Add dissector for ITU-t X.696 Octet Encoding Rules (OER).

Bug: 13766
Change-Id: Id1770d8b0bab73ef26af679cba4d88c65cbc21cc
Reviewed-on: https://code.wireshark.org/review/30242
Petri-Dish: Anders Broman <a.broman58@gmail.com>
Tested-by: Petri Dish Buildbot
Reviewed-by: Anders Broman <a.broman58@gmail.com>

1 files changed, 765 insertions, 0 deletions

diff --git a/epan/dissectors/packet-oer.c b/epan/dissectors/packet-oer.c
new file mode 100644
index 0000000000..abf818bc58
--- /dev/null
+++ b/epan/dissectors/packet-oer.c
@@ -0,0 +1,765 @@
+/* packet-oer.c
+ * Routines for ASN1 Octet Encoding Rules
+ *
+ * Copyright 2018, Anders Broman <anders.broman@ericsson.com>
+ *
+ * Wireshark - Network traffic analyzer
+ * By Gerald Combs <gerald@wireshark.org>
+ * Copyright 1998 Gerald Combs
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ * Ref: ITU-T X.696 (08/2015) https://www.itu.int/itu-t/recommendations/rec.aspx?rec=12487
+ * Based on the BER and PER dissectors by Ronnie Sahlberg.
+ */
+
+#include "config.h"
+
+#include <epan/packet.h>
+#include <epan/oids.h>
+#include <epan/asn1.h>
+#include <epan/expert.h>
+#include <epan/exceptions.h>
+
+#include "packet-oer.h"
+
+
+#define PNAME  "Ocetet Encoding Rules (ASN.1)"
+#define PSNAME "OER"
+#define PFNAME "oer"
+
+void proto_register_oer(void);
+void proto_reg_handoff_oer(void);
+
+/* Initialize the protocol and registered fields */
+static int proto_oer = -1;
+
+static int hf_oer_optional_field_bit = -1;
+static int hf_oer_class = -1;
+static int hf_oer_tag = -1;
+static int hf_oer_length_determinant = -1;
+static int hf_oer_extension_present_bit = -1;
+
+/* Initialize the subtree pointers */
+static int ett_oer = -1;
+static int ett_oer_sequence_of_item = -1;
+
+static expert_field ei_oer_not_decoded_yet = EI_INIT;
+static expert_field ei_oer_undecoded = EI_INIT;
+
+/* whether the OER helpers should put the internal OER fields into the tree or not. */
+static gboolean display_internal_oer_fields = FALSE;
+
+/*
+#define DEBUG_ENTRY(x) \
+printf("#%u  %s   tvb:0x%08x\n",actx->pinfo->num,x,(int)tvb);
+*/
+#define DEBUG_ENTRY(x) \
+	;
+
+#define SEQ_MAX_COMPONENTS 128
+
+/*
+* XXX - if the specified length is less than the remaining length
+* of data in the tvbuff, either 1) the specified length is bad and
+* we should report that with an expert info or 2) the tvbuff is
+* unreassembled and we should make the new tvbuff also be an
+* unreassembled tvbuff.
