sshrsa.c

大名鼎鼎的远程登录软件putty的Symbian版源码

void freersakey(struct RSAKey *key)
{
    if (key->modulus)
	freebn(key->modulus);
    if (key->exponent)
	freebn(key->exponent);
    if (key->private_exponent)
	freebn(key->private_exponent);
    if (key->comment)
	sfree(key->comment);
}

/* ----------------------------------------------------------------------
 * Implementation of the ssh-rsa signing key type. 
 */

static void getstring(char **data, int *datalen, char **p, int *length)
{
    *p = NULL;
    if (*datalen < 4)
	return;
    *length = GET_32BIT(*data);
    *datalen -= 4;
    *data += 4;
    if (*datalen < *length)
	return;
    *p = *data;
    *data += *length;
    *datalen -= *length;
}
static Bignum getmp(char **data, int *datalen)
{
    char *p;
    int length;
    Bignum b;

    getstring(data, datalen, &p, &length);
    if (!p)
	return NULL;
    b = bignum_from_bytes((unsigned char *)p, length);
    return b;
}

static void *rsa2_newkey(char *data, int len)
{
    char *p;
    int slen;
    struct RSAKey *rsa;

    rsa = snew(struct RSAKey);
    if (!rsa)
	return NULL;
    getstring(&data, &len, &p, &slen);

    if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) {
	sfree(rsa);
	return NULL;
    }
    rsa->exponent = getmp(&data, &len);
    rsa->modulus = getmp(&data, &len);
    rsa->private_exponent = NULL;
    rsa->comment = NULL;

    return rsa;
}

static void rsa2_freekey(void *key)
{
    struct RSAKey *rsa = (struct RSAKey *) key;
    freersakey(rsa);
    sfree(rsa);
}

static char *rsa2_fmtkey(void *key)
{
    struct RSAKey *rsa = (struct RSAKey *) key;
    char *p;
    int len;

    len = rsastr_len(rsa);
    p = snewn(len, char);
    rsastr_fmt(p, rsa);
    return p;
}

static unsigned char *rsa2_public_blob(void *key, int *len)
{
    struct RSAKey *rsa = (struct RSAKey *) key;
    int elen, mlen, bloblen;
    int i;
    unsigned char *blob, *p;

    elen = (bignum_bitcount(rsa->exponent) + 8) / 8;
    mlen = (bignum_bitcount(rsa->modulus) + 8) / 8;

    /*
     * string "ssh-rsa", mpint exp, mpint mod. Total 19+elen+mlen.
     * (three length fields, 12+7=19).
     */
    bloblen = 19 + elen + mlen;
    blob = snewn(bloblen, unsigned char);
    p = blob;
    PUT_32BIT(p, 7);
    p += 4;
    memcpy(p, "ssh-rsa", 7);
    p += 7;
    PUT_32BIT(p, elen);
    p += 4;
    for (i = elen; i--;)
	*p++ = bignum_byte(rsa->exponent, i);
    PUT_32BIT(p, mlen);
    p += 4;
    for (i = mlen; i--;)
	*p++ = bignum_byte(rsa->modulus, i);
    assert(p == blob + bloblen);
    *len = bloblen;
    return blob;
}

static unsigned char *rsa2_private_blob(void *key, int *len)
{
    struct RSAKey *rsa = (struct RSAKey *) key;
    int dlen, plen, qlen, ulen, bloblen;
    int i;
    unsigned char *blob, *p;

    dlen = (bignum_bitcount(rsa->private_exponent) + 8) / 8;
    plen = (bignum_bitcount(rsa->p) + 8) / 8;
    qlen = (bignum_bitcount(rsa->q) + 8) / 8;
    ulen = (bignum_bitcount(rsa->iqmp) + 8) / 8;

    /*
     * mpint private_exp, mpint p, mpint q, mpint iqmp. Total 16 +
     * sum of lengths.
     */
    bloblen = 16 + dlen + plen + qlen + ulen;
    blob = snewn(bloblen, unsigned char);
    p = blob;
    PUT_32BIT(p, dlen);
    p += 4;
    for (i = dlen; i--;)
	*p++ = bignum_byte(rsa->private_exponent, i);
    PUT_32BIT(p, plen);
    p += 4;
    for (i = plen; i--;)
	*p++ = bignum_byte(rsa->p, i);
    PUT_32BIT(p, qlen);
    p += 4;
    for (i = qlen; i--;)
	*p++ = bignum_byte(rsa->q, i);
    PUT_32BIT(p, ulen);
    p += 4;
    for (i = ulen; i--;)
	*p++ = bignum_byte(rsa->iqmp, i);
    assert(p == blob + bloblen);
    *len = bloblen;
    return blob;
}

