/* packet-oscore.c * Routines for Object Security for Constrained RESTful Environments dissection * Copyright 2017, Malisa Vucinic * * Wireshark - Network traffic analyzer * By Gerald Combs * Copyright 1998 Gerald Combs * * SPDX-License-Identifier: GPL-2.0-or-later */ /* * rfc8613 */ #include #include /* Should be first Wireshark include (other than config.h) */ #include #include /* Include only as needed */ #include #include #include /* Include only as needed */ #include #include #include "packet-ieee802154.h" /* We use CCM implementation available as part of 802.15.4 dissector */ #include "packet-coap.h" /* packet-coap.h includes packet-oscore.h */ /* Prototypes */ static unsigned oscore_alg_get_key_len(cose_aead_alg_t); static unsigned oscore_alg_get_iv_len(cose_aead_alg_t); static unsigned oscore_alg_get_tag_len(cose_aead_alg_t); static bool oscore_context_derive_params(oscore_context_t *); /* CBOR encoder prototypes */ static uint8_t cborencoder_put_text(uint8_t *buffer, const char *text, uint8_t text_len); static uint8_t cborencoder_put_null(uint8_t *buffer); static uint8_t cborencoder_put_unsigned(uint8_t *buffer, uint8_t value); static uint8_t cborencoder_put_bytes(uint8_t *buffer, const uint8_t *bytes, uint8_t bytes_len); static uint8_t cborencoder_put_array(uint8_t *buffer, uint8_t elements); /* (Required to prevent [-Wmissing-prototypes] warnings */ void proto_reg_handoff_oscore(void); void proto_register_oscore(void); /* Initialize the protocol and registered fields */ static int proto_oscore; static int proto_coap; static int hf_oscore_tag; static COAP_COMMON_LIST_T(dissect_oscore_hf); static expert_field ei_oscore_partial_iv_not_found; static expert_field ei_oscore_context_not_set; static expert_field ei_oscore_message_too_small; static expert_field ei_oscore_truncated; static expert_field ei_oscore_tag_check_failed; static expert_field ei_oscore_decrypt_error; static expert_field ei_oscore_cbc_mac_failed; static expert_field ei_oscore_piv_len_invalid; static expert_field ei_oscore_info_fetch_failed; /* Initialize the subtree pointers */ static int ett_oscore; /* UAT variables */ static uat_t *oscore_context_uat; static oscore_context_t *oscore_contexts; static unsigned num_oscore_contexts; /* Enumeration for COSE algorithms used by OSCORE */ static const value_string oscore_context_alg_vals[] = { { COSE_AES_CCM_16_64_128, "AES-CCM-16-64-128 (CCM*)"}, { 0, NULL } }; /* Field callbacks. */ UAT_CSTRING_CB_DEF(oscore_context_uat, master_secret_prefs, oscore_context_t) UAT_CSTRING_CB_DEF(oscore_context_uat, master_salt_prefs, oscore_context_t) UAT_CSTRING_CB_DEF(oscore_context_uat, id_context_prefs, oscore_context_t) UAT_CSTRING_CB_DEF(oscore_context_uat, sender_id_prefs, oscore_context_t) UAT_CSTRING_CB_DEF(oscore_context_uat, recipient_id_prefs, oscore_context_t) UAT_VS_DEF(oscore_context_uat, algorithm, oscore_context_t, cose_aead_alg_t, COSE_AES_CCM_16_64_128, "AES-CCM-16-64-128 (CCM*)") #define OSCORE_MIN_LENGTH 9 /* 1 byte for code plus 8 bytes for shortest authentication tag */ #define OSCORE_VERSION 1 /* rfc8613 */ #define TAG_MAX_LEN 16 #define AES_128_BLOCK_LEN 16 #define NONCE_MAX_LEN 13 /* longest nonce in RFC8152 is 13 bytes */ #define OSCORE_PIV_MAX_LEN 5 /* upper bound specified in the draft */ #define OSCORE_KID_MAX_LEN_CCM_STAR 7 /* upper bound on KID for AES-CCM-16-64-128 (CCM*) */ #define OSCORE_KID_MAX_LEN OSCORE_KID_MAX_LEN_CCM_STAR /* upper bound on KID coming from the default algorithm implemented */ #define OSCORE_KID_CONTEXT_MAX_LEN 64 /* Helper macros to correctly size the statically allocated buffers and verify if an overflow occurred */ #define OSCORE_INFO_MAX_LEN (1 + /* max return of cborencoder_put_array() */ \ 2 + OSCORE_KID_MAX_LEN + /* max 2 to encode length, KID following */ \ 2 + OSCORE_KID_CONTEXT_MAX_LEN + /* length + KID CONTEXT */ \ 2 + /* max return of cborencoder_put_unsigned() */ \ 2 + 3 + /* max 2 to encode length, "Key" following */ \ 2 /* max return of cborencoder_put_unsigned() */ ) #define OSCORE_EXTERNAL_AAD_MAX_LEN (1 + /* max return of cborencoder_put_array() */ \ 2 + /* max return of cborencoder_put_unsigned() */ \ 1 + /* max return of cborencoder_put_array() */ \ 2 + /* max return of cborencoder_put_unsigned() */ \ 2 + OSCORE_KID_MAX_LEN + /* max 2 to encode length, KID following */ \ 2 + OSCORE_PIV_MAX_LEN + /* max 2 to encode length, PIV following */ \ 1 + 0 /* 1 to encode length, 0 bytes following */ ) #define OSCORE_AAD_MAX_LEN (1 + /* max return of cborencoder_put_array() */ \ 2 + 8 +/* max 2 to encode length, "Encrypt0" following */ \ 1 + 0 + /* 1 to encode length, 0 bytes following */ \ 2 + OSCORE_EXTERNAL_AAD_MAX_LEN /* max 2 to encode length, external_aad following */ ) static void oscore_context_free_byte_arrays(oscore_context_t *rec) { if (rec->master_secret) { g_byte_array_free(rec->master_secret, true); } if (rec->master_salt) { g_byte_array_free(rec->master_salt, true); } if (rec->id_context) { g_byte_array_free(rec->id_context, true); } if (rec->sender_id) { g_byte_array_free(rec->sender_id, true); } if (rec->recipient_id) { g_byte_array_free(rec->recipient_id, true); } if (rec->request_decryption_key) { g_byte_array_free(rec->request_decryption_key, true); } if (rec->response_decryption_key) { g_byte_array_free(rec->response_decryption_key, true); } if (rec->common_iv) { g_byte_array_free(rec->common_iv, true); } } static void oscore_context_post_update_cb(void) { unsigned i; unsigned key_len; unsigned iv_len; for (i = 0; i < num_oscore_contexts; i++) { /* Make sure to free the memory if it was allocated previously. */ oscore_context_free_byte_arrays(&oscore_contexts[i]); oscore_contexts[i].master_secret = g_byte_array_new(); oscore_contexts[i].master_salt = g_byte_array_new(); oscore_contexts[i].id_context = g_byte_array_new(); oscore_contexts[i].sender_id = g_byte_array_new(); oscore_contexts[i].recipient_id = g_byte_array_new(); /* Convert strings to byte arrays */ hex_str_to_bytes(oscore_contexts[i].sender_id_prefs, oscore_contexts[i].sender_id, false); hex_str_to_bytes(oscore_contexts[i].recipient_id_prefs, oscore_contexts[i].recipient_id, false); hex_str_to_bytes(oscore_contexts[i].id_context_prefs, oscore_contexts[i].id_context, false); hex_str_to_bytes(oscore_contexts[i].master_secret_prefs, oscore_contexts[i].master_secret, false); hex_str_to_bytes(oscore_contexts[i].master_salt_prefs, oscore_contexts[i].master_salt, false); /* Algorithm-dependent key and IV length */ key_len = oscore_alg_get_key_len(oscore_contexts[i].algorithm); iv_len = oscore_alg_get_iv_len(oscore_contexts[i].algorithm); /* Allocate memory for derived parameters */ oscore_contexts[i].request_decryption_key = g_byte_array_sized_new(key_len); oscore_contexts[i].response_decryption_key = g_byte_array_sized_new(key_len); oscore_contexts[i].common_iv = g_byte_array_sized_new(iv_len); oscore_context_derive_params(&oscore_contexts[i]); } } /* Check user input, do not allocate any memory */ static bool oscore_context_update_cb(void *r, char **err) { oscore_context_t *rec = (oscore_context_t *) r; GByteArray *bytes; /* temp array to verify each parameter */ bytes = g_byte_array_new(); if (hex_str_to_bytes(rec->sender_id_prefs, bytes, false) == false) { *err = g_strdup("Sender ID is invalid."); g_byte_array_free(bytes, true); return false; } if (bytes->len > OSCORE_KID_MAX_LEN) { *err = ws_strdup_printf("Should be %u bytes or less.", OSCORE_KID_MAX_LEN); g_byte_array_free(bytes, true); return false; } if (hex_str_to_bytes(rec->recipient_id_prefs, bytes, false) == false) { *err = g_strdup("Recipient ID is invalid."); g_byte_array_free(bytes, true); return false; } if (bytes->len > OSCORE_KID_MAX_LEN) { *err = ws_strdup_printf("Should be %u bytes or less.", OSCORE_KID_MAX_LEN); g_byte_array_free(bytes, true); return