+*/
+static tvbuff_t *
+oer_tvb_new_subset_length(tvbuff_t *tvb, const gint backing_offset, const gint backing_length)
+{
+    gint length_remaining;
+
+    length_remaining = tvb_reported_length_remaining(tvb, backing_offset);
+    return tvb_new_subset_length(tvb, backing_offset, (length_remaining > backing_length) ? backing_length : length_remaining);
+}
+
+void dissect_oer_not_decoded_yet(proto_tree* tree, packet_info* pinfo, tvbuff_t *tvb, const char* reason)
+{
+    proto_tree_add_expert_format(tree, pinfo, &ei_oer_undecoded, tvb, 0, 0, "something unknown here [%s]", reason);
+    col_append_fstr(pinfo->cinfo, COL_INFO, "[UNKNOWN OER: %s]", reason);
+    THROW(ReportedBoundsError);
+}
+
+/* Given the ordinal of the option in the sequence, print the name. eg find the 1:th then the 2:nd etc*/
+static const char *
+index_get_optional_name(const oer_sequence_t *sequence, int idx)
+{
+    int i;
+    header_field_info *hfi;
+
+    for (i = 0; sequence[i].p_id; i++) {
+        if ((sequence[i].extension != ASN1_NOT_EXTENSION_ROOT) && (sequence[i].optional == ASN1_OPTIONAL)) {
+            if (idx == 0) {
+                hfi = proto_registrar_get_nth(*sequence[i].p_id);
+                return (hfi) ? hfi->name : "<unknown filed>";
+            }
+            idx--;
+        }
+    }
+    return "<unknown type>";
+}
+
+
+static const char *
+index_get_field_name(const oer_sequence_t *sequence, int idx)
+{
+    header_field_info *hfi;
+
+    hfi = proto_registrar_get_nth(*sequence[idx].p_id);
+    return (hfi) ? hfi->name : "<unknown filed>";
+}
+
+
+/* 8.6 Length determinant */
+static guint32
+dissect_oer_length_determinant(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, guint32 *length)
+{
+    proto_item *item;
+    guint8 oct, value_len;
+    guint32 len;
+
+    if (!length) {
+        length = &len;
+    }
+
+    /* 8.6.3 There are two forms of length determinant - a short form and a long form...
+     * 8.6.4 The short form of length determinant consists of a single octet. Bit 8 of this octet shall be set to '0',
+     * and bits 7 to 1 of this octet shall contain the length (0 to 127) encoded as an unsigned binary integer into 7 bits.
+     */
+    oct = tvb_get_guint8(tvb, offset);
+    if ((oct & 0x80) == 0) {
+        /* Short form */
+        *length = oct;
+        if (hf_index != -1) {
+            item = proto_tree_add_item(tree, hf_index, tvb, offset, 1, ENC_BIG_ENDIAN);
+            if (!display_internal_oer_fields) PROTO_ITEM_SET_HIDDEN(item);
+        }
+        offset++;
+
+        return offset;
+    }
+    offset++;
+    /* Long form */
+    /* 8.6.5 The long form of length determinant consists of an initial octet followed by one or more subsequent octets.
+     * Bit 8 of the initial octet shall be set to 1, and bits 7 to 1 of this octet shall indicate the number of subsequent octets (1 to 127).
+     * The length shall be encoded as a variable-size unsigned number into the subsequent octets.
+     */
+    value_len = oct & 0x7f;
+    switch (value_len) {
+    case 1:
+        *length = tvb_get_guint8(tvb, offset);
+        offset++;
+        break;
+    case 2:
+        *length = tvb_get_ntohs(tvb, offset);
+        offset+=2;
+        break;
+    case 3:
+        *length = tvb_get_ntoh24(tvb, offset);
+        offset+=3;
+        break;
+    case 4:
+        *length = tvb_get_ntohl(tvb, offset);
+        offset+=4;
+        break;
+    default:
+        proto_tree_add_expert_format(tree, actx->pinfo, &ei_oer_not_decoded_yet, tvb, offset, 1,
+            "Length determinant: Long form %u octets not handled", value_len);
+        return tvb_reported_length(tvb);
+    }
+
+    return offset;
+
+}
+
+/* 10 Encoding of integer values */
+
+guint32
+dissect_oer_constrained_integer(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, guint32 min, guint32 max, guint32 *value, gboolean has_extension _U_)
+{
+    DEBUG_ENTRY("dissect_oer_constrained_integer");
+    guint32 val = 0;
+
+    /* XXX We need to hndle negative numbers ?*/
+    if (min > 0) {
+        /* 10.2 There are two main cases:
+         *      a) The effective value constraint has a lower bound, and that lower bound is zero or positive.
