propagate from branch 'au.asn.ucc.matt.dropbear' (head 0501e6f661b5415eb76f3b312d183c3adfbfb712)

            to branch 'au.asn.ucc.matt.dropbear.cli-agent' (head 01038174ec27245b51bd43a66c01ad930880f67b)

--HG--
branch : agent-client
extra : convert_revision : 12b2f59db65e7339d340e95ac67d6d9ddb193c2b

2 files changed, 1023 insertions, 0 deletions

diff --git a/libtomcrypt/src/pk/dh/dh.c b/libtomcrypt/src/pk/dh/dh.c
new file mode 100644
index 0000000..a54f29b
--- /dev/null
+++ b/libtomcrypt/src/pk/dh/dh.c
@@ -0,0 +1,524 @@
+/* LibTomCrypt, modular cryptographic library -- Tom St Denis
+ *
+ * LibTomCrypt is a library that provides various cryptographic
+ * algorithms in a highly modular and flexible manner.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ *
+ * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.org
+ */
+#include "tomcrypt.h"
+
+/**
+  @file dh.c
+  DH crypto, Tom St Denis
+*/
+  
+#ifdef MDH
+
+/* max export size we'll encounter (smaller than this but lets round up a bit) */
+#define DH_BUF_SIZE 1200
+
+/* This holds the key settings.  ***MUST*** be organized by size from smallest to largest. */
+static const struct {
+    int size;
+    char *name, *base, *prime;
+} sets[] = {
+#ifdef DH768
+{
+   96,
+   "DH-768",
+   "4",
+   "F///////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "//////m3wvV"
+},
+#endif
+#ifdef DH1024
+{
+   128,
+   "DH-1024",
+   "4",
+   "F///////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////m3C47"
+},
+#endif
+#ifdef DH1280
+{
+   160,
+   "DH-1280",
+   "4",
+   "F///////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "//////////////////////////////m4kSN"
+},
+#endif
+#ifdef DH1536
+{
+   192,
+   "DH-1536",
+   "4",
+   "F///////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////m5uqd"
+},
+#endif
+#ifdef DH1792
+{
+   224,
+   "DH-1792",
+   "4",
+   "F///////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "//////////////////////////////////////////////////////mT/sd"
+},
+#endif
+#ifdef DH2048
+{
+   256,
+   "DH-2048",
+   "4",
+   "3///////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "/////////////////////////////////////////m8MPh"
+},
+#endif
+#ifdef DH2560
+{
+   320,
+   "DH-2560",
+   "4",
+   "3///////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "/////mKFpF"
+},
+#endif
+#ifdef DH3072
+{
+   384,
+   "DH-3072",
+   "4",
+   "3///////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "/////////////////////////////m32nN"
+},
+#endif
+#ifdef DH4096
+{
+   512,
+   "DH-4096",
+   "4",
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "////////////////////////////////////////////////////////////"
+   "/////////////////////m8pOF"
+},
+#endif
+{
+   0,
+   NULL,
+   NULL,
+   NULL
+}
+};
+
+static int is_valid_idx(int n)
+{
+   int x;
+
+   for (x = 0; sets[x].size; x++);
+   if ((n < 0) || (n >= x)) {
+      return 0;
+   }
+   return 1;
+}
+
+/**
+   Test the DH sub-system (can take a while)
+   @return CRYPT_OK if successful
+*/
+int dh_test(void)
+{
+    mp_int p, g, tmp;
+    int x, err, primality;
+
+    if ((err = mp_init_multi(&p, &g, &tmp, NULL)) != MP_OKAY)                 { goto error; }
+
+    for (x = 0; sets[x].size != 0; x++) {
+#if 0
+        printf("dh_test():testing size %d-bits\n", sets[x].size * 8);
+#endif
+        if ((err = mp_read_radix(&g,(char *)sets[x].base, 64)) != MP_OKAY)    { goto error; }
+        if ((err = mp_read_radix(&p,(char *)sets[x].prime, 64)) != MP_OKAY)   { goto error; }
+
+        /* ensure p is prime */
+        if ((err = is_prime(&p, &primality)) != CRYPT_OK)                     { goto done; }
+        if (primality == 0) {
+           err = CRYPT_FAIL_TESTVECTOR;
