#include <string.h>
#include <rx/xdr.h>
#include <rx/rx.h>
+#include <des.h>
+#include <des_prototypes.h>
#include "lifetimes.h"
#include "rxkad.h"
static int
krb5_des_decrypt(struct ktc_encryptionKey *, int, void *, size_t, void *,
size_t *);
-
-
+static int rxkad_derive_des_key(const void *, size_t,
+ struct ktc_encryptionKey *);
+static int compress_parity_bits(void *, size_t *);
+static void hmac_md5_iov(const void *, size_t, const struct iovec *,
+ unsigned int, void *);
int
}
/* Verify that decr_part.key is of right type */
- switch (decr_part.key.keytype) {
- case ETYPE_DES_CBC_CRC:
- case ETYPE_DES_CBC_MD4:
- case ETYPE_DES_CBC_MD5:
- break;
- default:
+ if (tkt_DeriveDesKey(decr_part.key.keytype, decr_part.key.keyvalue.data,
+ decr_part.key.keyvalue.length, session_key) != 0)
goto bad_ticket;
- }
-
- if (decr_part.key.keyvalue.length != 8)
- goto bad_ticket;
-
- /* Extract session key */
- memcpy(session_key, decr_part.key.keyvalue.data, 8);
-
/* Check lifetimes and host addresses, flags etc */
{
time_t now = time(0); /* Use fast time package instead??? */
return ret;
}
+
+/*
+ * Use NIST SP800-108 with HMAC(MD5) in counter mode as the PRF to derive a
+ * des key from another type of key.
+ *
+ * L is 64, as we take 64 random bits and turn them into a 56-bit des key.
+ * The output of hmac_md5 is 128 bits; we take the first 64 only, so n
+ * properly should be 1. However, we apply a slight variation due to the
+ * possibility of producing a weak des key. If the output key is weak, do NOT
+ * simply correct it, instead, the counter is advanced and the next output
+ * used. As such, we code so as to have n be the full 255 permitted by our
+ * encoding of the counter i in an 8-bit field. L itself is encoded as a
+ * 32-bit field, big-endian. We use the constant string "rxkad" as a label
+ * for this key derivation, the standard NUL byte separator, and omit a
+ * key-derivation context. The input key is unique to the krb5 service ticket,
+ * which is unlikely to be used in an other location. If it is used in such
+ * a fashion, both locations will derive the same des key from the PRF, but
+ * this is no different from if a krb5 des key had been used in the same way,
+ * as traditional krb5 rxkad uses the ticket session key directly as the token
+ * key.
+ */
+static int
+rxkad_derive_des_key(const void *in, size_t insize,
+ struct ktc_encryptionKey *out)
+{
+ unsigned char i;
+ char Lbuf[4]; /* bits of output, as 32 bit word, MSB first */
+ char tmp[16];
+ struct iovec iov[3];
+ des_cblock ktmp;
+
+ Lbuf[0] = 0;
+ Lbuf[1] = 0;
+ Lbuf[2] = 0;
+ Lbuf[3] = 64;
+
+ iov[0].iov_base = &i;
+ iov[0].iov_len = 1;
+ iov[1].iov_base = "rxkad";
+ iov[1].iov_len = strlen("rxkad") + 1; /* includes label and separator */
+ iov[2].iov_base = Lbuf;
+ iov[2].iov_len = 4;
+
+ /* stop when 8 bit counter wraps to 0 */
+ for (i = 1; i ; i++) {
+ hmac_md5_iov(in, insize, iov, 3, tmp);
+ memcpy(ktmp, tmp, 8);
+ des_fixup_key_parity(ktmp);
+ if (!des_is_weak_key(ktmp)) {
+ memcpy(out->data, ktmp, 8);
+ return 0;
+ }
+ }
+ return -1;
+}
+
+/*
+ * This is the inverse of the random-to-key for 3des specified in
+ * rfc3961, converting blocks of 8 bytes to blocks of 7 bytes by distributing
+ * the bits of each 8th byte as the lsb of the previous 7 bytes.
