ima: read and use signature hash algorithm

All files on the filesystem, currently, are hashed using the same hash
algorithm.  In preparation for files from different packages being
signed using different hash algorithms, this patch adds support for
reading the signature hash algorithm from the 'security.ima' extended
attribute and calculates the appropriate file data hash based on it.

Changelog:
- fix scripts Lindent and checkpatch msgs - Mimi
- fix md5 support for older version, which occupied 20 bytes in the
  xattr, not the expected 16 bytes.  Fix the comparison to compare
  only the first 16 bytes.

Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

1 files changed, 11 insertions, 1 deletions

diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index e531fe22e58..1dba98e2d7e 100644
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -139,17 +139,27 @@ int ima_must_measure(struct inode *inode, int mask, int function)
  * Return 0 on success, error code otherwise
  */
 int ima_collect_measurement(struct integrity_iint_cache *iint,
-			    struct file *file)
+			    struct file *file,
+			    struct evm_ima_xattr_data **xattr_value,
+			    int *xattr_len)
 {
 	struct inode *inode = file_inode(file);
 	const char *filename = file->f_dentry->d_name.name;
 	int result = 0;
 
+	if (xattr_value)
+		*xattr_len = ima_read_xattr(file->f_dentry, xattr_value);
+
 	if (!(iint->flags & IMA_COLLECTED)) {
 		u64 i_version = file_inode(file)->i_version;
 
 		/* use default hash algorithm */
 		iint->ima_hash.algo = ima_hash_algo;
+
+		if (xattr_value)
+			ima_get_hash_algo(*xattr_value, *xattr_len,
+					  &iint->ima_hash);
+
 		result = ima_calc_file_hash(file, &iint->ima_hash);
 		if (!result) {
 			iint->version = i_version;