backend/mech/token.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 *  token.c
 *
 *  Copyright (c) 1997, by Sun Microsystems, Inc.
 *  All rights reserved.
 *
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "dh_gssapi.h"
#include "crypto.h"

extern int
get_der_length(unsigned char **, unsigned int, unsigned int *);

extern unsigned int
der_length_size(unsigned int);

extern int
put_der_length(unsigned int, unsigned char **, unsigned int);

#define MSO_BIT (8*(sizeof (int) - 1))  /* Most significant octet bit */

static OM_uint32
__xdr_encode_token(XDR *, gss_buffer_t, dh_token_t, dh_key_set_t);

static OM_uint32
__xdr_decode_token(XDR *, gss_buffer_t,
        dh_token_t, dh_key_set_t, dh_signature_t);

/*
 * get_qop: For a Diffie-Hellman token_t, return the associate QOP
 */
static dh_qop_t
get_qop(dh_token_t t)
{
    dh_token_body_t body = &t->ver.dh_version_u.body;
    switch (body->type) {
    case DH_INIT_CNTX:
    case DH_ACCEPT_CNTX:
        return (DH_MECH_QOP);
    case DH_MIC:
        return (body->dh_token_body_desc_u.sign.qop);
    case DH_WRAP:
        return (body->dh_token_body_desc_u.seal.mic.qop);
    default:
        /* Should never get here */
        return (DH_MECH_QOP);
    }
}

/*
 * __make_ap_token: This routine generates a Diffie-Hellman serialized
 * token which has an ASN.1 application 0 header prepended. The unserialized
 * token supplied should be of type DH_INIT_CNTX.
 *
 * The ASN.1 applicationtion prefix is encoded as follows:
 *
 *  +------+
 *  | 0x60 |    1   TAG for APPLICATION 0
 *  +------+
 *  |      |
 *  ~      ~     app_size   DER encoded length of oid_size + token_size
 *  |      |
 *      +------+
 *  | 0x06 |    1   TAG for OID
 *  +------+
 *  |      |  der_length_size
 *  ~      ~  (mech->length) DER encoded length of mech->length
 *  |      |
 *  +------+
 *  |      |
 *  ~      ~  mech->length  OID elements (mech->elements)
 *  |      |
 *  +------+
 *  | 0x00 |       0-3  XDR padding
 *  +------+
 *  |      |
 *  ~      ~        Serialized DH token
 *  |      |
 *  +------+
 *  | 0x00 |       0-3  Left over XDR padding
 *  +------+
 *
 * We will define the token_size to be the sizeof the serialize token plus
 * 3 the maximum XDR paddinging that will be needed. Thus the XDR padding
 * plus the left over XDR padding will alway equal 3.
 */
OM_uint32
__make_ap_token(gss_buffer_t result, /* The serialized token */
        gss_OID mech, /* The mechanism this is for */
        dh_token_t token, /* The unserialized input token */
        dh_key_set_t keys /* The session keys to sign the token */)
{
    unsigned int size, hsize, token_size, app_size, oid_size, start;
    XDR xdrs;
    unsigned char *sv, *buf, *xdrmem;
    OM_uint32 stat;

    /* Allocate the signature for the input token */
    if ((stat = __alloc_sig(get_qop(token),
                &token->verifier))
        != DH_SUCCESS)
        return (stat);

    /*
     * We will first determine the size of the output token in
     * a bottom up fashion.
     */

    /* Fetch the size of a serialized DH token */
    token_size = xdr_sizeof((xdrproc_t)xdr_dh_token_desc, (void *)token);

    /*
     * The token itself needs to be pasted on to the ASN.1
     * application header on BYTES_PER_XDR_UNIT boundry. So we may
     *  need upto BYTES_PER_XDR_UNIT - 1 extra bytes.
     */
    token_size += BYTES_PER_XDR_UNIT -1;


    oid_size = mech->length;
    oid_size += der_length_size(mech->length);
    oid_size += 1;   /* tag x06 for Oid */
    /* bytes to store the length */
    app_size = der_length_size(oid_size + token_size);

    hsize = app_size + oid_size;
    hsize += 1;  /* tag 0x60  for application 0 */
    size = hsize + token_size;

