KEYS: trusted: Debugging as a feature

TPM_DEBUG, and other similar flags, are a non-standard way to specify a
feature in Linux kernel. Introduce CONFIG_TRUSTED_KEYS_DEBUG for trusted
keys, and use it to replace these ad-hoc feature flags.

Given that trusted keys debug dumps can contain sensitive data, harden the
feature as follows:

1. In the Kconfig description postulate that pr_debug() statements must be
   used.
2. Use pr_debug() statements in TPM 1.x driver to print the protocol dump.
3. Require trusted.debug=1 on the kernel command line (default: 0) to
   activate dumps at runtime, even when CONFIG_TRUSTED_KEYS_DEBUG=y.

Traces, when actually needed, can be easily enabled by providing
trusted.dyndbg='+p' and trusted.debug=1 in the kernel command-line.

Reported-by: Nayna Jain <nayna@linux.ibm.com>
Closes: https://lore.kernel.org/all/7f8b8478-5cd8-4d97-bfd0-341fd5cf10f9@linux.ibm.com/
Reviewed-by: Nayna Jain <nayna@linux.ibm.com>
Tested-by: Srish Srinivasan <ssrish@linux.ibm.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>

Documentation/admin-guide/kernel-parameters.txt

@@ -7875,6 +7875,22 @@ Kernel parameters
 			first trust source as a backend which is initialized
 			successfully during iteration.
 
+	trusted.debug=	[KEYS]
+			Format: <bool>
+			Enable trusted keys debug traces at runtime when
+			CONFIG_TRUSTED_KEYS_DEBUG=y.
+
+			To make the traces visible after enabling the option,
+			use trusted.dyndbg='+p' as needed. By convention,
+			the subsystem uses pr_debug() for these traces.
+
+			SAFETY: The traces can leak sensitive data, so be
+			cautious before enabling this. They remain inactive
+			unless this parameter is set this option to  a true
+			value.
+
+			Default: false
+
 	trusted.rng=	[KEYS]
 			Format: <string>
 			The RNG used to generate key material for trusted keys.

include/keys/trusted-type.h

@@ -83,18 +83,21 @@ struct trusted_key_source {
 
 extern struct key_type key_type_trusted;
 
-#define TRUSTED_DEBUG 0
+#ifdef CONFIG_TRUSTED_KEYS_DEBUG
+extern bool trusted_debug;
 
-#if TRUSTED_DEBUG
 static inline void dump_payload(struct trusted_key_payload *p)
 {
-	pr_info("key_len %d\n", p->key_len);
-	print_hex_dump(KERN_INFO, "key ", DUMP_PREFIX_NONE,
-		       16, 1, p->key, p->key_len, 0);
-	pr_info("bloblen %d\n", p->blob_len);
-	print_hex_dump(KERN_INFO, "blob ", DUMP_PREFIX_NONE,
-		       16, 1, p->blob, p->blob_len, 0);
-	pr_info("migratable %d\n", p->migratable);
+	if (!trusted_debug)
+		return;
+
+	pr_debug("key_len %d\n", p->key_len);
+	print_hex_dump_debug("key ", DUMP_PREFIX_NONE,
+			     16, 1, p->key, p->key_len, 0);
+	pr_debug("bloblen %d\n", p->blob_len);
+	print_hex_dump_debug("blob ", DUMP_PREFIX_NONE,
+			     16, 1, p->blob, p->blob_len, 0);
+	pr_debug("migratable %d\n", p->migratable);
 }
 #else
 static inline void dump_payload(struct trusted_key_payload *p)

security/keys/trusted-keys/Kconfig

@@ -1,10 +1,29 @@
 config HAVE_TRUSTED_KEYS
 	bool
 
+config HAVE_TRUSTED_KEYS_DEBUG
+	bool
+
+config TRUSTED_KEYS_DEBUG
+	bool "Debug trusted keys"
+	depends on HAVE_TRUSTED_KEYS_DEBUG
+	default n
+	help
+	  Trusted key backends and core code that support debug traces can
+	  opt-in that feature here. Traces must only use debug level output, as
+	  sensitive data may pass by. In the kernel-command line traces can be
+	  enabled via trusted.dyndbg='+p'.
+
+	  SAFETY: Debug dumps are inactive at runtime until trusted.debug is set
+	  to a true value on the kernel command-line. Use at your utmost
+	  consideration when enabling this feature on a production build. The
+	  general advice is not to do this.
+
 config TRUSTED_KEYS_TPM
 	bool "TPM-based trusted keys"
 	depends on TCG_TPM >= TRUSTED_KEYS
 	default y
+	select HAVE_TRUSTED_KEYS_DEBUG
 	select CRYPTO_HASH_INFO
 	select CRYPTO_LIB_SHA1
 	select CRYPTO_LIB_UTILS
@@ -23,6 +42,7 @@ config TRUSTED_KEYS_TEE
 	bool "TEE-based trusted keys"
 	depends on TEE >= TRUSTED_KEYS
 	default y
+	select HAVE_TRUSTED_KEYS_DEBUG
 	select HAVE_TRUSTED_KEYS
 	help
 	  Enable use of the Trusted Execution Environment (TEE) as trusted
@@ -33,6 +53,7 @@ config TRUSTED_KEYS_CAAM
 	depends on CRYPTO_DEV_FSL_CAAM_JR >= TRUSTED_KEYS
 	select CRYPTO_DEV_FSL_CAAM_BLOB_GEN
 	default y
+	select HAVE_TRUSTED_KEYS_DEBUG
 	select HAVE_TRUSTED_KEYS
 	help
 	  Enable use of NXP's Cryptographic Accelerator and Assurance Module
@@ -42,6 +63,7 @@ config TRUSTED_KEYS_DCP
 	bool "DCP-based trusted keys"
 	depends on CRYPTO_DEV_MXS_DCP >= TRUSTED_KEYS
 	default y
+	select HAVE_TRUSTED_KEYS_DEBUG
 	select HAVE_TRUSTED_KEYS
 	help
 	  Enable use of NXP's DCP (Data Co-Processor) as trusted key backend.
@@ -50,6 +72,7 @@ config TRUSTED_KEYS_PKWM
 	bool "PKWM-based trusted keys"
 	depends on PSERIES_PLPKS >= TRUSTED_KEYS
 	default y
+	select HAVE_TRUSTED_KEYS_DEBUG
 	select HAVE_TRUSTED_KEYS
 	help
 	  Enable use of IBM PowerVM Key Wrapping Module (PKWM) as a trusted key backend.

