static int b64_read()

in crypto/decrepit/bio/base64_bio.c [118:316]

• 159 lines of code
• 39 McCabe index (conditional complexity)

static int b64_read(BIO *b, char *out, int outl) {
  int ret = 0, i, ii, j, k, x, n, num, ret_code = 0;
  BIO_B64_CTX *ctx;
  uint8_t *p, *q;

  if (out == NULL) {
    return 0;
  }
  ctx = (BIO_B64_CTX *) b->ptr;

  if (ctx == NULL || b->next_bio == NULL) {
    return 0;
  }

  BIO_clear_retry_flags(b);

  if (ctx->encode != B64_DECODE) {
    ctx->encode = B64_DECODE;
    ctx->buf_len = 0;
    ctx->buf_off = 0;
    ctx->tmp_len = 0;
    EVP_DecodeInit(&ctx->base64);
  }

  // First check if there are bytes decoded/encoded
  if (ctx->buf_len > 0) {
    assert(ctx->buf_len >= ctx->buf_off);
    i = ctx->buf_len - ctx->buf_off;
    if (i > outl) {
      i = outl;
    }
    assert(ctx->buf_off + i < (int)sizeof(ctx->buf));
    OPENSSL_memcpy(out, &ctx->buf[ctx->buf_off], i);
    ret = i;
    out += i;
    outl -= i;
    ctx->buf_off += i;
    if (ctx->buf_len == ctx->buf_off) {
      ctx->buf_len = 0;
      ctx->buf_off = 0;
    }
  }

  // At this point, we have room of outl bytes and an empty buffer, so we
  // should read in some more.

  ret_code = 0;
  while (outl > 0) {
    if (ctx->cont <= 0) {
      break;
    }

    i = BIO_read(b->next_bio, &(ctx->tmp[ctx->tmp_len]),
                 B64_BLOCK_SIZE - ctx->tmp_len);

    if (i <= 0) {
      ret_code = i;

      // Should we continue next time we are called?
      if (!BIO_should_retry(b->next_bio)) {
        ctx->cont = i;
        // If buffer empty break
        if (ctx->tmp_len == 0) {
          break;
        } else {
          // Fall through and process what we have
          i = 0;
        }
      } else {
        // else we retry and add more data to buffer
        break;
      }
    }
    i += ctx->tmp_len;
    ctx->tmp_len = i;

    // We need to scan, a line at a time until we have a valid line if we are
    // starting.
    if (ctx->start && (BIO_test_flags(b, BIO_FLAGS_BASE64_NO_NL))) {
      // ctx->start = 1;
      ctx->tmp_len = 0;
    } else if (ctx->start) {
      q = p = (uint8_t *)ctx->tmp;
      num = 0;
      for (j = 0; j < i; j++) {
        if (*(q++) != '\n') {
          continue;
        }

        // due to a previous very long line, we need to keep on scanning for a
        // '\n' before we even start looking for base64 encoded stuff.
        if (ctx->tmp_nl) {
          p = q;
          ctx->tmp_nl = 0;
          continue;
        }

        k = EVP_DecodeUpdate(&(ctx->base64), (uint8_t *)ctx->buf, &num, p,
                             q - p);

        if (k <= 0 && num == 0 && ctx->start) {
          EVP_DecodeInit(&ctx->base64);
        } else {
          if (p != (uint8_t *)&(ctx->tmp[0])) {
            i -= (p - (uint8_t *)&(ctx->tmp[0]));
            for (x = 0; x < i; x++) {
              ctx->tmp[x] = p[x];
            }
          }
          EVP_DecodeInit(&ctx->base64);
          ctx->start = 0;
          break;
        }
        p = q;
      }

      // we fell off the end without starting
      if (j == i && num == 0) {
        // Is this is one long chunk?, if so, keep on reading until a new
        // line.
        if (p == (uint8_t *)&(ctx->tmp[0])) {
          // Check buffer full
          if (i == B64_BLOCK_SIZE) {
            ctx->tmp_nl = 1;
            ctx->tmp_len = 0;
          }
        } else if (p != q) {  // finished on a '\n'
          n = q - p;
          for (ii = 0; ii < n; ii++) {
            ctx->tmp[ii] = p[ii];
          }
          ctx->tmp_len = n;
        }
        // else finished on a '\n'
        continue;
      } else {
        ctx->tmp_len = 0;
      }
    } else if (i < B64_BLOCK_SIZE && ctx->cont > 0) {
      // If buffer isn't full and we can retry then restart to read in more
      // data.
      continue;
    }

    if (BIO_test_flags(b, BIO_FLAGS_BASE64_NO_NL)) {
      int z, jj;

      jj = i & ~3;  // process per 4
      z = EVP_DecodeBlock((uint8_t *)ctx->buf, (uint8_t *)ctx->tmp, jj);
      if (jj > 2) {
        if (ctx->tmp[jj - 1] == '=') {
          z--;
          if (ctx->tmp[jj - 2] == '=') {
            z--;
          }
        }
      }
      // z is now number of output bytes and jj is the number consumed.
      if (jj != i) {
        OPENSSL_memmove(ctx->tmp, &ctx->tmp[jj], i - jj);
        ctx->tmp_len = i - jj;
      }
      ctx->buf_len = 0;
      if (z > 0) {
        ctx->buf_len = z;
      }
      i = z;
    } else {
      i = EVP_DecodeUpdate(&(ctx->base64), (uint8_t *)ctx->buf,
                           &ctx->buf_len, (uint8_t *)ctx->tmp, i);
      ctx->tmp_len = 0;
    }
    ctx->buf_off = 0;
    if (i < 0) {
      ret_code = 0;
      ctx->buf_len = 0;
      break;
    }

    if (ctx->buf_len <= outl) {
      i = ctx->buf_len;
    } else {
      i = outl;
    }

    OPENSSL_memcpy(out, ctx->buf, i);
    ret += i;
    ctx->buf_off = i;
    if (ctx->buf_off == ctx->buf_len) {
      ctx->buf_len = 0;
      ctx->buf_off = 0;
    }
    outl -= i;
    out += i;
  }

  BIO_copy_next_retry(b);
  return ret == 0 ? ret_code : ret;
}