From: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Date: Thu, 27 Jun 2019 23:19:29 -0300
Subject: ima: Factor xattr_verify() out of ima_appraise_measurement()
Patch-mainline: v5.4-rc1
Git-commit: a5fbeb615ca42f913ace3291d636e96feabcc545
References: jsc#SLE-9870

Verify xattr signature in a separate function so that the logic in
ima_appraise_measurement() remains clear when it gains the ability to also
verify an appended module signature.

The code in the switch statement is unchanged except for having to
dereference the status and cause variables (since they're now pointers),
and fixing the style of a block comment to appease checkpatch.

Suggested-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Acked-by: Lee, Chun-Yi <jlee@suse.com>
---
 security/integrity/ima/ima_appraise.c |  141 +++++++++++++++++++---------------
 1 file changed, 81 insertions(+), 60 deletions(-)

--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -200,6 +200,83 @@ int ima_read_xattr(struct dentry *dentry
 }
 
 /*
+ * xattr_verify - verify xattr digest or signature
+ *
+ * Verify whether the hash or signature matches the file contents.
+ *
+ * Return 0 on success, error code otherwise.
+ */
+static int xattr_verify(enum ima_hooks func, struct integrity_iint_cache *iint,
+			struct evm_ima_xattr_data *xattr_value, int xattr_len,
+			enum integrity_status *status, const char **cause)
+{
+	int rc = -EINVAL, hash_start = 0;
+
+	switch (xattr_value->type) {
+	case IMA_XATTR_DIGEST_NG:
+		/* first byte contains algorithm id */
+		hash_start = 1;
+		/* fall through */
+	case IMA_XATTR_DIGEST:
+		if (iint->flags & IMA_DIGSIG_REQUIRED) {
+			*cause = "IMA-signature-required";
+			*status = INTEGRITY_FAIL;
+			break;
+		}
+		clear_bit(IMA_DIGSIG, &iint->atomic_flags);
+		if (xattr_len - sizeof(xattr_value->type) - hash_start >=
+				iint->ima_hash->length)
+			/*
+			 * xattr length may be longer. md5 hash in previous
+			 * version occupied 20 bytes in xattr, instead of 16
+			 */
+			rc = memcmp(&xattr_value->data[hash_start],
+				    iint->ima_hash->digest,
+				    iint->ima_hash->length);
+		else
+			rc = -EINVAL;
+		if (rc) {
+			*cause = "invalid-hash";
+			*status = INTEGRITY_FAIL;
+			break;
+		}
+		*status = INTEGRITY_PASS;
+		break;
+	case EVM_IMA_XATTR_DIGSIG:
+		set_bit(IMA_DIGSIG, &iint->atomic_flags);
+		rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
+					     (const char *)xattr_value,
+					     xattr_len,
+					     iint->ima_hash->digest,
+					     iint->ima_hash->length);
+		if (rc == -EOPNOTSUPP) {
+			*status = INTEGRITY_UNKNOWN;
+			break;
+		}
+		if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc &&
+		    func == KEXEC_KERNEL_CHECK)
+			rc = integrity_digsig_verify(INTEGRITY_KEYRING_PLATFORM,
+						     (const char *)xattr_value,
+						     xattr_len,
+						     iint->ima_hash->digest,
+						     iint->ima_hash->length);
+		if (rc) {
+			*cause = "invalid-signature";
+			*status = INTEGRITY_FAIL;
+		} else {
+			*status = INTEGRITY_PASS;
+		}
+		break;
+	default:
+		*status = INTEGRITY_UNKNOWN;
+		*cause = "unknown-ima-data";
+		break;
+	}
+
+	return rc;
+}
+
+/*
  * ima_appraise_measurement - appraise file measurement
  *
  * Call evm_verifyxattr() to verify the integrity of 'security.ima'.
@@ -218,7 +295,7 @@ int ima_appraise_measurement(enum ima_ho
 	struct dentry *dentry = file_dentry(file);
 	struct inode *inode = d_backing_inode(dentry);
 	enum integrity_status status = INTEGRITY_UNKNOWN;
-	int rc = xattr_len, hash_start = 0;
+	int rc = xattr_len;
 
 	if (!(inode->i_opflags & IOP_XATTR))
 		return INTEGRITY_UNKNOWN;
@@ -256,65 +333,9 @@ int ima_appraise_measurement(enum ima_ho
 		WARN_ONCE(true, "Unexpected integrity status %d\n", status);
 	}
 
-	switch (xattr_value->type) {
-	case IMA_XATTR_DIGEST_NG:
-		/* first byte contains algorithm id */
-		hash_start = 1;
-		/* fall through */
-	case IMA_XATTR_DIGEST:
-		if (iint->flags & IMA_DIGSIG_REQUIRED) {
-			cause = "IMA-signature-required";
-			status = INTEGRITY_FAIL;
-			break;
-		}
-		clear_bit(IMA_DIGSIG, &iint->atomic_flags);
-		if (xattr_len - sizeof(xattr_value->type) - hash_start >=
-				iint->ima_hash->length)
-			/* xattr length may be longer. md5 hash in previous
-			   version occupied 20 bytes in xattr, instead of 16
-			 */
-			rc = memcmp(&xattr_value->data[hash_start],
-				    iint->ima_hash->digest,
-				    iint->ima_hash->length);
-		else
-			rc = -EINVAL;
-		if (rc) {
-			cause = "invalid-hash";
-			status = INTEGRITY_FAIL;
-			break;
-		}
-		status = INTEGRITY_PASS;
-		break;
-	case EVM_IMA_XATTR_DIGSIG:
-		set_bit(IMA_DIGSIG, &iint->atomic_flags);
-		rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
-					     (const char *)xattr_value,
-					     xattr_len,
-					     iint->ima_hash->digest,
-					     iint->ima_hash->length);
-		if (rc == -EOPNOTSUPP) {
-			status = INTEGRITY_UNKNOWN;
-			break;
-		}
-		if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc &&
-		    func == KEXEC_KERNEL_CHECK)
-			rc = integrity_digsig_verify(INTEGRITY_KEYRING_PLATFORM,
-						     (const char *)xattr_value,
-						     xattr_len,
-						     iint->ima_hash->digest,
-						     iint->ima_hash->length);
-		if (rc) {
-			cause = "invalid-signature";
-			status = INTEGRITY_FAIL;
-		} else {
-			status = INTEGRITY_PASS;
-		}
-		break;
-	default:
-		status = INTEGRITY_UNKNOWN;
-		cause = "unknown-ima-data";
-		break;
-	}
+	if (xattr_value)
+		rc = xattr_verify(func, iint, xattr_value, xattr_len, &status,
+				  &cause);
 
 out:
 	/*