source: filezilla/trunk/fuentes/src/putty/ssharcf.c @ 130

Last change on this file since 130 was 130, checked in by jrpelegrina, 3 years ago

First release to xenial

File size: 2.8 KB
Line 
1/*
2 * Arcfour (RC4) implementation for PuTTY.
3 *
4 * Coded from Schneier.
5 */
6
7#include <assert.h>
8#include "ssh.h"
9
10typedef struct {
11    unsigned char i, j, s[256];
12} ArcfourContext;
13
14static void arcfour_block(void *handle, unsigned char *blk, int len)
15{
16    ArcfourContext *ctx = (ArcfourContext *)handle;
17    unsigned k;
18    unsigned char tmp, i, j, *s;
19
20    s = ctx->s;
21    i = ctx->i; j = ctx->j;
22    for (k = 0; (int)k < len; k++) {
23        i  = (i + 1) & 0xff;
24        j  = (j + s[i]) & 0xff;
25        tmp = s[i]; s[i] = s[j]; s[j] = tmp;
26        blk[k] ^= s[(s[i]+s[j]) & 0xff];
27    }
28    ctx->i = i; ctx->j = j;
29}
30
31static void arcfour_setkey(ArcfourContext *ctx, unsigned char const *key,
32                           unsigned keybytes)
33{
34    unsigned char tmp, k[256], *s;
35    unsigned i, j;
36
37    s = ctx->s;
38    assert(keybytes <= 256);
39    ctx->i = ctx->j = 0;
40    for (i = 0; i < 256; i++) {
41        s[i] = i;
42        k[i] = key[i % keybytes];
43    }
44    j = 0;
45    for (i = 0; i < 256; i++) {
46        j = (j + s[i] + k[i]) & 0xff;
47        tmp = s[i]; s[i] = s[j]; s[j] = tmp;
48    }
49}
50
51/* -- Interface with PuTTY -- */
52
53/*
54 * We don't implement Arcfour in SSH-1 because it's utterly insecure in
55 * several ways.  See CERT Vulnerability Notes VU#25309, VU#665372,
56 * and VU#565052.
57 *
58 * We don't implement the "arcfour" algorithm in SSH-2 because it doesn't
59 * stir the cipher state before emitting keystream, and hence is likely
60 * to leak data about the key.
61 */
62
63static void *arcfour_make_context(void)
64{
65    return snew(ArcfourContext);
66}
67
68static void arcfour_free_context(void *handle)
69{
70    sfree(handle);
71}
72
73static void arcfour_stir(ArcfourContext *ctx)
74{
75    unsigned char *junk = snewn(1536, unsigned char);
76    memset(junk, 0, 1536);
77    arcfour_block(ctx, junk, 1536);
78    smemclr(junk, 1536);
79    sfree(junk);
80}
81
82static void arcfour128_key(void *handle, unsigned char *key)
83{
84    ArcfourContext *ctx = (ArcfourContext *)handle;
85    arcfour_setkey(ctx, key, 16);
86    arcfour_stir(ctx);
87}
88
89static void arcfour256_key(void *handle, unsigned char *key)
90{
91    ArcfourContext *ctx = (ArcfourContext *)handle;
92    arcfour_setkey(ctx, key, 32);
93    arcfour_stir(ctx);
94}
95
96static void arcfour_iv(void *handle, unsigned char *key)
97{
98
99}
100
101const struct ssh2_cipher ssh_arcfour128_ssh2 = {
102    arcfour_make_context, arcfour_free_context, arcfour_iv, arcfour128_key,
103    arcfour_block, arcfour_block, NULL, NULL,
104    "arcfour128",
105    1, 128, 16, 0, "Arcfour-128",
106    NULL
107};
108
109const struct ssh2_cipher ssh_arcfour256_ssh2 = {
110    arcfour_make_context, arcfour_free_context, arcfour_iv, arcfour256_key,
111    arcfour_block, arcfour_block, NULL, NULL,
112    "arcfour256",
113    1, 256, 32, 0, "Arcfour-256",
114    NULL
115};
116
117static const struct ssh2_cipher *const arcfour_list[] = {
118    &ssh_arcfour256_ssh2,
119    &ssh_arcfour128_ssh2,
120};
121
122const struct ssh2_ciphers ssh2_arcfour = {
123    sizeof(arcfour_list) / sizeof(*arcfour_list),
124    arcfour_list
125};
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