krb5/mech/k5sealv3.c

/*
 * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */


/*
 * lib/gssapi/krb5/k5sealv3.c
 *
 * Copyright 2003,2004 by the Massachusetts Institute of Technology.
 * All Rights Reserved.
 *
 * Export of this software from the United States of America may
 *   require a specific license from the United States Government.
 *   It is the responsibility of any person or organization contemplating
 *   export to obtain such a license before exporting.
 *
 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
 * distribute this software and its documentation for any purpose and
 * without fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright notice and
 * this permission notice appear in supporting documentation, and that
 * the name of M.I.T. not be used in advertising or publicity pertaining
 * to distribution of the software without specific, written prior
 * permission.  Furthermore if you modify this software you must label
 * your software as modified software and not distribute it in such a
 * fashion that it might be confused with the original M.I.T. software.
 * M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is" without express
 * or implied warranty.
 *
 *
 */
/* draft-ietf-krb-wg-gssapi-cfx-05 */

#ifndef _KERNEL
#include <assert.h>
#include <stdarg.h>

#define ASSERT assert
#endif

/* Solaris Kerberos */
#include "k5-int.h"		/* for zap() */
#include "k5-platform.h"

/* Solaris Kerberos */
#include "k5-platform-store_16.h"
#include "k5-platform-store_64.h"
#include "k5-platform-load_16.h"
#include "k5-platform-load_64.h"

#include "gssapiP_krb5.h"
#include <sys/int_limits.h>

static int
rotate_left (void *ptr, size_t bufsiz, size_t rc)
{
    /* Optimize for receiving.  After some debugging is done, the MIT
       implementation won't do any rotates on sending, and while
       debugging, they'll be randomly chosen.

       Return 1 for success, 0 for failure (ENOMEM).  */
    void *tbuf;

    if (bufsiz == 0)
	return 1;
    rc = rc % bufsiz;
    if (rc == 0)
	return 1;

    tbuf = MALLOC(rc);
    if (tbuf == 0)
	return 0;
    (void) memcpy(tbuf, ptr, rc);
    (void) memmove(ptr, (char *)ptr + rc, bufsiz - rc);
    (void) memcpy((char *)ptr + bufsiz - rc, tbuf, rc);
    FREE(tbuf, rc);
    return 1;
}

static const gss_buffer_desc empty_message = { 0, 0 };

#define FLAG_SENDER_IS_ACCEPTOR	0x01
#define FLAG_WRAP_CONFIDENTIAL	0x02
#define FLAG_ACCEPTOR_SUBKEY	0x04

krb5_error_code
gss_krb5int_make_seal_token_v3 (krb5_context context,
				krb5_gss_ctx_id_rec *ctx,
				const gss_buffer_desc * message,
				gss_buffer_t token,
				int conf_req_flag, int toktype)
{
    size_t bufsize = 16;
    unsigned char *outbuf = 0;
    krb5_error_code err;
    int key_usage;
    unsigned char acceptor_flag;
    const gss_buffer_desc *message2 = message;
#ifdef CFX_EXERCISE
    size_t rrc;
#endif
    size_t ec;
    unsigned short tok_id;
    krb5_checksum sum;
    krb5_keyblock *key;

    ASSERT(toktype != KG_TOK_SEAL_MSG || ctx->enc != 0);
    ASSERT(ctx->big_endian == 0);

    acceptor_flag = ctx->initiate ? 0 : FLAG_SENDER_IS_ACCEPTOR;
    key_usage = (toktype == KG_TOK_WRAP_MSG
		 ? (ctx->initiate
		    ? KG_USAGE_INITIATOR_SEAL
		    : KG_USAGE_ACCEPTOR_SEAL)
		 : (ctx->initiate
		    ? KG_USAGE_INITIATOR_SIGN
		    : KG_USAGE_ACCEPTOR_SIGN));
    if (ctx->have_acceptor_subkey) {
	key = ctx->acceptor_subkey;
    } else {
	key = ctx->enc;
    }

#ifdef _KERNEL
    context->kef_cipher_mt = get_cipher_mech_type(context, key);
    context->kef_hash_mt = get_hash_mech_type(context, key);

    if ((err = init_key_kef(context->kef_cipher_mt, key))) {
	return (GSS_S_FAILURE);
    }

