#include "wget.h"
#include "gen-md5.h"
+#include "ftp.h"
-/* Dictionary for integer-word translations. */
-static char Wp[2048][4] = {
+/* Dictionary for integer-word translations. Available in appendix D
+ of rfc2289. */
+ static char Wp[2048][4] = {
{ 'A', '\0', '\0', '\0' },
{ 'A', 'B', 'E', '\0' },
{ 'A', 'C', 'E', '\0' },
};
/* Extract LENGTH bits from the char array S starting with bit number
- START. */
-static unsigned long
-extract (const char *s, int start, int length)
+ START. It always reads three consecutive octects, which means it
+ can read past end of data when START is at the edge of the region. */
+
+static uint32_t
+extract (const unsigned char *s, int start, int length)
{
unsigned char cl = s[start / 8];
unsigned char cc = s[start / 8 + 1];
unsigned char cr = s[start / 8 + 2];
- unsigned long x = ((long)(cl << 8 | cc) << 8 | cr);
-
- x = x >> (24 - (length + (start % 8)));
- x = (x & (0xffff >> (16 - length)));
+ uint32_t x;
+ x = (uint32_t)(cl << 8 | cc) << 8 | cr;
+ x >>= 24 - (length + (start % 8));
+ x &= (0xffff >> (16 - length));
return x;
}
-#define STRLEN4(s) (!*(s) ? 0 : \
- (!*(s + 1) ? 1 : \
- (!*(s + 2) ? 2 : \
- (!*(s + 3) ? 3 : 4))))
+/* Length of a string known to be at least 1 and at most 4 chars
+ long. */
+
+#define STRLEN_1_4(s) (!(s)[1] ? 1 : !(s)[2] ? 2 : !(s)[3] ? 3 : 4)
/* Encode 8 bytes in C as a string of English words and store them to
STORE. Returns STORE. */
+
static char *
-btoe (char *store, const char *c)
+btoe (char *store, const unsigned char *c)
{
- char cp[10]; /* add in room for the parity 2 bits +
+ unsigned char cp[10]; /* add in room for the parity 2 bits +
extract() slop. */
int p, i;
- char *ostore = store;
+ char *store_beg = store;
*store = '\0';
+
/* Workaround for extract() reads beyond end of data */
xzero (cp);
memcpy (cp, c, 8);
- /* Compute parity. */
+
+ /* Compute parity and append it to CP. */
for (p = 0, i = 0; i < 64; i += 2)
p += extract (cp, i, 2);
-
cp[8] = (char)p << 6;
+
+ /* The 64 bits of input and the two parity bits comprise 66 bits of
+ data that are now in CP. We convert that information, 11 bits at
+ a time, to English words indexed from Wp. Since there are 2048
+ (2^11) words in Wp, every 11-bit combination corresponds to a
+ distinct word. */
memcpy (store, &Wp[extract (cp, 0, 11)][0], 4);
- store += STRLEN4 (store);
+ store += STRLEN_1_4 (store);
*store++ = ' ';
memcpy (store, &Wp[extract (cp, 11, 11)][0], 4);
- store += STRLEN4 (store);
+ store += STRLEN_1_4 (store);
*store++ = ' ';
memcpy (store, &Wp[extract (cp, 22, 11)][0], 4);
- store += STRLEN4 (store);
+ store += STRLEN_1_4 (store);
*store++ = ' ';
memcpy (store, &Wp[extract (cp, 33, 11)][0], 4);
- store += STRLEN4 (store);
+ store += STRLEN_1_4 (store);
*store++ = ' ';
memcpy (store, &Wp[extract (cp, 44, 11)][0], 4);
- store += STRLEN4 (store);
+ store += STRLEN_1_4 (store);
*store++ = ' ';
memcpy (store, &Wp[extract (cp, 55, 11)][0], 4);
+ store[4] = '\0'; /* make sure the string is terminated */
- store[4] = '\0'; /* make sure the string is zero-terminated */
+ DEBUGP (("wrote `%s' to STORE\n", store_beg));
+ return store_beg;
+}
- DEBUGP (("store is `%s'\n", ostore));
+/* Calculate the MD5 checksum of SRC in one step. The MD5 context
+ must be declared as md5_ctx. */
+#define DO_MD5(src, len, dest) do { \
+ gen_md5_init (md5_ctx); \
+ gen_md5_update ((unsigned char *) (src), (len), md5_ctx); \
+ gen_md5_finish (md5_ctx, (unsigned char *) (dest)); \
+} while (0)
- return ostore;
-}
+/* Calculate the SKEY response, based on the sequence, seed
+ (challenge), and the secret password. The calculated response is
+ used instead of the real password when logging in to SKEY-enabled
+ servers.
+
+ The result is calculated like this:
+
+ + Concatenate SEED and PASS and calculate the 16-byte MD5 checksum.
+
+ + Shorten the checksum to eight bytes by folding the second eight
+ bytes onto the first eight using XOR. The resulting eight-byte
+ sequence is the key.
+
+ + MD5-process the key, fold the checksum to eight bytes and store
+ it back to the key. Repeat this crunching SEQUENCE times.
+ (Sequence is a number that gets decremented every time the user
+ logs in to the server. Therefore an eavesdropper would have to
+ invert the hash function in order to guess the next one-time
+ password.)
+
+ + Convert the resulting 64-bit key to 6 English words separated by
+ spaces (see btoe for details) and return the resulting ASCII
+ string.
+
+ All this is described in section 6 of rfc2289 in more detail. */
-/* #### Document me! */
const char *
-calculate_skey_response (int sequence, const char *seed, const char *pass)
+skey_response (int sequence, const char *seed, const char *pass)
{
- char key[8];
- static char buf[33];
+ unsigned char key[8];
- ALLOCA_MD5_CONTEXT (ctx);
- unsigned long results[4]; /* #### this looks 32-bit-minded */
- char *feed = (char *) alloca (strlen (seed) + strlen (pass) + 1);
+ /* Room to hold 6 four-letter words (heh), 5 space separators, and
+ the terminating \0. 24+5+1 == 30 */
+ static char english[30];
+
+ ALLOCA_MD5_CONTEXT (md5_ctx);
+ uint32_t checksum[4];
+ char *feed = (char *) alloca (strlen (seed) + strlen (pass) + 1);
strcpy (feed, seed);
strcat (feed, pass);
- gen_md5_init (ctx);
- gen_md5_update ((unsigned char *)feed, strlen (feed), ctx);
- gen_md5_finish (ctx, (unsigned char *)results);
-
- results[0] ^= results[2];
- results[1] ^= results[3];
- memcpy (key, (char *) results, 8);
+ DO_MD5 (feed, strlen (feed), checksum);
+ checksum[0] ^= checksum[2];
+ checksum[1] ^= checksum[3];
+ memcpy (key, checksum, 8);
- while (0 < sequence--)
+ while (sequence-- > 0)
{
- gen_md5_init (ctx);
- gen_md5_update ((unsigned char *)key, 8, ctx);
- gen_md5_finish (ctx, (unsigned char *)results);
- results[0] ^= results[2];
- results[1] ^= results[3];
- memcpy (key, (char *) results, 8);
+ DO_MD5 (key, 8, checksum);
+ checksum[0] ^= checksum[2];
+ checksum[1] ^= checksum[3];
+ memcpy (key, checksum, 8);
}
- btoe (buf, key);
- return buf;
+ return btoe (english, key);
}
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