+         */
+        if (max < 0x100) {
+            /* One octet */
+            proto_tree_add_item_ret_uint(tree, hf_index, tvb, offset, 1, ENC_BIG_ENDIAN, &val);
+            offset++;
+        } else if (max < 0x10000) {
+            /* Two octets */
+            proto_tree_add_item_ret_uint(tree, hf_index, tvb, offset, 2, ENC_BIG_ENDIAN, &val);
+            offset += 2;
+        } else if (max == 0xFFFFFFFF) {
+            /* Four octets */
+            proto_tree_add_item_ret_uint(tree, hf_index, tvb, offset, 4, ENC_BIG_ENDIAN, &val);
+            offset += 4;
+        } else {
+            /* To large not handlet yet*/
+            dissect_oer_not_decoded_yet(tree, actx->pinfo, tvb, "constrained_integer to large value");
+        }
+
+    } else {
+        /* b) The effective value constraint has either a negative lower bound or no lower bound. */
+        dissect_oer_not_decoded_yet(tree, actx->pinfo, tvb, "constrained_integer negative value");
+    }
+
+    if (value) {
+        *value = val;
+    }
+
+    return offset;
+
+}
+
+guint32
+dissect_oer_constrained_integer_64b(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, guint64 min, guint64 max, guint64 *value, gboolean has_extension _U_)
+{
+    guint64 val = 0;
+
+    /* XXX Negative numbers ???*/
+    if (min > 0) {
+        /* 10.2 There are two main cases:
+        *      a) The effective value constraint has a lower bound, and that lower bound is zero or positive.
+        */
+        /* 10.3 */
+        if (max < 0x100) {
+            /* One octet, upper bound is less than or equal to 2 exp 8 - 1 (255) */
+            proto_tree_add_item_ret_uint64(tree, hf_index, tvb, offset, 1, ENC_BIG_ENDIAN, &val);
+            offset++;
+        } else if (max < 0x10000) {
+            /* Two octets, upper bound is less than or equal to 2 exp 16 - 1 (65535), */
+            proto_tree_add_item_ret_uint64(tree, hf_index, tvb, offset, 2, ENC_BIG_ENDIAN, &val);
+            offset += 2;
+        } else if (max < 0x100000000) {
+            /* Four octets, upper bound is less than or equal to 2 exp 32 - 1 (4294967295), */
+            proto_tree_add_item_ret_uint64(tree, hf_index, tvb, offset, 4, ENC_BIG_ENDIAN, &val);
+            offset += 4;
+        } else if (max == G_GUINT64_CONSTANT(18446744073709551615)) {
+            /* Eight octets, upper bound is less than or equal to 2 exp 64 - 1 (4294967295), */
+            proto_tree_add_item_ret_uint64(tree, hf_index, tvb, offset, 8, ENC_BIG_ENDIAN, &val);
+            offset += 8;
+        } else {
+            /* eight-octet, upper bound is less than or equal to 2 exp 64 - 1 (18446744073709551615) */
+            /* To large not handlet yet*/
+            dissect_oer_not_decoded_yet(tree, actx->pinfo, tvb, "constrained_integer to large value");
+        }
+
+    } else {
+        /* b) The effective value constraint has either a negative lower bound or no lower bound. */
+        dissect_oer_not_decoded_yet(tree, actx->pinfo, tvb, "constrained_integer negative value");
+    }
+
+    if (value) {
+        *value = val;
+    }
+
+    return offset;
+
+}
+
+guint32
+dissect_oer_constrained_integer_64b_no_ub(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, guint64 min, guint64 max _U_, guint64 *value, gboolean has_extension _U_)
+{
+    guint64 val = 0;
+    guint32 length;
+
+    /* Negative numbers ???*/
+    if (min > 0) {
+
+        /* (the effective value constraint has either an upper bound greater than 2 exp 64-1 or no upper bound)
+        * every value of the integer type shall be encoded as a length determinant (see 8.6)
+        * followed by a variable-size unsigned number
+        * (occupying at least as many whole octets as are necessary to carry the value).