#endif /* _KERNEL */

#ifdef CFX_EXERCISE
    {
	static int initialized = 0;
	if (!initialized) {
	    srand(time(0));
	    initialized = 1;
	}
    }
#endif

    if (toktype == KG_TOK_WRAP_MSG && conf_req_flag) {
	krb5_data plain;
	krb5_enc_data cipher;
	size_t ec_max;
	size_t tlen;

	/* 300: Adds some slop.  */
	if (SIZE_MAX - 300 < message->length)
	    return ENOMEM;
	ec_max = SIZE_MAX - message->length - 300;
	if (ec_max > 0xffff)
	    ec_max = 0xffff;
	/*
	 * EC should really be a multiple (1) of the number of octets that
	 * the cryptosystem would pad by if we didn't have the filler.
	 *
	 * For AES-CTS this will always be 0 and we expect no further
	 * enctypes, so there should be no issue here.
	 */
	ec = 0;
	plain.length = message->length + 16 + ec;
	plain.data = MALLOC(plain.length);
	if (plain.data == NULL)
	    return ENOMEM;

	/* Get size of ciphertext.  */
	if ((err = krb5_c_encrypt_length(context,
		ctx->enc->enctype, plain.length, &tlen))) {
	    FREE(plain.data, plain.length);
	    return (err);
        }

	bufsize = 16 + tlen;
	/* Allocate space for header plus encrypted data.  */
	outbuf = MALLOC(bufsize);
	if (outbuf == NULL) {
	    FREE(plain.data, plain.length);
	    return ENOMEM;
	}

	/* TOK_ID */
	store_16_be(0x0504, outbuf);
	/* flags */
	outbuf[2] = (acceptor_flag
		     | (conf_req_flag ? FLAG_WRAP_CONFIDENTIAL : 0)
		     | (ctx->have_acceptor_subkey ? FLAG_ACCEPTOR_SUBKEY : 0));
	/* filler */
	outbuf[3] = 0xff;
	/* EC */
	store_16_be(ec, outbuf+4);
	/* RRC */
	store_16_be(0, outbuf+6);
	store_64_be(ctx->seq_send, outbuf+8);

	(void) memcpy(plain.data, message->value, message->length);
	(void) memset(plain.data + message->length, 'x', ec);
	(void) memcpy(plain.data + message->length + ec, outbuf, 16);

	/* Should really use scatter/gather crypto interfaces */
	cipher.ciphertext.data = (char *)outbuf + 16;
	cipher.ciphertext.length = bufsize - 16;
	cipher.enctype = key->enctype;
	err = krb5_c_encrypt(context, key, key_usage, 0, &plain, &cipher);
	(void) bzero(plain.data, plain.length);
	FREE(plain.data, plain.length);
	plain.data = 0;
	if (err)
	    goto error;

	/* Now that we know we're returning a valid token....  */
	ctx->seq_send++;

#ifdef CFX_EXERCISE
	rrc = rand() & 0xffff;
	if (rotate_left(outbuf+16, bufsize-16,
			(bufsize-16) - (rrc % (bufsize - 16))))
	    store_16_be(rrc, outbuf+6);
	/* If the rotate fails, don't worry about it.  */
#endif
    } else if (toktype == KG_TOK_WRAP_MSG && !conf_req_flag) {
	krb5_data plain;

	/* Here, message is the application-supplied data; message2 is
	   what goes into the output token.  They may be the same, or
	   message2 may be empty (for MIC).  */

	tok_id = 0x0504;

    wrap_with_checksum:
	plain.length = message->length + 16;
	plain.data = MALLOC(message->length + 16);
	if (plain.data == NULL)
	    return ENOMEM;

	if (ctx->cksum_size > 0xffff) {
	    FREE(plain.data, plain.length);
	    return EINVAL;
	}

	bufsize = 16 + message2->length + ctx->cksum_size;
	outbuf = MALLOC(bufsize);
	if (outbuf == NULL) {
	    FREE(plain.data, plain.length);
	    plain.data = 0;
	    err = ENOMEM;
	    goto error;
	}