false; } if (hex_str_to_bytes(rec->id_context_prefs, bytes, false) == false) { *err = g_strdup("ID Context is invalid."); g_byte_array_free(bytes, true); return false; } if (bytes->len > OSCORE_KID_CONTEXT_MAX_LEN) { *err = ws_strdup_printf("Should be %u bytes or less.", OSCORE_KID_CONTEXT_MAX_LEN); g_byte_array_free(bytes, true); return false; } if (hex_str_to_bytes(rec->master_secret_prefs, bytes, false) == false) { *err = g_strdup("Master Secret is invalid."); g_byte_array_free(bytes, true); return false; } /* No max length check on Master Secret. We use GByteArray to allocate memory * and pass it to the context derivation routine */ if (bytes->len == 0) { *err = g_strdup("Master Secret is mandatory."); g_byte_array_free(bytes, true); return false; } if (hex_str_to_bytes(rec->master_salt_prefs, bytes, false) == false) { *err = g_strdup("Master Salt is invalid."); g_byte_array_free(bytes, true); return false; } /* No (max) length check on optional Master Salt. We use GByteArray to allocate memory * and pass it to the context derivation routine */ g_byte_array_free(bytes, true); return true; } static void* oscore_context_copy_cb(void *n, const void *o, size_t siz _U_) { oscore_context_t *new_record = (oscore_context_t *) n; const oscore_context_t *old_record = (const oscore_context_t *) o; /* Pre-Shared Parameters */ new_record->master_secret_prefs = g_strdup(old_record->master_secret_prefs); new_record->master_salt_prefs = g_strdup(old_record->master_salt_prefs); new_record->id_context_prefs = g_strdup(old_record->id_context_prefs); new_record->sender_id_prefs = g_strdup(old_record->sender_id_prefs); new_record->recipient_id_prefs = g_strdup(old_record->recipient_id_prefs); new_record->algorithm = old_record->algorithm; /* Initialize all to NULL, overwrite as needed */ new_record->master_secret = NULL; new_record->master_salt = NULL; new_record->id_context = NULL; new_record->sender_id = NULL; new_record->recipient_id = NULL; new_record->request_decryption_key = NULL; new_record->response_decryption_key = NULL; new_record->common_iv = NULL; /* We rely on oscore_context_post_update_cb() to convert strings to GByteArrays and derive params */ return new_record; } static void oscore_context_free_cb(void *r) { oscore_context_t *rec = (oscore_context_t *) r; /* User-configured strings */ g_free(rec->master_secret_prefs); g_free(rec->master_salt_prefs); g_free(rec->id_context_prefs); g_free(rec->sender_id_prefs); g_free(rec->recipient_id_prefs); /* Allocated byte arrays */ oscore_context_free_byte_arrays(rec); } /* GByteArrays within the oscore_context_t object should be initialized before calling this function */ static bool oscore_context_derive_params(oscore_context_t *context) { const char *iv_label = "IV"; const char *key_label = "Key"; uint8_t prk[32]; /* Pseudo-random key from HKDF-Extract step. 32 for SHA256. */ unsigned key_len; unsigned iv_len; uint8_t info_buf[OSCORE_INFO_MAX_LEN]; unsigned info_len; GByteArray *info; key_len = oscore_alg_get_key_len(context->algorithm); iv_len = oscore_alg_get_iv_len(context->algorithm); info = g_byte_array_new(); /* Common HKDF-Extract step on master salt */ hkdf_extract(GCRY_MD_SHA256, context->master_salt->data, context->master_salt->len, context->master_secret->data, context->master_secret->len, prk); /* Request Decryption Key */ info_len = 0; info_len += cborencoder_put_array(&info_buf[info_len], 5); info_len += cborencoder_put_bytes(&info_buf[info_len], context->sender_id->data, context->sender_id->len); if (context->id_context->len) { info_len += cborencoder_put_bytes(&info_buf[info_len], context->id_context->data, context->id_context->len); } else { info_len += cborencoder_put_null(&info_buf[info_len]); } info_len += cborencoder_put_unsigned(&info_buf[info_len], context->algorithm); info_len += cborencoder_put_text(&info_buf[info_len], key_label, 3); info_len += cborencoder_put_unsigned(&info_buf[info_len], key_len); /* sender_id->len comes from user input, it is validated by the UAT callback and the max length is accounted for * in OSCORE_INFO_MAX_LEN */ DISSECTOR_ASSERT(info_len < OSCORE_INFO_MAX_LEN); g_byte_array_append(info, info_buf, info_len); g_byte_array_set_size(context->request_decryption_key, key_len); hkdf_expand(GCRY_MD_SHA256, prk, sizeof(prk), info->data, info->len, context->request_decryption_key->data, key_len); /* 32 for SHA256 */ /* Response Decryption Key */ info_len = 0; g_byte_array_set_size(info, 0); info_len += cborencoder_put_array(&info_buf[info_len], 5); info_len += cborencoder_put_bytes(&info_buf[info_len], context->recipient_id->data, context->recipient_id->len); if (context->id_context->len) { info_len += cborencoder_put_bytes(&info_buf[info_len], context->id_context->data, context->id_context->len); } else { info_len += cborencoder_put_null(&info_buf[info_len]); } info_len += cborencoder_put_unsigned(&info_buf[info_len], context->algorithm); info_len += cborencoder_put_text(&info_buf[info_len], key_label, 3); info_len += cborencoder_put_unsigned(&info_buf[info_len], key_len); /* recipient_id->len comes from user input, it is validated by the UAT callback and the max length is accounted for * in OSCORE_INFO_MAX_LEN */ DISSECTOR_ASSERT(info_len < OSCORE_INFO_MAX_LEN); g_byte_array_append(info, info_buf, info_len); g_byte_array_set_size(context->response_decryption_key, key_len); hkdf_expand(GCRY_MD_SHA256, prk, sizeof(prk), info->data, info->len, context->response_decryption_key->data, key_len); /* 32 for SHA256 */ /* Common IV */ info_len = 0; g_byte_array_set_size(info, 0); info_len += cborencoder_put_array(&info_buf[info_len], 5); info_len += cborencoder_put_bytes(&info_buf[info_len], NULL, 0); if (context->id_context->len) { info_len += cborencoder_put_bytes(&info_buf[info_len], context->id_context->data, context->id_context->len); } else { info_len += cborencoder_put_null(&info_buf[info_len]); } info_len += cborencoder_put_unsigned(&info_buf[info_len], context->algorithm); info_len += cborencoder_put_text(&info_buf[info_len], iv_label, 2); info_len += cborencoder_put_unsigned(&info_buf[info_len], iv_len); /* all static lengths, accounted for in OSCORE_INFO_MAX_LEN */ DISSECTOR_ASSERT(info_len < OSCORE_INFO_MAX_LEN); g_byte_array_append(info, info_buf, info_len); g_byte_array_set_size(context->common_iv, iv_len); hkdf_expand(GCRY_MD_SHA256, prk, sizeof(prk), info->data, info->len, context->common_iv->data, iv_len); /* 32 for SHA256 */ g_byte_array_free(info, true); return true; } static unsigned oscore_alg_get_key_len(cose_aead_alg_t algorithm) { switch(algorithm) { case COSE_AES_CCM_16_64_128: return 16; /* RFC8152 */ /* unsupported */ default: return 0; } } static unsigned oscore_alg_get_tag_len(cose_aead_alg_t algorithm) { switch(algorithm) { case COSE_AES_CCM_16_64_128: return 8; /* RFC8152 */ /* unsupported */ default: return 0; } } static unsigned oscore_alg_get_iv_len(cose_aead_alg_t algorithm) { switch(algorithm) { case COSE_AES_CCM_16_64_128: return 13; /* RFC8152 */ /* unsupported */ default: return 0; } } static oscore_context_t * oscore_find_context(oscore_info_t *info) { unsigned i; for (i = 0; i < num_oscore_contexts; i++) { if ((info->kid_len == oscore_contexts[i].sender_id->len) && memcmp(oscore_contexts[i].sender_id->data, info->kid, info->kid_len) == 0 && (info->kid_context_len == oscore_contexts[i].id_context->len) && memcmp(oscore_contexts[i].id_context->data, info->kid_context, info->kid_context_len) == 0) { return &oscore_contexts[i]; } } return NULL; } /** CBOR encoding functions needed to construct HKDF info and aad. Author Martin Gunnarsson Modified by Malisa Vucinic */ static uint8_t cborencoder_put_text(uint8_t *buffer, const char *text, uint8_t text_len) { uint8_t ret = 0; if(text_len > 23 ){ buffer[ret++] = 0x78; buffer[ret++] = text_len; } else { buffer[ret++] = (0x60 | text_len); } if (text_len != 0 && text != NULL) { memcpy(&buffer[ret], text, text_len); ret += text_len; } return ret; } static uint8_t cborencoder_put_array(uint8_t *buffer, uint8_t elements) { uint8_t ret = 0; if(elements > 15){ return 0; } buffer[ret++] = (0x80 | elements); return ret; } static uint8_t cborencoder_put_bytes(uint8_t *buffer, const uint8_t *bytes, uint8_t bytes_len) { uint8_t ret = 0; if(bytes_len > 23){ buffer[ret++] = 0x58; buffer[ret++] = bytes_len; } else { buffer[ret++] = (0x40 | bytes_len); } if (bytes_len != 0 && bytes != NULL){ memcpy(&buffer[ret], bytes, bytes_len); ret += bytes_len; } return ret; } static uint8_t cborencoder_put_unsigned(uint8_t *buffer, uint8_t value) { uint8_t ret = 0; if(value > 0x17 ){ buffer[ret++] = 0x18; buffer[ret++] = value; return ret; } buffer[ret++] = value; return ret; } static uint8_t cborencoder_put_null(uint8_t *buffer) { uint8_t ret = 0; buffer[ret++] = 0xf6; return ret; } /* out should hold NONCE_MAX_LEN bytes at most */ static void oscore_create_nonce(uint8_t *out, oscore_context_t *context, oscore_info_t *info) { unsigned i = 0; char piv_extended[NONCE_MAX_LEN] = { 0 }; unsigned nonce_len; uint8_t *piv; uint8_t piv_len; GByteArray *piv_generator; DISSECTOR_ASSERT(out != NULL); DISSECTOR_ASSERT(context != NULL); DISSECTOR_ASSERT(info != NULL); nonce_len = oscore_alg_get_iv_len(context->algorithm); DISSECTOR_ASSERT(nonce_len <= NONCE_MAX_LEN); /* Recipient ID is the PIV generator ID if the PIV is present in the response */ if (info->response && info->piv_len) { piv_generator = context->recipient_id; piv = info->piv; piv_len = info->piv_len; } else { piv_generator = context->sender_id; piv = info->request_piv; piv_len = info->request_piv_len; } /* AEAD nonce is the XOR of Common IV left-padded to AEAD nonce length and the concatenation of: * Step 3: Size of ID of the entity that generated PIV (1 byte), * Step 2: ID of the entity that generated PIV (left-padded to "AEAD nonce length - 6 bytes"), * Step 1: Partial IV (left-padded to OSCORE_PIV_MAX_LEN bytes). */ /* Step 1 */ DISSECTOR_ASSERT(piv_len <= OSCORE_PIV_MAX_LEN); memcpy(&piv_extended[nonce_len - piv_len], piv, piv_len); /* Step 2 */ DISSECTOR_ASSERT(piv_generator->len <= nonce_len - 6); memcpy(&piv_extended[nonce_len - OSCORE_PIV_MAX_LEN - piv_generator->len], piv_generator->data, piv_generator->len); /* Step 3 */ piv_extended[0] = piv_generator->len; /* Now XOR with Common IV */ for (i = 0; i < nonce_len; i++) { out[i] = piv_extended[i] ^ context->common_iv->data[i]; } } static oscore_decryption_status_t oscore_decrypt_and_verify(tvbuff_t *tvb_ciphertext, packet_info *pinfo, int *offset, proto_tree *tree, oscore_context_t *context, oscore_info_t *info, tvbuff_t **tvb_plaintext) { bool have_tag = false; uint8_t nonce[NONCE_MAX_LEN]; uint8_t tmp[AES_128_BLOCK_LEN]; uint8_t *text; uint8_t rx_tag[TAG_MAX_LEN]; unsigned tag_len = 0; uint8_t gen_tag[TAG_MAX_LEN]; uint8_t external_aad[OSCORE_EXTERNAL_AAD_MAX_LEN]; uint8_t external_aad_len = 0; uint8_t aad[OSCORE_AAD_MAX_LEN]; uint8_t aad_len = 0; uint8_t *decryption_key; int ciphertext_captured_len; int ciphertext_reported_len; const char *encrypt0 = "Encrypt0"; proto_item *item = NULL; tag_len = oscore_alg_get_tag_len(context->algorithm); ciphertext_reported_len = tvb_reported_length_remaining(tvb_ciphertext, *offset + tag_len); if (ciphertext_reported_len == 0) { return STATUS_ERROR_MESSAGE_TOO_SMALL; } /* Check if the payload is truncated. */ if (tvb_bytes_exist(tvb_ciphertext, *offset, ciphertext_reported_len)) { ciphertext_captured_len = ciphertext_reported_len; } else { ciphertext_captured_len = tvb_captured_length_remaining(tvb_ciphertext, *offset); } /* Check if the tag is present in the captured data. */ have_tag = tvb_bytes_exist(tvb_ciphertext, *offset + ciphertext_reported_len, tag_len); if (have_tag) { DISSECTOR_ASSERT(tag_len <= sizeof(rx_tag)); tvb_memcpy(tvb_ciphertext, rx_tag, *offset + ciphertext_reported_len, tag_len); } if (info->response) { decryption_key = context->response_decryption_key->data; } else { decryption_key = context->request_decryption_key->data; } /* Create nonce to use for decryption and authenticity check */ oscore_create_nonce(nonce, context, info); /* * Create the CCM* initial block for decryption (Adata=0, M=0, counter=0). * XXX: This only handles AES-CCM-16-64-128, add generic algorithm handling * */ ccm_init_block(tmp, false, 0, 0, 0, 0, 0, nonce); /* * Make a copy of the ciphertext in heap memory. * * We will decrypt the message in-place and then use the buffer as the * real data for the new tvb. */ text = (uint8_t *)tvb_memdup(pinfo->pool, tvb_ciphertext, *offset, ciphertext_captured_len); /* * Perform CTR-mode transformation and decrypt the tag. * XXX: This only handles AES-CCM-16-64-128, add generic algorithm handling * */ if(ccm_ctr_encrypt(decryption_key, tmp, rx_tag, text, ciphertext_captured_len) == false) { return STATUS_ERROR_DECRYPT_FAILED; } /* Create a tvbuff for the plaintext. */ *tvb_plaintext = tvb_new_real_data(text, ciphertext_captured_len, ciphertext_reported_len); tvb_set_child_real_data_tvbuff(tvb_ciphertext, *tvb_plaintext); add_new_data_source(pinfo, *tvb_plaintext, "Decrypted OSCORE"); if (have_tag) { /* Construct external_aad to be able to verify the tag */ /* Note that OSCORE_EXTERNAL_AAD_MAX_LEN calculation depends on the following construct. * If this is updated - e.g. due to spec changes, added support for Class I options, or added * support for other algorithms which would change max length of KID - do not forget to update the macro. * */ external_aad_len += cborencoder_put_array(&external_aad[external_aad_len], 5); /* 5 elements in the array */ external_aad_len += cborencoder_put_unsigned(&external_aad[external_aad_len], OSCORE_VERSION); external_aad_len += cborencoder_put_array(&external_aad[external_aad_len], 1); external_aad_len += cborencoder_put_unsigned(&external_aad[external_aad_len], context->algorithm); external_aad_len += cborencoder_put_bytes(&external_aad[external_aad_len], info->kid, info->kid_len); external_aad_len += cborencoder_put_bytes(&external_aad[external_aad_len], info->request_piv, info->request_piv_len); external_aad_len += cborencoder_put_bytes(&external_aad[external_aad_len], NULL, 0); // Class I options not implemented/standardized yet /* info->kid_len and info->piv_len come from the lower layer, other parameters are local. * we end up here only if kid_len is matched to the one from the configured context through oscore_find_context() * and piv_len is verified in the main dissection routine */ DISSECTOR_ASSERT(external_aad_len < OSCORE_EXTERNAL_AAD_MAX_LEN); /* Note that OSCORE_AAD_MAX_LEN calculation depends on the following construct. * If the construct below is modified, do not forget to update the macro. * */ aad_len += cborencoder_put_array(&aad[aad_len], 3); // COSE Encrypt0 structure with 3 elements aad_len += cborencoder_put_text(&aad[aad_len], encrypt0, 8); /* Text string "Encrypt0" */ aad_len += cborencoder_put_bytes(&aad[aad_len], NULL, 0); /* Empty byte string */ aad_len += cborencoder_put_bytes(&aad[aad_len], external_aad, external_aad_len); /* OSCORE external_aad */ DISSECTOR_ASSERT(aad_len < OSCORE_AAD_MAX_LEN); /* Compute CBC-MAC authentication tag. */ /* * Create the CCM* initial block for authentication (Adata!=0, M!