Subject: Re: [PATCH 5/6] keys/trusted_keys: establish PKWM as a trusted source

From: Jarkko Sakkinen <[email-masked]>
Date: Sat, 13 Dec 2025 21:22:17 +0200

On Sat, Dec 13, 2025 at 10:56:17AM +0530, Srish Srinivasan wrote:
> The wrapping key does not exist by default and is generated by the
> hypervisor as a part of PKWM initialization. This key is then persisted by
> the hypervisor and is used to wrap trusted keys. These are variable length
> symmetric keys, which in the case of PowerVM Key Wrapping Module (PKWM) are
> generated using the kernel RNG. PKWM can be used as a trust source through
> the following example keyctl command
> 
> keyctl add trusted my_trusted_key "new 32" @u
> 
> Use the wrap_flags command option to set the secure boot requirement for
> the wrapping request through the following keyctl commands
> 
> case1: no secure boot requirement. (default)
> keyctl usage: keyctl add trusted my_trusted_key "new 32" @u
> 	      OR
> 	      keyctl add trusted my_trusted_key "new 32 wrap_flags=0x00" @u
> 
> case2: secure boot required to in either audit or enforce mode. set bit 0
> keyctl usage: keyctl add trusted my_trusted_key "new 32 wrap_flags=0x01" @u
> 
> case3: secure boot required to be in enforce mode. set bit 1
> keyctl usage: keyctl add trusted my_trusted_key "new 32 wrap_flags=0x02" @u
> 
> NOTE:
> -> Setting the secure boot requirement is NOT a must.
> -> Only either of the secure boot requirement options should be set. Not
> both.
> -> All the other bits are requied to be not set.
> -> Set the kernel parameter trusted.source=pkwm to choose PKWM as the
> backend for trusted keys implementation.
> -> CONFIG_PSERIES_PLPKS must be enabled to build PKWM.
> 
> Add PKWM, which is a combination of IBM PowerVM and Power LPAR Platform
> KeyStore, as a new trust source for trusted keys.
> 
> Signed-off-by: Srish Srinivasan <[email-masked]>
> ---
>  MAINTAINERS                               |   9 ++
>  include/keys/trusted-type.h               |   7 +-
>  include/keys/trusted_pkwm.h               |  30 ++++
>  security/keys/trusted-keys/Kconfig        |   8 ++
>  security/keys/trusted-keys/Makefile       |   2 +
>  security/keys/trusted-keys/trusted_core.c |   6 +-
>  security/keys/trusted-keys/trusted_pkwm.c | 168 ++++++++++++++++++++++
>  7 files changed, 228 insertions(+), 2 deletions(-)
>  create mode 100644 include/keys/trusted_pkwm.h
>  create mode 100644 security/keys/trusted-keys/trusted_pkwm.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index aff3e162180d..bf78ab78a309 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -13993,6 +13993,15 @@ S:	Supported
>  F:	include/keys/trusted_dcp.h
>  F:	security/keys/trusted-keys/trusted_dcp.c
>  
> +KEYS-TRUSTED-PLPKS
> +M:	Srish Srinivasan <[email-masked]>
> +M:	Nayna Jain <[email-masked]>
> +L:	[email-masked]
> +L:	[email-masked]
> +S:	Supported
> +F:	include/keys/trusted_plpks.h
> +F:	security/keys/trusted-keys/trusted_pkwm.c
> +
>  KEYS-TRUSTED-TEE
>  M:	Sumit Garg <[email-masked]>
>  L:	[email-masked]
> diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
> index 4eb64548a74f..45c6c538df22 100644
> --- a/include/keys/trusted-type.h
> +++ b/include/keys/trusted-type.h
> @@ -19,7 +19,11 @@
>  
>  #define MIN_KEY_SIZE			32
>  #define MAX_KEY_SIZE			128
> -#define MAX_BLOB_SIZE			512
> +#if IS_ENABLED(CONFIG_TRUSTED_KEYS_PKWM)
> +#define MAX_BLOB_SIZE			1152
> +#else
> +#define MAX_BLOB_SIZE                   512
> +#endif
>  #define MAX_PCRINFO_SIZE		64
>  #define MAX_DIGEST_SIZE			64
>  
> @@ -46,6 +50,7 @@ struct trusted_key_options {
>  	uint32_t policydigest_len;
>  	unsigned char policydigest[MAX_DIGEST_SIZE];
>  	uint32_t policyhandle;
> +	uint16_t wrap_flags;
>  };
>  
>  struct trusted_key_ops {
> diff --git a/include/keys/trusted_pkwm.h b/include/keys/trusted_pkwm.h
> new file mode 100644
> index 000000000000..736edfc1e1dd
> --- /dev/null
> +++ b/include/keys/trusted_pkwm.h
> @@ -0,0 +1,30 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __PKWM_TRUSTED_KEY_H
> +#define __PKWM_TRUSTED_KEY_H
> +
> +#include <keys/trusted-type.h>
> +
> +extern struct trusted_key_ops pkwm_trusted_key_ops;
> +
> +#define PKWM_DEBUG 0
> +
> +#if PKWM_DEBUG
> +static inline void dump_options(struct trusted_key_options *o)
> +{
> +	bool sb_audit_or_enforce_bit = o->policyhandle & BIT(0);
> +	bool sb_enforce_bit = o->policyhandle & BIT(1);
> +
> +	if (sb_audit_or_enforce_bit)
> +		pr_info("secure boot mode: audit or enforce");
> +	else if (sb_enforce_bit)
> +		pr_info("secure boot mode: enforce");
> +	else
> +		pr_info("secure boot mode: disabled");
> +}
> +#else
> +static inline void dump_options(struct trusted_key_options *o)
> +{
> +}
> +#endif