	/* TOK_ID */
	store_16_be(tok_id, outbuf);
	/* flags */
	outbuf[2] = (acceptor_flag
		     | (ctx->have_acceptor_subkey ? FLAG_ACCEPTOR_SUBKEY : 0));
	/* filler */
	outbuf[3] = 0xff;
	if (toktype == KG_TOK_WRAP_MSG) {
	    /* Use 0 for checksum calculation, substitute
	       checksum length later.  */
	    /* EC */
	    store_16_be(0, outbuf+4);
	    /* RRC */
	    store_16_be(0, outbuf+6);
	} else {
	    /* MIC and DEL store 0xFF in EC and RRC.  */
	    store_16_be(0xffff, outbuf+4);
	    store_16_be(0xffff, outbuf+6);
	}
	store_64_be(ctx->seq_send, outbuf+8);

	(void) memcpy(plain.data, message->value, message->length);
	(void) memcpy(plain.data + message->length, outbuf, 16);

	/* Fill in the output token -- data contents, if any, and
	   space for the checksum.  */
	if (message2->length)
	    (void) memcpy(outbuf + 16, message2->value, message2->length);

	sum.contents = outbuf + 16 + message2->length;
	sum.length = ctx->cksum_size;

	err = krb5_c_make_checksum(context, ctx->cksumtype, key,
				   key_usage, &plain, &sum);
	bzero(plain.data, plain.length);
	FREE(plain.data, plain.length);
	plain.data = 0;
	if (err) {
	    bzero(outbuf,bufsize);
	    err = KRB5KRB_AP_ERR_BAD_INTEGRITY;
	    goto error;
	}
	if (sum.length != ctx->cksum_size) {
	    err = KRB5KRB_AP_ERR_BAD_INTEGRITY;
	    goto error;
	}
	(void) memcpy(outbuf + 16 + message2->length, sum.contents,
	    ctx->cksum_size);
	krb5_free_checksum_contents(context, &sum);
	sum.contents = 0;
	/* Now that we know we're actually generating the token...  */
	ctx->seq_send++;

	if (toktype == KG_TOK_WRAP_MSG) {
#ifdef CFX_EXERCISE
	    rrc = rand() & 0xffff;
	    /* If the rotate fails, don't worry about it.  */
	    if (rotate_left(outbuf+16, bufsize-16,
			    (bufsize-16) - (rrc % (bufsize - 16))))
		store_16_be(rrc, outbuf+6);
#endif
	    /* Fix up EC field.  */
	    store_16_be(ctx->cksum_size, outbuf+4);
	} else {
	    store_16_be(0xffff, outbuf+6);
	}
    } else if (toktype == KG_TOK_MIC_MSG) {
	tok_id = 0x0404;
	message2 = &empty_message;
	goto wrap_with_checksum;
    } else if (toktype == KG_TOK_DEL_CTX) {
	/*
	 * Solaris Kerberos:
	 * No token should be generated for context deletion. Just
	 * return.
	 */
	return 0;
    } else {
	err = KRB5KRB_AP_ERR_BAD_INTEGRITY;
	goto error;
    }

    token->value = outbuf;
    token->length = bufsize;
    return 0;

error:
    FREE(outbuf, bufsize);
    token->value = NULL;
    token->length = 0;
    return err;
}

/* message_buffer is an input if SIGN, output if SEAL, and ignored if DEL_CTX
   conf_state is only valid if SEAL. */

OM_uint32
gss_krb5int_unseal_token_v3(krb5_context *contextptr,
			    OM_uint32 *minor_status,
			    krb5_gss_ctx_id_rec *ctx,
			    unsigned char *ptr, int bodysize,
			    gss_buffer_t message_buffer,
			    int *conf_state, int *qop_state, int toktype)
{
    krb5_context context = *contextptr;
    krb5_data plain;
    gssint_uint64 seqnum;
    size_t ec, rrc;
    int key_usage;
    unsigned char acceptor_flag;
    krb5_checksum sum;
    krb5_error_code err;
    krb5_boolean valid;
    krb5_keyblock *key;

