[RFC PATCH 2/2] evm: output EVM digest calculation info needed for debugging

[Mimi Zohar <zohar@xxxxxxxxxxxxx>]

Convert and output the binary data used in calculating the EVM digest
to a hexadecimal string.

Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
---
 security/integrity/evm/evm.h        |  1 +
 security/integrity/evm/evm_crypto.c |  7 +++++++
 security/integrity/evm/evm_main.c   | 19 +++++++++++++++++++
 3 files changed, 27 insertions(+)

diff --git a/security/integrity/evm/evm.h b/security/integrity/evm/evm.h
index 0d44f41d16f8..3d2d2da8fa97 100644
--- a/security/integrity/evm/evm.h
+++ b/security/integrity/evm/evm.h
@@ -64,5 +64,6 @@ int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name,
 int evm_init_hmac(struct inode *inode, const struct xattr *xattr,
 		  char *hmac_val);
 int evm_init_secfs(void);
+void evm_bin2hex_print(const char *prefix, const void *src, size_t count);
 
 #endif
diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
index 1628e2ca9862..7601aa29c6d3 100644
--- a/security/integrity/evm/evm_crypto.c
+++ b/security/integrity/evm/evm_crypto.c
@@ -175,6 +175,8 @@ static void hmac_add_misc(struct shash_desc *desc, struct inode *inode,
 	    type != EVM_XATTR_PORTABLE_DIGSIG)
 		crypto_shash_update(desc, (u8 *)&inode->i_sb->s_uuid, UUID_SIZE);
 	crypto_shash_final(desc, digest);
+
+	evm_bin2hex_print("hmac_misc", &hmac_misc, sizeof(struct h_misc));
 }
 
 /*
@@ -230,6 +232,9 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
 					     req_xattr_value_len);
 			if (is_ima)
 				ima_present = true;
+
+			evm_bin2hex_print(req_xattr_name, req_xattr_value,
+				      req_xattr_value_len);
 			continue;
 		}
 		size = vfs_getxattr_alloc(&init_user_ns, dentry, xattr->name,
@@ -246,6 +251,8 @@ static int evm_calc_hmac_or_hash(struct dentry *dentry,
 		crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size);
 		if (is_ima)
 			ima_present = true;
+
+		evm_bin2hex_print(xattr->name, xattr_value, xattr_size);
 	}
 	hmac_add_misc(desc, inode, type, data->digest);
 
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 2c226e634ae9..03d963fe2e67 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -155,6 +155,23 @@ static int evm_find_protected_xattrs(struct dentry *dentry)
 	return count;
 }
 
+void evm_bin2hex_print(const char *prefix, const void *src, size_t count)
+{
+#ifdef DEBUG
+	char *asciihex, *p;
+
+	p = asciihex = kmalloc(count * 2 + 1, GFP_KERNEL);
+	if (!asciihex)
+		return;
+
+	p = bin2hex(p, src, count);
+	*p = 0;
+	printk("%s: (%lu) %.*s\n", prefix, count, (int) count * 2, asciihex);
+
+	kfree(asciihex);
+#endif
+}
+
 /*
  * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
  *
@@ -272,6 +289,8 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
 		else
 			evm_status = INTEGRITY_FAIL;
 	}
+
+	evm_bin2hex_print("evm digest", digest.digest, digest.hdr.length);
 out:
 	if (iint)
 		iint->evm_status = evm_status;
-- 
2.27.0