pgpdsakey.c

vc环境下的pgp源码

 * Yes, there *is* a reason that this is a function and not a variable.
 * On a hardware device with an automatic timeout,
 * it actually might need to do some work to find out.
 */
static int
dsaIslocked(PGPSecKey const *seckey)
{
	DSAsecPlus const *sec = (DSAsecPlus *)seckey->priv;

	ASSERTDSA(seckey->pkAlg);
	return sec->locked;
}

/*
 * Return the algorithm and (symmetric) key size used for locking/unlocking
 * the secret key.
 */
static PGPError
dsaLockingAlgorithm(
	PGPSecKey const *seckey,
	PGPCipherAlgorithm *pAlg,
	PGPSize *pAlgKeySize
	)
{
	DSAsecPlus *sec = (DSAsecPlus *)seckey->priv;
	PGPCipherVTBL const *cipher;
	PGPByte alg;
	int i;

	ASSERTDSA(seckey->pkAlg);

	if( IsntNull( pAlg ) )
		*pAlg = (PGPCipherAlgorithm) 0;
	if( IsntNull( pAlgKeySize ) )
		*pAlgKeySize = (PGPSize) 0;

	/* Check packet for basic consistency */
	i = pgpBnParse(sec->cryptkey, sec->cklen, 4, NULL, NULL, NULL, NULL);
	if (i < 0)
		return (PGPError)i;

	/* Get the encryption algorithm (cipher number).  0 == no encryption */
	alg = sec->cryptkey[i] & 255;

	/* New style has 255 then algorithm value */
	if (alg == 255)
		alg = sec->cryptkey[i+1] & 255;

	cipher = pgpCipherGetVTBL( (PGPCipherAlgorithm)alg);
	if (!cipher)
		return kPGPError_BadCipherNumber;

	/* Success */
	if( IsntNull( pAlg ) )
		*pAlg = (PGPCipherAlgorithm) alg;
	if( IsntNull( pAlgKeySize ) )
		*pAlgKeySize = cipher->keysize;

	return kPGPError_NoErr;
}


/*
 * Return the StringToKey type for unlocking the given key.  We use
 * kPGPStringToKey_Literal to flag a secret split unlocking buffer.
 * Returns kPGPStringToKey_Simple if key has no passphrase.
 */
static PGPError
dsaS2KType(
	PGPSecKey const *seckey,
	PGPStringToKeyType *s2kType
	)
{
	DSAsecPlus *sec = (DSAsecPlus *)seckey->priv;
	PGPByte alg;
	int i;

	ASSERTDSA(seckey->pkAlg);

	/* note that 0 is a valid type, but use it as default anyway */
	if( IsntNull( s2kType ) )
		*s2kType = (PGPStringToKeyType) 0;

	/* Check packet for basic consistency */
	i = pgpBnParse(sec->cryptkey, sec->cklen, 4, NULL, NULL, NULL, NULL);
	if (i < 0)
		return (PGPError)i;

	/* Get the encryption algorithm (cipher number).  0 == no encryption */
	alg = sec->cryptkey[i] & 255;

	if (alg == 255) {
		/* New style has 255 then algorithm value then S2K */
		*s2kType = (PGPStringToKeyType) sec->cryptkey[i+2];
	} else {
		/* Unencrypted or old-style simple encryption */
		*s2kType = kPGPStringToKey_Simple;
	}

	return kPGPError_NoErr;
}

/*
 * Convert a passphrase into a s2k literal buffer for the key.
 * Returns error code.  Output buffer will be size of the *pAlgKeySize
 * parameter from pgpSecKeyLockingalgorithm.
 */
static PGPError
dsaConvertPassphrase(PGPSecKey *seckey, PGPEnv const *env,
	  char const *phrase, PGPSize plen, PGPByte *outbuf)
{
	DSAsecPlus *sec = (DSAsecPlus *)seckey->priv;
	PGPStringToKey *s2k;
	PGPByte alg;
	PGPBoolean hasS2K;
	PGPCipherVTBL const *cipher;
	int i;

	ASSERTDSA(seckey->pkAlg);
	pgpAssert (IsntNull( outbuf ) );

	/* Check packet for basic consistency */
	i = pgpBnParse(sec->cryptkey, sec->cklen, 4, NULL, NULL, NULL, NULL);
	if (i < 0)
		return (PGPError)i;

	/* Get the encryption algorithm (cipher number).  0 == no encryption */
	alg = sec->cryptkey[i++] & 255;

	hasS2K = (alg == 255);

	/* New style has 255 then algorithm value */
	if (hasS2K)
		alg = sec->cryptkey[i++] & 255;

