Fix gss_process_context_token() [CVE-2014-5352]

[MITKRB5-SA-2015-001] The krb5 gss_process_context_token() should not
actually delete the context; that leaves the caller with a dangling
pointer and no way to know that it is invalid.  Instead, mark the
context as terminated, and check for terminated contexts in the GSS
functions which expect established contexts.  Also add checks in
export_sec_context and pseudo_random, and adjust t_prf.c for the
pseudo_random check.

ticket: 8055 (new)
target_version: 1.13.1
tags: pullup
make_seal_token_v1 (krb5_context context,
                    krb5_key enc,
                    krb5_key seq,
                    uint64_t *seqnum,
                    int direction,
                    gss_buffer_t text,
                    gss_buffer_t token,
                    int signalg,
                    size_t cksum_size,
                    int sealalg,
                    int do_encrypt,
                    int toktype,
                    gss_OID oid)
{
    krb5_error_code code;
    size_t sumlen;
    char *data_ptr;
    krb5_data plaind;
    krb5_checksum md5cksum;
    krb5_checksum cksum;
    /* msglen contains the message length
     * we are signing/encrypting.  tmsglen
     * contains the length of the message
     * we plan to write out to the token.
     * tlen is the length of the token
     * including header. */
    unsigned int conflen=0, tmsglen, tlen, msglen;
    unsigned char *t, *ptr;
    unsigned char *plain;
    unsigned char pad;
    krb5_keyusage sign_usage = KG_USAGE_SIGN;


    assert((!do_encrypt) || (toktype == KG_TOK_SEAL_MSG));
    /* create the token buffer */
    /* Do we need confounder? */
    if (do_encrypt || toktype == KG_TOK_SEAL_MSG)
        conflen = kg_confounder_size(context, enc->keyblock.enctype);
    else conflen = 0;

    if (toktype == KG_TOK_SEAL_MSG) {
        switch (sealalg) {
        case SEAL_ALG_MICROSOFT_RC4:
            msglen = conflen + text->length+1;
            pad = 1;
            break;
        default:
            /* XXX knows that des block size is 8 */
            msglen = (conflen+text->length+8)&(~7);
            pad = 8-(text->length%8);
        }
        tmsglen = msglen;
    } else {
        tmsglen = 0;
        msglen = text->length;
        pad = 0;
    }
    tlen = g_token_size((gss_OID) oid, 14+cksum_size+tmsglen);

    if ((t = (unsigned char *) gssalloc_malloc(tlen)) == NULL)
        return(ENOMEM);

    /*** fill in the token */

    ptr = t;
    g_make_token_header(oid, 14+cksum_size+tmsglen, &ptr, toktype);

    /* 0..1 SIGN_ALG */
    store_16_le(signalg, &ptr[0]);

    /* 2..3 SEAL_ALG or Filler */
    if ((toktype == KG_TOK_SEAL_MSG) && do_encrypt) {
        store_16_le(sealalg, &ptr[2]);
    } else {
        /* No seal */
        ptr[2] = 0xff;
        ptr[3] = 0xff;
    }

    /* 4..5 Filler */
    ptr[4] = 0xff;
    ptr[5] = 0xff;

    /* pad the plaintext, encrypt if needed, and stick it in the token */

    /* initialize the the cksum */
    switch (signalg) {
    case SGN_ALG_DES_MAC_MD5:
    case SGN_ALG_MD2_5:
        md5cksum.checksum_type = CKSUMTYPE_RSA_MD5;
        break;
    case SGN_ALG_HMAC_SHA1_DES3_KD:
        md5cksum.checksum_type = CKSUMTYPE_HMAC_SHA1_DES3;
        break;
    case SGN_ALG_HMAC_MD5:
        md5cksum.checksum_type = CKSUMTYPE_HMAC_MD5_ARCFOUR;
        if (toktype != KG_TOK_SEAL_MSG)
            sign_usage = 15;
        break;
    default:
    case SGN_ALG_DES_MAC:
        abort ();
    }

    code = krb5_c_checksum_length(context, md5cksum.checksum_type, &sumlen);
    if (code) {
        gssalloc_free(t);
        return(code);
    }
    md5cksum.length = sumlen;


    if ((plain = (unsigned char *) xmalloc(msglen ? msglen : 1)) == NULL) {
        gssalloc_free(t);
        return(ENOMEM);
    }

    if (conflen) {
        if ((code = kg_make_confounder(context, enc->keyblock.enctype,
                                       plain))) {
            xfree(plain);
            gssalloc_free(t);
            return(code);
        }
    }

    memcpy(plain+conflen, text->value, text->length);
    if (pad) memset(plain+conflen+text->length, pad, pad);