+           goto done;
+        }
+
+        if ((err = mp_sub_d(&p, 1, &tmp)) != MP_OKAY)                         { goto error; }
+        if ((err = mp_div_2(&tmp, &tmp)) != MP_OKAY)                          { goto error; }
+
+        /* ensure (p-1)/2 is prime */
+        if ((err = is_prime(&tmp, &primality)) != CRYPT_OK)                   { goto done; }
+        if (primality == 0) {
+           err = CRYPT_FAIL_TESTVECTOR;
+           goto done;
+        }
+
+        /* now see if g^((p-1)/2) mod p is in fact 1 */
+        if ((err = mp_exptmod(&g, &tmp, &p, &tmp)) != MP_OKAY)                { goto error; }
+        if (mp_cmp_d(&tmp, 1)) {
+           err = CRYPT_FAIL_TESTVECTOR;
+           goto done;
+        }
+    }
+    err = CRYPT_OK;
+    goto done;
+error:
+    err = mpi_to_ltc_error(err);
+done:
+    mp_clear_multi(&tmp, &g, &p, NULL);
+    return err;
+}
+
+/**
+   Get the min and max DH key sizes (octets)
+   @param low    [out] The smallest key size supported
+   @param high   [out] The largest key size supported
+*/
+void dh_sizes(int *low, int *high)
+{
+   int x;
+   LTC_ARGCHK(low != NULL);
+   LTC_ARGCHK(high != NULL);
+   *low  = INT_MAX;
+   *high = 0;
+   for (x = 0; sets[x].size != 0; x++) {
+       if (*low > sets[x].size)  *low  = sets[x].size;
+       if (*high < sets[x].size) *high = sets[x].size;
+   }
+}
+
+/**
+  Returns the key size of a given DH key (octets)
+  @param key   The DH key to get the size of
+  @return The size if valid or INT_MAX if not
+*/
+int dh_get_size(dh_key *key)
+{
+    LTC_ARGCHK(key != NULL);
+    if (is_valid_idx(key->idx) == 1) {
+        return sets[key->idx].size;
+    } else {
+        return INT_MAX; /* large value that would cause dh_make_key() to fail */
+    }
+}
+
+/**
+  Make a DH key [private key pair]
+  @param prng     An active PRNG state
+  @param wprng    The index for the PRNG you desire to use
+  @param keysize  The key size (octets) desired
+  @param key      [out] Where the newly created DH key will be stored
+  @return CRYPT_OK if successful, note: on error all allocated memory will be freed automatically.
+*/
+int dh_make_key(prng_state *prng, int wprng, int keysize, dh_key *key)
+{
+   unsigned char *buf;
+   unsigned long x;
+   mp_int p, g;
+   int err;
+
+   LTC_ARGCHK(key  != NULL);
+
+   /* good prng? */
+   if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* find key size */
+   for (x = 0; (keysize > sets[x].size) && (sets[x].size != 0); x++);
+#ifdef FAST_PK
+   keysize = MIN(sets[x].size, 32);
+#else
+   keysize = sets[x].size;
+#endif
+
+   if (sets[x].size == 0) {
+      return CRYPT_INVALID_KEYSIZE;
+   }
+   key->idx = x;
+
+   /* allocate buffer */
+   buf = XMALLOC(keysize);
+   if (buf == NULL) {
+      return CRYPT_MEM;
+   }
+
+   /* make up random string */
+   if (prng_descriptor[wprng].read(buf, keysize, prng) != (unsigned long)keysize) {
+      err = CRYPT_ERROR_READPRNG; 
+      goto error2;
+   }
+
+   /* init parameters */
+   if ((err = mp_init_multi(&g, &p, &key->x, &key->y, NULL)) != MP_OKAY) {
+      goto error;
+   }
+   if ((err = mp_read_radix(&g, sets[key->idx].base, 64)) != MP_OKAY)      { goto error; }
+   if ((err = mp_read_radix(&p, sets[key->idx].prime, 64)) != MP_OKAY)     { goto error; }
+
+   /* load the x value */
+   if ((err = mp_read_unsigned_bin(&key->x, buf, keysize)) != MP_OKAY)     { goto error; }
+   if ((err = mp_exptmod(&g, &key->x, &p, &key->y)) != MP_OKAY)            { goto error; }
+   key->type = PK_PRIVATE;
+
+   if ((err = mp_shrink(&key->x)) != MP_OKAY)                              { goto error; }
+   if ((err = mp_shrink(&key->y)) != MP_OKAY)                              { goto error; }