static void *rsa2_createkey(unsigned char *pub_blob, int pub_len,
			    unsigned char *priv_blob, int priv_len)
{
    struct RSAKey *rsa;
    char *pb = (char *) priv_blob;

    rsa = rsa2_newkey((char *) pub_blob, pub_len);
    rsa->private_exponent = getmp(&pb, &priv_len);
    rsa->p = getmp(&pb, &priv_len);
    rsa->q = getmp(&pb, &priv_len);
    rsa->iqmp = getmp(&pb, &priv_len);

    if (!rsa_verify(rsa)) {
	rsa2_freekey(rsa);
	return NULL;
    }

    return rsa;
}

static void *rsa2_openssh_createkey(unsigned char **blob, int *len)
{
    char **b = (char **) blob;
    struct RSAKey *rsa;

    rsa = snew(struct RSAKey);
    if (!rsa)
	return NULL;
    rsa->comment = NULL;

    rsa->modulus = getmp(b, len);
    rsa->exponent = getmp(b, len);
    rsa->private_exponent = getmp(b, len);
    rsa->iqmp = getmp(b, len);
    rsa->p = getmp(b, len);
    rsa->q = getmp(b, len);

    if (!rsa->modulus || !rsa->exponent || !rsa->private_exponent ||
	!rsa->iqmp || !rsa->p || !rsa->q) {
	sfree(rsa->modulus);
	sfree(rsa->exponent);
	sfree(rsa->private_exponent);
	sfree(rsa->iqmp);
	sfree(rsa->p);
	sfree(rsa->q);
	sfree(rsa);
	return NULL;
    }

    return rsa;
}

static int rsa2_openssh_fmtkey(void *key, unsigned char *blob, int len)
{
    struct RSAKey *rsa = (struct RSAKey *) key;
    int bloblen, i;

    bloblen =
	ssh2_bignum_length(rsa->modulus) +
	ssh2_bignum_length(rsa->exponent) +
	ssh2_bignum_length(rsa->private_exponent) +
	ssh2_bignum_length(rsa->iqmp) +
	ssh2_bignum_length(rsa->p) + ssh2_bignum_length(rsa->q);

    if (bloblen > len)
	return bloblen;

    bloblen = 0;
#define ENC(x) \
    PUT_32BIT(blob+bloblen, ssh2_bignum_length((x))-4); bloblen += 4; \
    for (i = ssh2_bignum_length((x))-4; i-- ;) blob[bloblen++]=bignum_byte((x),i);
    ENC(rsa->modulus);
    ENC(rsa->exponent);
    ENC(rsa->private_exponent);
    ENC(rsa->iqmp);
    ENC(rsa->p);
    ENC(rsa->q);

    return bloblen;
}

static int rsa2_pubkey_bits(void *blob, int len)
{
    struct RSAKey *rsa;
    int ret;

    rsa = rsa2_newkey((char *) blob, len);
    ret = bignum_bitcount(rsa->modulus);
    rsa2_freekey(rsa);

    return ret;
}

static char *rsa2_fingerprint(void *key)
{
    struct RSAKey *rsa = (struct RSAKey *) key;
    struct MD5Context md5c;
    unsigned char digest[16], lenbuf[4];
    char buffer[16 * 3 + 40];
    char *ret;
    int numlen, i;

    MD5Init(&md5c);
    MD5Update(&md5c, (unsigned char *)"\0\0\0\7ssh-rsa", 11);

#define ADD_BIGNUM(bignum) \
    numlen = (bignum_bitcount(bignum)+8)/8; \
    PUT_32BIT(lenbuf, numlen); MD5Update(&md5c, lenbuf, 4); \
    for (i = numlen; i-- ;) { \
        unsigned char c = bignum_byte(bignum, i); \
        MD5Update(&md5c, &c, 1); \
    }
    ADD_BIGNUM(rsa->exponent);
    ADD_BIGNUM(rsa->modulus);
#undef ADD_BIGNUM

    MD5Final(digest, &md5c);

    sprintf(buffer, "ssh-rsa %d ", bignum_bitcount(rsa->modulus));
    for (i = 0; i < 16; i++)
	sprintf(buffer + strlen(buffer), "%s%02x", i ? ":" : "",
		digest[i]);
    ret = snewn(strlen(buffer) + 1, char);
    if (ret)
	strcpy(ret, buffer);
    return ret;
}

