diff options
| -rw-r--r-- | common/ap_ro_integrity_check.c | 172 |
1 files changed, 71 insertions, 101 deletions
diff --git a/common/ap_ro_integrity_check.c b/common/ap_ro_integrity_check.c index d1df192469..22538c055d 100644 --- a/common/ap_ro_integrity_check.c +++ b/common/ap_ro_integrity_check.c @@ -708,21 +708,16 @@ static enum ap_ro_check_vc_errors ap_ro_check_unsupported(int add_flash_event) * * @param offset offset of the fmap in the flash * @param nareas number of areas in fmap - * @param fmap container to save FMAP area information in * @param gscvd container to save RO_GSCVD area information in * * @return zero on success, -1 if both areas not found. */ -static int find_areas(uint32_t offset, uint16_t nareas, - struct fmap_area_header *fmap, +static int find_gscvd(uint32_t offset, uint16_t nareas, struct fmap_area_header *gscvd) { uint16_t i; struct fmap_area_header fmah; - fmap->area_offset = 0; - gscvd->area_offset = 0; - if (nareas > 64) { CPRINTS("%s: too many areas: %d", __func__, nareas); return -1; @@ -733,90 +728,19 @@ static int find_areas(uint32_t offset, uint16_t nareas, return -1; if (!memcmp(fmah.area_name, GSCVD_AREA_NAME, - sizeof(GSCVD_AREA_NAME))) + sizeof(GSCVD_AREA_NAME))) { memcpy(gscvd, &fmah, sizeof(*gscvd)); - else if (!memcmp(fmah.area_name, FMAP_AREA_NAME, - sizeof(FMAP_AREA_NAME))) - memcpy(fmap, &fmah, sizeof(*fmap)); - - if (fmap->area_offset && gscvd->area_offset) return 0; - + } offset += sizeof(fmah); } - CPRINTS("Could not find %s or %s area", GSCVD_AREA_NAME, - FMAP_AREA_NAME); + CPRINTS("Could not find %s area", GSCVD_AREA_NAME); return -1; } /** - * Find FMAP header in AP flash and copy it into the passed in structure. - * - * Verify validity of the found header. - * - * @param fmh pointer to the header to copy to - * - * @return offset of FMAP in AP flash, or zero, if not found. - */ -static uint32_t find_fmap(struct fmap_header *fmh) -{ - uint32_t offset; - uint32_t step = MAX_SUPPORTED_FLASH_SIZE / 2; - uint32_t skip_mask = ~(MAX_SUPPORTED_FLASH_SIZE - 1); - bool fmap_found = false; - - do { - for (offset = 0; offset < MAX_SUPPORTED_FLASH_SIZE; - offset += step) { - if ((offset & skip_mask) == 0) - continue; - - if (read_ap_spi(fmh->fmap_signature, offset, - sizeof(fmh->fmap_signature), __LINE__)) - return 0; - - if (!memcmp(fmh->fmap_signature, FMAP_SIGNATURE, - sizeof(fmh->fmap_signature))) { - /* - * TODO(vbendeb): address the possibility of a - * fake FMAP placed in addition to the real - * one. - */ - fmap_found = true; - break; - } - } - step >>= 1; - skip_mask >>= 1; - - } while ((step >= LOWEST_FMAP_ALIGNMENT) && !fmap_found); - - if (!fmap_found) { - CPRINTS("Could not find FMAP"); - return 0; - } - - /* Read the rest of fmap header. */ - if (read_ap_spi( - &fmh->fmap_ver_major, offset + sizeof(fmh->fmap_signature), - sizeof(*fmh) - sizeof(fmh->fmap_signature), - __LINE__)) - return 0; - - /* Verify fmap validity. */ - if ((fmh->fmap_ver_major != FMAP_MAJOR_VERSION) || - (fmh->fmap_ver_minor != FMAP_MINOR_VERSION) || - (fmh->fmap_size > MAX_SUPPORTED_FLASH_SIZE)) { - CPRINTS("invalid FMAP contents"); - return 0; - } - - return offset; -} - -/** * Read gsc verification data from AP flash. * * @param fmap_offset offset of FMAP in AP flash, used for validity check @@ -1211,7 +1135,10 @@ static int save_gvd_hash(struct gvd_container *gvdc) } /** - * Verify gsc_verification_data cache. + * Verify that GVD in the AP flash has not changed. + * + * Calculate the GVD SHA256 digest and compare it with the cached digest + * value. * * @param gvdc pointer to the gsc_verification_data container * @param