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cbfs: Add unverified_area APIs 

This patch adds a new ..._unverified_area_... group of functions to the
cbfs_map/_load/_alloc() APIs. These functions can be used to access
custom FMAP sections and are meant to replace the existing
cbfs_locate_file_in_region(). The name is intended to highlight that
accesses through this API will not be verified when CBFS_VERIFICATION is
enabled and should always be treated as if they may return malicious
data. (Due to laziness I'm not adding the combination of this API with
the ..._type_... variant at this point, since it seems very unlikely
that we'll ever have a use case for that. If we ever do, it should be
easy to add later.)

(Also remove the 'inline' from cbfs_file_hash_mismatch(). I'm not sure
why I put it there in the first place, probably a bad copy&paste.)

Signed-off-by: Julius Werner <jwerner@chromium.org>
Change-Id: I402265900f7075aa0c2f58d812c67ea63ddf2900
Reviewed-on: https://review.coreboot.org/c/coreboot/+/59678
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>
This commit is contained in:
Julius Werner 2021-04-15 23:25:44 -07:00
parent 0cd6ab338c
commit 05714ccab7
2 changed files with 151 additions and 78 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

47
src/include/cbfs.h
View File

@ -55,6 +55,11 @@
* section), even when running in an RW stage from one of the RW CBFSs. Only relevant if
* CONFIG(VBOOT) is set.
*
* ..._unverified_area_...: Will look for the CBFS file in the named FMAP area, rather than
* any of the default (RO or RW) CBFSs. Files accessed this way are *not* verified in any
* way (even if CONFIG(CBFS_VERIFICATION) is enabled) and should always be treated as
* untrusted (potentially malicious) data. Mutually exclusive with the ..._ro_... variant.
*
* ..._type_...: May pass in an extra enum cbfs_type *type parameter. If the value it points to
* is CBFS_TYPE_QUERY, it will be replaced with the actual CBFS type of the found file. If
* it is anything else, the type will be compared with the actually found type, and the
@ -76,11 +81,15 @@ static inline size_t cbfs_type_load(const char *name, void *buf, size_t size,
enum cbfs_type *type);
static inline size_t cbfs_ro_type_load(const char *name, void *buf, size_t size,
enum cbfs_type *type);
static inline size_t cbfs_unverified_area_load(const char *area, const char *name,
void *buf, size_t size);
static inline void *cbfs_map(const char *name, size_t *size_out);
static inline void *cbfs_ro_map(const char *name, size_t *size_out);
static inline void *cbfs_type_map(const char *name, size_t *size_out, enum cbfs_type *type);
static inline void *cbfs_ro_type_map(const char *name, size_t *size_out, enum cbfs_type *type);
static inline void *cbfs_unverified_area_map(const char *area, const char *name,
size_t *size_out);
static inline void *cbfs_alloc(const char *name, cbfs_allocator_t allocator, void *arg,
size_t *size_out);
@ -90,6 +99,9 @@ static inline void *cbfs_type_alloc(const char *name, cbfs_allocator_t allocator
size_t *size_out, enum cbfs_type *type);
static inline void *cbfs_ro_type_alloc(const char *name, cbfs_allocator_t allocator, void *arg,
