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LZH: check CRC after reading file data #1263

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Jul 29, 2024
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LZH: check CRC after reading file data #1263

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37 changes: 21 additions & 16 deletions libclamav_rust/src/scanners.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -209,21 +209,6 @@ pub unsafe extern "C" fn scan_lha_lzh(ctx: *mut cli_ctx) -> cl_error_t {
// Get the file header.
let header = decoder.header();

// Verify the CRC check. This is important because LHA/LZH does not have particularly identifiable magic bytes.
match decoder.crc_check() {
Ok(crc) => {
// CRC is valid. Very likely it is indeed an LHA/LZH archive.
debug!("CRC check passed. Very likely this is an LHA or LZH archive. CRC: {crc}");
}
Err(err) => {
// Error checking CRC.
// Use debug-level because may not actually be an LHA/LZH archive.
// LHA/LZH does not have particularly identifiable magic bytes.
debug!("An error occurred when checking the CRC of this LHA or LZH archive: {err}");
// break;
}
}

let filepath = header.parse_pathname();
let filename = filepath.to_string_lossy();
if header.is_directory() {
Expand Down Expand Up @@ -254,11 +239,31 @@ pub unsafe extern "C" fn scan_lha_lzh(ctx: *mut cli_ctx) -> cl_error_t {
debug!("err: unsupported compression method");
} else {
// Read the file into a buffer.
let mut file_data = Vec::<u8>::new();
let mut file_data: Vec<u8> = Vec::<u8>::new();

match decoder.read_to_end(&mut file_data) {
Ok(bytes_read) => {
if bytes_read > 0 {
debug!(
"Read {bytes_read} bytes from file {filename} in the LHA archive."
);

// Verify the CRC check *after* reading the file.
match decoder.crc_check() {
Ok(crc) => {
// CRC is valid. Very likely this is an LHA or LZH archive.
debug!("CRC check passed. Very likely this is an LHA or LZH archive. CRC: {crc}");
}
Err(err) => {
// Error checking CRC.
debug!("An error occurred when checking the CRC of this LHA or LZH archive: {err}");

// Allow the scan to continue even with a CRC error, for now.
// break;
}
}

// Scan the file.
let ret =
magic_scan(ctx, &file_data, Some(filename.to_string()));
if ret != cl_error_t_CL_SUCCESS {
Expand Down
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