Added option to ImageHandler() to open file read-only. am: 4e71bfd373
Change-Id: I534585479213ff9df7f2960473568e1609781735
diff --git a/aftltool.py b/aftltool.py
index 0fe2d07..192ad9b 100755
--- a/aftltool.py
+++ b/aftltool.py
@@ -1169,7 +1169,7 @@
"""
# Reads and parses the vbmeta image.
try:
- image = avbtool.ImageHandler(image_filename)
+ image = avbtool.ImageHandler(image_filename, read_only=True)
except (IOError, ValueError) as e:
sys.stderr.write('The image does not contain a valid VBMeta structure: '
'{}.\n'.format(e))
@@ -1212,7 +1212,7 @@
return None
try:
- image = avbtool.ImageHandler(image_filename)
+ image = avbtool.ImageHandler(image_filename, read_only=True)
except ValueError as e:
sys.stderr.write('The image does not contain a valid VBMeta structure: '
'{}.\n'.format(e))
diff --git a/avbtool.py b/avbtool.py
index 4b9c594..13bb288 100755
--- a/avbtool.py
+++ b/avbtool.py
@@ -732,11 +732,12 @@
NUM_CHUNKS_AND_BLOCKS_FORMAT = '<II'
NUM_CHUNKS_AND_BLOCKS_OFFSET = 16
- def __init__(self, image_filename):
+ def __init__(self, image_filename, read_only=False):
"""Initializes an image handler.
Arguments:
image_filename: The name of the file to operate on.
+ read_only: True if file is only opened for read-only operations.
Raises:
ValueError: If data in the file is invalid.
@@ -745,6 +746,7 @@
self._num_total_blocks = 0
self._num_total_chunks = 0
self._file_pos = 0
+ self._read_only = read_only
self._read_header()
def _read_header(self):
@@ -759,7 +761,10 @@
self.is_sparse = False
self.block_size = 4096
self._file_pos = 0
- self._image = open(self.filename, 'r+b')
+ if self._read_only:
+ self._image = open(self.filename, 'rb')
+ else:
+ self._image = open(self.filename, 'r+b')
self._image.seek(0, os.SEEK_END)
self.image_size = self._image.tell()
@@ -885,9 +890,15 @@
Arguments:
num_bytes: Size in number of bytes of the DONT_CARE chunk.
+
+ Raises
+ OSError: If ImageHandler was initialized in read-only mode.
"""
assert num_bytes % self.block_size == 0
+ if self._read_only:
+ raise OSError('ImageHandler is in read-only mode.')
+
if not self.is_sparse:
self._image.seek(0, os.SEEK_END)
# This is more efficient that writing NUL bytes since it'll add
@@ -916,9 +927,15 @@
Arguments:
data: Data to append as bytes.
+
+ Raises
+ OSError: If ImageHandler was initialized in read-only mode.
"""
assert len(data) % self.block_size == 0
+ if self._read_only:
+ raise OSError('ImageHandler is in read-only mode.')
+
if not self.is_sparse:
self._image.seek(0, os.SEEK_END)
self._image.write(data)
@@ -947,11 +964,17 @@
Arguments:
fill_data: Fill data to append - must be four bytes.
size: Number of chunk - must be a multiple of four and the block size.
+
+ Raises
+ OSError: If ImageHandler was initialized in read-only mode.
"""
assert len(fill_data) == 4
assert size % 4 == 0
assert size % self.block_size == 0
+ if self._read_only:
+ raise OSError('ImageHandler is in read-only mode.')
+
if not self.is_sparse:
self._image.seek(0, os.SEEK_END)
self._image.write(fill_data * (size//4))
@@ -1051,7 +1074,11 @@
Raises:
ValueError: If desired size isn't a multiple of the block size.
+ OSError: If ImageHandler was initialized in read-only mode.
"""
+ if self._read_only:
+ raise OSError('ImageHandler is in read-only mode.')