+
+   /* free up ram */
+   err = CRYPT_OK;
+   goto done;
+error:
+   err = mpi_to_ltc_error(err);
+error2:
+   mp_clear_multi(&key->x, &key->y, NULL);
+done:
+#ifdef LTC_CLEAN_STACK
+   zeromem(buf, keysize);
+#endif
+   mp_clear_multi(&p, &g, NULL);
+   XFREE(buf);
+   return err;
+}
+
+/**
+  Free the allocated ram for a DH key
+  @param key   The key which you wish to free
+*/ 
+void dh_free(dh_key *key)
+{
+   LTC_ARGCHK(key != NULL);
+   mp_clear_multi(&key->x, &key->y, NULL);
+}
+
+/**
+  Export a DH key to a binary packet
+  @param out    [out] The destination for the key
+  @param outlen [in/out] The max size and resulting size of the DH key
+  @param type   Which type of key (PK_PRIVATE or PK_PUBLIC)
+  @param key    The key you wish to export
+  @return CRYPT_OK if successful
+*/
+int dh_export(unsigned char *out, unsigned long *outlen, int type, dh_key *key)
+{
+   unsigned long y, z;
+   int err;
+
+   LTC_ARGCHK(out    != NULL);
+   LTC_ARGCHK(outlen != NULL);
+   LTC_ARGCHK(key    != NULL);
+
+   /* can we store the static header?  */
+   if (*outlen < (PACKET_SIZE + 2)) {
+      return CRYPT_BUFFER_OVERFLOW;
+   }
+   
+   if (type == PK_PRIVATE && key->type != PK_PRIVATE) {
+      return CRYPT_PK_NOT_PRIVATE;
+   }
+
+   /* header */
+   y = PACKET_SIZE;
+
+   /* header */
+   out[y++] = type;
+   out[y++] = (unsigned char)(sets[key->idx].size / 8);
+
+   /* export y */
+   OUTPUT_BIGNUM(&key->y, out, y, z);
+
+   if (type == PK_PRIVATE) {
+      /* export x */
+      OUTPUT_BIGNUM(&key->x, out, y, z);
+   }
+
+   /* store header */
+   packet_store_header(out, PACKET_SECT_DH, PACKET_SUB_KEY);
+
+   /* store len */
+   *outlen = y;
+   return CRYPT_OK;
+}
+
+/**
+  Import a DH key from a binary packet
+  @param in     The packet to read
+  @param inlen  The length of the input packet
+  @param key    [out] Where to import the key to
+  @return CRYPT_OK if successful, on error all allocated memory is freed automatically
+*/
+int dh_import(const unsigned char *in, unsigned long inlen, dh_key *key)
+{
+   unsigned long x, y, s;
+   int err;
+
+   LTC_ARGCHK(in  != NULL);
+   LTC_ARGCHK(key != NULL);
+
+   /* make sure valid length */
+   if ((2+PACKET_SIZE) > inlen) {
+      return CRYPT_INVALID_PACKET;
+   }
+
+   /* check type byte */
+   if ((err = packet_valid_header((unsigned char *)in, PACKET_SECT_DH, PACKET_SUB_KEY)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* init */
+   if ((err = mp_init_multi(&key->x, &key->y, NULL)) != MP_OKAY) {
+      return mpi_to_ltc_error(err);
+   }
+
+   /* advance past packet header */
+   y = PACKET_SIZE;
+
+   /* key type, e.g. private, public */
+   key->type = (int)in[y++];
+
+   /* key size in bytes */
+   s  = (unsigned long)in[y++] * 8;
+
+   for (x = 0; (s > (unsigned long)sets[x].size) && (sets[x].size != 0); x++);
+   if (sets[x].size == 0) {
+      err = CRYPT_INVALID_KEYSIZE;
+      goto error;
+   }
+   key->idx = (int)x;
+
+   /* type check both values */
+   if ((key->type != PK_PUBLIC) && (key->type != PK_PRIVATE))  {
+      err = CRYPT_PK_TYPE_MISMATCH;
+      goto error;
+   }
+
+   /* is the key idx valid? */
+   if (is_valid_idx(key->idx) != 1) {
+      err = CRYPT_PK_TYPE_MISMATCH;
+      goto error;
+   }
+
+   /* load public value g^x mod p*/
+   INPUT_BIGNUM(&key->y, in, x, y, inlen);
+
+   if (key->type == PK_PRIVATE) {
+      INPUT_BIGNUM(&key->x, in, x, y, inlen);
+   }
+
+   /* eliminate private key if public */
+   if (key->type == PK_PUBLIC) {
+      mp_clear(&key->x);
+   }
+
+   return CRYPT_OK;
+error:
+   mp_clear_multi(&key->y, &key->x, NULL);
+   return err;
+}
+
+/**
+   Create a DH shared secret.