=0, counter=l(m)). * XXX: This only handles AES-CCM-16-64-128, add generic algorithm handling * */ DISSECTOR_ASSERT(tag_len <= sizeof(gen_tag)); ccm_init_block(tmp, true, tag_len, 0, 0, 0, ciphertext_captured_len, nonce); /* text is already a raw buffer containing the plaintext since we just decrypted it in-place */ if (!ccm_cbc_mac(decryption_key, tmp, aad, aad_len, text, ciphertext_captured_len, gen_tag)) { return STATUS_ERROR_CBCMAC_FAILED; } /* Compare the received tag with the one we generated. */ else if (memcmp(gen_tag, rx_tag, tag_len) != 0) { return STATUS_ERROR_TAG_CHECK_FAILED; } /* Display the tag. */ if (tag_len) { item = proto_tree_add_bytes(tree, hf_oscore_tag, tvb_ciphertext, ciphertext_captured_len, tag_len, rx_tag); proto_item_set_generated(item); } return STATUS_SUCCESS_DECRYPTED_TAG_CHECKED; } /* if (have_tag) */ return STATUS_SUCCESS_DECRYPTED_TAG_TRUNCATED; } /* Code to actually dissect the packets */ static int oscore_dissect(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data) { /* Set up structures needed to add the protocol subtree and manage it */ proto_item *ti; proto_tree *oscore_tree; /* Other misc. local variables. */ int offset = 0; oscore_info_t *info = (oscore_info_t *) data; oscore_context_t *context = NULL; oscore_decryption_status_t status; tvbuff_t *tvb_decrypted = NULL; coap_info *coinfo; int oscore_length; uint8_t code_class; /* Check that the packet is long enough for it to belong to us. */ if (tvb_reported_length(tvb) < OSCORE_MIN_LENGTH) { return 0; } /* Set the Protocol column to the constant string of oscore */ col_set_str(pinfo->cinfo, COL_PROTOCOL, "OSCORE"); /* create display subtree for the protocol */ ti = proto_tree_add_item(tree, proto_oscore, tvb, 0, -1, ENC_NA); oscore_tree = proto_item_add_subtree(ti, ett_oscore); if (info->piv == NULL && info->request_piv == NULL) { expert_add_info(pinfo, oscore_tree, &ei_oscore_partial_iv_not_found); return tvb_reported_length(tvb); } if ((context = oscore_find_context(info)) == NULL) { expert_add_info(pinfo, oscore_tree, &ei_oscore_context_not_set); return tvb_reported_length(tvb); } if (info->piv_len > OSCORE_PIV_MAX_LEN) { expert_add_info(pinfo, oscore_tree, &ei_oscore_piv_len_invalid); return tvb_reported_length(tvb); } status = oscore_decrypt_and_verify(tvb, pinfo, &offset, oscore_tree, context, info, &tvb_decrypted); switch (status) { case STATUS_ERROR_DECRYPT_FAILED: expert_add_info(pinfo, oscore_tree, &ei_oscore_decrypt_error); return tvb_reported_length(tvb); case STATUS_ERROR_CBCMAC_FAILED: expert_add_info(pinfo, oscore_tree, &ei_oscore_cbc_mac_failed); return tvb_reported_length(tvb); case STATUS_ERROR_TAG_CHECK_FAILED: expert_add_info(pinfo, oscore_tree, &ei_oscore_tag_check_failed); return tvb_reported_length(tvb); case STATUS_ERROR_MESSAGE_TOO_SMALL: expert_add_info(pinfo, oscore_tree, &ei_oscore_message_too_small); return tvb_reported_length(tvb); case STATUS_SUCCESS_DECRYPTED_TAG_TRUNCATED: expert_add_info(pinfo, oscore_tree, &ei_oscore_truncated); /* do not return, attempt dissection */ break; case STATUS_SUCCESS_DECRYPTED_TAG_CHECKED: break; } DISSECTOR_ASSERT(tvb_decrypted); oscore_length = tvb_reported_length(tvb_decrypted); /* Fetch CoAP info */ coinfo = (coap_info *)p_get_proto_data(wmem_file_scope(), pinfo, proto_coap, 0); if (coinfo) { dissect_coap_code(tvb_decrypted, oscore_tree, &offset, &dissect_oscore_hf, &code_class); offset = dissect_coap_options(tvb_decrypted, pinfo, oscore_tree, offset, oscore_length, code_class, coinfo, &dissect_oscore_hf); if (oscore_length > offset) { dissect_coap_payload(tvb_decrypted, pinfo, oscore_tree, tree, offset, oscore_length, code_class, coinfo, &dissect_oscore_hf, true); } } else { /* We don't support OSCORE over HTTP at the moment, where coinfo fetch will fail */ expert_add_info(pinfo, oscore_tree, &ei_oscore_info_fetch_failed); } return tvb_captured_length(tvb); } /* Register the protocol with Wireshark. * * This format is required because a script is used to build the C function that * calls all the protocol registration. */ void proto_register_oscore(void) { module_t *oscore_module; expert_module_t *expert_oscore; static hf_register_info hf[] = { { &hf_oscore_tag, { "Decrypted Authentication Tag", "oscore.tag", FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL } }, COAP_COMMON_HF_LIST(dissect_oscore_hf, "oscore") }; /* Setup