+        */
+        offset = dissect_oer_length_determinant(tvb, offset, actx, tree, hf_oer_length_determinant, &length);
+        if (length < 5) {
+            proto_tree_add_item_ret_uint64(tree, hf_index, tvb, offset, length, ENC_BIG_ENDIAN, &val);
+            offset += length;
+        } else {
+            dissect_oer_not_decoded_yet(tree, actx->pinfo, tvb, "constrained_integer NO_BOUND to many octets");
+        }
+    }
+    if (value) {
+        *value = val;
+    }
+
+    return offset;
+
+}
+
+guint32
+dissect_oer_integer(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, gint32 *value)
+{
+    guint32 val, length;
+    /* 10.4 e) (the effective value constraint has a lower bound less than -263, no lower bound,
+     * an upper bound greater than 2 exp 63-1, or no upper bound) every value of the integer type
+     * shall be encoded as a length determinant (see 8.6) followed by a variable-size signed number
+     * (occupying at least as many whole octets as are necessary to carry the value).
+     */
+    offset = dissect_oer_length_determinant(tvb, offset, actx, tree, hf_oer_length_determinant, &length);
+    if (length < 5) {
+        proto_tree_add_item_ret_uint(tree, hf_index, tvb, offset, length, ENC_BIG_ENDIAN, &val);
+        offset += length;
+    } else {
+        dissect_oer_not_decoded_yet(tree, actx->pinfo, tvb, "constrained_integer NO_BOUND to many octets");
+    }
+
+    if (value) {
+        *value = val;
+    }
+
+    return offset;
+
+}
+/* 11 Encoding of enumerated values */
+guint32
+dissect_oer_enumerated(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, guint32 root_num _U_, guint32 *value, gboolean has_extension _U_, guint32 ext_num _U_, guint32 *value_map _U_)
+{
+    int old_offset = offset;
+    guint32 val;
+    /* 11.2 There are two forms of enumerated type encoding - a short form and a long form... */
+
+    offset = dissect_oer_length_determinant(tvb, offset, actx, tree, -1 /*Don't show length value as internal field*/, &val);
+    actx->created_item = proto_tree_add_uint(tree, hf_index, tvb, old_offset, offset - old_offset, val);
+
+    if (value) {
+        *value = val;
+    }
+
+    return offset;
+
+
+}
+/* 13 Encoding of bitstring values */
+
+/* 13.1 General
+ * The encoding of a bitstring value depends on the effective size constraint of the bitstring type (see 8.2.8).
+ *  If the lower and upper bounds of the effective size constraint are identical, 13.2 applies, otherwise 13.3 applies.
+ */
+guint32
+dissect_oer_bit_string(tvbuff_t *tvb, guint32 offset _U_, asn1_ctx_t *actx, proto_tree *tree, int hf_index _U_, int min_len _U_, int max_len _U_, gboolean has_extension _U_, tvbuff_t **value_tvb _U_, int *len _U_)
+{
+    dissect_oer_not_decoded_yet(tree, actx->pinfo, tvb, "Encoding of bitstring values not handled yet");
+
+    return tvb_reported_length(tvb);
+}
+
+/* 14 Encoding of octet string values */
+guint32
+dissect_oer_octet_string(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, int min_len, int max_len, gboolean has_extension _U_, tvbuff_t **value_tvb)
+{
+    guint length;
+    /* 14.1 For an octetstring type in which the lower and upper bounds of the effective size constraint are identical,
+     * the encoding shall consist of the octets of the octetstring value (zero or more octets), with no length determinant.
+     */
+    if ((min_len != NO_BOUND ) && (min_len == max_len)) {
+        actx->created_item = proto_tree_add_item(tree, hf_index, tvb, offset, min_len, ENC_NA);
+        if (value_tvb) {
+            *value_tvb = oer_tvb_new_subset_length(tvb, offset, min_len);
+        }
+        return offset + min_len;
+    }
+
+    /* 14.2 For any other octetstring type, the encoding shall consist of a length determinant (see 8.6)
+     * followed by the octets of the octetstring value (zero or more octets).
