This patch checks the size for the EVM_IMA_XATTR_DIGSIG and
EVM_XATTR_PORTABLE_DIGSIG types to ensure that the algorithm is read from
the buffer returned by vfs_getxattr_alloc().
Cc: stable@xxxxxxxxxxxxxxx # 4.19.x
Fixes: 5feeb61183dde ("evm: Allow non-SHA1 digital signatures")
Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>
---
security/integrity/evm/evm_main.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 744c105b48d1..4e9f5e8b21d5 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -181,6 +181,12 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
break;
case EVM_IMA_XATTR_DIGSIG:
case EVM_XATTR_PORTABLE_DIGSIG:
+ /* accept xattr with non-empty signature field */
+ if (xattr_len <= sizeof(struct signature_v2_hdr)) {
+ evm_status = INTEGRITY_FAIL;
+ goto out;
+ }
+
hdr = (struct signature_v2_hdr *)xattr_data;
digest.hdr.algo = hdr->hash_algo;
rc = evm_calc_hash(dentry, xattr_name, xattr_value,
--
2.17.1