+
if not self.is_sparse:
self._image.truncate(size)
self._read_header()
@@ -1467,7 +1494,7 @@
image = image_containing_descriptor
else:
image_filename = os.path.join(image_dir, self.partition_name + image_ext)
- image = ImageHandler(image_filename)
+ image = ImageHandler(image_filename, read_only=True)
# Generate the hashtree and checks that it matches what's in the file.
digest_size = len(hashlib.new(self.hash_algorithm).digest())
digest_padding = round_to_pow2(digest_size) - digest_size
@@ -1635,7 +1662,7 @@
image = image_containing_descriptor
else:
image_filename = os.path.join(image_dir, self.partition_name + image_ext)
- image = ImageHandler(image_filename)
+ image = ImageHandler(image_filename, read_only=True)
data = image.read(self.image_size)
ha = hashlib.new(self.hash_algorithm)
ha.update(self.salt)
@@ -2169,7 +2196,7 @@
Raises:
AvbError: If there's no footer in the image.
"""
- image = ImageHandler(image_filename)
+ image = ImageHandler(image_filename, read_only=True)
(footer, _, _, _) = self._parse_image(image)
if not footer:
raise AvbError('Given image does not have a footer.')
@@ -2365,7 +2392,7 @@
image_filename: Image file to get information from (file object).
output: Output file to write human-readable information to (file object).
"""
- image = ImageHandler(image_filename)
+ image = ImageHandler(image_filename, read_only=True)
o = output
(footer, header, descriptors, image_size) = self._parse_image(image)
@@ -2460,7 +2487,7 @@
print('Verifying image {} using embedded public key'.format(
image_filename))
- image = ImageHandler(image_filename)
+ image = ImageHandler(image_filename, read_only=True)
(footer, header, descriptors, _) = self._parse_image(image)
offset = 0
if footer:
@@ -2553,7 +2580,7 @@
Raises:
AvbError: If getting the partition digests from the image fails.
"""
- image = ImageHandler(image_filename)
+ image = ImageHandler(image_filename, read_only=True)
(_, _, descriptors, _) = self._parse_image(image)
for desc in descriptors:
@@ -2590,7 +2617,7 @@
image_dir = os.path.dirname(image_filename)
image_ext = os.path.splitext(image_filename)[1]
- image = ImageHandler(image_filename)
+ image = ImageHandler(image_filename, read_only=True)
(footer, header, descriptors, _) = self._parse_image(image)
offset = 0
if footer:
@@ -2607,7 +2634,7 @@
if isinstance(desc, AvbChainPartitionDescriptor):
ch_image_filename = os.path.join(image_dir,
desc.partition_name + image_ext)
- ch_image = ImageHandler(ch_image_filename)
+ ch_image = ImageHandler(ch_image_filename, read_only=True)
(ch_footer, ch_header, _, _) = self._parse_image(ch_image)
ch_offset = 0
ch_size = (ch_header.SIZE + ch_header.authentication_data_block_size +
@@ -2630,7 +2657,7 @@
output: Output file to write human-readable information to (file object).
"""
- image = ImageHandler(image_filename)
+ image = ImageHandler(image_filename, read_only=True)
_, _, descriptors, _ = self._parse_image(image)
image_dir = os.path.dirname(image_filename)
@@ -2641,7 +2668,7 @@
if isinstance(desc, AvbChainPartitionDescriptor):
ch_image_filename = os.path.join(image_dir,
desc.partition_name + image_ext)
- ch_image = ImageHandler(ch_image_filename)
+ ch_image = ImageHandler(ch_image_filename, read_only=True)
_, _, ch_descriptors, _ = self._parse_image(ch_image)
for ch_desc in ch_descriptors:
if isinstance(ch_desc, AvbKernelCmdlineDescriptor):
@@ -2871,7 +2898,8 @@
# Use the bump logic in AvbVBMetaHeader to calculate the max required
# version of all included descriptors.
for image in include_descriptors_from_image:
- (_, image_header, _, _) = self._parse_image(ImageHandler(image.name))
+ (_, image_header, _, _) = self._parse_image(ImageHandler(
+ image.name, read_only=True))
tmp_header.bump_required_libavb_version_minor(
image_header.required_libavb_version_minor)