size_t *size_out, enum cbfs_type *type);
static inline void *cbfs_unverified_area_alloc(const char *area, const char *name,
cbfs_allocator_t allocator, void *arg,
size_t *size_out);
static inline void *cbfs_cbmem_alloc(const char *name, uint32_t cbmem_id, size_t *size_out);
static inline void *cbfs_ro_cbmem_alloc(const char *name, uint32_t cbmem_id, size_t *size_out);
@ -97,6 +109,8 @@ static inline void *cbfs_type_cbmem_alloc(const char *name, uint32_t cbmem_id, s
enum cbfs_type *type);
static inline void *cbfs_ro_type_cbmem_alloc(const char *name, uint32_t cbmem_id,
size_t *size_out, enum cbfs_type *type);
static inline void *cbfs_unverified_area_cbmem_alloc(const char *area, const char *name,
uint32_t cbmem_id, size_t *size_out);
/*
* Starts the processes of preloading a file into RAM.
@ -194,6 +208,9 @@ cb_err_t _cbfs_boot_lookup(const char *name, bool force_ro,
void *_cbfs_alloc(const char *name, cbfs_allocator_t allocator, void *arg,
size_t *size_out, bool force_ro, enum cbfs_type *type);
void *_cbfs_unverified_area_alloc(const char *area, const char *name,
cbfs_allocator_t allocator, void *arg, size_t *size_out);
struct _cbfs_default_allocator_arg {
void *buf;
size_t buf_size;
@ -229,6 +246,13 @@ static inline void *cbfs_ro_type_alloc(const char *name, cbfs_allocator_t alloca
return _cbfs_alloc(name, allocator, arg, size_out, true, type);
}
static inline void *cbfs_unverified_area_alloc(const char *area, const char *name,
cbfs_allocator_t allocator, void *arg,
size_t *size_out)
{
return _cbfs_unverified_area_alloc(area, name, allocator, arg, size_out);
}
static inline void *cbfs_map(const char *name, size_t *size_out)
{
return cbfs_type_map(name, size_out, NULL);
@ -249,6 +273,12 @@ static inline void *cbfs_ro_type_map(const char *name, size_t *size_out, enum cb
return cbfs_ro_type_alloc(name, NULL, NULL, size_out, type);
}
static inline void *cbfs_unverified_area_map(const char *area, const char *name,
size_t *size_out)
{
return _cbfs_unverified_area_alloc(area, name, NULL, NULL, size_out);
}
static inline size_t _cbfs_load(const char *name, void *buf, size_t size, bool force_ro,
enum cbfs_type *type)
{
@ -281,6 +311,16 @@ static inline size_t cbfs_ro_type_load(const char *name, void *buf, size_t size,
return _cbfs_load(name, buf, size, true, type);
}
static inline size_t cbfs_unverified_area_load(const char *area, const char *name,
void *buf, size_t size)
{
struct _cbfs_default_allocator_arg arg = { .buf = buf, .buf_size = size };
if (_cbfs_unverified_area_alloc(area, name, _cbfs_default_allocator, &arg, &size))
return size;
else
return 0;
}
static inline void *cbfs_cbmem_alloc(const char *name, uint32_t cbmem_id, size_t *size_out)
{
return cbfs_type_cbmem_alloc(name, cbmem_id, size_out, NULL);
@ -305,6 +345,13 @@ static inline void *cbfs_ro_type_cbmem_alloc(const char *name, uint32_t cbmem_id
size_out, type);
}
static inline void *cbfs_unverified_area_cbmem_alloc(const char *area, const char *name,
uint32_t cbmem_id, size_t *size_out)
{
return _cbfs_unverified_area_alloc(area, name, _cbfs_cbmem_allocator,
(void *)(uintptr_t)cbmem_id, size_out);
}
static inline size_t cbfs_get_size(const char *name)
{
union cbfs_mdata mdata;