    /* Allocate a buffer to serialize into */
    buf = New(unsigned char, size);
    if (buf == NULL) {
        __free_signature(&token->verifier);
        return (DH_NOMEM_FAILURE);
    }

    result->value = sv = buf;
    result->length = size;

    /* ASN.1 application 0 header */

    /* Encode the tag */
    *buf++ = 0x60;
    /* Encode the app length */
    put_der_length(oid_size + token_size, &buf, app_size);

    /* Encode the OID tag */
    *buf++ = 0x06;
    /* Encode the OID length */
    put_der_length(mech->length, &buf, oid_size);
    /* Encode the OID elemeents */
    memcpy(buf, mech->elements, mech->length);

    /* Encode the Diffie-Hellmam token */
    /*
     * Token has to be on BYTES_PER_XDR_UNIT boundry. (RNDUP is
     * from xdr.h)
     */
    start = RNDUP(hsize);
    /* Buffer for xdrmem_create to use */
    xdrmem = &sv[start];

    xdrmem_create(&xdrs, (caddr_t)xdrmem, token_size, XDR_ENCODE);
    /* Paste the DH token on */
    if ((stat = __xdr_encode_token(&xdrs, NULL, token, keys))
        != DH_SUCCESS) {
        __free_signature(&token->verifier);
        __dh_release_buffer(result);
    }

    /* We're done with the signature, the token has been serialized */
    __free_signature(&token->verifier);

    return (stat);
}

/*
 * __make_token: Given an unserialized DH token, serialize it puting the
 * serialized output in result. If this token has a type of DH_MIC, then
 * the optional message, msg, should be supplied. The mic caluclated will be
 * over the message as well as the serialized token.
 */
OM_uint32
__make_token(gss_buffer_t result, /* Serialized token goes here */
        gss_buffer_t msg,   /* Optional message for DH_MIC tokens */
        dh_token_t token,   /* The token to encode */
        dh_key_set_t keys   /* The keys to encrypt the check sum with */)
{
    unsigned int token_size;
    XDR xdrs;
    unsigned char *buf;
    OM_uint32 stat;

    /* Allocate a signature for this token */
    if ((stat = __alloc_sig(get_qop(token),
                &token->verifier))
        != DH_SUCCESS)
        return (stat);

    /* Get the output token size to know how much to allocate */
    token_size = xdr_sizeof((xdrproc_t)xdr_dh_token_desc, (void *)token);

    /* Allocate the buffer to hold the serialized token */
    buf = New(unsigned char, token_size);
    if (buf == NULL) {
        __free_signature(&token->verifier);
        return (DH_NOMEM_FAILURE);
    }

    /* Set the result */
    result->length = token_size;
    result->value = (void *)buf;

    /* Create the xdr stream using the allocated buffer */
    xdrmem_create(&xdrs, (char *)buf, token_size, XDR_ENCODE);

    /* Encode the token */
    if ((stat = __xdr_encode_token(&xdrs, msg, token, keys))
        != DH_SUCCESS) {
        __free_signature(&token->verifier);
        __dh_release_buffer(result);
    }

    /* Release the signature */
    __free_signature(&token->verifier);
    return (stat);
}

/*
 * __get_ap_token: This routine deserializes a Diffie-Hellman serialized
 * token which has an ASN.1 application 0 header prepended. The resulting
 * unserialized token supplied should be of type DH_INIT_CNTX..
 *
 * The ASN.1 applicationtion prefix  and token is encoded as follows:
 *
 *  +------+
 *  | 0x60 |    1   TAG for APPLICATION 0
 *  +------+
 *  |      |
 *  ~      ~     app_size   DER encoded length of oid_size + token_size
 *  |      |
 *      +------+
 *  | 0x06 |    1   TAG for OID
 *  +------+
 *  |      |  der_length_size
 *  ~      ~  (mech->length) DER encoded length of mech->length
 *  |      |
 *  +------+
 *  |      |
 *  ~      ~  mech->length  OID elements (mech->elements)
 *  |      |
 *  +------+
 *  | 0x00 |       0-3  XDR padding
 *  +------+
 *  |      |
 *  ~      ~        Serialized DH token
 *  |      |
 *  +------+
 *  | 0x00 |       0-3  Left over XDR padding
 *  +------+
 *
 * We will define the token_size to be the sizeof the serialize token plus
 * 3 the maximum XDR paddinging that will be needed. Thus the XDR padding
 * plus the left over XDR padding will alway equal 3.
 */
OM_uint32
__get_ap_token(gss_buffer_t input, /* The token to deserialize */
        gss_OID mech, /* This context's OID */
        dh_token_t token, /* The resulting token */
        dh_signature_t sig /* The signature found over the input token */)
{
    unsigned char *buf, *p;
    unsigned int oid_len, token_len, bytes, hsize;
    int len;
    OM_uint32 stat;
    XDR xdrs;