    /* compute the checksum */

    /* 8 = head of token body as specified by mech spec */
    if (! (data_ptr = xmalloc(8 + msglen))) {
        xfree(plain);
        gssalloc_free(t);
        return(ENOMEM);
    }
    (void) memcpy(data_ptr, ptr-2, 8);
    (void) memcpy(data_ptr+8, plain, msglen);
    plaind.length = 8 + msglen;
    plaind.data = data_ptr;
    code = krb5_k_make_checksum(context, md5cksum.checksum_type, seq,
                                sign_usage, &plaind, &md5cksum);
    xfree(data_ptr);

    if (code) {
        xfree(plain);
        gssalloc_free(t);
        return(code);
    }
    switch(signalg) {
    case SGN_ALG_DES_MAC_MD5:
    case 3:

        code = kg_encrypt_inplace(context, seq, KG_USAGE_SEAL,
                                  (g_OID_equal(oid, gss_mech_krb5_old) ?
                                   seq->keyblock.contents : NULL),
                                  md5cksum.contents, 16);
        if (code) {
            krb5_free_checksum_contents(context, &md5cksum);
            xfree (plain);
            gssalloc_free(t);
            return code;
        }

        cksum.length = cksum_size;
        cksum.contents = md5cksum.contents + 16 - cksum.length;

        memcpy(ptr+14, cksum.contents, cksum.length);
        break;

    case SGN_ALG_HMAC_SHA1_DES3_KD:
        /*
         * Using key derivation, the call to krb5_c_make_checksum
         * already dealt with encrypting.
         */
        if (md5cksum.length != cksum_size)
            abort ();
        memcpy (ptr+14, md5cksum.contents, md5cksum.length);
        break;
    case SGN_ALG_HMAC_MD5:
        memcpy (ptr+14, md5cksum.contents, cksum_size);
        break;
    }

    krb5_free_checksum_contents(context, &md5cksum);

    /* create the seq_num */

    if ((code = kg_make_seq_num(context, seq, direction?0:0xff,
                                (krb5_ui_4)*seqnum, ptr+14, ptr+6))) {
        xfree (plain);
        gssalloc_free(t);
        return(code);
    }

    if (do_encrypt) {
        switch(sealalg) {
        case SEAL_ALG_MICROSOFT_RC4:
        {
            unsigned char bigend_seqnum[4];
            krb5_keyblock *enc_key;
            int i;
            store_32_be(*seqnum, bigend_seqnum);
            code = krb5_k_key_keyblock(context, enc, &enc_key);
            if (code)
            {
                xfree(plain);
                gssalloc_free(t);
                return(code);
            }
            assert (enc_key->length == 16);
            for (i = 0; i <= 15; i++)
                ((char *) enc_key->contents)[i] ^=0xf0;
            code = kg_arcfour_docrypt (enc_key, 0,
                                       bigend_seqnum, 4,
                                       plain, tmsglen,
                                       ptr+14+cksum_size);
            krb5_free_keyblock (context, enc_key);
            if (code)
            {
                xfree(plain);
                gssalloc_free(t);
                return(code);
            }
        }
        break;
        default:
            if ((code = kg_encrypt(context, enc, KG_USAGE_SEAL, NULL,
                                   (krb5_pointer) plain,
                                   (krb5_pointer) (ptr+cksum_size+14),
                                   tmsglen))) {
                xfree(plain);
                gssalloc_free(t);
                return(code);
            }
        }
    }else {
        if (tmsglen)
            memcpy(ptr+14+cksum_size, plain, tmsglen);
    }
    xfree(plain);


