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RAS MD5 Tweaks; #359
Disable Fist Byte Correction on MD5 password hash following observations based on real world system; Improve BPTC127x77 Decoder Logic; Tweak Debug code to show checksum diff if there is no actual diff;
This commit is contained in:
lwvmobile
253
src/bptc.c
253
src/bptc.c
@@ -362,21 +362,15 @@ uint32_t BPTC_196x96_Extract_Data(uint8_t InputDeInteleavedData[196], uint8_t DM
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/*
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* @brief : This function extract the 77 bits of a deinteleaved 128 bits
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* buffer using BPTC (128,77).
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* BPTC (128,77) extract with iterative Hamming + parity-guided repair
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* and diagnostic logging.
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* See ETSI TS 102 361-1 B.2.1
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*
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* @note : See DMR standard ETSI TS 102 361-1 chapter B.2.1 for details
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*
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* @param InputDeInteleavedData : Pointer of DMR input data deinterleaved (128 bytes
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act as a 16 x 8 byte data matrix)
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*
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* @param DMRDataExtracted : Pointer where the DMR data will be written (77 bytes)
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* DMRDataExtracted[0..71] = Util data (hamming corrected)
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* DMRDataExtracted[72..76] = 5 bit of CRC extracted (to be checked)
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*
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* @return 0 = All is OK
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* Other = Error - Irrecoverable Hamming parity check error number
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* Enable/disable chatter with BPTC_128x77_DEBUG (1 = on).
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*/
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// #define BPTC_128x77_DEBUG 1
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uint32_t BPTC_128x77_Extract_Data(uint8_t InputDataMatrix[8][16], uint8_t DMRDataExtracted[77])
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{
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uint32_t i, j, k;
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@@ -387,106 +381,189 @@ uint32_t BPTC_128x77_Extract_Data(uint8_t InputDataMatrix[8][16], uint8_t DMRDat
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uint32_t ParityCheckErrorNb = 0;
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uint32_t NbOfOne;
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/* First step : Reconstitute the BPTC 16x8 matrix */
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for(i = 0; i < 8; i++)
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uint8_t row_bad[7];
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uint8_t col_bad[16];
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for (i = 0; i < 8; i++)
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{
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for(j = 0; j < 16; j++)
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{
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/* Only the LSBit of the byte is stored */
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for (j = 0; j < 16; j++)
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DataMatrix[i][j] = (InputDataMatrix[i][j] & 1);
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}
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}
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/* Process the the Hamming (16,11,4) code
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* check on each line.
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* Do not check the last line (line nb 8) */
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for(i = 0; i < 7; i++)
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/* ---------- Pass 1: Hamming (16,11,4) on rows 0..6 ---------- */
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memset(row_bad, 0, sizeof(row_bad));
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for (i = 0; i < 7; i++)
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{
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/* Get a full line */
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for(j = 0; j < 16; j++)
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{
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for (j = 0; j < 16; j++)
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LineUncorrected[j] = DataMatrix[i][j];
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}
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/* Apply Hamming (16,11,4) code correction */
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if(Hamming_16_11_4_decode(LineUncorrected, LineCorrected, 1) == false)
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if (Hamming_16_11_4_decode(LineUncorrected, LineCorrected, 1) == false)
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{
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HammingIrrecoverableErrorNb++;
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row_bad[i] = 1;
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#if BPTC_128x77_DEBUG
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fprintf(stderr, " BPTC128 P1 Hamming FAIL row=%u rx=", (unsigned)i);
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for (j = 0; j < 16; j++)
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fprintf(stderr, "%u", LineUncorrected[j] & 1);
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fprintf(stderr, "\n");
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#endif
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for (j = 0; j < 11; j++)
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DataMatrix[i][j] = LineUncorrected[j];
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}
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/* Re-inject the line in the matrix (only the util data [11 bit],
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* not the Hamming part [4 bit]) */
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for(j = 0; j < 11; j++)
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else
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{
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DataMatrix[i][j] = LineCorrected[j];
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for (j = 0; j < 11; j++)
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DataMatrix[i][j] = LineCorrected[j];
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}
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}
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#if BPTC_128x77_DEBUG
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if (HammingIrrecoverableErrorNb)
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fprintf(stderr, " BPTC128 P1 Hamming irrecoverable rows=%u\n",
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(unsigned)HammingIrrecoverableErrorNb);
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#endif
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/* Extract the DMR data (77 bit) from the matrix */
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k = 0;
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/* 2 first lines */
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for(i = 0; i < 2; i++)
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{
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for(j = 0; j < 11; j++)
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{
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DMRDataExtracted[k] = DataMatrix[i][j];
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k++;
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}
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}
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/* 5 Next lines */
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for(i = 2; i < 7; i++)