182
src/lib/cbfs.c
View File

@ -190,30 +190,37 @@ static inline bool cbfs_lzma_enabled(void)
return true;
}
static inline bool cbfs_file_hash_mismatch(const void *buffer, size_t size,
const struct vb2_hash *file_hash)
static bool cbfs_file_hash_mismatch(const void *buffer, size_t size,
const union cbfs_mdata *mdata, bool skip_verification)
{
/* Avoid linking hash functions when verification is disabled. */
if (!CONFIG(CBFS_VERIFICATION))
if (!CONFIG(CBFS_VERIFICATION) || skip_verification)
return false;
/* If there is no file hash, always count that as a mismatch. */
if (file_hash && vb2_hash_verify(buffer, size, file_hash) == VB2_SUCCESS)
return false;
const struct vb2_hash *hash = cbfs_file_hash(mdata);
if (!hash) {
ERROR("'%s' does not have a file hash!\n", mdata->h.filename);
return true;
}
printk(BIOS_CRIT, "CBFS file hash mismatch!\n");
return true;
if (vb2_hash_verify(buffer, size, hash) != VB2_SUCCESS) {
ERROR("'%s' file hash mismatch!\n", mdata->h.filename);
return true;
}
return false;
}
static size_t cbfs_load_and_decompress(const struct region_device *rdev, void *buffer,
size_t buffer_size, uint32_t compression,
const struct vb2_hash *file_hash)
const union cbfs_mdata *mdata, bool skip_verification)
{
size_t in_size = region_device_sz(rdev);
size_t out_size = 0;
void *map;
DEBUG("Decompressing %zu bytes to %p with algo %d\n", in_size, buffer, compression);
DEBUG("Decompressing %zu bytes from '%s' to %p with algo %d\n",
in_size, mdata->h.filename, buffer, compression);
switch (compression) {
case CBFS_COMPRESS_NONE:
@ -221,7 +228,7 @@ static size_t cbfs_load_and_decompress(const struct region_device *rdev, void *b
return 0;
if (rdev_readat(rdev, buffer, 0, in_size) != in_size)
return 0;
if (cbfs_file_hash_mismatch(buffer, in_size, file_hash))
if (cbfs_file_hash_mismatch(buffer, in_size, mdata, skip_verification))
return 0;
return in_size;
@ -235,7 +242,7 @@ static size_t cbfs_load_and_decompress(const struct region_device *rdev, void *b
if (map == NULL)
return 0;
if (!cbfs_file_hash_mismatch(map, in_size, file_hash)) {
if (!cbfs_file_hash_mismatch(map, in_size, mdata, skip_verification)) {
timestamp_add_now(TS_START_ULZ4F);
out_size = ulz4fn(map, in_size, buffer, buffer_size);
timestamp_add_now(TS_END_ULZ4F);
@ -252,7 +259,7 @@ static size_t cbfs_load_and_decompress(const struct region_device *rdev, void *b
if (map == NULL)
return 0;
if (!cbfs_file_hash_mismatch(map, in_size, file_hash)) {
if (!cbfs_file_hash_mismatch(map, in_size, mdata, skip_verification)) {
/* Note: timestamp not useful for memory-mapped media (x86) */
timestamp_add_now(TS_START_ULZMA);
out_size = ulzman(map, in_size, buffer, buffer_size);
@ -411,13 +418,64 @@ out:
return err;
}
static void *do_alloc(union cbfs_mdata *mdata, struct region_device *rdev,
cbfs_allocator_t allocator, void *arg, size_t *size_out,
bool skip_verification)
{
size_t size = region_device_sz(rdev);
void *loc = NULL;
uint32_t compression = CBFS_COMPRESS_NONE;
const struct cbfs_file_attr_compression *cattr = cbfs_find_attr(mdata,
CBFS_FILE_ATTR_TAG_COMPRESSION, sizeof(*cattr));
if (cattr) {
compression = be32toh(cattr->compression);
size = be32toh(cattr->decompressed_size);
}
if (size_out)
*size_out = size;
/* allocator == NULL means do a cbfs_map() */
if (allocator) {
loc = allocator(arg, size, mdata);
} else if (compression == CBFS_COMPRESS_NONE) {
void *mapping = rdev_mmap_full(rdev);
if (!mapping)
return NULL;
if (cbfs_file_hash_mismatch(mapping, size, mdata, skip_verification)) {
rdev_munmap(rdev, mapping);
return NULL;
}
return mapping;
} else if (!cbfs_cache.size) {
/* In order to use the cbfs_cache you need to add a CBFS_CACHE to your
* memlayout. For stages that don't have .data sections (x86 pre-RAM),
* it is not possible to add a CBFS_CACHE. */
ERROR("Cannot map compressed file %s without cbfs_cache\n", mdata->h.filename);
return NULL;
} else {
loc = mem_pool_alloc(&cbfs_cache, size);
}
if (!loc) {
ERROR("'%s' allocation failure\n", mdata->h.filename);
return NULL;
}
size = cbfs_load_and_decompress(rdev, loc, size, compression, mdata, skip_verification);
if (!size)
return NULL;
return loc;
}
void *_cbfs_alloc(const char *name, cbfs_allocator_t allocator, void *arg,
