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[v2,03/12] evm: Check size of security.evm before using it

Message ID 20200904092339.19598-4-roberto.sassu@huawei.com
State New
Headers show
Series [v2,01/12] ima: Don't ignore errors from crypto_shash_update() | expand

Commit Message

Roberto Sassu Sept. 4, 2020, 9:23 a.m. UTC 
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@vger.kernel.org # 4.19.x
Fixes: 5feeb61183dde ("evm: Allow non-SHA1 digital signatures")
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
---
 security/integrity/evm/evm_main.c | 6 ++++++
 1 file changed, 6 insertions(+)
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Patch

diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 0d36259b690d..e4b47759ba1c 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,