+     */
+    offset = dissect_oer_length_determinant(tvb, offset, actx, tree, hf_oer_length_determinant, &length);
+    actx->created_item = proto_tree_add_item(tree, hf_index, tvb, offset, length, ENC_NA);
+    offset = offset + length;
+
+    return offset;
+
+}
+
+/* 15 Encoding of the null value */
+guint32
+dissect_oer_null(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx _U_, proto_tree *tree, int hf_index)
+{
+    /* The encoding of the null value shall be empty. */
+    proto_item *ti_tmp;
+
+    ti_tmp = proto_tree_add_item(tree, hf_index, tvb, offset, 1, ENC_BIG_ENDIAN);
+    proto_item_append_text(ti_tmp, ": NULL");
+
+    return offset;
+}
+
+static const value_string oer_class_vals[] = {
+    {   0, "universal" },
+    {   1, "application" },
+    {   2, "context-specific" },
+    {   3, "private" },
+    { 0, NULL }
+};
+
+static const value_string oer_extension_present_bit_vals[] = {
+    {   0, "Not present" },
+    {   1, "Present" },
+    { 0, NULL }
+};
+
+
+
+/* 16 Encoding of sequence values */
+guint32
+dissect_oer_sequence(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *parent_tree, int hf_index, gint ett_index, const oer_sequence_t *sequence)
+{
+    guint64 optional_field_flag;
+    proto_item *item;
+    proto_tree *tree;
+    guint32 old_offset = offset;
+    guint32 i, j, num_opts;
+    guint32 optional_mask[SEQ_MAX_COMPONENTS >> 5];
+    int bit_offset = 0;
+
+    DEBUG_ENTRY("dissect_oer_sequence");
+
+    item = proto_tree_add_item(parent_tree, hf_index, tvb, offset, 0, ENC_BIG_ENDIAN);
+    tree = proto_item_add_subtree(item, ett_index);
+
+
+    /* first check if there should be an extension bit for this SEQUENSE.
+    * we do this by just checking the first entry
+    */
+    bit_offset = offset << 3;
+    if (sequence[0].extension == ASN1_NO_EXTENSIONS) {
+        /*extension_present=0;  ?? */
+    } else {
+        /* 16.2.2 The extension bit shall be present (as bit 8 of the first octet of the preamble)
+         * if, and only if, the sequence type definition contains an extension marker...
+         */
+        actx->created_item = proto_tree_add_bits_item(tree, hf_oer_extension_present_bit, tvb, bit_offset, 1, ENC_BIG_ENDIAN);
+        bit_offset++;
+        if (!display_internal_oer_fields) PROTO_ITEM_SET_HIDDEN(actx->created_item);
+    }
+    /* The presence bitmap is encoded as a bit string with a fixed size constraint (see 16.2.3),
+    * and has one bit for each field of the sequence type that has the keyword OPTIONAL or DEFAULT,
+    * in specification order.
+    */
+    num_opts = 0;
+    for (i = 0; sequence[i].p_id; i++) {
+        if ((sequence[i].extension != ASN1_NOT_EXTENSION_ROOT) && (sequence[i].optional == ASN1_OPTIONAL)) {
+            num_opts++;
+        }
+    }
+    if (num_opts > SEQ_MAX_COMPONENTS) {
+        dissect_oer_not_decoded_yet(tree, actx->pinfo, tvb, "too many optional/default components");
+    }
+
+    memset(optional_mask, 0, sizeof(optional_mask));
+    for (i = 0; i<num_opts; i++) {
+        actx->created_item = proto_tree_add_bits_ret_val(tree, hf_oer_optional_field_bit, tvb, bit_offset, 1, &optional_field_flag, ENC_BIG_ENDIAN);
+        bit_offset++;
+        if (tree) {
+            proto_item_append_text(actx->created_item, " (%s %s present)",
+                index_get_optional_name(sequence, i), optional_field_flag ? "is" : "is NOT");
+        }
+        if (!display_internal_oer_fields) PROTO_ITEM_SET_HIDDEN(actx->created_item);
+        if (optional_field_flag) {
+            optional_mask[i >> 5] |= 0x80000000 >> (i & 0x1f);
+        }
+    }
+    if (num_opts > 0) {
+        guint8 len = num_opts >> 3;
+        guint8 remaining_bits = num_opts % 8;
+        if (remaining_bits) {
+            len++;
+        }
+        offset += len;
+    }
+
+    /*  */
+    for (i = 0, j = 0; sequence[i].p_id; i++) {