	/* Now we are looking at the s2k object if there is one. */
	if (alg == 0) {
		/* Key is not locked */
		return kPGPError_BadParams;
	}
	cipher = pgpCipherGetVTBL( (PGPCipherAlgorithm)alg);
	if( IsNull( cipher ) )
		return kPGPError_BadCipherNumber;

	if (hasS2K) {
		pgpS2Kdecode(&s2k, env, sec->cryptkey+i, sec->cklen-i);
	} else {
		s2k = pgpS2Ksimple(env, pgpHashByNumber(kPGPHashAlgorithm_MD5));
	}
	if (IsNull( s2k ) )
		return kPGPError_OutOfMemory;
	pgpStringToKey(s2k, phrase, plen, outbuf, cipher->keysize);
	pgpS2Kdestroy (s2k);
	
	return kPGPError_NoErr;
}


/*
 * Try to decrypt the secret key wih the given passphrase.  Returns >0
 * if it was the correct passphrase. =0 if it was not, and <0 on error.
 * Does not alter the key even if it's the wrong passphrase and already
 * unlocked.  A NULL passphrae will work if the key is unencrypted.
 * 
 * A (secret) key's DSA-specific part is:
 *
 *  0                2+u  MPI for prime p
 *  2+u              2+v  MPI for order q
 *  4+u+v            2+w  MPI for generator g
 *  6+u+v+w	     2+x  MPI for public key y
 *  8+u+v+w+x        1    Encryption algorithm (0 for none, 1 for IDEA)
 *  9+u+v+w+x        t    Encryption IV: 0 or 8 bytes
 *  9+t+u+v+w+x      2+y  MPI for x (discrete log of public key)
 * 11+t+u+v+w+x+y    2    Checksum
 * 13+t+u+v+w+x+y
 *
 * Actually, that's the old-style, if pgpS2KoldVers is true.
 * If it's false, the algoruthm is 255, and is followed by the
 * algorithm, then the (varaible-length, self-delimiting)
 * string-to-key descriptor.
 */

static int
dsaUnlock(PGPSecKey *seckey, PGPEnv const *env,
	  char const *phrase, size_t plen, PGPBoolean hashedPhrase)
{
	DSAsecPlus *sec = (DSAsecPlus *)seckey->priv;
	BigNum x;
	PGPCFBContext *cfb = NULL;
	unsigned v;
	unsigned alg;
	unsigned checksum;
	int i;
	PGPMemoryMgrRef		mgr	= NULL;
	
	mgr	= PGPGetContextMemoryMgr( seckey->context );

	bnBegin(&x, mgr, TRUE);

	ASSERTDSA(seckey->pkAlg);

	/* Check packet for basic consistency */
	i = pgpBnParse(sec->cryptkey, sec->cklen, 4, &v, NULL, NULL, NULL);
	if (i <= 0)
		goto fail;

	/* OK, read the public data */
	i = pgpBnGetPlain(&sec->s.p, sec->cryptkey+v, sec->cklen-v);
	if (i <= 0)
		goto fail;
	v += i;
	i = pgpBnGetPlain(&sec->s.q, sec->cryptkey+v, sec->cklen-v);
	if (i <= 0)
		goto fail;
	v += i;
	i = pgpBnGetPlain(&sec->s.g, sec->cryptkey+v, sec->cklen-v);
	if (i <= 0)
		goto fail;
	v += i;
	i = pgpBnGetPlain(&sec->s.y, sec->cryptkey+v, sec->cklen-v);
	if (i <= 0)
		goto fail;
	v += i;

	/* Get the encryption algorithm (cipher number).  0 == no encryption */
	alg  = sec->cryptkey[v];

	/* If the phrase is empty, set it to NULL */
	if (plen == 0)
		phrase = NULL;
	/*
	 * We need a pass if it is encrypted, and we cannot have a
	 * password if it is NOT encrypted.  I.e., this is a logical
	 * xor (^^)
	 */
	if (!phrase != !sec->cryptkey[v])
		goto badpass;

	i = pgpCipherSetup(sec->cryptkey + v, sec->cklen - v, phrase, plen,
					   hashedPhrase, env, &cfb);
	if (i < 0)
		goto done;
	v += i;

	checksum = 0;
	i = pgpBnGetNew(&x, sec->cryptkey + v, sec->cklen - v, cfb, &checksum);
	if (i <= 0)
		goto badpass;
	v += i;
	if (bnCmp(&x, &sec->s.q) >= 0)
		goto badpass;	/* Wrong passphrase: x must be < q */

	/* Check that we ended in the right place */
	if (sec->cklen - v != 2) {
		i = kPGPError_KEY_LONG;
		goto fail;
	}
	checksum &= 0xffff;
	if (checksum != pgpChecksumGetNew(sec->cryptkey+v, cfb))
		goto badpass;