+ */
+static int
+compress_parity_bits(void *buffer, size_t *bufsiz)
+{
+ unsigned char *cb, tmp;
+ int i, j, nk;
+
+ if (*bufsiz % 8 != 0)
+ return 1;
+ cb = (unsigned char *)buffer;
+ nk = *bufsiz / 8;
+ for (i = 0; i < nk; i++) {
+ tmp = cb[8 * i + 7] >> 1;
+ for (j = 0; j < 7; j++) {
+ cb[8 * i + j] &= 0xfe;
+ cb[8 * i + j] |= tmp & 0x1;
+ tmp >>= 1;
+ }
+ }
+ for (i = 1; i < nk; i++)
+ memmove(cb + 7 * i, cb + 8 * i, 7);
+ *bufsiz = 7 * nk;
+ return 0;
+}
+
+/* HMAC: Keyed-Hashing for Message Authentication, using MD5 as the hash.
+ * See RFC 2104.
+ *
+ * The constants 64 and 16 are the input block size and output length,
+ * respectively, of md5.
+ */
+static void
+hmac_md5_iov(const void *key, size_t ks,
+ const struct iovec *data, unsigned int niov, void *output)
+{
+ MD5_CTX md5;
+ const unsigned char *kp;
+ unsigned int i;
+ unsigned char tmp[16], tmpk[16], i_pad[64], o_pad[64];
+ if (ks > 64) {
+ MD5_Init(&md5);
+ MD5_Update(&md5, key, ks);
+ MD5_Final(tmpk, &md5);
+ key = tmpk;
+ ks = 16;
+ }
+ kp = key;
+ for (i = 0; i < ks; i++)
+ i_pad[i] = kp[i] ^ 0x36;
+ memset(i_pad + ks, 0x36, 64 - ks);
+ MD5_Init(&md5);
+ MD5_Update(&md5, i_pad, 64);
+ for (i = 0; i < niov; i++)
+ MD5_Update(&md5, data[i].iov_base, data[i].iov_len);
+ MD5_Final(tmp, &md5);
+ for (i = 0; i < ks; i++)
+ o_pad[i] = kp[i] ^ 0x5c;
+ memset(o_pad + ks, 0x5c, 64 - ks);
+ MD5_Init(&md5);
+ MD5_Update(&md5, o_pad, 64);
+ MD5_Update(&md5, tmp, 16);
+ MD5_Final(output, &md5);
+}
+
+/*
+ * Enctype-specific knowledge about how to derive a des key from a given
+ * key. If given a des key, use it directly; otherwise, perform any
+ * parity fixup that may be needed and pass through to the hmad-md5 bits.
+ */
+int
+tkt_DeriveDesKey(int enctype, void *keydata, size_t keylen,
+ struct ktc_encryptionKey *output)
+{
+ switch (enctype) {
+ case ETYPE_DES_CBC_CRC:
+ case ETYPE_DES_CBC_MD4:
+ case ETYPE_DES_CBC_MD5:
+ if (keylen != 8)
+ return 1;
+
+ /* Extract session key */
+ memcpy(output, keydata, 8);
+ break;
+ case ETYPE_NULL:
+ case 4:
+ case 6:
+ case 8:
+ case 9:
+ case 10:
+ case 11:
+ case 12:
+ case 13:
+ case 14:
+ case 15:
+ return 1;
+ /*In order to become a "Cryptographic Key" as specified in
+ * SP800-108, it must be indistinguishable from a random bitstring. */
+ case ETYPE_DES3_CBC_MD5:
+ case ETYPE_OLD_DES3_CBC_SHA1:
+ case ETYPE_DES3_CBC_SHA1:
+ if (compress_parity_bits(keydata, &keylen))
+ return 1;
+ /* FALLTHROUGH */
+ default:
+ if (enctype < 0)
+ return 1;
+ if (keylen < 7)
+ return 1;
+ if (rxkad_derive_des_key(keydata, keylen, output) != 0)
+ return 1;
+ }
+ return 0;
+}
projects / packages / o / openafs.git / commitdiff