    ASSERT(toktype != KG_TOK_SEAL_MSG || ctx->enc != 0);
    ASSERT(ctx->big_endian == 0);
    ASSERT(ctx->proto == 1);

    if (qop_state)
	*qop_state = GSS_C_QOP_DEFAULT;

    acceptor_flag = ctx->initiate ? FLAG_SENDER_IS_ACCEPTOR : 0;
    key_usage = (toktype == KG_TOK_WRAP_MSG
		 ? (!ctx->initiate
		    ? KG_USAGE_INITIATOR_SEAL
		    : KG_USAGE_ACCEPTOR_SEAL)
		 : (!ctx->initiate
		    ? KG_USAGE_INITIATOR_SIGN
		    : KG_USAGE_ACCEPTOR_SIGN));

    /* Oops.  I wrote this code assuming ptr would be at the start of
       the token header.  */
    ptr -= 2;
    bodysize += 2;

    if (bodysize < 16) {
    defective:
	*minor_status = 0;
	return GSS_S_DEFECTIVE_TOKEN;
    }
    if ((ptr[2] & FLAG_SENDER_IS_ACCEPTOR) != acceptor_flag) {
	*minor_status = (OM_uint32)G_BAD_DIRECTION;
	return GSS_S_BAD_SIG;
    }

    /* Two things to note here.

       First, we can't really enforce the use of the acceptor's subkey,
       if we're the acceptor; the initiator may have sent messages
       before getting the subkey.  We could probably enforce it if
       we're the initiator.

       Second, if someone tweaks the code to not set the flag telling
       the krb5 library to generate a new subkey in the AP-REP
       message, the MIT library may include a subkey anyways --
       namely, a copy of the AP-REQ subkey, if it was provided.  So
       the initiator may think we wanted a subkey, and set the flag,
       even though we weren't trying to set the subkey.  The "other"
       key, the one not asserted by the acceptor, will have the same
       value in that case, though, so we can just ignore the flag.  */
    if (ctx->have_acceptor_subkey && (ptr[2] & FLAG_ACCEPTOR_SUBKEY)) {
	key = ctx->acceptor_subkey;
    } else {
	key = ctx->enc;
    }

#ifdef _KERNEL
    context->kef_cipher_mt = get_cipher_mech_type(context, key);
    context->kef_hash_mt = get_hash_mech_type(context, key);

    if ((err = init_key_kef(context->kef_cipher_mt, key))) {
	return (GSS_S_FAILURE);
    }
#endif /* _KERNEL */

    if (toktype == KG_TOK_WRAP_MSG) {
	if (load_16_be(ptr) != 0x0504)
	    goto defective;
	if (ptr[3] != 0xff)
	    goto defective;
	ec = load_16_be(ptr+4);
	rrc = load_16_be(ptr+6);
	seqnum = load_64_be(ptr+8);
	if (!rotate_left(ptr+16, bodysize-16, rrc)) {
	no_mem:
	    *minor_status = ENOMEM;
	    return GSS_S_FAILURE;
	}
	if (ptr[2] & FLAG_WRAP_CONFIDENTIAL) {
	    /* confidentiality */
	    krb5_enc_data cipher;
	    unsigned char *althdr;
            size_t plainlen;

	    if (conf_state)
		*conf_state = 1;
	    /* Do we have no decrypt_size function?