	/*
	 * Note that the "nomem" case calls bnEnd()
	 * more than once, but this is guaranteed harmless.
 	 */
	if (bnCopy(&sec->s.x, &x) < 0)
		goto nomem;

	i = 1;	/* Decrypted! */
	sec->locked = 0;
	goto done;

nomem:
	i = kPGPError_OutOfMemory;
	goto done;
fail:
	if (!i)
		i = kPGPError_KeyPacketTruncated;
	goto done;
badpass:
	i = 0;	/* Incorrect passphrase */
	goto done;
done:
	bnEnd(&x);
	if (cfb)
		PGPFreeCFBContext(cfb);
	return i;
}

/*
 * Relock the key.
 */
static void
dsaLock(PGPSecKey *seckey)
{
	DSAsecPlus *sec = (DSAsecPlus *)seckey->priv;

	ASSERTDSA(seckey->pkAlg);
	sec->locked = 1;
	/* bnEnd is documented as also doing a bnBegin */
	bnEnd(&sec->s.x);
}

/*
 * Try to decrypt the given esk.  If the key is locked, try the given
 * passphrase.  It may or may not leave the key unlocked in such a case.
 * (Some hardware implementations may insist on a password per usage.)
 */
static int
dsaDecrypt(PGPSecKey *seckey, PGPEnv const *env,
	   PGPByte const *esk, size_t esklen,
	   PGPByte *key, size_t *keylen, char const *phrase, size_t plen,
	   PGPPublicKeyMessageFormat format)
{
	(void)seckey;
	(void)env;
	(void)esk;
	(void)esklen;
	(void)key;
	(void)keylen;
	(void)phrase;
	(void)plen;
	(void)format;
	return kPGPError_PublicKeyUnimplemented;
}

/*
 * Return the size of the buffer needed, worst-case, for the decrypted
 * output.
 */
static size_t
dsaSecMaxdecrypted(PGPSecKey const *seckey, PGPPublicKeyMessageFormat format)
{
	(void)seckey;
	(void)format;
	return kPGPError_PublicKeyUnimplemented;
}

static size_t
dsaSecMaxesk(PGPSecKey const *seckey, PGPPublicKeyMessageFormat format)
{
	(void)seckey;
	(void)format;
	return kPGPError_PublicKeyUnimplemented;
}

static size_t
dsaSecMaxsig(PGPSecKey const *seckey, PGPPublicKeyMessageFormat format)
{
	DSAsecPlus const *sec = (DSAsecPlus *)seckey->priv;

	ASSERTDSA(seckey->pkAlg);
	if (format == kPGPPublicKeyMessageFormat_PGP)
		return 2*( 2 + bnBytes(&sec->s.q) );
	else if (format == kPGPPublicKeyMessageFormat_PKCS1 ||
			 format == kPGPPublicKeyMessageFormat_IKE)
		return 2*( bnBytes(&sec->s.q) );
	else if (format == kPGPPublicKeyMessageFormat_X509) {
		/* SEQUENCE, length, INT, INT */
		PGPUInt32 len;
		PGPUInt32 qbytes = bnBytes(&sec->s.q);
		len = 2*(pgpBnX509LenLen(qbytes+1) + 1 + qbytes+1);
		return 1 + pgpBnX509LenLen(len) + len;
	}

	pgpAssert(0);
	return 0;
}

/*
 * Helper function: seed a RandomContext from a BigNum.
 * Be very sure to leave nothing in memory!
 */
static void
pgpRandomBnSeed(PGPRandomContext const *rc, BigNum const *bn)
{
	PGPByte buf[32];	/* Big enough for 99.9% of all keys */
	unsigned bytes = (bnBits(bn) + 7)/8;
	unsigned off = 0;

	while (bytes > sizeof(buf)) {
		bnExtractLittleBytes(bn, buf, off, sizeof(buf));
		pgpRandomAddBytes(rc, buf, sizeof(buf));
		bytes -= sizeof(buf);
		off += sizeof(buf);
	}
	bnExtractLittleBytes(bn, buf, off, bytes);
	pgpRandomAddBytes(rc, buf, bytes);

	pgpClearMemory( buf,  sizeof(buf));
}



static int
dsaSign(PGPSecKey *seckey, PGPHashVTBL const *h, PGPByte const *hash,
	PGPByte *sig, size_t *siglen, PGPRandomContext const *rc,
	PGPPublicKeyMessageFormat format)
{
#if PGP_SIGN_DISABLE /* [ */

	(void)seckey;
	(void)h;
	(void)hash;
	(void)sig;
	(void)siglen;
	(void)rc;
	(void)format;
	return kPGPError_FeatureNotAvailable;