Please use pr_debug() instead of emulating this with 'PKWM_DEBUG'.

> +
> +#endif
> diff --git a/security/keys/trusted-keys/Kconfig b/security/keys/trusted-keys/Kconfig
> index 204a68c1429d..9e00482d886a 100644
> --- a/security/keys/trusted-keys/Kconfig
> +++ b/security/keys/trusted-keys/Kconfig
> @@ -46,6 +46,14 @@ config TRUSTED_KEYS_DCP
>  	help
>  	  Enable use of NXP's DCP (Data Co-Processor) as trusted key backend.
>  
> +config TRUSTED_KEYS_PKWM
> +	bool "PKWM-based trusted keys"
> +	depends on PSERIES_PLPKS >= TRUSTED_KEYS
> +	default y
> +	select HAVE_TRUSTED_KEYS
> +	help
> +	  Enable use of IBM PowerVM Key Wrapping Module (PKWM) as a trusted key backend.
> +
>  if !HAVE_TRUSTED_KEYS
>  	comment "No trust source selected!"
>  endif
> diff --git a/security/keys/trusted-keys/Makefile b/security/keys/trusted-keys/Makefile
> index f0f3b27f688b..5fc053a21dad 100644
> --- a/security/keys/trusted-keys/Makefile
> +++ b/security/keys/trusted-keys/Makefile
> @@ -16,3 +16,5 @@ trusted-$(CONFIG_TRUSTED_KEYS_TEE) += trusted_tee.o
>  trusted-$(CONFIG_TRUSTED_KEYS_CAAM) += trusted_caam.o
>  
>  trusted-$(CONFIG_TRUSTED_KEYS_DCP) += trusted_dcp.o
> +
> +trusted-$(CONFIG_TRUSTED_KEYS_PKWM) += trusted_pkwm.o
> diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c
> index b1680ee53f86..2d328de170e8 100644
> --- a/security/keys/trusted-keys/trusted_core.c
> +++ b/security/keys/trusted-keys/trusted_core.c
> @@ -12,6 +12,7 @@
>  #include <keys/trusted_caam.h>
>  #include <keys/trusted_dcp.h>
>  #include <keys/trusted_tpm.h>
> +#include <keys/trusted_pkwm.h>
>  #include <linux/capability.h>
>  #include <linux/err.h>
>  #include <linux/init.h>
> @@ -31,7 +32,7 @@ MODULE_PARM_DESC(rng, "Select trusted key RNG");
>  
>  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 or dcp)");
> +MODULE_PARM_DESC(source, "Select trusted keys source (tpm, tee, caam, dcp or pkwm)");
>  
>  static const struct trusted_key_source trusted_key_sources[] = {
>  #if defined(CONFIG_TRUSTED_KEYS_TPM)
> @@ -46,6 +47,9 @@ static const struct trusted_key_source trusted_key_sources[] = {
>  #if defined(CONFIG_TRUSTED_KEYS_DCP)
>  	{ "dcp", &dcp_trusted_key_ops },
>  #endif
> +#if defined(CONFIG_TRUSTED_KEYS_PKWM)
> +	{ "pkwm", &pkwm_trusted_key_ops },
> +#endif
>  };
>  
>  DEFINE_STATIC_CALL_NULL(trusted_key_seal, *trusted_key_sources[0].ops->seal);
> diff --git a/security/keys/trusted-keys/trusted_pkwm.c b/security/keys/trusted-keys/trusted_pkwm.c
> new file mode 100644
> index 000000000000..7968601dcf42
> --- /dev/null
> +++ b/security/keys/trusted-keys/trusted_pkwm.c
> @@ -0,0 +1,168 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2025 IBM Corporation, Srish Srinivasan <[email-masked]>
> + */
> +
> +#include <keys/trusted_pkwm.h>
> +#include <keys/trusted-type.h>
> +#include <linux/build_bug.h>
> +#include <linux/key-type.h>
> +#include <linux/parser.h>
> +#include <asm/plpks.h>
> +
> +enum {
> +	Opt_err,
> +	Opt_wrap_flags,
> +};
> +
> +static const match_table_t key_tokens = {
> +	{Opt_wrap_flags, "wrap_flags=%s"},
> +	{Opt_err, NULL}
> +};
> +
> +static int getoptions(char *datablob, struct trusted_key_options **opt)
> +{
> +	substring_t args[MAX_OPT_ARGS];
> +	char *p = datablob;
> +	int token;
> +	int res;
> +	unsigned long wrap_flags;
> +	unsigned long token_mask = 0;
> +
> +	if (!datablob)