+   @param private_key     The private DH key in the pair
+   @param public_key      The public DH key in the pair 
+   @param out             [out] The destination of the shared data
+   @param outlen          [in/out] The max size and resulting size of the shared data.
+   @return CRYPT_OK if successful
+*/
+int dh_shared_secret(dh_key *private_key, dh_key *public_key,
+                     unsigned char *out, unsigned long *outlen)
+{
+   mp_int tmp, p;
+   unsigned long x;
+   int err;
+
+   LTC_ARGCHK(private_key != NULL);
+   LTC_ARGCHK(public_key  != NULL);
+   LTC_ARGCHK(out         != NULL);
+   LTC_ARGCHK(outlen      != NULL);
+
+   /* types valid? */
+   if (private_key->type != PK_PRIVATE) {
+      return CRYPT_PK_NOT_PRIVATE;
+   }
+
+   /* same idx? */
+   if (private_key->idx != public_key->idx) {
+      return CRYPT_PK_TYPE_MISMATCH;
+   }
+
+   /* compute y^x mod p */
+   if ((err = mp_init_multi(&tmp, &p, NULL)) != MP_OKAY) {
+      return mpi_to_ltc_error(err);
+   }
+
+   if ((err = mp_read_radix(&p, (char *)sets[private_key->idx].prime, 64)) != MP_OKAY)     { goto error; }
+   if ((err = mp_exptmod(&public_key->y, &private_key->x, &p, &tmp)) != MP_OKAY)           { goto error; }
+
+   /* enough space for output? */
+   x = (unsigned long)mp_unsigned_bin_size(&tmp);
+   if (*outlen < x) {
+      err = CRYPT_BUFFER_OVERFLOW;
+      goto done;
+   }
+   if ((err = mp_to_unsigned_bin(&tmp, out)) != MP_OKAY)                                   { goto error; }
+   *outlen = x;
+   err = CRYPT_OK;
+   goto done;
+error:
+   err = mpi_to_ltc_error(err);
+done:
+   mp_clear_multi(&p, &tmp, NULL);
+   return err;
+}
+
+#include "dh_sys.c"
+
+#endif
+
+
+/* $Source: /cvs/libtom/libtomcrypt/src/pk/dh/dh.c,v $ */
+/* $Revision: 1.3 $ */
+/* $Date: 2005/05/05 14:35:59 $ */
diff --git a/libtomcrypt/src/pk/dh/dh_sys.c b/libtomcrypt/src/pk/dh/dh_sys.c
new file mode 100644
index 0000000..4f10556
--- /dev/null
+++ b/libtomcrypt/src/pk/dh/dh_sys.c
@@ -0,0 +1,499 @@
+/* LibTomCrypt, modular cryptographic library -- Tom St Denis
+ *
+ * LibTomCrypt is a library that provides various cryptographic
+ * algorithms in a highly modular and flexible manner.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ *
+ * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.org
+ */
+
+/**
+  @file dh_sys.c
+  DH Crypto, Tom St Denis
+*/
+  
+/**
+  Encrypt a short symmetric key with a public DH key
+  @param in        The symmetric key to encrypt
+  @param inlen     The length of the key (octets)
+  @param out       [out] The ciphertext
+  @param outlen    [in/out]  The max size and resulting size of the ciphertext
+  @param prng      An active PRNG state
+  @param wprng     The index of the PRNG desired
+  @param hash      The index of the hash desired (must produce a digest of size >= the size of the plaintext)
+  @param key       The public key you wish to encrypt with.
