1) & 0xff;
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j = (j + s[i]) & 0xff;
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tmp = s[i]; s[i] = s[j]; s[j] = tmp;
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blk[k] ^= s[(s[i]+s[j]) & 0xff];
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}
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ctx->i = i; ctx->j = j;
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}
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static void arcfour_setkey(ArcfourContext *ctx, unsigned char const *key,
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unsigned keybytes)
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{
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unsigned char tmp, k[256], *s;
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unsigned i, j;
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s = ctx->s;
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assert(keybytes <= 256);
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ctx->i = ctx->j = 0;
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for (i = 0; i < 256; i++) {
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s[i] = i;
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k[i] = key[i % keybytes];
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}
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j = 0;
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for (i = 0; i < 256; i++) {
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j = (j + s[i] + k[i]) & 0xff;
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tmp = s[i]; s[i] = s[j]; s[j] = tmp;
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}
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}
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/* -- Interface with PuTTY -- */
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/*
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* We don't implement Arcfour in SSH-1 because it's utterly insecure in
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* several ways. See CERT Vulnerability Notes VU#25309, VU#665372,
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* and VU#565052.
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*
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* We don't implement the "arcfour" algorithm in SSH-2 because it doesn't
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* stir the cipher state before emitting keystream, and hence is likely
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* to leak data about the key.
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*/
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static ssh_cipher *arcfour_new(const ssh_cipheralg *alg)
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{
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ArcfourContext *ctx = snew(ArcfourContext);
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ctx->ciph.vt = alg;
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return &ctx->ciph;
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}
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static void arcfour_free(ssh_cipher *cipher)
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{
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ArcfourContext *ctx = container_of(cipher, ArcfourContext, ciph);
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smemclr(ctx, sizeof(*ctx));
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sfree(ctx);
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}
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static void arcfour_stir(ArcfourContext *ctx)
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{
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unsigned char *junk = snewn(1536, unsigned char);
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memset(junk, 0, 1536);
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arcfour_block(ctx, junk, 1536);
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smemclr(junk, 1536);
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sfree(junk);
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}
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static void arcfour_ssh2_setiv(ssh_cipher *cipher, const void *key)
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{
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/* As a pure stream cipher, Arcfour has no IV separate from the key */
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}
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static void arcfour_ssh2_setkey(ssh_cipher *cipher, const void *key)
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{
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ArcfourContext *ctx = container_of(cipher, ArcfourContext, ciph);
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arcfour_setkey(ctx, key, ctx->ciph.vt->padded_keybytes);
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arcfour_stir(ctx);
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}
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static void arcfour_ssh2_block(ssh_cipher *cipher, void *blk, int len)
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{
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ArcfourContext *ctx = container_of(cipher, ArcfourContext, ciph);
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arcfour_block(ctx, blk, len);
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}
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const ssh_cipheralg ssh_arcfour128_ssh2 = {
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.new = arcfour_new,
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.free = arcfour_free,
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.setiv = arcfour_ssh2_setiv,
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.setkey = arcfour_ssh2_setkey,
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.encrypt = arcfour_ssh2_block,
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.decrypt = arcfour_ssh2_block,
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.ssh2_id = "arcfour128",
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.blksize = 1,
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.real_keybits = 128,
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.padded_keybytes = 16,
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.flags = 0,
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.text_name = "Arcfour-128",
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};
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const ssh_cipheralg ssh_arcfour256_ssh2 = {
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.new = arcfour_new,
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.free = arcfour_free,
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.setiv = arcfour_ssh2_setiv,
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.setkey = arcfour_ssh2_setkey,
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.encrypt = arcfour_ssh2_block,
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.decrypt = arcfour_ssh2_block,
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.ssh2_id = "arcfour256",
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.blksize = 1,
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.real_keybits = 256,
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.padded_keybytes = 32,
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.flags = 0,
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.text_name = "Arcfour-256",
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};
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static const ssh_cipheralg *const arcfour_list[] = {
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&ssh_arcfour256_ssh2,
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&ssh_arcfour128_ssh2,
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};
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const ssh2_ciphers ssh2_arcfour = { lenof(arcfour_list), arcfour_list };
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