Working model finished

app/main.c

@@ -0,0 +1,217 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include "rfc6238.h"
+
+#define T0 0
+#define DIGITS 6
+#define VALIDITY 30
+#define TIME 2
+
+
+/*******************************Code Taken from elsewhere********************************/
+
+char b32_decode_char(char c);
+void b32_decode(char** dst, size_t* dstlen, const char* src, size_t srclen);
+
+void b32_decode(char** dst, size_t* dstlen, const char* src, size_t srclen)
+{
+    size_t padlen = 0;   // Number of ='s in padding
+    size_t lastlen = 0;  // Length of last quantum in characters
+
+    *dst = NULL;
+    *dstlen = 0;
+
+    // Check padding
+    for (size_t i = 1; i < srclen; i++)
+    {
+        if (src[srclen - i] == '=')
+            padlen++;
+        else
+            break;
+    }
+
+    // Check source material
+    for (size_t i = 0; i < srclen - padlen; i++)
+    {
+        if (b32_decode_char(src[i]) > 0x1F)
+        {
+            // ERROR: one or more characters cannot be decoded
+            return;
+        }
+    }
+
+    // Calculate the length of the last quantum in src
+    lastlen = (srclen - padlen) % 8;
+
+    // How many quantums do we have?
+    size_t qmax = (srclen - padlen) / 8;
+
+    if (lastlen > 0)
+    {
+        // Last quantum is a partial quantum
+        // ... qmax rounded down
+        qmax += 1;
+    }
+    else
+    {
+        // Last quantum is a full quantum
+        // ... length of last quantum is 8, not 0
+        lastlen = 8;
+    }
+
+    // Calculate dst buffer size
+    *dstlen = ((srclen - padlen) / 8) * 5;
+
+    switch (lastlen)
+    {
+    case 8:
+        break;
+    case 7:
+        *dstlen += 4;
+        break;
+    case 5:
+        *dstlen += 3;
+        break;
+    case 4:
+        *dstlen += 2;
+        break;
+    case 2:
+        *dstlen += 1;
+        break;
+    default:
+        // ERROR: Not a multiple of a byte.
+        *dstlen = 0;
+        break;
+    }
+
+    if (dstlen == 0)
+    {
+        // Either empty src, or an error occurred
+        return;
+    }
+
+    // Allocate dst buffer
+    *dst = (char*)malloc(sizeof(char) * (*dstlen));
+
+    // Loop variables
+    size_t qlen;
+    char* pdst = *dst;
+    const char* psrc = src;
+
+    // Decode each quantum
+    for (size_t q = 0; q < qmax; q++)
+    {
+        // Are we on the last quantum?
+        if (q == qmax - 1)
+            qlen = lastlen;
+        else
+            qlen = 8;
+
+        // dst       0           1          2          3           4 
+        //      [11111 111][11 11111 1][1111 1111][1 11111 11][111 11111]
+        // src     0      1      2      3       4      5      6      7
+
+        switch (qlen)
+        {
+            // 8 = 5 bytes in quantum
+        case 8:
+            pdst[4] = b32_decode_char(psrc[7]);
+            pdst[4] |= b32_decode_char(psrc[6]) << 5;
+            // 7 = 4 bytes in quantum
+        case 7:
+            pdst[3] = b32_decode_char(psrc[6]) >> 3;
+            pdst[3] |= (b32_decode_char(psrc[5]) & 0x1F) << 2;
+            pdst[3] |= b32_decode_char(psrc[4]) << 7;
+            // 5 = 3 bytes in quantum
+        case 5:
+            pdst[2] = b32_decode_char(psrc[4]) >> 1;
+            pdst[2] |= b32_decode_char(psrc[3]) << 4;
+            // 4 = 2 bytes in quantum
+        case 4:
+            pdst[1] = b32_decode_char(psrc[3]) >> 4;
+            pdst[1] |= (b32_decode_char(psrc[2]) & 0x1F) << 1;
+            pdst[1] |= b32_decode_char(psrc[1]) << 6;
+            // 2 = 1 byte in quantum
+        case 2:
+            pdst[0] = b32_decode_char(psrc[1]) >> 2;
+            pdst[0] |= b32_decode_char(psrc[0]) << 3;
+            break;
+        default:
+            break; // TODO error
+        }
+
+        // Move quantum pointers forward
+        psrc += 8;
+        pdst += 5;
+    }
+}
+
+char b32_decode_char(char c)
+{
+    if (c >= 'A' && c <= 'Z')
+        return c - 'A';
+    else if (c >= '2' && c <= '7')
+        return c - '2' + 26;
+    // ... handle lowercase here???
+    else if (c >= 'a' && c <= 'z')
+        return c - 'a';
+    else
+        return 0xFF; // ERROR 
+}
+
+/*******************************Code Taken from elsewhere********************************/
+
+
+int main(int argc, char* argv[]) {
+
+
+    char key[50];
+    char* k;
+    char* decodeKey;
+    size_t sz_dKey;
+    uint32_t result;
+
+    if (argc <= 1) {
+        printf("Please provide your secret key!!!!!\n");
+        return 0;
+    }
+
+    unsigned int sz_key = strlen(argv[1]);
+
+    if (sz_key > 50) {
+        printf("base-32 secret key cannot be more than 50 characters.\n");
+        return 0;
+    }
+
+
+    //validate the key...
+    for (int i = 0; i < sz_key; i++) {
+
+        if ((argv[1][i] < 'A' && argv[1][i] > 'Z') ||
+            (argv[1][i] < '2' && argv[1][i] > '9') ||
+            (argv[1][i] == '=')) {
+
+            printf("Invalid base-32 encoded key.\nPlease enter correct base-32 encoded key.\n");
+            return 0;
+        }
+    }
+
+
+    strncpy(key, argv[1], sz_key);
+
+
+    k = key;
+
+
+    b32_decode(&decodeKey, &sz_dKey, k, (size_t)sz_key);
+
+    time_t t = floor((time(NULL) - T0) / VALIDITY);
+
+    result = TOTP((uint8_t*)decodeKey, sz_dKey, (uint64_t)t, DIGITS);
+
+    printf("The resulting OTP value is : %06u\n", result);
+
+    return 0;
+}