> +		return 0;
> +
> +	while ((p = strsep(&datablob, " \t"))) {
> +		if (*p == '\0' || *p == ' ' || *p == '\t')
> +			continue;
> +
> +		token = match_token(p, key_tokens, args);
> +		if (test_and_set_bit(token, &token_mask))
> +			return -EINVAL;
> +
> +		switch (token) {
> +		case Opt_wrap_flags:
> +			res = kstrtoul(args[0].from, 16, &wrap_flags);
> +			if (res < 0 || wrap_flags > 2)
> +				return -EINVAL;
> +			(*opt)->wrap_flags = wrap_flags;
> +			break;
> +		default:
> +			return -EINVAL;
> +		}
> +	}
> +	return 0;
> +}
> +
> +static struct trusted_key_options *trusted_options_alloc(void)
> +{
> +	struct trusted_key_options *options;
> +
> +	options = kzalloc(sizeof(*options), GFP_KERNEL);
> +	return options;
> +}
> +
> +static int trusted_pkwm_seal(struct trusted_key_payload *p, char *datablob)
> +{
> +	struct trusted_key_options *options = NULL;
> +	u8 *input_buf, *output_buf;
> +	u32 output_len, input_len;
> +	int rc;
> +
> +	options = trusted_options_alloc();
> +	if (!options)
> +		return -ENOMEM;
> +
> +	rc = getoptions(datablob, &options);
> +	if (rc < 0)
> +		goto out;
> +	dump_options(options);
> +
> +	input_len = p->key_len;
> +	input_buf = kmalloc(ALIGN(input_len, 4096), GFP_KERNEL);
> +	if (!input_buf) {
> +		pr_err("Input buffer allocation failed. Returning -ENOMEM.");
> +		return -ENOMEM;
> +	}
> +
> +	memcpy(input_buf, p->key, p->key_len);
> +
> +	rc = plpks_wrap_object(&input_buf, input_len, options->wrap_flags,
> +			       &output_buf, &output_len);
> +	if (!rc) {
> +		memcpy(p->blob, output_buf, output_len);
> +		p->blob_len = output_len;
> +		dump_payload(p);
> +	} else {
> +		pr_err("Invalid argument");
> +	}
> +
> +	kfree(input_buf);
> +	kfree(output_buf);
> +
> +out:
> +	kfree_sensitive(options);
> +	return rc;
> +}
> +
> +static int trusted_pkwm_unseal(struct trusted_key_payload *p, char *datablob)
> +{
> +	u8 *input_buf, *output_buf;
> +	u32 input_len, output_len;
> +	int rc;
> +
> +	input_len = p->blob_len;
> +	input_buf = kmalloc(ALIGN(input_len, 4096), GFP_KERNEL);
> +	if (!input_buf)
> +		return -ENOMEM;
> +
> +	memcpy(input_buf, p->blob, p->blob_len);
> +
> +	rc = plpks_unwrap_object(&input_buf, input_len, &output_buf,
> +				 &output_len);
> +	if (!rc) {
> +		memcpy(p->key, output_buf, output_len);
> +		p->key_len = output_len;
> +		dump_payload(p);
> +	} else {
> +		pr_err("Invalid argument");

I don't get this error message. What does this mean? pr_err() is used
when you have actual malfunction.

> +	}
> +
> +	kfree(input_buf);
> +	kfree(output_buf);
> +
> +	return rc;
> +}
> +
> +static int trusted_pkwm_init(void)
> +{
> +	int ret;
> +
> +	if (!plpks_wrapping_is_supported()) {
> +		pr_err("H_PKS_WRAP_OBJECT interface not supported\n");
> +
> +		return -ENODEV;
> +	}
> +
> +	ret = plpks_gen_wrapping_key();
> +	if (ret) {
> +		pr_err("Failed to generate default wrapping key\n");
> +
> +		return -EINVAL;
> +	}
> +
> +	return register_key_type(&key_type_trusted);
> +}
> +
> +static void trusted_pkwm_exit(void)
> +{
> +	unregister_key_type(&key_type_trusted);
> +}
> +
> +struct trusted_key_ops pkwm_trusted_key_ops = {
> +	.migratable = 0, /* non-migratable */
> +	.init = trusted_pkwm_init,
> +	.seal = trusted_pkwm_seal,
> +	.unseal = trusted_pkwm_unseal,
> +	.exit = trusted_pkwm_exit,
> +};
> -- 
> 2.47.3
> 

BR, Jarkko