/* packet-oer.c * Routines for ASN1 Octet Encoding Rules * * Copyright 2018, Anders Broman * * Wireshark - Network traffic analyzer * By Gerald Combs * 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 #include #include #include #include #include "packet-oer.h" #define PNAME "Octet 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; static int hf_oer_open_type_length = -1; /* Initialize the subtree pointers */ static int ett_oer = -1; static int ett_oer_sequence_of_item = -1; static int ett_oer_open_type = -1; static expert_field ei_oer_not_decoded_yet = EI_INIT; static expert_field ei_oer_undecoded = EI_INIT; static expert_field ei_oer_open_type = 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); } static 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 : ""; } idx--; } } return ""; } 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 : ""; } /* 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; } *length = 0; /* 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; } /* 9 Encoding of Boolean values */ guint32 dissect_oer_boolean(tvbuff_t* tvb, guint32 offset, asn1_ctx_t* actx, proto_tree* tree, int hf_index, gboolean* bool_val) { guint32 val = 0; DEBUG_ENTRY("dissect_oer_boolean"); actx->created_item = proto_tree_add_item_ret_uint(tree, hf_index, tvb, offset, 1, ENC_BIG_ENDIAN, &val); offset++; if (bool_val) { *bool_val = (gboolean)val; } 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, gint64 min, gint64 max, guint32 *value, gboolean has_extension _U_) { DEBUG_ENTRY("dissect_oer_constrained_integer"); guint32 val = 0; 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. */ if ((min >= -128) && (max <= 127)) { /* 10.4 a a) If the lower bound is greater than or equal to -2^7 (-128) and the upper bound is less than or equal to 2^7-1 (127), * then every value of the integer type shall be encoded as a fixed-size signed number in a one-octet word; */ proto_tree_add_item_ret_int(tree, hf_index, tvb, offset, 1, ENC_BIG_ENDIAN, &val); offset++; } else if ((min >= -32768) && (max <= 32767)) { /* if the lower bound is greater than or equal to -2^15 (-32768) and the upper bound is less than or equal to 2^15-1 (32767), * then every value of the integer type shall be encoded as a fixed-size signed number in a two octet word; */ proto_tree_add_item_ret_int(tree, hf_index, tvb, offset, 2, ENC_BIG_ENDIAN, &val); offset += 2; } else if ((min >= -2147483648LL) && (max <= 2147483647)) { /* if the lower bound is greater than or equal to -2^31 (-2147483648) and the upper bound is less than or equal to 2^31-1 (2147483647), * then every value of the integer type shall be encoded as a fixed-size signed number in a four-octet word */ proto_tree_add_item_ret_int(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"); } } 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, gint64 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, gint64 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 > 0) { 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"); } } else { dissect_oer_not_decoded_yet(tree, actx->pinfo, tvb, "constrained_integer unexpected length"); } } 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 = 0, 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 > 0) { 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"); } } else { dissect_oer_not_decoded_yet(tree, actx->pinfo, tvb, "constrained_integer unexpected length"); } 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_, int * const *named_bits _U_, gint num_named_bits _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); } static guint32 dissect_oer_bit_string_unconstr(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_, int * const *named_bits _U_, gint num_named_bits _U_, tvbuff_t **value_tvb _U_, guint8 * const values, int values_size, int *len _U_) { int length; guint8 unused_bit_count = 0; offset = dissect_oer_length_determinant(tvb, offset, actx, tree, -1 /*Don't show length value as internal field*/, &length); if (length > 0) { unused_bit_count = tvb_get_guint8(tvb, offset); if (unused_bit_count > 7) { dissect_oer_not_decoded_yet(tree, actx->pinfo, tvb, "too high unused bit count"); return offset + length; } offset += 1; length -= 1; } *len = length; if (values) { memset(values, 0, values_size); if (length > values_size) { dissect_oer_not_decoded_yet(tree, actx->pinfo, tvb, "too many bitstring elements"); } for (int i = 0; i < length; i++) { guint8 value = tvb_get_guint8(tvb, offset); if (i + 1 == length) { /* unused bits of the last octet shall be set to zeros */ value &= (0xFF << unused_bit_count); } if (i < values_size) { values[i] = value; } offset += 1; } } return offset; } /* 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); if (value_tvb) { *value_tvb = oer_tvb_new_subset_length(tvb, offset, length); } 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; guint64 extensions_present = 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_ret_val(tree, hf_oer_extension_present_bit, tvb, bit_offset, 1, &extensions_present, 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; icreated_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)); } } } if (extensions_present) { /* Parse the Extension Bitmap */ int ext_bmp_len; guint8 extension_mask[SEQ_MAX_COMPONENTS >> 3]; offset = dissect_oer_bit_string_unconstr(tvb, offset, actx, tree, hf_index, NO_BOUND, NO_BOUND, FALSE, NULL, 0, NULL, extension_mask, SEQ_MAX_COMPONENTS >> 3, &ext_bmp_len); /* find first extension */ int seq_pos; for (seq_pos = 0; sequence[seq_pos].p_id; seq_pos++) { if (sequence[seq_pos].extension == ASN1_NOT_EXTENSION_ROOT) { break; } } for (int bitstr_pos = 0; bitstr_pos < ext_bmp_len; bitstr_pos++) { gint8 octet = extension_mask[bitstr_pos]; for (int octet_pos = 0; octet_pos < 8; octet_pos++) { gboolean ext_present = ((octet << octet_pos) & (0x80)) >> 7; if (ext_present) { /* If any extensions still known - use functions */ if (sequence[seq_pos].p_id) { guint length; offset = dissect_oer_length_determinant(tvb, offset, actx, tree, hf_oer_length_determinant, &length); if (sequence[seq_pos].func) { offset = sequence[seq_pos].func(tvb, offset, actx, tree, *sequence[seq_pos].p_id); } else { dissect_oer_not_decoded_yet(tree, actx->pinfo, tvb, index_get_field_name(sequence, seq_pos )); } } else { offset = dissect_oer_octet_string(tvb, offset, actx, tree, hf_index, NO_BOUND, NO_BOUND, FALSE, NULL); } } /* if still within known sequence elements - move to next */ if (sequence[seq_pos].p_id) { seq_pos++; } } } } 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; ipinfo, &ei_oer_not_decoded_yet, tvb, offset, 1, "sequence_of Occurrence %u octets not handled", occ_len); return tvb_reported_length(tvb); } offset = offset + occ_len; hfi = proto_registrar_get_nth(hf_index); if (FT_IS_UINT(hfi->type)) { item = proto_tree_add_uint(parent_tree, hf_index, tvb, old_offset, occ_len, occurrence); proto_item_append_text(item, (occurrence == 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, occurrence); 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, "Choice, 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); /* For known extensions parse length prefix */ if (choice->extension == ASN1_NOT_EXTENSION_ROOT) { guint length; offset = dissect_oer_length_determinant(tvb, offset, actx, tree, hf_oer_length_determinant, &length); } 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++; } /* None of the known choice options matched, parse the contents as an extension */ // XXX : should check if the extensions are present in the CHOICE defintion offset = dissect_oer_octet_string(tvb, offset, actx, tree, hf_index, NO_BOUND, NO_BOUND, FALSE, NULL); return offset; } /* 21 Encoding of object identifier values * The encoding of an object identifier value shall consist of a length determinant (see 8.6) followed by a series of octets, * which are the contents octets of BER encoding of the object identifier value (see Rec. ITU-T X.690 | ISO/IEC 8825-1,8.19). */ static guint32 dissect_oer_any_oid(tvbuff_t* tvb, guint32 offset, asn1_ctx_t* actx, proto_tree* tree, int hf_index, tvbuff_t** value_tvb, gboolean is_absolute) { guint length; const char* str; header_field_info* hfi; DEBUG_ENTRY("dissect_oer_any_oid"); offset = dissect_oer_length_determinant(tvb, offset, actx, tree, hf_oer_length_determinant, &length); actx->created_item = NULL; hfi = proto_registrar_get_nth(hf_index); if ((is_absolute && hfi->type == FT_OID) || (!is_absolute && hfi->type == FT_REL_OID)) { actx->created_item = proto_tree_add_item(tree, hf_index, tvb, offset, length, ENC_BIG_ENDIAN); } else