    /* that's it.  return the token */

    (*seqnum)++;
    *seqnum &= 0xffffffffL;

    token->length = tlen;
    token->value = (void *) t;

    return(0);
}

make_seal_token_v1 (krb5_context context,
                    krb5_key enc,
                    krb5_key seq,
                    uint64_t *seqnum,
                    int direction,
                    gss_buffer_t text,
                    gss_buffer_t token,
                    int signalg,
                    size_t cksum_size,
                    int sealalg,
                    int do_encrypt,
                    int toktype,
                    gss_OID oid)
{
    krb5_error_code code;
    size_t sumlen;
    char *data_ptr;
    krb5_data plaind;
    krb5_checksum md5cksum;
    krb5_checksum cksum;
    /* msglen contains the message length
     * we are signing/encrypting.  tmsglen
     * contains the length of the message
     * we plan to write out to the token.
     * tlen is the length of the token
     * including header. */
    unsigned int conflen=0, tmsglen, tlen, msglen;
    unsigned char *t, *ptr;
    unsigned char *plain;
    unsigned char pad;
    krb5_keyusage sign_usage = KG_USAGE_SIGN;


    assert((!do_encrypt) || (toktype == KG_TOK_SEAL_MSG));
    /* create the token buffer */
    /* Do we need confounder? */
    if (do_encrypt || toktype == KG_TOK_SEAL_MSG)
        conflen = kg_confounder_size(context, enc->keyblock.enctype);
    else conflen = 0;

    if (toktype == KG_TOK_SEAL_MSG) {
        switch (sealalg) {
        case SEAL_ALG_MICROSOFT_RC4:
            msglen = conflen + text->length+1;
            pad = 1;
            break;
        default:
            /* XXX knows that des block size is 8 */
            msglen = (conflen+text->length+8)&(~7);
            pad = 8-(text->length%8);
        }
        tmsglen = msglen;
    } else {
        tmsglen = 0;
        msglen = text->length;
        pad = 0;
    }
    tlen = g_token_size((gss_OID) oid, 14+cksum_size+tmsglen);

    if ((t = (unsigned char *) gssalloc_malloc(tlen)) == NULL)
        return(ENOMEM);

    /*** fill in the token */

    ptr = t;
    g_make_token_header(oid, 14+cksum_size+tmsglen, &ptr, toktype);

    /* 0..1 SIGN_ALG */
    store_16_le(signalg, &ptr[0]);

    /* 2..3 SEAL_ALG or Filler */
    if ((toktype == KG_TOK_SEAL_MSG) && do_encrypt) {
        store_16_le(sealalg, &ptr[2]);
    } else {
        /* No seal */
        ptr[2] = 0xff;
        ptr[3] = 0xff;
    }

    /* 4..5 Filler */
    ptr[4] = 0xff;
    ptr[5] = 0xff;

    /* pad the plaintext, encrypt if needed, and stick it in the token */

    /* initialize the the cksum */
    switch (signalg) {
    case SGN_ALG_DES_MAC_MD5:
    case SGN_ALG_MD2_5:
        md5cksum.checksum_type = CKSUMTYPE_RSA_MD5;
        break;
    case SGN_ALG_HMAC_SHA1_DES3_KD:
        md5cksum.checksum_type = CKSUMTYPE_HMAC_SHA1_DES3;
        break;
    case SGN_ALG_HMAC_MD5:
        md5cksum.checksum_type = CKSUMTYPE_HMAC_MD5_ARCFOUR;
        if (toktype != KG_TOK_SEAL_MSG)
            sign_usage = 15;
        break;
    default:
    case SGN_ALG_DES_MAC:
        abort ();
    }

    code = krb5_c_checksum_length(context, md5cksum.checksum_type, &sumlen);
    if (code) {
        gssalloc_free(t);
        return(code);
    }
    md5cksum.length = sumlen;


    if ((plain = (unsigned char *) xmalloc(msglen ? msglen : 1)) == NULL) {
        gssalloc_free(t);
        return(ENOMEM);
    }

    if (conflen) {
        if ((code = kg_make_confounder(context, enc->keyblock.enctype,
                                       plain))) {
            xfree(plain);
            gssalloc_free(t);
            return(code);
        }
    }

    memcpy(plain+conflen, text->value, text->length);
    if (pad) memset(plain+conflen+text->length, pad, pad);