    /* Set p and buf to point to the beginning of the token */
    p = buf = (unsigned char *)input->value;

    /* Check that this is an ASN.1 APPLICATION 0 token */
    if (*p++ != 0x60)
        return (DH_DECODE_FAILURE);

    /* Determine the length for the DER encoding of the packet length */
    if ((len = get_der_length(&p, input->length - 1, &bytes)) < 0)
        return (DH_DECODE_FAILURE);

    /*
     * See if the number of bytes specified by the
     * encoded length is all there
     */
    if (input->length - 1 - bytes != len)
        return (DH_DECODE_FAILURE);

    /*
     * Running total of the APPLICATION 0 prefix so far. One for the
     * tag (0x60) and the bytes necessary to encode the length of the
     * packet.
     */
    hsize = 1 + bytes;

    /* Check that we're now looking at an OID */
    if (*p++ != 0x06)
        return (DH_DECODE_FAILURE);

    /* Get OID length and the number of bytes that to encode it */
    oid_len = get_der_length(&p, len - 1, &bytes);

    /*
     * Now add the byte for the OID tag, plus the bytes for the oid
     * length, plus the oid length its self. That is, add the size
     * of the encoding of the OID to the running total of the
     * APPLICATION 0 header. The result is the total size of the header.
     */
    hsize += 1 + bytes + oid_len;

    /*
     * The DH token length is the application length minus the length
     * of the OID encoding.
     */
    token_len = len - 1 - bytes - oid_len;

    /* Sanity check the token length */
    if (input->length - hsize != token_len)
        return (DH_DECODE_FAILURE);

    /* Check that this token is for this OID */
    if (mech->length != oid_len)
        return (DH_DECODE_FAILURE);
    if (memcmp(mech->elements, p, oid_len) != 0)
        return (DH_DECODE_FAILURE);

    /* Round up the header size to XDR boundry */
    hsize = RNDUP(hsize);

    /* Get the start of XDR encoded token */
    p = &buf[hsize];

    /* Create and XDR stream to decode from */
    xdrmem_create(&xdrs, (caddr_t)p, token_len, XDR_DECODE);

    /*
     * Clear the deserialized token (we'll have the xdr routines
     * do the the allocations).
     */
    memset(token, 0, sizeof (dh_token_desc));

    /* Zero out the signature */
    memset(sig, 0, sizeof (*sig));

    /*
     * Decode the DH_INIT_CNTX token. Note that at this point we have no
     * session keys established, so that keys is null. The unencrypted
     * signature will be made available to the caller in sig. The
     * caller can then attempt to decrypt the session keys in token
     * and encrypt the returned sig  with those keys to check the
     * integrity of the token.
     */
    if ((stat = __xdr_decode_token(&xdrs, NULL, token, NULL, sig))
        != DH_SUCCESS) {
        xdr_free(xdr_dh_token_desc, (char *)token);
        return (stat);
    }

    return (stat);
}

/*
 * __get_token: Deserialize a supplied Diffie-Hellman token. Note the
 * session keys should always be supplied to this routine. The message
 * should only be supplied if the token is of DH_MIC type.
 */
OM_uint32
__get_token(gss_buffer_t input, /* The token to deserialize */
        gss_buffer_t msg, /* Optional message to generate verifier over */
        dh_token_t token,    /* The decode token */
        dh_key_set_t keys    /* The session keys */)
{
    XDR xdrs;
    dh_signature sig;
    OM_uint32 stat;

    /* Create a an XDR stream out of the input token */
    xdrmem_create(&xdrs, (caddr_t)input->value, input->length, XDR_DECODE);