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{
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for(j = 0; j < 10; j++)
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{
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DMRDataExtracted[k] = DataMatrix[i][j];
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k++;
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}
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}
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/* 5 bit of CRC */
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for(i = 2; i < 7; i++)
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{
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DMRDataExtracted[k] = DataMatrix[i][10];
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k++;
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}
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/* Verify the data integrity by checking
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* all column parity bit */
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/* ---------- Column even-parity check (row 7) ---------- */
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memset(col_bad, 0, sizeof(col_bad));
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ParityCheckErrorNb = 0;
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for(i = 0; i < 16; i++)
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for (i = 0; i < 16; i++)
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{
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NbOfOne = 0;
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/* Get a full column */
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for(j = 0; j < 7; j++)
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{
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for (j = 0; j < 7; j++)
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NbOfOne += DataMatrix[j][i];
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}
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/* Check the parity bit (number of "1"
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* must be even) */
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if((NbOfOne % 2) != DataMatrix[7][i])
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if ((NbOfOne % 2) != DataMatrix[7][i])
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{
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ParityCheckErrorNb++;
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col_bad[i] = 1;
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#if BPTC_128x77_DEBUG
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fprintf(stderr,
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" BPTC128 P1 parity FAIL col=%u sum7=%u parity_bit=%u (expect even)\n",
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(unsigned)i, (unsigned)NbOfOne, (unsigned)DataMatrix[7][i]);
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#endif
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}
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}
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#if BPTC_128x77_DEBUG
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if (ParityCheckErrorNb)
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fprintf(stderr, " BPTC128 P1 parity bad columns=%u\n",
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(unsigned)ParityCheckErrorNb);
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#endif
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/* ---------- Parity-guided single-bit repair ---------- */
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{
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uint32_t n_bad_rows = 0, n_bad_cols = 0;
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uint32_t br = 0, bc = 0;
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for (i = 0; i < 7; i++)
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if (row_bad[i]) { n_bad_rows++; br = i; }
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for (i = 0; i < 16; i++)
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if (col_bad[i]) { n_bad_cols++; bc = i; }
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#if BPTC_128x77_DEBUG
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fprintf(stderr,
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" BPTC128 repair candidates: bad_rows=%u bad_cols=%u",
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(unsigned)n_bad_rows, (unsigned)n_bad_cols);
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if (n_bad_rows == 1)
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fprintf(stderr, " row=%u", (unsigned)br);
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if (n_bad_cols == 1)
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fprintf(stderr, " col=%u", (unsigned)bc);
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fprintf(stderr, "\n");
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#endif
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if (n_bad_rows == 1 && n_bad_cols == 1 && bc < 11)
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{
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DataMatrix[br][bc] ^= 1;
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row_bad[br] = 0;
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#if BPTC_128x77_DEBUG
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fprintf(stderr,
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" BPTC128 parity-guided FLIP at row=%u col=%u -> %u\n",
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(unsigned)br, (unsigned)bc, (unsigned)DataMatrix[br][bc]);
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#endif
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}
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#if BPTC_128x77_DEBUG
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else if (n_bad_rows || n_bad_cols)
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{
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fprintf(stderr,
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" BPTC128 no single-intersection flip "
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"(need exactly 1 bad row and 1 data col)\n");
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}
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#endif
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}
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/* ---------- Pass 2: Hamming (16,11,4) again ---------- */
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HammingIrrecoverableErrorNb = 0;
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for (i = 0; i < 7; i++)
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{
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for (j = 0; j < 16; j++)
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LineUncorrected[j] = DataMatrix[i][j];
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if (Hamming_16_11_4_decode(LineUncorrected, LineCorrected, 1) == false)
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{
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HammingIrrecoverableErrorNb++;
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#if BPTC_128x77_DEBUG
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fprintf(stderr, " BPTC128 P2 Hamming FAIL row=%u rx=", (unsigned)i);
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for (j = 0; j < 16; j++)
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fprintf(stderr, "%u", LineUncorrected[j] & 1);
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fprintf(stderr, "\n");
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#endif
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for (j = 0; j < 11; j++)
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DataMatrix[i][j] = LineUncorrected[j];
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}
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else
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{
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for (j = 0; j < 11; j++)
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DataMatrix[i][j] = LineCorrected[j];
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}
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}
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#if BPTC_128x77_DEBUG
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if (HammingIrrecoverableErrorNb)