if (FT_IS_STRING(hfi->type)) { str = oid_encoded2string(actx->pinfo->pool, tvb_get_ptr(tvb, offset, length), length); actx->created_item = proto_tree_add_string(tree, hf_index, tvb, offset, length, str); if (actx->created_item) { /* see if we know the name of this oid */ str = oid_resolved_from_encoded(actx->pinfo->pool, tvb_get_ptr(tvb, offset, length), length); if (str) { proto_item_append_text(actx->created_item, " (%s)", str); } } } else { DISSECTOR_ASSERT_NOT_REACHED(); } if (value_tvb) *value_tvb = tvb_new_subset_length(tvb, offset, length); return offset; } guint32 dissect_oer_object_identifier(tvbuff_t* tvb, guint32 offset, asn1_ctx_t* actx, proto_tree* tree, int hf_index, tvbuff_t** value_tvb) { return dissect_oer_any_oid(tvb, offset, actx, tree, hf_index, value_tvb, TRUE); } /* 27 Encoding of values of the restricted character string types * 27.1 The encoding of a restricted character string type depends on whether the type is a known-multiplier character * string type or not. The following types are known-multiplier character string types: * IA5String, VisibleString, ISO646String, PrintableString, NumericString, BMPString, and UniversalString. */ guint32 dissect_oer_IA5String(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_) { guint32 length = 0; /* 27.2 For a known-multiplier character string type in which the lower and upper bounds of the effective size constraint * are identical, the encoding shall consist of the series of octets specified in 27.4, with no length determinant. */ if ((min_len == max_len) && (min_len != NO_BOUND )){ length = min_len; } else { 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_ASCII | ENC_NA); return offset + length; } 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 = 0; /* 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; } /* 30 Encoding of open type values *NOTE – An open type is an ASN.1 type that can take any abstract value of any ASN.1 type. Each value of an open type consists * of: * a) a contained type; and * b) a value of the contained type. * The encoding of an open type value shall consist of a length determinant (see 8.6) followed by a series of octets, which * are the encoding of the value of the contained type. */ static guint32 dissect_oer_open_type_internal(tvbuff_t* tvb, guint32 offset, asn1_ctx_t* actx, proto_tree* tree, int hf_index, void* type_cb, asn1_cb_variant variant) { int type_length, start_offset; tvbuff_t* val_tvb = NULL; proto_tree* subtree = tree; start_offset = offset; offset = dissect_oer_length_determinant(tvb, offset, actx, tree, hf_oer_open_type_length, &type_length); val_tvb = tvb_new_subset_length(tvb, offset, type_length); actx->created_item = proto_tree_add_item(tree, hf_index, val_tvb, 0, type_length, ENC_BIG_ENDIAN); subtree = proto_item_add_subtree(actx->created_item, ett_oer_open_type); if (variant == CB_NEW_DISSECTOR) { add_new_data_source(actx->pinfo, val_tvb, "OCTET STRING"); } if (type_cb) { switch (variant) { case CB_ASN1_ENC: ((oer_type_fn)type_cb)(val_tvb, 0, actx, tree, hf_index); break; case CB_NEW_DISSECTOR: /* Pas actx->private_data as "data" to the called function */ ((dissector_t)type_cb)(val_tvb, actx->pinfo, subtree, actx->private_data); break; case CB_DISSECTOR_HANDLE: break; } } else { actx->created_item = proto_tree_add_expert(tree, actx->pinfo, &ei_oer_open_type, tvb, start_offset, offset - start_offset); } return offset; } guint32 dissect_oer_open_type(tvbuff_t* tvb, guint32 offset, asn1_ctx_t* actx, proto_tree* tree, int hf_index, oer_type_fn type_cb) { return dissect_oer_open_type_internal(tvb, offset, actx, tree, hf_index, (void*)type_cb, CB_ASN1_ENC); } /*--- 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 } }, { &hf_oer_open_type_length, { "Open Type Length", "oer.open_type_length", FT_UINT32, BASE_DEC, NULL, 0x0, NULL, HFILL } }, }; /* List of subtrees hf_oer_extension*/ static gint *ett[] = { &ett_oer, &ett_oer_sequence_of_item, &ett_oer_open_type, }; 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 } }, { &ei_oer_open_type, { "oer.open_type.unknown", PI_PROTOCOL, PI_WARN, "Unknown Open Type", 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 - https://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: */