+        if ((sequence[i].extension == ASN1_NO_EXTENSIONS)
+            || (sequence[i].extension == ASN1_EXTENSION_ROOT)) {
+            if (sequence[i].optional == ASN1_OPTIONAL) {
+                gboolean is_present;
+                if (num_opts == 0) {
+                    continue;
+                }
+                is_present = (0x80000000 >> (j & 0x1f))&optional_mask[j >> 5];
+                num_opts--;
+                j++;
+                if (!is_present) {
+                    continue;
+                }
+            }
+            if (sequence[i].func) {
+                offset = sequence[i].func(tvb, offset, actx, tree, *sequence[i].p_id);
+            } else {
+                dissect_oer_not_decoded_yet(tree, actx->pinfo, tvb, index_get_field_name(sequence, i));
+            }
+        }
+    }
+
+
+    /* XXX We do not handle extensions */
+
+    proto_item_set_len(item, offset - old_offset);
+    actx->created_item = item;
+    return offset;
+}
+
+/* 17 Encoding of sequence-of values */
+
+static guint32
+dissect_oer_sequence_of_helper(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, oer_type_fn func, int hf_index, guint32 length)
+{
+    guint32 i;
+
+    DEBUG_ENTRY("dissect_oer_sequence_of_helper");
+    for (i = 0; i<length; i++) {
+        guint32 lold_offset = offset;
+        proto_item *litem;
+        proto_tree *ltree;
+
+        ltree = proto_tree_add_subtree_format(tree, tvb, offset, 0, ett_oer_sequence_of_item, &litem, "Item %d", i);
+
+        offset = (*func)(tvb, offset, actx, ltree, hf_index);
+        proto_item_set_len(litem, offset - lold_offset);
+    }
+
+    return offset;
+}
+
+guint32
+dissect_oer_sequence_of(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *parent_tree, int hf_index, gint ett_index, const oer_sequence_t *seq)
+{
+    proto_item *item;
+    proto_tree *tree;
+    guint32 old_offset = offset;
+    guint32 occ_len, occurence;
+    header_field_info *hfi;
+
+    DEBUG_ENTRY("dissect_oer_sequence_of");
+
+    /* 17.1 The encoding of a sequence-of value shall consist of a quantity field...*/
+
+    /* 17.2 The quantity field shall be a non-negative integer value indicating the number of occurrences.
+     * This number shall be encoded as a length determinant (see 8.6) followed by a variable-size unsigned number
+     * (occupying at least as many whole octets as are necessary to carry the value).
+     */
+    offset = dissect_oer_length_determinant(tvb, offset, actx, parent_tree, hf_oer_length_determinant, &occ_len);
+
+    switch (occ_len) {
+    case 1:
+        occurence = tvb_get_guint8(tvb, offset);
+        break;
+    case 2:
+        occurence = tvb_get_ntohs(tvb, offset);
+        break;
+    case 3:
+        occurence = tvb_get_ntoh24(tvb, offset);
+        break;
+    case 4:
+        occurence = tvb_get_ntohl(tvb, offset);
+        break;
+    default:
+        proto_tree_add_expert_format(parent_tree, actx->pinfo, &ei_oer_not_decoded_yet, tvb, offset, 1,
+            "sequence_of Occurance %u octets not handled", occ_len);
+        return tvb_reported_length(tvb);
+    }
+
+    offset = offset + occ_len;
+    hfi = proto_registrar_get_nth(hf_index);
+    if (IS_FT_UINT(hfi->type)) {
+        item = proto_tree_add_uint(parent_tree, hf_index, tvb, old_offset, occ_len, occurence);
+        proto_item_append_text(item, (occurence == 1) ? " item" : " items");
+    } else {
+        item = proto_tree_add_item(parent_tree, hf_index, tvb, old_offset, 0, ENC_BIG_ENDIAN);
+    }
+    tree = proto_item_add_subtree(item, ett_index);
+
+    offset = dissect_oer_sequence_of_helper(tvb, offset, actx, tree, seq->func, *seq->p_id, occurence);
+
+
+    proto_item_set_len(item, offset - old_offset);
+    return offset;
+
+}
+
+/* As we are using the per ASN1 generator define this "dummy" function */
+guint32