security/keys/trusted-keys/trusted_caam.c

@@ -28,10 +28,13 @@ static const match_table_t key_tokens = {
 	{opt_err, NULL}
 };
 
-#ifdef CAAM_DEBUG
+#ifdef CONFIG_TRUSTED_KEYS_DEBUG
 static inline void dump_options(const struct caam_pkey_info *pkey_info)
 {
-	pr_info("key encryption algo %d\n", pkey_info->key_enc_algo);
+	if (!trusted_debug)
+		return;
+
+	pr_debug("key encryption algo %d\n", pkey_info->key_enc_algo);
 }
 #else
 static inline void dump_options(const struct caam_pkey_info *pkey_info)

security/keys/trusted-keys/trusted_core.c

@@ -31,6 +31,12 @@ static char *trusted_rng = "default";
 module_param_named(rng, trusted_rng, charp, 0);
 MODULE_PARM_DESC(rng, "Select trusted key RNG");
 
+#ifdef CONFIG_TRUSTED_KEYS_DEBUG
+bool trusted_debug;
+module_param_named(debug, trusted_debug, bool, 0);
+MODULE_PARM_DESC(debug, "Enable trusted keys debug traces (default: 0)");
+#endif
+
 static char *trusted_key_source;
 module_param_named(source, trusted_key_source, charp, 0);
 MODULE_PARM_DESC(source, "Select trusted keys source (tpm, tee, caam, dcp or pkwm)");

security/keys/trusted-keys/trusted_tpm1.c

@@ -46,38 +46,44 @@ enum {
 	SRK_keytype = 4
 };
 
-#define TPM_DEBUG 0
-
-#if TPM_DEBUG
+#ifdef CONFIG_TRUSTED_KEYS_DEBUG
 static inline void dump_options(struct trusted_key_options *o)
 {
-	pr_info("sealing key type %d\n", o->keytype);
-	pr_info("sealing key handle %0X\n", o->keyhandle);
-	pr_info("pcrlock %d\n", o->pcrlock);
-	pr_info("pcrinfo %d\n", o->pcrinfo_len);
-	print_hex_dump(KERN_INFO, "pcrinfo ", DUMP_PREFIX_NONE,
-		       16, 1, o->pcrinfo, o->pcrinfo_len, 0);
+	if (!trusted_debug)
+		return;
+
+	pr_debug("sealing key type %d\n", o->keytype);
+	pr_debug("sealing key handle %0X\n", o->keyhandle);
+	pr_debug("pcrlock %d\n", o->pcrlock);
+	pr_debug("pcrinfo %d\n", o->pcrinfo_len);
+	print_hex_dump_debug("pcrinfo ", DUMP_PREFIX_NONE,
+			     16, 1, o->pcrinfo, o->pcrinfo_len, 0);
 }
 
 static inline void dump_sess(struct osapsess *s)
 {
-	print_hex_dump(KERN_INFO, "trusted-key: handle ", DUMP_PREFIX_NONE,
-		       16, 1, &s->handle, 4, 0);
-	pr_info("secret:\n");
-	print_hex_dump(KERN_INFO, "", DUMP_PREFIX_NONE,
-		       16, 1, &s->secret, SHA1_DIGEST_SIZE, 0);
-	pr_info("trusted-key: enonce:\n");
-	print_hex_dump(KERN_INFO, "", DUMP_PREFIX_NONE,
-		       16, 1, &s->enonce, SHA1_DIGEST_SIZE, 0);
+	if (!trusted_debug)
+		return;
+
+	print_hex_dump_debug("trusted-key: handle ", DUMP_PREFIX_NONE,
+			     16, 1, &s->handle, 4, 0);
+	pr_debug("secret:\n");
+	print_hex_dump_debug("", DUMP_PREFIX_NONE,
+			     16, 1, &s->secret, SHA1_DIGEST_SIZE, 0);
+	pr_debug("trusted-key: enonce:\n");
+	print_hex_dump_debug("", DUMP_PREFIX_NONE,
+			     16, 1, &s->enonce, SHA1_DIGEST_SIZE, 0);
 }
 
 static inline void dump_tpm_buf(unsigned char *buf)
 {
 	int len;
 
-	pr_info("\ntpm buffer\n");
+	if (!trusted_debug)
+		return;
+	pr_debug("\ntpm buffer\n");
 	len = LOAD32(buf, TPM_SIZE_OFFSET);
-	print_hex_dump(KERN_INFO, "", DUMP_PREFIX_NONE, 16, 1, buf, len, 0);
+	print_hex_dump_debug("", DUMP_PREFIX_NONE, 16, 1, buf, len, 0);
 }
 #else
 static inline void dump_options(struct trusted_key_options *o)