    /* Clear the token_desc and signature. */
    memset(token, 0, sizeof (dh_token_desc));
    memset(&sig, 0, sizeof (sig));

    /* Decode the token */
    if ((stat = __xdr_decode_token(&xdrs, msg, token, keys, &sig))
        != DH_SUCCESS)
        /* If we fail release the deserialized token */
        xdr_free(xdr_dh_token_desc, (char *)token);

    /* We always free the signature */
    __free_signature(&sig);

    return (stat);
}

/*
 * Warning these routines assumes that xdrs was created with xdrmem_create!
 */

/*
 * __xdr_encode_token: Given an allocated xdrs stream serialize the supplied
 * token_desc pointed to by objp, using keys to encrypt the signature. If
 * msg is non null then calculate the signature over msg as well as the
 * serialized token. Note this protocol is designed with the signature as
 * the last part of any token. In this way the signature that is calculated is
 * always done over the entire token. All fields in any token are thus
 * protected from tampering
 */
static OM_uint32
__xdr_encode_token(register XDR *xdrs, gss_buffer_t msg,
        dh_token_desc *objp, dh_key_set_t keys)
{
    OM_uint32 stat;

    /* Check that xdrs is valid */
    if (xdrs == 0 || xdrs->x_op != XDR_ENCODE)
        return (DH_BADARG_FAILURE);

    /* Encode the protocol versioned body */
    if (!xdr_dh_version(xdrs, &objp->ver))
        return (DH_ENCODE_FAILURE);

    /* Calculate the signature */
    stat = __mk_sig(get_qop(objp), xdrs->x_base,
            xdr_getpos(xdrs), msg, keys,
            &objp->verifier);

    if (stat != DH_SUCCESS)
        return (stat);

    /* Encode the signature */
    if (!xdr_dh_signature(xdrs, &objp->verifier))
        return (DH_ENCODE_FAILURE);

    return (DH_SUCCESS);
}

/*
 * __xdr_decode_token: Decode a token from an XDR stream into a token_desc
 * pointed to by objp. We will calculate a signature over the serialized
 * token and an optional message. The calculated signature will be
 * returned to the caller in sig. If the supplied keys are available this
 * routine will compare that the verifier in the deserialized token is
 * the same as the calculated signature over the input stream. This is
 * the usual case. However if the supplied serialized token is DH_INIT_CNTX,
 * the keys have not yet been established. So we just give the caller back
 * our raw signature (Non encrypted) and the deserialized token. Higher in
 * the food chain (currently __dh_gss_accept_sec_context), we will attempt
 * to decrypt the session keys and call __verify_sig with the decrypted
 * session keys the signature returned from this routine and the deserialized
 * token.
 *
 * Note it is assumed that sig does point to a valid uninitialized signature.
 */

static OM_uint32
__xdr_decode_token(register XDR *xdrs, gss_buffer_t msg,
        dh_token_desc *objp, dh_key_set_t keys, dh_signature_t sig)
{
    OM_uint32 stat;

    /* Check that we are decoding */
    if (xdrs == 0 || xdrs->x_op != XDR_DECODE)
        return (DH_BADARG_FAILURE);

    /* Decode the protocol versioned body */
    if (!xdr_dh_version(xdrs, &objp->ver))
        return (DH_DECODE_FAILURE);

    /* Allocate the signature for this tokens QOP */
    if ((stat = __alloc_sig(get_qop(objp), sig)) != DH_SUCCESS)
        return (stat);

    /*
     * Call __mk_sig in crypto.c to calculate the signature based on
     * the decoded QOP. __mk_sig will encrypt the signature with the
     * supplied keys if they are available. If keys is null the signature
     * will be just the unencrypted check sum.
     */
    stat = __mk_sig(get_qop(objp), xdrs->x_base,
            xdr_getpos(xdrs), msg, keys, sig);
    if (stat != DH_SUCCESS)
        return (stat);

    /* Now decode the supplied signature */
    if (!xdr_dh_signature(xdrs, &objp->verifier))
        return (stat);

    /*
     * If we have keys then we can check that the signatures
     * are the same
     */
    if (keys && !__cmpsig(sig, &objp->verifier))
        return (DH_VERIFIER_MISMATCH);

    return (DH_SUCCESS);
}