	       For all current cryptosystems, the ciphertext size will
	       be larger than the plaintext size.  */
	    cipher.enctype = key->enctype;
	    cipher.ciphertext.length = bodysize - 16;
	    cipher.ciphertext.data = (char *)ptr + 16;
	    plain.length = plainlen = bodysize - 16;
	    plain.data = MALLOC(plain.length);
	    if (plain.data == NULL)
		goto no_mem;
	    err = krb5_c_decrypt(context, key, key_usage, 0,
				 &cipher, &plain);
	    if (err) {
		goto error;
	    }
	    /* Don't use bodysize here!  Use the fact that
	       plain.length has been adjusted to the
	       correct length.  */
	    althdr = (uchar_t *)plain.data + plain.length - 16;
	    if (load_16_be(althdr) != 0x0504
		|| althdr[2] != ptr[2]
		|| althdr[3] != ptr[3]
		|| memcmp(althdr+8, ptr+8, 8)) {
		FREE(plain.data, plainlen);
		goto defective;
	    }
	    message_buffer->length = plain.length - ec - 16;
	    message_buffer->value = MALLOC(message_buffer->length);
	    if (message_buffer->value == NULL) {
		FREE(plain.data, plainlen);
		goto no_mem;
	    }
	    (void) memcpy(message_buffer->value, plain.data,
			message_buffer->length);
	    FREE(plain.data, plainlen);
	} else {
	    /* no confidentiality */
	    if (conf_state)
		*conf_state = 0;
	    if (ec + 16 < ec)
		/* overflow check */
		goto defective;
	    if (ec + 16 > bodysize)
		goto defective;
	    /* We have: header | msg | cksum.
	       We need cksum(msg | header).
	       Rotate the first two.  */
	    store_16_be(0, ptr+4);
	    store_16_be(0, ptr+6);
	    plain.length = bodysize-ec;
	    plain.data = (char *)ptr;
	    if (!rotate_left(ptr, bodysize-ec, 16))
		goto no_mem;
	    sum.length = ec;
	    if (sum.length != ctx->cksum_size) {
		*minor_status = 0;
		return GSS_S_BAD_SIG;
	    }
	    sum.contents = ptr+bodysize-ec;
	    sum.checksum_type = ctx->cksumtype;
	    err = krb5_c_verify_checksum(context, key, key_usage,
					 &plain, &sum, &valid);
	    if (err) {
		*minor_status = err;
		return GSS_S_BAD_SIG;
	    }
	    if (!valid) {
		*minor_status = 0;
		return GSS_S_BAD_SIG;
	    }
	    message_buffer->length = plain.length - 16;
	    message_buffer->value = MALLOC(message_buffer->length);
	    if (message_buffer->value == NULL)
		goto no_mem;
	    (void) memcpy(message_buffer->value,
		plain.data, message_buffer->length);

		/*
		 * Solaris Kerberos: Restore the original token.
		 * This allows the token to be detected as a duplicate if it
		 * is passed in to gss_unwrap() again.
		 */
		if (!rotate_left(ptr, bodysize-ec, bodysize - ec - 16))
			goto no_mem;
		store_16_be(ec, ptr+4);
		store_16_be(rrc, ptr+6);
	}
	err = g_order_check(&ctx->seqstate, seqnum);
	*minor_status = 0;
	return err;
    } else if (toktype == KG_TOK_MIC_MSG) {
	/* wrap token, no confidentiality */
	if (load_16_be(ptr) != 0x0404)
	    goto defective;
    verify_mic_1:
	if (ptr[3] != 0xff)
	    goto defective;
	if (load_32_be(ptr+4) != (ulong_t)0xffffffffU)
	    goto defective;
	seqnum = load_64_be(ptr+8);
	plain.length = message_buffer->length + 16;
	plain.data = MALLOC(plain.length);
	if (plain.data == NULL)
	    goto no_mem;
	if (message_buffer->length)
	    (void) memcpy(plain.data,
		message_buffer->value, message_buffer->length);
	(void) memcpy(plain.data + message_buffer->length, ptr, 16);
	sum.length = bodysize - 16;
	sum.contents = ptr + 16;
	sum.checksum_type = ctx->cksumtype;
	err = krb5_c_verify_checksum(context, key, key_usage,
				     &plain, &sum, &valid);
	if (err) {
	error:
	    FREE(plain.data, plain.length);
	    *minor_status = err;
	    return GSS_S_BAD_SIG; /* XXX */
	}
	FREE(plain.data, plain.length);
	if (!valid) {
	    *minor_status = 0;
	    return GSS_S_BAD_SIG;
	}
	err = g_order_check(&ctx->seqstate, seqnum);
	*minor_status = 0;
	return err;
    } else if (toktype == KG_TOK_DEL_CTX) {
	if (load_16_be(ptr) != 0x0405)
	    goto defective;
	message_buffer = (gss_buffer_t)&empty_message;
	goto verify_mic_1;
    } else {
	goto defective;
    }
}