+dissect_oer_constrained_sequence_of(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *parent_tree, int hf_index, gint ett_index, const oer_sequence_t *seq, int min_len _U_, int max_len _U_ , gboolean has_extension _U_)
+{
+    return dissect_oer_sequence_of(tvb, offset, actx, parent_tree, hf_index, ett_index, seq);
+
+}
+/* 20 Encoding of choice values */
+guint32
+dissect_oer_choice(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, gint ett_index, const oer_choice_t *choice, gint *value)
+{
+    proto_tree *choice_tree;
+    proto_item *item, *choice_item;
+    int bit_offset = offset << 3;
+    guint64 oer_class;
+    guint8 tag, oct;
+    int old_offset = offset;
+
+    /* 20.1 The encoding of a value of a choice type shall consist of the encoding of the outermost tag of the type of the chosen alternative
+     * as specified in 8.7, followed by the encoding of the value of the chosen alternative.
+     */
+
+    /* 8.7.2.1 Bits 8 and 7 of the first octet shall denote the tag class */
+    item = proto_tree_add_bits_ret_val(tree, hf_oer_class, tvb, bit_offset, 2, &oer_class, ENC_BIG_ENDIAN);
+    if (!display_internal_oer_fields) PROTO_ITEM_SET_HIDDEN(item);
+    bit_offset += 2;
+
+    tag = tvb_get_bits8(tvb, bit_offset, 6);
+    offset++;
+    /* 8.7.2.3 If the tag number is greater or equal to 63, Bits 6 to 1 of the initial octet shall be set to '111111'B.*/
+    if (tag == 0x3f) {
+        /* The tag number shall be encoded into bits 7 to 1 of each subsequent octet (seven bits in each octet),
+         * with bit 1 of the final subsequent octet containing the least significant bit of the tag number ("big-endian" encoding).
+         */
+        oct = tvb_get_guint8(tvb, offset);
+        if ((oct & 0x80) == 0x80) {
+            dissect_oer_not_decoded_yet(tree, actx->pinfo, tvb, "Choise, Tag value > 0x7f not implemented yet");
+        } else {
+            /* Bits 7 to 1 of the first subsequent octet shall not be all set to 0.*/
+            tag = oct;
+            item = proto_tree_add_uint(tree, hf_oer_tag, tvb, offset, 1, tag);
+            if (!display_internal_oer_fields) PROTO_ITEM_SET_HIDDEN(item);
+        }
+    } else {
+        /* Tag value in first octet */
+        item = proto_tree_add_bits_item(tree, hf_oer_tag, tvb, bit_offset, 6, ENC_BIG_ENDIAN);
+        if (!display_internal_oer_fields) PROTO_ITEM_SET_HIDDEN(item);
+    }
+
+    /* 20.2 If the choice type contains an extension marker in the "AlternativeTypeLists" and the chosen alternative
+     * is one of the extension additions, then the value of the chosen alternative shall be encoded as if it were contained
+     * in an open type (see clause 30), otherwise it shall be encoded normally.
+     */
+    if (value) {
+        (*value) = -1;
+    }
+
+    /* XXX Extension handling is not implemented */
+    while (choice->func) {
+        if (choice->value == tag) {
+            choice_item = proto_tree_add_uint(tree, hf_index, tvb, old_offset, 0, choice->value);
+            choice_tree = proto_item_add_subtree(choice_item, ett_index);
+            offset = choice->func(tvb, offset, actx, choice_tree, *choice->p_id);
+            proto_item_set_len(choice_item, offset - old_offset);
+            if (value) {
+                (*value) = tag;
+            }
+            return offset;
+        }
+        choice++;
+    }
+
+    dissect_oer_not_decoded_yet(tree, actx->pinfo, tvb, "Choise : No matching tag");
+
+    return tvb_reported_length(tvb);
+}
+
+/* 27 Encoding of values of the restricted character string types */
+
+guint32
+dissect_oer_UTF8String(tvbuff_t *tvb, guint32 offset, asn1_ctx_t *actx, proto_tree *tree, int hf_index, int min_len _U_, int max_len _U_, gboolean has_extension _U_)
+{
+    guint32 length;
+    /* 27.3 For every other character string type, the encoding shall consist of a length determinant
+     * (see 8.6) followed by the series of octets specified in 27.4.