#else /* PGP_SIGN_DISABLE */  /* ]  [ */

	DSAsecPlus *sec = (DSAsecPlus *)seckey->priv;
	BigNum r, s, bn, k;
	unsigned t;
	unsigned qbits;
	unsigned qbytes;
	int i;
	PGPRandomContext *rc2;
	PGPMemoryMgrRef		mgr	= NULL;
	
	mgr	= PGPGetContextMemoryMgr( seckey->context );

	(void)h;
	/* We don't need this argument, although other algorithms may... */
	(void)format;

	ASSERTDSA(seckey->pkAlg);
	/* Allow generalizations of SHA as long as they are big enough */
#if 0
	pgpAssert(h->algorithm == kPGPHashAlgorithm_SHA);
#else
	pgpAssert(h->hashsize*8 >= bnBits(&sec->s.q));
	/* Make sure that q is the right size of we are using regular SHA hash */
	pgpAssert( ! (h->algorithm == kPGPHashAlgorithm_SHA
				&& bnBits(&sec->s.q) != h->hashsize*8) );
#endif

	if (sec->locked)
		return kPGPError_KeyIsLocked;

	/*
	 * DSA requires a secret k.  This k is *very* important
	 * to keep secret.  Consider, the DSA signing equations are:
	 * r = (g^k mod p) mod q, and
	 * s = k^-1 * (H(m) + x*r) mod q,
	 * so if you know k (and, the signature r, s and H), then
	 * x = r^-1 * (k*s - H(m))
	 * If we ever pick two k values the same, then
	 * r = (g^k mod p) mod q is the same for both signatures, and
	 * s1 = k^-1 * (H1 + x * r) 
	 * s2 = k^-1 * (H2 + x * r) 
	 * k = (H1-H2) / (s1-s2)
	 * and proceed from there.
	 *
	 * So we need to make *very* sure there's no problem.  To make
	 * sure, we add a layer on top of the passed-in RNG.  We assume
	 * the passed-in RNG is good enough to never repeat (not a
	 * difficult task), and apply an additional X9.17 generator on
	 * top of that, seeded with the secret x, which is destroyed
	 * before leaving this function.
	 *
	 * In addition, we add entropy from the hash to the original RNG.
	 * This will prevent us from using the same k value twice if the
	 * messages are different.
	 */
	pgpRandomAddBytes(rc, hash, bnBytes(&sec->s.q));
	rc2 = pgpRandomCreateX9_17( rc->context, kPGPCipherAlgorithm_CAST5, rc);
	if (!rc2)
		return kPGPError_OutOfMemory;
	pgpRandomBnSeed(rc2, &sec->s.x);

	/*
	 * Of these values, only k is inherently sensitive, but others may
	 * hold some intermediate results we would prefer not to have leaked.
	 * So mark all as sensitive.
	 */
	bnBegin(&r, mgr, TRUE );
	bnBegin(&s, mgr, TRUE );
	bnBegin(&bn, mgr, TRUE );
	bnBegin(&k, mgr, TRUE );

	/*
	 * Choose the random k value to be used for this signature.
	 * Make it a bit bigger than q so it is fairly uniform mod q.
	 */
	qbits = bnBits(&sec->s.q);
	qbytes = bnBytes(&sec->s.q);
	if (pgpBnGenRand(&k, rc2, qbits+8, 0, 1, qbits) < 0 ||
	    bnMod(&k, &k, &sec->s.q) < 0)
		goto nomem;
	
	/* Raise g to k power mod p then mod q to get r */
	if (bnExpMod(&r, &sec->s.g, &k, &sec->s.p) < 0 ||
	    bnMod(&r, &r, &sec->s.q) < 0)
		goto nomem;
	      
	/* r*x mod q into s */
	if (bnMul(&s, &r, &sec->s.x) < 0 ||
	    bnMod(&s, &s, &sec->s.q) < 0)
		goto nomem;

	/* Pack message hash M into buffer bn */
	if (bnInsertBigBytes(&bn, hash, 0, bnBytes(&sec->s.q)) < 0)
		goto nomem;
	if (bnMod(&bn, &bn, &sec->s.q) < 0)
		goto nomem;

	/* Add into s */
	if (bnAdd(&s, &bn) < 0 ||
	    bnMod(&s, &s, &sec->s.q) < 0)
		goto nomem;

	/* Divide by k, mod q (k inverse held in bn) */
	if (bnInv(&bn, &k, &sec->s.q) < 0 ||
	    bnMul(&s, &s, &bn) < 0 ||
	    bnMod(&s, &s, &sec->s.q) < 0)
		goto nomem;

	/* That's it, now to pack r and then s into the buffer */
	t = 0;
	if (format == kPGPPublicKeyMessageFormat_X509) {
		/* Put in SEQUENCE header for 509 sig data */
		PGPUInt32 len_seq, lenlen_seq;
		/* Count size of sequence, counting a 0 byte if hi bit is set */
		if (8*qbytes == bnBits(&r))