    /* compute the checksum */

    /* 8 = head of token body as specified by mech spec */
    if (! (data_ptr = xmalloc(8 + msglen))) {
        xfree(plain);
        gssalloc_free(t);
        return(ENOMEM);
    }
    (void) memcpy(data_ptr, ptr-2, 8);
    (void) memcpy(data_ptr+8, plain, msglen);
    plaind.length = 8 + msglen;
    plaind.data = data_ptr;
    code = krb5_k_make_checksum(context, md5cksum.checksum_type, seq,
                                sign_usage, &plaind, &md5cksum);
    xfree(data_ptr);

    if (code) {
        xfree(plain);
        gssalloc_free(t);
        return(code);
    }
    switch(signalg) {
    case SGN_ALG_DES_MAC_MD5:
    case 3:

        code = kg_encrypt_inplace(context, seq, KG_USAGE_SEAL,
                                  (g_OID_equal(oid, gss_mech_krb5_old) ?
                                   seq->keyblock.contents : NULL),
                                  md5cksum.contents, 16);
        if (code) {
            krb5_free_checksum_contents(context, &md5cksum);
            xfree (plain);
            gssalloc_free(t);
            return code;
        }

        cksum.length = cksum_size;
        cksum.contents = md5cksum.contents + 16 - cksum.length;

        memcpy(ptr+14, cksum.contents, cksum.length);
        break;

    case SGN_ALG_HMAC_SHA1_DES3_KD:
        /*
         * Using key derivation, the call to krb5_c_make_checksum
         * already dealt with encrypting.
         */
        if (md5cksum.length != cksum_size)
            abort ();
        memcpy (ptr+14, md5cksum.contents, md5cksum.length);
        break;
    case SGN_ALG_HMAC_MD5:
        memcpy (ptr+14, md5cksum.contents, cksum_size);
        break;
    }

    krb5_free_checksum_contents(context, &md5cksum);

    /* create the seq_num */

    if ((code = kg_make_seq_num(context, seq, direction?0:0xff,
                                (krb5_ui_4)*seqnum, ptr+14, ptr+6))) {
        xfree (plain);
        gssalloc_free(t);
        return(code);
    }

    if (do_encrypt) {
        switch(sealalg) {
        case SEAL_ALG_MICROSOFT_RC4:
        {
            unsigned char bigend_seqnum[4];
            krb5_keyblock *enc_key;
            int i;
            store_32_be(*seqnum, bigend_seqnum);
            code = krb5_k_key_keyblock(context, enc, &enc_key);
            if (code)
            {
                xfree(plain);
                gssalloc_free(t);
                return(code);
            }
            assert (enc_key->length == 16);
            for (i = 0; i <= 15; i++)
                ((char *) enc_key->contents)[i] ^=0xf0;
            code = kg_arcfour_docrypt (enc_key, 0,
                                       bigend_seqnum, 4,
                                       plain, tmsglen,
                                       ptr+14+cksum_size);
            krb5_free_keyblock (context, enc_key);
            if (code)
            {
                xfree(plain);
                gssalloc_free(t);
                return(code);
            }
        }
        break;
        default:
            if ((code = kg_encrypt(context, enc, KG_USAGE_SEAL, NULL,
                                   (krb5_pointer) plain,
                                   (krb5_pointer) (ptr+cksum_size+14),
                                   tmsglen))) {
                xfree(plain);
                gssalloc_free(t);
                return(code);
            }
        }
    }else {
        if (tmsglen)
            memcpy(ptr+14+cksum_size, plain, tmsglen);
    }
    xfree(plain);


    /* that's it.  return the token */

    (*seqnum)++;
    *seqnum &= 0xffffffffL;

    token->length = tlen;
    token->value = (void *) t;

    return(0);
}