protocol subtree array */ static int *ett[] = { &ett_oscore, COAP_COMMON_ETT_LIST(dissect_oscore_hf) }; /* Setup protocol expert items */ static ei_register_info ei[] = { { &ei_oscore_partial_iv_not_found, { "oscore.partial_iv_not_found", PI_UNDECODED, PI_WARN, "Partial IV not found - can't decrypt", EXPFILL } }, { &ei_oscore_context_not_set, { "oscore.context_not_set", PI_UNDECODED, PI_WARN, "Security context not set - can't decrypt", EXPFILL } }, { &ei_oscore_message_too_small, { "oscore.message_too_small", PI_UNDECODED, PI_WARN, "Message too small", EXPFILL } }, { &ei_oscore_truncated, { "oscore.truncated", PI_UNDECODED, PI_WARN, "Message truncated, cannot verify authentication tag, but decryption is attempted", EXPFILL } }, { &ei_oscore_cbc_mac_failed, { "oscore.cbc_mac_failed", PI_UNDECODED, PI_WARN, "Call to CBC-MAC failed", EXPFILL } }, { &ei_oscore_tag_check_failed, { "oscore.tag_check_failed", PI_UNDECODED, PI_WARN, "Authentication tag check failed", EXPFILL } }, { &ei_oscore_decrypt_error, { "oscore.decrypt_error", PI_UNDECODED, PI_WARN, "Decryption error", EXPFILL } }, { &ei_oscore_info_fetch_failed, { "oscore.info_fetch_failed", PI_UNDECODED, PI_WARN, "Failed to fetch info from the lower layer - OSCORE over HTTP is not supported", EXPFILL } }, { &ei_oscore_piv_len_invalid, { "oscore.piv_len_invalid", PI_UNDECODED, PI_WARN, "Partial IV length from the lower layer is invalid", EXPFILL } }, COAP_COMMON_EI_LIST(dissect_oscore_hf, "oscore") }; static uat_field_t oscore_context_uat_flds[] = { UAT_FLD_CSTRING(oscore_context_uat,sender_id_prefs,"Sender ID", "Sender ID as HEX string. Should be 7 bytes or less. Mandatory."), UAT_FLD_CSTRING(oscore_context_uat,recipient_id_prefs,"Recipient ID", "Recipient ID as HEX string. Should be 7 bytes or less. Mandatory."), UAT_FLD_CSTRING(oscore_context_uat,master_secret_prefs,"Master Secret", "Master Secret as HEX string. Mandatory."), UAT_FLD_CSTRING(oscore_context_uat,master_salt_prefs,"Master Salt", "Master Salt as HEX string. Optional."), UAT_FLD_CSTRING(oscore_context_uat,id_context_prefs,"ID Context", "ID Context as HEX string. Optional."), UAT_FLD_VS(oscore_context_uat, algorithm, "Algorithm", oscore_context_alg_vals, "Decryption algorithm."), UAT_END_FIELDS }; /* Register the protocol name and description */ proto_oscore = proto_register_protocol("Object Security for Constrained RESTful Environments", "OSCORE", "oscore"); /* Required function calls to register the header fields and subtrees */ proto_register_field_array(proto_oscore, hf, array_length(hf)); proto_register_subtree_array(ett, array_length(ett)); /* Required function calls to register expert items */ expert_oscore = expert_register_protocol(proto_oscore); expert_register_field_array(expert_oscore, ei, array_length(ei)); oscore_module = prefs_register_protocol(proto_oscore, NULL); /* Create a UAT for security context management. */ oscore_context_uat = uat_new("Security Contexts", sizeof(oscore_context_t), /* record size */ "oscore_contexts", /* filename */ true, /* from_profile */ &oscore_contexts, /* data_ptr */ &num_oscore_contexts, /* numitems_ptr */ UAT_AFFECTS_DISSECTION, /* affects dissection of packets, but not set of named fields */ NULL, /* help */ oscore_context_copy_cb, /* copy callback */ oscore_context_update_cb, /* update callback */ oscore_context_free_cb, /* free callback */ oscore_context_post_update_cb, /* post update callback */ NULL, /* reset callback */ oscore_context_uat_flds); /* UAT field definitions */ prefs_register_uat_preference(oscore_module, "contexts", "Security Contexts", "Security context configuration data", oscore_context_uat); register_dissector("oscore", oscore_dissect, proto_oscore); proto_coap = proto_get_id_by_short_name("CoAP"); } /* We're called only by dissector name. */ void proto_reg_handoff_oscore(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: */