+  @return CRYPT_OK if successful
+*/
+int dh_encrypt_key(const unsigned char *in,   unsigned long inlen,
+                         unsigned char *out,  unsigned long *outlen,
+                         prng_state *prng, int wprng, int hash,
+                         dh_key *key)
+{
+    unsigned char *pub_expt, *dh_shared, *skey;
+    dh_key        pubkey;
+    unsigned long x, y, z, hashsize, pubkeysize;
+    int           err;
+
+    LTC_ARGCHK(in != NULL);
+    LTC_ARGCHK(out   != NULL);
+    LTC_ARGCHK(outlen   != NULL);
+    LTC_ARGCHK(key   != NULL);
+
+    /* check that wprng/hash are not invalid */
+    if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
+       return err;
+    }
+
+    if ((err = hash_is_valid(hash)) != CRYPT_OK) {
+       return err;
+    }
+
+    if (inlen > hash_descriptor[hash].hashsize)  {
+        return CRYPT_INVALID_HASH;
+    }
+
+    /* allocate memory */
+    pub_expt  = XMALLOC(DH_BUF_SIZE);
+    dh_shared = XMALLOC(DH_BUF_SIZE);
+    skey      = XMALLOC(MAXBLOCKSIZE);
+    if (pub_expt == NULL || dh_shared == NULL || skey == NULL) {
+       if (pub_expt != NULL) {
+          XFREE(pub_expt);
+       }
+       if (dh_shared != NULL) {
+          XFREE(dh_shared);
+       }
+       if (skey != NULL) {
+          XFREE(skey);
+       }
+       return CRYPT_MEM;
+    }
+
+    /* make a random key and export the public copy */
+    if ((err = dh_make_key(prng, wprng, dh_get_size(key), &pubkey)) != CRYPT_OK) {
+       goto LBL_ERR;
+    }
+
+    pubkeysize = DH_BUF_SIZE;
+    if ((err = dh_export(pub_expt, &pubkeysize, PK_PUBLIC, &pubkey)) != CRYPT_OK) {
+       dh_free(&pubkey);
+       goto LBL_ERR;
+    }
+
+    /* now check if the out buffer is big enough */
+    if (*outlen < (1 + 4 + 4 + PACKET_SIZE + pubkeysize + inlen)) {
+       dh_free(&pubkey);
+       err = CRYPT_BUFFER_OVERFLOW;
+       goto LBL_ERR;
+    }
+
+    /* make random key */
+    hashsize  = hash_descriptor[hash].hashsize;
+
+    x = DH_BUF_SIZE;
+    if ((err = dh_shared_secret(&pubkey, key, dh_shared, &x)) != CRYPT_OK) {
+       dh_free(&pubkey);
+       goto LBL_ERR;
+    }
+    dh_free(&pubkey);
+
+    z = MAXBLOCKSIZE;
+    if ((err = hash_memory(hash, dh_shared, x, skey, &z)) != CRYPT_OK) {
+       goto LBL_ERR;
+    }
+
+    /* store header */
+    packet_store_header(out, PACKET_SECT_DH, PACKET_SUB_ENC_KEY);
+
+    /* output header */
+    y = PACKET_SIZE;
+
+    /* size of hash name and the name itself */
+    out[y++] = hash_descriptor[hash].ID;
+
+    /* length of DH pubkey and the key itself */
+    STORE32L(pubkeysize, out+y);
+    y += 4;
+    for (x = 0; x < pubkeysize; x++, y++) {
+        out[y] = pub_expt[x];
+    }
+
+    /* Store the encrypted key */
+    STORE32L(inlen, out+y);
+    y += 4;
+
+    for (x = 0; x < inlen; x++, y++) {
+      out[y] = skey[x] ^ in[x];
+    }
+    *outlen = y;
+
+    err = CRYPT_OK;
+LBL_ERR:
+#ifdef LTC_CLEAN_STACK
+    /* clean up */
+    zeromem(pub_expt,  DH_BUF_SIZE);
+    zeromem(dh_shared, DH_BUF_SIZE);
+    zeromem(skey,      MAXBLOCKSIZE);
+#endif
+    XFREE(skey);
+    XFREE(dh_shared);
+    XFREE(pub_expt);
+
+    return err;
+}
+
+/**
+   Decrypt a DH encrypted symmetric key
+   @param in       The DH encrypted packet
+   @param inlen    The length of the DH encrypted packet
+   @param out      The plaintext
+   @param outlen   [in/out]  The max size and resulting size of the plaintext