size_t *size_out, bool force_ro, enum cbfs_type *type)
{
struct region_device rdev;
bool preload_successful = false;
union cbfs_mdata mdata;
void *loc = NULL;
DEBUG("%s(name='%s', alloc=%p(%p), force_ro=%s, type=%d)\n", __func__, name, allocator,
arg, force_ro ? "true" : "false", type ? *type : -1);
@ -436,72 +494,44 @@ void *_cbfs_alloc(const char *name, cbfs_allocator_t allocator, void *arg,
}
}
size_t size = region_device_sz(&rdev);
uint32_t compression = CBFS_COMPRESS_NONE;
const struct cbfs_file_attr_compression *cattr = cbfs_find_attr(&mdata,
CBFS_FILE_ATTR_TAG_COMPRESSION, sizeof(*cattr));
if (cattr) {
compression = be32toh(cattr->compression);
size = be32toh(cattr->decompressed_size);
}
if (size_out)
*size_out = size;
const struct vb2_hash *file_hash = NULL;
if (CONFIG(CBFS_VERIFICATION))
file_hash = cbfs_file_hash(&mdata);
/* Update the rdev with the preload content */
if (!force_ro && get_preload_rdev(&rdev, name) == CB_SUCCESS)
preload_successful = true;
/* allocator == NULL means do a cbfs_map() */
if (allocator) {
loc = allocator(arg, size, &mdata);
} else if (compression == CBFS_COMPRESS_NONE) {
void *mapping = rdev_mmap_full(&rdev);
void *ret = do_alloc(&mdata, &rdev, allocator, arg, size_out, false);
if (!mapping)
goto out;
if (cbfs_file_hash_mismatch(mapping, size, file_hash)) {
rdev_munmap(&rdev, mapping);
goto out;
}
return mapping;
} else if (!cbfs_cache.size) {
/*
* In order to use the cbfs_cache you need to add a CBFS_CACHE to your
* memlayout. For stages that don't have .data sections (x86 pre-RAM),
* it is not possible to add a CBFS_CACHE.
*/
ERROR("Cannot map compressed file %s without cbfs_cache\n", mdata.h.filename);
goto out;
} else {
loc = mem_pool_alloc(&cbfs_cache, size);
}
if (!loc) {
ERROR("'%s' allocation failure\n", mdata.h.filename);
goto out;
}
size = cbfs_load_and_decompress(&rdev, loc, size, compression, file_hash);
if (!size)
loc = NULL;
out:
/*
* When using cbfs_preload we need to free the preload buffer after populating the
* destination buffer.
*/
/* When using cbfs_preload we need to free the preload buffer after populating the
* destination buffer. We know we must have a mem_rdev here, so extra mmap is fine. */
if (preload_successful)
cbfs_unmap(rdev_mmap_full(&rdev));
return loc;
return ret;
}
void *_cbfs_unverified_area_alloc(const char *area, const char *name,
cbfs_allocator_t allocator, void *arg, size_t *size_out)
{
struct region_device area_rdev, file_rdev;
union cbfs_mdata mdata;
size_t data_offset;
DEBUG("%s(area='%s', name='%s', alloc=%p(%p))\n", __func__, area, name, allocator, arg);
if (fmap_locate_area_as_rdev(area, &area_rdev))
return NULL;
if (cbfs_lookup(&area_rdev, name, &mdata, &data_offset, NULL)) {
ERROR("'%s' not found in '%s'\n", name, area);
return NULL;
}
if (rdev_chain(&file_rdev, &area_rdev, data_offset, be32toh(mdata.h.len)))
return NULL;
if (tspi_measure_cbfs_hook(&file_rdev, name, be32toh(mdata.h.type)))
ERROR("error measuring '%s' in '%s'\n", name, area);
return do_alloc(&mdata, &file_rdev, allocator, arg, size_out, true);
}
void *_cbfs_default_allocator(void *arg, size_t size, const union cbfs_mdata *unused)
@ -546,17 +576,13 @@ cb_err_t cbfs_prog_stage_load(struct prog *pstage)
prog_set_entry(pstage, prog_start(pstage) +
be32toh(sattr->entry_offset), NULL);
const struct vb2_hash *file_hash = NULL;
if (CONFIG(CBFS_VERIFICATION))
file_hash = cbfs_file_hash(&mdata);
/* Hacky way to not load programs over read only media. The stages
* that would hit this path initialize themselves. */
if ((ENV_BOOTBLOCK || ENV_SEPARATE_VERSTAGE) &&
!CONFIG(NO_XIP_EARLY_STAGES) && CONFIG(BOOT_DEVICE_MEMORY_MAPPED)) {
void *mapping = rdev_mmap_full(&rdev);
rdev_munmap(&rdev, mapping);
if (cbfs_file_hash_mismatch(mapping, region_device_sz(&rdev), file_hash))
if (cbfs_file_hash_mismatch(mapping, region_device_sz(&rdev), &mdata, false))
return CB_CBFS_HASH_MISMATCH;
if (mapping == prog_start(pstage))
return CB_SUCCESS;
@ -573,7 +599,7 @@ cb_err_t cbfs_prog_stage_load(struct prog *pstage)
}
size_t fsize = cbfs_load_and_decompress(&rdev, prog_start(pstage), prog_size(pstage),
compression, file_hash);
compression, &mdata, false);
if (!fsize)
return CB_ERR;