/*
 * This is the magic ASN.1/DER prefix that goes in the decoded
 * signature, between the string of FFs and the actual SHA hash
 * value. The meaning of it is:
 * 
 * 00 -- this marks the end of the FFs; not part of the ASN.1 bit itself
 * 
 * 30 21 -- a constructed SEQUENCE of length 0x21
 *    30 09 -- a constructed sub-SEQUENCE of length 9
 *       06 05 -- an object identifier, length 5
 *          2B 0E 03 02 1A -- object id { 1 3 14 3 2 26 }
 *                            (the 1,3 comes from 0x2B = 43 = 40*1+3)
 *       05 00 -- NULL
 *    04 14 -- a primitive OCTET STRING of length 0x14
 *       [0x14 bytes of hash data follows]
 * 
 * The object id in the middle there is listed as `id-sha1' in
 * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1d2.asn (the
 * ASN module for PKCS #1) and its expanded form is as follows:
 * 
 * id-sha1                OBJECT IDENTIFIER ::= {
 *    iso(1) identified-organization(3) oiw(14) secsig(3)
 *    algorithms(2) 26 }
 */
static const unsigned char asn1_weird_stuff[] = {
    0x00, 0x30, 0x21, 0x30, 0x09, 0x06, 0x05, 0x2B,
    0x0E, 0x03, 0x02, 0x1A, 0x05, 0x00, 0x04, 0x14,
};

#define ASN1_LEN ( (int) sizeof(asn1_weird_stuff) )

static int rsa2_verifysig(void *key, char *sig, int siglen,
			  char *data, int datalen)
{
    struct RSAKey *rsa = (struct RSAKey *) key;
    Bignum in, out;
    char *p;
    int slen;
    int bytes, i, j, ret;
    unsigned char hash[20];

    getstring(&sig, &siglen, &p, &slen);
    if (!p || slen != 7 || memcmp(p, "ssh-rsa", 7)) {
	return 0;
    }
    in = getmp(&sig, &siglen);
    out = modpow(in, rsa->exponent, rsa->modulus);
    freebn(in);

    ret = 1;

    bytes = (bignum_bitcount(rsa->modulus)+7) / 8;
    /* Top (partial) byte should be zero. */
    if (bignum_byte(out, bytes - 1) != 0)
	ret = 0;
    /* First whole byte should be 1. */
    if (bignum_byte(out, bytes - 2) != 1)
	ret = 0;
    /* Most of the rest should be FF. */
    for (i = bytes - 3; i >= 20 + ASN1_LEN; i--) {
	if (bignum_byte(out, i) != 0xFF)
	    ret = 0;
    }
    /* Then we expect to see the asn1_weird_stuff. */
    for (i = 20 + ASN1_LEN - 1, j = 0; i >= 20; i--, j++) {
	if (bignum_byte(out, i) != asn1_weird_stuff[j])
	    ret = 0;
    }
    /* Finally, we expect to see the SHA-1 hash of the signed data. */
    SHA_Simple(data, datalen, hash);
    for (i = 19, j = 0; i >= 0; i--, j++) {
	if (bignum_byte(out, i) != hash[j])
	    ret = 0;
    }
    freebn(out);

    return ret;
}

static unsigned char *rsa2_sign(void *key, char *data, int datalen,
				int *siglen)
{
    struct RSAKey *rsa = (struct RSAKey *) key;
    unsigned char *bytes;
    int nbytes;
    unsigned char hash[20];
    Bignum in, out;
    int i, j;

    SHA_Simple(data, datalen, hash);

    nbytes = (bignum_bitcount(rsa->modulus) - 1) / 8;
    bytes = snewn(nbytes, unsigned char);

    bytes[0] = 1;
    for (i = 1; i < nbytes - 20 - ASN1_LEN; i++)
	bytes[i] = 0xFF;
    for (i = nbytes - 20 - ASN1_LEN, j = 0; i < nbytes - 20; i++, j++)
	bytes[i] = asn1_weird_stuff[j];
    for (i = nbytes - 20, j = 0; i < nbytes; i++, j++)
	bytes[i] = hash[j];

    in = bignum_from_bytes(bytes, nbytes);
    sfree(bytes);

    out = rsa_privkey_op(in, rsa);
    freebn(in);

    nbytes = (bignum_bitcount(out) + 7) / 8;
    bytes = snewn(4 + 7 + 4 + nbytes, unsigned char);
    PUT_32BIT(bytes, 7);
    memcpy(bytes + 4, "ssh-rsa", 7);
    PUT_32BIT(bytes + 4 + 7, nbytes);
    for (i = 0; i < nbytes; i++)
	bytes[4 + 7 + 4 + i] = bignum_byte(out, nbytes - 1 - i);
    freebn(out);

    *siglen = 4 + 7 + 4 + nbytes;
    return bytes;
}

const struct ssh_signkey ssh_rsa = {
    rsa2_newkey,
    rsa2_freekey,
    rsa2_fmtkey,
    rsa2_public_blob,
    rsa2_private_blob,
    rsa2_createkey,
    rsa2_openssh_createkey,
    rsa2_openssh_fmtkey,
    rsa2_pubkey_bits,
    rsa2_fingerprint,
    rsa2_verifysig,
    rsa2_sign,
    "ssh-rsa",
    "rsa2"
};