mirror of https://github.com/arendst/Tasmota.git
109 lines
3.1 KiB
C++
109 lines
3.1 KiB
C++
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#include "GcmParser.h"
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#include "tasmota_options.h"
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#ifdef USE_TLS
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#include "lwip/def.h"
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#include <t_bearssl.h>
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GCMParser::GCMParser(uint8_t *encryption_key, uint8_t *authentication_key) {
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memcpy(this->encryption_key, encryption_key, 16);
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memcpy(this->authentication_key, authentication_key, 16);
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use_auth = 0;
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for (uint16_t cnt = 0; cnt < 16; cnt++) {
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if (authentication_key[cnt]) {
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use_auth |= 1;
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}
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}
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}
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int8_t GCMParser::parse(uint8_t *d, DataParserContext &ctx) {
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if(ctx.length < 12) return DATA_PARSE_INCOMPLETE;
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uint8_t* ptr = (uint8_t*) d;
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if(*ptr != GCM_TAG) return DATA_PARSE_BOUNDRY_FLAG_MISSING;
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ptr++;
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// Encrypted APDU
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// http://www.weigu.lu/tutorials/sensors2bus/04_encryption/index.html
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uint8_t systemTitleLength = *ptr;
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ptr++;
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uint8_t initialization_vector[12];
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memcpy(ctx.system_title, ptr, systemTitleLength);
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memcpy(initialization_vector, ctx.system_title, systemTitleLength);
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int len = 0;
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int headersize = 2 + systemTitleLength;
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ptr += systemTitleLength;
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if(((*ptr) & 0xFF) == 0x81) {
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ptr++;
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len = *ptr;
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// 1-byte payload length
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ptr++;
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headersize += 2;
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} else if(((*ptr) & 0xFF) == 0x82) {
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GCMSizeDef* h = (GCMSizeDef*) ptr;
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// 2-byte payload length
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len = (ntohs(h->format) & 0xFFFF);
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ptr += 3;
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headersize += 3;
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} else if(((*ptr) & 0xFF) == 0x4f) {
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// ???????? single frame did only decode with this compare
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ptr++;
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headersize++;
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} else if(((*ptr) & 0xFF) == 0x5e) {
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// ???????? single frame did only decode with this compare
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ptr++;
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headersize++;
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}
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if(len + headersize > ctx.length)
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return DATA_PARSE_INCOMPLETE;
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uint8_t additional_authenticated_data[17];
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memcpy(additional_authenticated_data, ptr, 1);
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// Security tag
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uint8_t sec = *ptr;
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ptr++;
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headersize++;
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// Frame counter
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memcpy(initialization_vector + 8, ptr, 4);
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ptr += 4;
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headersize += 4;
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int footersize = 0;
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// Authentication enabled
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uint8_t authentication_tag[12];
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uint8_t authkeylen = 0, aadlen = 0;
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if((sec & 0x10) == 0x10) {
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authkeylen = 12;
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aadlen = 17;
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footersize += authkeylen;
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memcpy(additional_authenticated_data + 1, authentication_key, 16);
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memcpy(authentication_tag, ptr + len - footersize - 5, authkeylen);
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}
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br_gcm_context gcm_ctx;
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br_aes_small_ctr_keys ctr_ctx;
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br_aes_small_ctr_init(&ctr_ctx, encryption_key, 16);
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br_gcm_init(&gcm_ctx, &ctr_ctx.vtable, &br_ghash_ctmul32);
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br_gcm_reset(&gcm_ctx, initialization_vector, 12);
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if (use_auth && authkeylen > 0) {
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br_gcm_aad_inject(&gcm_ctx, additional_authenticated_data, aadlen);
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}
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br_gcm_flip(&gcm_ctx);
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br_gcm_run(&gcm_ctx, 0, ptr , ctx.length - headersize);
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if (use_auth && authkeylen > 0 && br_gcm_check_tag_trunc(&gcm_ctx, authentication_tag, authkeylen) != 1) {
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return GCM_AUTH_FAILED;
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}
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ctx.length -= footersize + headersize;
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return ptr - d;
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}
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#endif // USE_TLS
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