diff options
Diffstat (limited to 'common/rwsig.c')
| -rw-r--r-- | common/rwsig.c | 92 |
1 files changed, 84 insertions, 8 deletions
diff --git a/common/rwsig.c b/common/rwsig.c index ee1bd6c9fc..1ad3ed37f9 100644 --- a/common/rwsig.c +++ b/common/rwsig.c @@ -15,6 +15,7 @@ #include "system.h" #include "usb_pd.h" #include "util.h" +#include "vb21_struct.h" /* Console output macros */ #define CPRINTF(format, args...) cprintf(CC_SYSTEM, format, ## args) @@ -24,12 +25,44 @@ static uint32_t * const rw_rst = (uint32_t *)(CONFIG_PROGRAM_MEMORY_BASE + CONFIG_RW_MEM_OFF + 4); +/* + * Check that memory between rwdata[start] and rwdata[len-1] is filled + * with ones. data, start and len must be aligned on 4-byte boundary. + */ +static int check_padding(const uint8_t *data, + unsigned int start, unsigned int len) +{ + unsigned int i; + const uint32_t *data32 = (const uint32_t *)data; + + if ((start % 4) != 0 || (len % 4) != 0) + return 0; + + for (i = start/4; i < len/4; i++) { + if (data32[i] != 0xffffffff) + return 0; + } + + return 1; +} + void check_rw_signature(void) { struct sha256_ctx ctx; - int good, res; + int res; + const struct rsa_public_key *key; + const uint8_t *sig; uint8_t *hash; uint32_t *rsa_workbuf; + const uint8_t *rwdata = (uint8_t *)CONFIG_PROGRAM_MEMORY_BASE + + CONFIG_RW_MEM_OFF; + int good = 0; + + unsigned int rwlen; +#ifdef CONFIG_RWSIG_TYPE_RWSIG + const struct vb21_packed_key *vb21_key; + const struct vb21_signature *vb21_sig; +#endif /* Only the Read-Only firmware needs to do the signature check */ if (system_get_image_copy() != SYSTEM_IMAGE_RO) @@ -48,17 +81,60 @@ void check_rw_signature(void) return; } +#ifdef CONFIG_RWSIG_TYPE_USBPD1 + key = (const struct rsa_public_key *)CONFIG_RO_PUBKEY_ADDR; + sig = (const uint8_t *)CONFIG_RW_SIG_ADDR; + rwlen = CONFIG_RW_SIZE - CONFIG_RW_SIG_SIZE; +#elif defined(CONFIG_RWSIG_TYPE_RWSIG) + vb21_key = (const struct vb21_packed_key *)CONFIG_RO_PUBKEY_ADDR; + vb21_sig = (const struct vb21_signature *)CONFIG_RW_SIG_ADDR; + + if (vb21_key->c.magic != VB21_MAGIC_PACKED_KEY || + vb21_key->key_size != sizeof(struct rsa_public_key)) { + CPRINTS("Invalid key."); + goto out; + } + + key = (const struct rsa_public_key *) + ((const uint8_t *)vb21_key + vb21_key->key_offset); + + /* + * TODO(crbug.com/690773): We could verify other parameters such + * as sig_alg/hash_alg actually matches what we build for. + */ + if (vb21_sig->c.magic != VB21_MAGIC_SIGNATURE || + vb21_sig->sig_size != RSANUMBYTES || + vb21_key->sig_alg != vb21_sig->sig_alg || + vb21_key->hash_alg != vb21_sig->hash_alg || + /* Sanity check signature offset and data size. */ + vb21_sig->sig_offset < sizeof(vb21_sig) || + (vb21_sig->sig_offset + RSANUMBYTES) > CONFIG_RW_SIG_SIZE || + vb21_sig->data_size > (CONFIG_RW_SIZE - CONFIG_RW_SIG_SIZE)) { + CPRINTS("Invalid signature."); + goto out; + } + + sig = (const uint8_t *)vb21_sig + vb21_sig->sig_offset; + rwlen = vb21_sig->data_size; +#endif + + /* + * Check that unverified RW region is actually filled with ones. + */ + good = check_padding(rwdata, rwlen, + CONFIG_RW_SIZE - CONFIG_RW_SIG_SIZE); + if (!good) { + CPRINTS("Invalid padding."); + goto out; + } + /* SHA-256 Hash of the RW firmware */ - /* TODO(crosbug.com/p/44803): Do we have to hash the whole region? */ SHA256_init(&ctx); - SHA256_update(&ctx, (void *)CONFIG_PROGRAM_MEMORY_BASE - + CONFIG_RW_MEM_OFF, - CONFIG_RW_SIZE - CONFIG_RW_SIG_SIZE); + SHA256_update(&ctx, rwdata, rwlen); hash = SHA256_final(&ctx); - good = rsa_verify((const struct rsa_public_key *)CONFIG_RO_PUBKEY_ADDR, - (const uint8_t *)CONFIG_RW_SIG_ADDR, - hash, rsa_workbuf); + good = rsa_verify(key, sig, hash, rsa_workbuf); +out: if (good) { CPRINTS("RW image verified"); /* Jump to the RW firmware */ |