descriptor pointer to the descriptor containing cached hash value to @@ -1241,9 +1168,8 @@ static int gvd_cache_check(const struct gvd_container *gvdc, /** * Validate cached AP RO GVD entry. * - * If a non NULL descriptor value is passed, the function does not try to - * verify the gsc_verification_data signature, it just verifies that the - * locally cached hash of gsc_verification_data matches. + * Check if the locally cached hash of gsc_verification_data matches and if + * so, verify the hash of the AP RO ranges stored in GVD. * * @param descriptor points to locally cached hash of gsc_verification_data. * @@ -1274,36 +1200,28 @@ static int8_t validate_cached_ap_ro_v2(const struct gvd_descriptor *descriptor) EC_SUCCESS ? 0 : -1; } -/* - ** +/** * Try validating AP RO. * - * This function looks for gsc_verification_data structure in AP flash through - * FMAP, and then verifies cryptographically the validity of the contents, - * starting with the hash of the root key, then signature of the key block, - * and then signature of gsc_verification_data and the hash of the RO ranges. + * This function receives an offset of FMAP in the AP flash and the number of + * areas in the FMAP. The function looks for the RO_GSCVD area, and if found + * tries to cryptographically verify the GVD, starting with the hash of the + * root key, then signature of the key block, and then signature of + * gsc_verification_data and the hash of the RO ranges. * * @return zero on success, non zero on failure. */ -static int8_t validate_and_cache_ap_ro_v2_from_flash(void) +static int8_t check_fmap_location(uint32_t fmap_offset, uint16_t nareas) { - uint32_t fmap_offset; - struct fmap_header fmh; struct gvd_container gvdc; struct kb_container kbc; struct vb_rsa_pubk pubk; - struct fmap_area_header fmap; struct fmap_area_header gscvd; struct vb2_packed_key *rootk = NULL; - int rv = -1; - fmap_offset = find_fmap(&fmh); - if (!fmap_offset) - return -1; - - if (find_areas(fmap_offset + sizeof(fmh), fmh.fmap_nareas, - &fmap, &gscvd)) + if (find_gscvd(fmap_offset + sizeof(struct fmap_header), nareas, + &gscvd)) return -1; gvdc.offset = gscvd.area_offset; @@ -1349,6 +1267,58 @@ exit: return rv; } +/* + * Iterate through AP flash at 4K intervals looking for FMAP. Once FMAP is + * found call a function to verify the FMAP GVD section. Return if + * verification succeeds, if it fails - keep scanning the flash looking for + * more FMAP sections. + * + * Return zero if a valid GVD was found, -1 otherwise. + */ +static int8_t validate_and_cache_ap_ro_v2_from_flash(void) +{ + uint32_t offset; + struct fmap_header fmh; + bool fmap_found = false; + + for (offset = 0; offset < MAX_SUPPORTED_FLASH_SIZE; + offset += LOWEST_FMAP_ALIGNMENT) { + + if (read_ap_spi(fmh.fmap_signature, offset, + sizeof(fmh.fmap_signature), __LINE__)) + return -1; + + if (memcmp(fmh.fmap_signature, FMAP_SIGNATURE, + sizeof(fmh.fmap_signature))) + continue; /* Not an FMAP candidate. */ + + /* Read the rest of fmap header. */ + if (read_ap_spi(&fmh.fmap_ver_major, offset + + sizeof(fmh.fmap_signature), + sizeof(fmh) - sizeof(fmh.fmap_signature), + __LINE__)) + return -1; + + /* Verify fmap validity. */ + if ((fmh.fmap_ver_major != FMAP_MAJOR_VERSION) || + (fmh.fmap_ver_minor != FMAP_MINOR_VERSION) || + (fmh.fmap_size > MAX_SUPPORTED_FLASH_SIZE)) { + CPRINTS("invalid FMAP contents at %x", offset); + continue; + } + + fmap_found = true; + + if (!check_fmap_location(offset, fmh.fmap_nareas)) + return 0; + } + + if (!fmap_found) + CPRINTS("Could not find FMAP"); + + return -1; +} + static uint8_t do_ap_ro_check(void) { int rv; |