+   @param key      The private DH key corresponding to the public key that encrypted the plaintext
+   @return CRYPT_OK if successful
+*/
+int dh_decrypt_key(const unsigned char *in, unsigned long inlen,
+                         unsigned char *out, unsigned long *outlen, 
+                         dh_key *key)
+{
+   unsigned char *shared_secret, *skey;
+   unsigned long  x, y, z, hashsize, keysize;
+   int            hash, err;
+   dh_key         pubkey;
+
+   LTC_ARGCHK(in     != NULL);
+   LTC_ARGCHK(out != NULL);
+   LTC_ARGCHK(outlen != NULL);
+   LTC_ARGCHK(key    != NULL);
+
+   /* right key type? */
+   if (key->type != PK_PRIVATE) {
+      return CRYPT_PK_NOT_PRIVATE;
+   }
+
+   /* allocate ram */
+   shared_secret = XMALLOC(DH_BUF_SIZE);
+   skey          = XMALLOC(MAXBLOCKSIZE);
+   if (shared_secret == NULL || skey == NULL) {
+      if (shared_secret != NULL) {
+         XFREE(shared_secret);
+      }
+      if (skey != NULL) {
+         XFREE(skey);
+      }
+      return CRYPT_MEM;
+   }
+
+   /* check if initial header should fit */
+   if (inlen < PACKET_SIZE+1+4+4) {
+      err =  CRYPT_INVALID_PACKET;
+      goto LBL_ERR;
+   } else {
+      inlen -= PACKET_SIZE+1+4+4;
+   }
+
+   /* is header correct? */
+   if ((err = packet_valid_header((unsigned char *)in, PACKET_SECT_DH, PACKET_SUB_ENC_KEY)) != CRYPT_OK)  {
+      goto LBL_ERR;
+   }
+
+   /* now lets get the hash name */
+   y = PACKET_SIZE;
+   hash = find_hash_id(in[y++]);
+   if (hash == -1) {
+      err = CRYPT_INVALID_HASH;
+      goto LBL_ERR;
+   }
+
+   /* common values */
+   hashsize  = hash_descriptor[hash].hashsize;
+
+   /* get public key */
+   LOAD32L(x, in+y);
+   
+   /* now check if the imported key will fit */
+   if (inlen < x) {
+      err = CRYPT_INVALID_PACKET;
+      goto LBL_ERR;
+   } else {
+      inlen -= x;
+   }
+   
+   y += 4;
+   if ((err = dh_import(in+y, x, &pubkey)) != CRYPT_OK) {
+      goto LBL_ERR;
+   }
+   y += x;
+
+   /* make shared key */
+   x = DH_BUF_SIZE;
+   if ((err = dh_shared_secret(key, &pubkey, shared_secret, &x)) != CRYPT_OK) {
+      dh_free(&pubkey);
+      goto LBL_ERR;
+   }
+   dh_free(&pubkey);
+
+   z = MAXBLOCKSIZE;
+   if ((err = hash_memory(hash, shared_secret, x, skey, &z)) != CRYPT_OK) {
+      goto LBL_ERR;
+   }
+
+   /* load in the encrypted key */
+   LOAD32L(keysize, in+y);
+   
+   /* will the out fit as part of the input */
+   if (inlen < keysize) {
+      err = CRYPT_INVALID_PACKET;
+      goto LBL_ERR;
+   } else {
+      inlen -= keysize;
+   }
+   
+   if (keysize > *outlen) {
+       err = CRYPT_BUFFER_OVERFLOW;
+       goto LBL_ERR;
+   }
+   y += 4;
+
+   *outlen = keysize;
+
+   for (x = 0; x < keysize; x++, y++) {
+      out[x] = skey[x] ^ in[y];
+   }
+
+   err = CRYPT_OK;
+LBL_ERR:
+#ifdef LTC_CLEAN_STACK
+   zeromem(shared_secret, DH_BUF_SIZE);
+   zeromem(skey,          MAXBLOCKSIZE);
+#endif
+
+   XFREE(skey);
+   XFREE(shared_secret);
+
+   return err;
+}
+
+/* perform an ElGamal Signature of a hash 
+ *
+ * The math works as follows.  x is the private key, M is the message to sign
+ 
+ 1.  pick a random k
+ 2.  compute a = g^k mod p
+ 3.  compute b = (M - xa)/k mod p
+ 4.  Send (a,b)
+ 
+ Now to verify with y=g^x mod p, a and b
+ 
+ 1.  compute y^a * a^b = g^(xa) * g^(k*(M-xa)/k)
+                       = g^(xa + (M - xa))
+                       = g^M [all mod p]
+                       
+ 2.  Compare against g^M mod p [based on input hash].
