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authorFlorent Revest <revest@google.com>2020-01-13 10:42:44 +0100
committerMimi Zohar <zohar@linux.ibm.com>2020-01-22 15:22:51 -0500
commit6beea7afcc72b86986080ea1d228a42f2000f2a9 (patch)
treef4dcbae6ca30de7fd291c6e84ee384bcfc0945d9 /security/integrity
parent5350ceb0b7befba9f607fd4c09b1a424e117fe1c (diff)
ima: add the ability to query the cached hash of a given file
This allows other parts of the kernel (perhaps a stacked LSM allowing system monitoring, eg. the proposed KRSI LSM [1]) to retrieve the hash of a given file from IMA if it's present in the iint cache. It's true that the existence of the hash means that it's also in the audit logs or in /sys/kernel/security/ima/ascii_runtime_measurements, but it can be difficult to pull that information out for every subsequent exec. This is especially true if a given host has been up for a long time and the file was first measured a long time ago. It should be kept in mind that this function gives access to cached entries which can be removed, for instance on security_inode_free(). This is based on Peter Moody's patch: https://sourceforge.net/p/linux-ima/mailman/message/33036180/ [1] https://lkml.org/lkml/2019/9/10/393 Signed-off-by: Florent Revest <revest@google.com> Reviewed-by: KP Singh <kpsingh@chromium.org> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Diffstat (limited to 'security/integrity')
-rw-r--r--security/integrity/ima/ima_main.c49
1 files changed, 49 insertions, 0 deletions
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 2272c3255c7d..9fe949c6a530 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -446,6 +446,55 @@ int ima_file_check(struct file *file, int mask)
EXPORT_SYMBOL_GPL(ima_file_check);
/**
+ * ima_file_hash - return the stored measurement if a file has been hashed and
+ * is in the iint cache.
+ * @file: pointer to the file
+ * @buf: buffer in which to store the hash
+ * @buf_size: length of the buffer
+ *
+ * On success, return the hash algorithm (as defined in the enum hash_algo).
+ * If buf is not NULL, this function also outputs the hash into buf.
+ * If the hash is larger than buf_size, then only buf_size bytes will be copied.
+ * It generally just makes sense to pass a buffer capable of holding the largest
+ * possible hash: IMA_MAX_DIGEST_SIZE.
+ * The file hash returned is based on the entire file, including the appended
+ * signature.
+ *
+ * If IMA is disabled or if no measurement is available, return -EOPNOTSUPP.
+ * If the parameters are incorrect, return -EINVAL.
+ */
+int ima_file_hash(struct file *file, char *buf, size_t buf_size)
+{
+ struct inode *inode;
+ struct integrity_iint_cache *iint;
+ int hash_algo;
+
+ if (!file)
+ return -EINVAL;
+
+ if (!ima_policy_flag)
+ return -EOPNOTSUPP;
+
+ inode = file_inode(file);
+ iint = integrity_iint_find(inode);
+ if (!iint)
+ return -EOPNOTSUPP;
+
+ mutex_lock(&iint->mutex);
+ if (buf) {
+ size_t copied_size;
+
+ copied_size = min_t(size_t, iint->ima_hash->length, buf_size);
+ memcpy(buf, iint->ima_hash->digest, copied_size);
+ }
+ hash_algo = iint->ima_hash->algo;
+ mutex_unlock(&iint->mutex);
+
+ return hash_algo;
+}
+EXPORT_SYMBOL_GPL(ima_file_hash);
+
+/**
* ima_post_create_tmpfile - mark newly created tmpfile as new
* @file : newly created tmpfile
*