+     */
+    offset = dissect_oer_length_determinant(tvb, offset, actx, tree, hf_oer_length_determinant, &length);
+    actx->created_item = proto_tree_add_item( tree, hf_index, tvb, offset, length, ENC_UTF_8 | ENC_NA);
+
+    return offset + length;
+
+}
+
+/*--- proto_register_oer ----------------------------------------------*/
+void proto_register_oer(void) {
+
+    /* List of fields */
+    static hf_register_info hf[] = {
+        { &hf_oer_optional_field_bit,
+        { "Optional Field Bit", "oer.optional_field_bit",
+            FT_UINT8, BASE_DEC, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_oer_class,
+        { "Class", "oer.class",
+            FT_UINT8, BASE_DEC, VALS(oer_class_vals), 0x0,
+            NULL, HFILL }
+        },
+        { &hf_oer_tag,
+        { "Tag", "oer.tag",
+            FT_UINT32, BASE_DEC, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_oer_length_determinant,
+        { "length_determinant", "oer.length_determinant",
+            FT_UINT32, BASE_DEC, NULL, 0x0,
+            NULL, HFILL }
+        },
+        { &hf_oer_extension_present_bit,
+        { "Extension Present Bit", "oer.extension_present_bit",
+        FT_UINT8, BASE_DEC, VALS(oer_extension_present_bit_vals), 0x00,
+        NULL, HFILL } },
+
+    };
+
+    /* List of subtrees hf_oer_extension*/
+    static gint *ett[] = {
+        &ett_oer,
+        &ett_oer_sequence_of_item,
+    };
+
+    module_t *oer_module;
+    expert_module_t* expert_oer;
+
+    /* Register protocol */
+    proto_oer = proto_register_protocol(PNAME, PSNAME, PFNAME);
+
+    /* Register fields and subtrees */
+    proto_register_field_array(proto_oer, hf, array_length(hf));
+    proto_register_subtree_array(ett, array_length(ett));
+
+    static ei_register_info ei[] = {
+        { &ei_oer_not_decoded_yet,
+            { "oer.not_decoded_yet", PI_UNDECODED, PI_WARN, "Not decoded yet", EXPFILL }},
+        { &ei_oer_undecoded,
+            { "oer.error.undecoded", PI_UNDECODED, PI_WARN, "OER: Something unknown here", EXPFILL } },
+    };
+
+    expert_oer = expert_register_protocol(proto_oer);
+    expert_register_field_array(expert_oer, ei, array_length(ei));
+
+    oer_module = prefs_register_protocol(proto_oer, NULL);
+    prefs_register_bool_preference(oer_module, "display_internal_oer_fields",
+        "Display the internal OER fields in the tree",
+        "Whether the dissector should put the internal OER data in the tree or if it should hide it",
+        &display_internal_oer_fields);
+
+
+    proto_set_cant_toggle(proto_oer);
+
+}
+
+
+        /*--- proto_reg_handoff_oer -------------------------------------------*/
+void proto_reg_handoff_oer(void) {
+
+}
+
+/*
+* Editor modelines  -  http://www.wireshark.org/tools/modelines.html
+*
+* Local variables:
+* c-basic-offset: 4
+* tab-width: 8
+* indent-tabs-mode: nil
+* End:
+*
+* vi: set shiftwidth=4 tabstop=8 expandtab:
+* :indentSize=4:tabSize=8:noTabs=true:
+*/