+ 3.  If result of #2 == result of #1 then signature valid 
+*/
+
+/**
+  Sign a message digest using a DH private key 
+  @param in      The data to sign
+  @param inlen   The length of the input (octets)
+  @param out     [out] The destination of the signature
+  @param outlen  [in/out] The max size and resulting size of the output
+  @param prng    An active PRNG state
+  @param wprng   The index of the PRNG desired
+  @param key     A private DH key
+  @return CRYPT_OK if successful
+*/
+int dh_sign_hash(const unsigned char *in,  unsigned long inlen,
+                       unsigned char *out, unsigned long *outlen,
+                       prng_state *prng, int wprng, dh_key *key)
+{
+   mp_int         a, b, k, m, g, p, p1, tmp;
+   unsigned char *buf;
+   unsigned long  x, y;
+   int            err;
+
+   LTC_ARGCHK(in     != NULL);
+   LTC_ARGCHK(out    != NULL);
+   LTC_ARGCHK(outlen != NULL);
+   LTC_ARGCHK(key    != NULL);
+
+   /* check parameters */
+   if (key->type != PK_PRIVATE) {
+      return CRYPT_PK_NOT_PRIVATE;
+   }
+
+   if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* is the IDX valid ?  */
+   if (is_valid_idx(key->idx) != 1) {
+      return CRYPT_PK_INVALID_TYPE;
+   }
+
+   /* allocate ram for buf */
+   buf = XMALLOC(520);
+
+   /* make up a random value k,
+    * since the order of the group is prime
+    * we need not check if gcd(k, r) is 1 
+    */
+   if (prng_descriptor[wprng].read(buf, sets[key->idx].size, prng) != 
+       (unsigned long)(sets[key->idx].size)) {
+      err = CRYPT_ERROR_READPRNG;
+      goto LBL_ERR;
+   }
+
+   /* init bignums */
+   if ((err = mp_init_multi(&a, &b, &k, &m, &p, &g, &p1, &tmp, NULL)) != MP_OKAY) { 
+      err = mpi_to_ltc_error(err);
+      goto LBL_ERR;
+   }
+
+   /* load k and m */
+   if ((err = mp_read_unsigned_bin(&m, (unsigned char *)in, inlen)) != MP_OKAY)        { goto error; }
+   if ((err = mp_read_unsigned_bin(&k, buf, sets[key->idx].size)) != MP_OKAY)          { goto error; }
+
+   /* load g, p and p1 */
+   if ((err = mp_read_radix(&g, sets[key->idx].base, 64)) != MP_OKAY)               { goto error; }
+   if ((err = mp_read_radix(&p, sets[key->idx].prime, 64)) != MP_OKAY)              { goto error; }
+   if ((err = mp_sub_d(&p, 1, &p1)) != MP_OKAY)                                     { goto error; }
+   if ((err = mp_div_2(&p1, &p1)) != MP_OKAY)                                       { goto error; } /* p1 = (p-1)/2 */
+
+   /* now get a = g^k mod p */
+   if ((err = mp_exptmod(&g, &k, &p, &a)) != MP_OKAY)                               { goto error; }
+
+   /* now find M = xa + kb mod p1 or just b = (M - xa)/k mod p1 */
+   if ((err = mp_invmod(&k, &p1, &k)) != MP_OKAY)                                   { goto error; } /* k = 1/k mod p1 */
+   if ((err = mp_mulmod(&a, &key->x, &p1, &tmp)) != MP_OKAY)                        { goto error; } /* tmp = xa */
+   if ((err = mp_submod(&m, &tmp, &p1, &tmp)) != MP_OKAY)                           { goto error; } /* tmp = M - xa */
+   if ((err = mp_mulmod(&k, &tmp, &p1, &b)) != MP_OKAY)                             { goto error; } /* b = (M - xa)/k */
+   
+   /* check for overflow */
+   if ((unsigned long)(PACKET_SIZE + 4 + 4 + mp_unsigned_bin_size(&a) + mp_unsigned_bin_size(&b)) > *outlen) {
+      err = CRYPT_BUFFER_OVERFLOW;
+      goto LBL_ERR;
+   }
+   
+   /* store header  */
+   y = PACKET_SIZE;
+
+   /* now store them both (a,b) */
+   x = (unsigned long)mp_unsigned_bin_size(&a);
