src/security/vboot/vbnv.c

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2
   3 #include <assert.h>
   4 #include <string.h>
   5 #include <types.h>
   6 #include <security/vboot/misc.h>
   7 #include <security/vboot/vbnv.h>
   8 #include <security/vboot/vbnv_layout.h>
   9 #include <vb2_api.h>
  10
  11 static bool vbnv_initialized;
  12
  13 /* Return CRC-8 of the data, using x^8 + x^2 + x + 1 polynomial. */
  14 static uint8_t crc8_vbnv(const uint8_t *data, int len)
  15 {
  16         unsigned int crc = 0;
  17         int i, j;
  18
  19         for (j = len; j; j--, data++) {
  20                 crc ^= (*data << 8);
  21                 for (i = 8; i; i--) {
  22                         if (crc & 0x8000)
  23                                 crc ^= (0x1070 << 3);
  24                         crc <<= 1;
  25                 }
  26         }
  27
  28         return (uint8_t)(crc >> 8);
  29 }
  30
  31 void vbnv_reset(uint8_t *vbnv_copy)
  32 {
  33         memset(vbnv_copy, 0, VBOOT_VBNV_BLOCK_SIZE);
  34 }
  35
  36 /* Verify VBNV header and checksum. */
  37 int verify_vbnv(uint8_t *vbnv_copy)
  38 {
  39         return (HEADER_SIGNATURE == (vbnv_copy[HEADER_OFFSET] & HEADER_MASK)) &&
  40                 (crc8_vbnv(vbnv_copy, CRC_OFFSET) == vbnv_copy[CRC_OFFSET]);
  41 }
  42
  43 /* Re-generate VBNV checksum. */
  44 void regen_vbnv_crc(uint8_t *vbnv_copy)
  45 {
  46         vbnv_copy[CRC_OFFSET] = crc8_vbnv(vbnv_copy, CRC_OFFSET);
  47 }
  48
  49 /*
  50  * Read VBNV data from configured storage backend.
  51  * If VBNV verification fails, reset the vbnv copy.
  52  */
  53 void read_vbnv(uint8_t *vbnv_copy)
  54 {
  55         if (CONFIG(VBOOT_VBNV_CMOS))
  56                 read_vbnv_cmos(vbnv_copy);
  57         else if (CONFIG(VBOOT_VBNV_FLASH))
  58                 read_vbnv_flash(vbnv_copy);
  59         else
  60                 dead_code();
  61
  62         /* Check data for consistency */
  63         if (!verify_vbnv(vbnv_copy))
  64                 vbnv_reset(vbnv_copy);
  65 }
  66
  67 /*
  68  * Write VBNV data to configured storage backend.
  69  * This assumes that the caller has updated the CRC already.
  70  */
  71 void save_vbnv(const uint8_t *vbnv_copy)
  72 {
  73         if (CONFIG(VBOOT_VBNV_CMOS))
  74                 save_vbnv_cmos(vbnv_copy);
  75         else if (CONFIG(VBOOT_VBNV_FLASH))
  76                 save_vbnv_flash(vbnv_copy);
  77         else
  78                 dead_code();
  79 }
  80
  81 /* Read the USB Device Controller(UDC) enable flag from VBNV. */
  82 int vbnv_udc_enable_flag(void)
  83 {
  84         struct vb2_context *ctx = vboot_get_context();
  85         return (ctx->nvdata[DEV_FLAGS_OFFSET] & DEV_ENABLE_UDC) ? 1 : 0;
  86 }
  87
  88 void vbnv_init(void)
  89 {
  90         struct vb2_context *ctx;
  91
  92         /* NV data already initialized and read */
  93         if (vbnv_initialized)
  94                 return;
  95
  96         ctx = vboot_get_context();
  97         if (CONFIG(VBOOT_VBNV_CMOS))
  98                 vbnv_init_cmos(ctx->nvdata);
  99         read_vbnv(ctx->nvdata);
 100         vbnv_initialized = true;
 101 }