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fprintf(stderr, " BPTC128 P2 Hamming irrecoverable rows=%u\n",
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(unsigned)HammingIrrecoverableErrorNb);
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#endif
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/* ---------- Final column parity recount ---------- */
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ParityCheckErrorNb = 0;
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for (i = 0; i < 16; i++)
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{
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NbOfOne = 0;
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for (j = 0; j < 7; j++)
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NbOfOne += DataMatrix[j][i];
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if ((NbOfOne % 2) != DataMatrix[7][i])
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{
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ParityCheckErrorNb++;
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#if BPTC_128x77_DEBUG
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fprintf(stderr,
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" BPTC128 P2 parity FAIL col=%u sum7=%u parity_bit=%u\n",
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(unsigned)i, (unsigned)NbOfOne, (unsigned)DataMatrix[7][i]);
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#endif
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}
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}
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/* Return the number of irrecoverable Hamming errors +
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* the number of parity check error */
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#if BPTC_128x77_DEBUG
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fprintf(stderr,
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" BPTC128 result: Hamming_err=%u parity_err=%u total=%u\n",
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(unsigned)HammingIrrecoverableErrorNb,
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(unsigned)ParityCheckErrorNb,
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(unsigned)(HammingIrrecoverableErrorNb + ParityCheckErrorNb));
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#endif
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/* ---------- Extract 77 bits ---------- */
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k = 0;
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for (i = 0; i < 2; i++)
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{
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for (j = 0; j < 11; j++)
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DMRDataExtracted[k++] = DataMatrix[i][j];
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}
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for (i = 2; i < 7; i++)
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{
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for (j = 0; j < 10; j++)
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DMRDataExtracted[k++] = DataMatrix[i][j];
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}
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for (i = 2; i < 7; i++)
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DMRDataExtracted[k++] = DataMatrix[i][10];
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return (HammingIrrecoverableErrorNb + ParityCheckErrorNb);
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//observation shows some parity check error is okay,
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//as long as the hamming is completely okay, may be worth it
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//to only check parity bits on columns
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if (HammingIrrecoverableErrorNb == 0 && ParityCheckErrorNb < 2)
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return (HammingIrrecoverableErrorNb);
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else return (HammingIrrecoverableErrorNb + ParityCheckErrorNb);
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} /* End BPTC_128x77_Extract_Data() */
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}
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/*
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* @brief : This function extract the 32 bits of a deinteleaved 32 bits
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@@ -432,19 +432,22 @@ void ras_effective_key_creation(dsd_state * state, char * input)
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ctx.digest[6] += 2;
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}
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//SEED low5 non-zero value (no change to 5-bit EMB checksum mod 31)
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if ((ctx.digest[0] & 0x1F) == 0)
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{
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fprintf (stderr, " Byte %d: %02X -> %02X; ", 1, ctx.digest[0], ctx.digest[0]+2);
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ctx.digest[0] += 2;
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}
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//UPDATE: I have now observed a system that has a 5-bit differential value of 0
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//so that means that the low5 effective key value can be either 0, or 0x1F
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//SEED low5 plus 1F (no change to 5-bit EMB checksum mod 31)
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else if ((ctx.digest[0] & 0x1F) == 0x1F)
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{
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fprintf (stderr, " Byte %d: %02X -> %02X; ", 1, ctx.digest[0], ctx.digest[0]+2);
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ctx.digest[0] += 2;
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}
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// //SEED low5 non-zero value (no change to 5-bit EMB checksum mod 31)
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// if ((ctx.digest[0] & 0x1F) == 0)
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// {
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// fprintf (stderr, " Byte %d: %02X -> %02X; ", 1, ctx.digest[0], ctx.digest[0]+2);
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// ctx.digest[0] += 2;
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// }
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// //SEED low5 plus 1F (no change to 5-bit EMB checksum mod 31)
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// else if ((ctx.digest[0] & 0x1F) == 0x1F)
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// {
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// fprintf (stderr, " Byte %d: %02X -> %02X; ", 1, ctx.digest[0], ctx.digest[0]+2);
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// ctx.digest[0] += 2;
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// }
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unsigned long long int effective_key = 0;
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for (int i = 0; i < 7; i++)
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@@ -663,7 +663,7 @@ void dmr_data_burst_handler(dsd_opts * opts, dsd_state * state, uint8_t info[196
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//calculation should be 5-bit portion of RAS Effective Key's Last byte & 0x1F
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//5-bit + CRCComputed % 31 = CRCExtracted
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#ifdef DEBUG_RAS
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if (opts->payload == 1 && is_emb && is_ras && CRCExtracted != CRCComputed && state->ras_effective_key == 0)
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if (opts->payload == 1 && is_emb && is_ras)
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{
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int32_t diff = ((int32_t)CRCExtracted - (int32_t)CRCComputed + 31) % 31;
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fprintf (stderr, " CRC CMP: %02X EXT: %02X DIFF: %02X", CRCComputed, CRCExtracted, diff);
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