+   STORE32L(x, out+y);  y += 4;
+   if ((err = mp_to_unsigned_bin(&a, out+y)) != MP_OKAY)                            { goto error; }
+   y += x;
+
+   x = (unsigned long)mp_unsigned_bin_size(&b);
+   STORE32L(x, out+y);  y += 4;
+   if ((err = mp_to_unsigned_bin(&b, out+y)) != MP_OKAY)                            { goto error; }
+   y += x;
+
+   /* check if size too big */
+   if (*outlen < y) {
+      err = CRYPT_BUFFER_OVERFLOW;
+      goto LBL_ERR;
+   }
+
+   /* store header */
+   packet_store_header(out, PACKET_SECT_DH, PACKET_SUB_SIGNED);
+   *outlen = y;
+
+   err = CRYPT_OK;
+   goto LBL_ERR;
+error:
+   err = mpi_to_ltc_error(err);
+LBL_ERR:
+   mp_clear_multi(&tmp, &p1, &g, &p, &m, &k, &b, &a, NULL);
+
+   XFREE(buf);
+
+   return err;
+}
+
+
+/**
+   Verify the signature given
+   @param sig        The signature
+   @param siglen     The length of the signature (octets)
+   @param hash       The hash that was signed
+   @param hashlen    The length of the hash (octets)
+   @param stat       [out] Result of signature comparison, 1==valid, 0==invalid
+   @param key        The public DH key that signed the hash
+   @return CRYPT_OK if succsessful (even if signature is invalid)
+*/
+int dh_verify_hash(const unsigned char *sig, unsigned long siglen,
+                   const unsigned char *hash, unsigned long hashlen, 
+                         int *stat, dh_key *key)
+{
+   mp_int        a, b, p, g, m, tmp;
+   unsigned long x, y;
+   int           err;
+
+   LTC_ARGCHK(sig  != NULL);
+   LTC_ARGCHK(hash != NULL);
+   LTC_ARGCHK(stat != NULL);
+   LTC_ARGCHK(key  != NULL);
+
+   /* default to invalid */
+   *stat = 0;
+
+   /* check initial input length */
+   if (siglen < PACKET_SIZE+4+4) {
+      return CRYPT_INVALID_PACKET;
+   } 
+
+   /* header ok? */
+   if ((err = packet_valid_header((unsigned char *)sig, PACKET_SECT_DH, PACKET_SUB_SIGNED)) != CRYPT_OK) {
+      return err;
+   }
+   
+   /* get hash out of packet */
+   y = PACKET_SIZE;
+
+   /* init all bignums */
+   if ((err = mp_init_multi(&a, &p, &b, &g, &m, &tmp, NULL)) != MP_OKAY) { 
+      return mpi_to_ltc_error(err);
+   }
+
+   /* load a and b */
+   INPUT_BIGNUM(&a, sig, x, y, siglen);
+   INPUT_BIGNUM(&b, sig, x, y, siglen);
+
+   /* load p and g */
+   if ((err = mp_read_radix(&p, sets[key->idx].prime, 64)) != MP_OKAY)              { goto error1; }
+   if ((err = mp_read_radix(&g, sets[key->idx].base, 64)) != MP_OKAY)               { goto error1; }
+
+   /* load m */
+   if ((err = mp_read_unsigned_bin(&m, (unsigned char *)hash, hashlen)) != MP_OKAY) { goto error1; }
+
+   /* find g^m mod p */
+   if ((err = mp_exptmod(&g, &m, &p, &m)) != MP_OKAY)                { goto error1; } /* m = g^m mod p */
+
+   /* find y^a * a^b */
+   if ((err = mp_exptmod(&key->y, &a, &p, &tmp)) != MP_OKAY)         { goto error1; } /* tmp = y^a mod p */
+   if ((err = mp_exptmod(&a, &b, &p, &a)) != MP_OKAY)                { goto error1; } /* a = a^b mod p */
+   if ((err = mp_mulmod(&a, &tmp, &p, &a)) != MP_OKAY)               { goto error1; } /* a = y^a * a^b mod p */
+
+   /* y^a * a^b == g^m ??? */
+   if (mp_cmp(&a, &m) == 0) {
+      *stat = 1;
+   }
+
+   /* clean up */
+   err = CRYPT_OK;
+   goto done;
+error1:
+   err = mpi_to_ltc_error(err);
+error:
+done:
+   mp_clear_multi(&tmp, &m, &g, &p, &b, &a, NULL);
+   return err;
+}
+
+
+/* $Source: /cvs/libtom/libtomcrypt/src/pk/dh/dh_sys.c,v $ */
+/* $Revision: 1.3 $ */
+/* $Date: 2005/05/05 14:35:59 $ */