diff options
Diffstat (limited to 'arch/powerpc/platforms/pseries/plpks-secvar.c')
-rw-r--r-- | arch/powerpc/platforms/pseries/plpks-secvar.c | 217 |
1 files changed, 217 insertions, 0 deletions
diff --git a/arch/powerpc/platforms/pseries/plpks-secvar.c b/arch/powerpc/platforms/pseries/plpks-secvar.c new file mode 100644 index 0000000000..257fd1f8bc --- /dev/null +++ b/arch/powerpc/platforms/pseries/plpks-secvar.c @@ -0,0 +1,217 @@ +// SPDX-License-Identifier: GPL-2.0-only + +// Secure variable implementation using the PowerVM LPAR Platform KeyStore (PLPKS) +// +// Copyright 2022, 2023 IBM Corporation +// Authors: Russell Currey +// Andrew Donnellan +// Nayna Jain + +#define pr_fmt(fmt) "secvar: "fmt + +#include <linux/printk.h> +#include <linux/init.h> +#include <linux/types.h> +#include <linux/slab.h> +#include <linux/string.h> +#include <linux/kobject.h> +#include <linux/nls.h> +#include <asm/machdep.h> +#include <asm/secvar.h> +#include <asm/plpks.h> + +// Config attributes for sysfs +#define PLPKS_CONFIG_ATTR(name, fmt, func) \ + static ssize_t name##_show(struct kobject *kobj, \ + struct kobj_attribute *attr, \ + char *buf) \ + { \ + return sysfs_emit(buf, fmt, func()); \ + } \ + static struct kobj_attribute attr_##name = __ATTR_RO(name) + +PLPKS_CONFIG_ATTR(version, "%u\n", plpks_get_version); +PLPKS_CONFIG_ATTR(max_object_size, "%u\n", plpks_get_maxobjectsize); +PLPKS_CONFIG_ATTR(total_size, "%u\n", plpks_get_totalsize); +PLPKS_CONFIG_ATTR(used_space, "%u\n", plpks_get_usedspace); +PLPKS_CONFIG_ATTR(supported_policies, "%08x\n", plpks_get_supportedpolicies); +PLPKS_CONFIG_ATTR(signed_update_algorithms, "%016llx\n", plpks_get_signedupdatealgorithms); + +static const struct attribute *config_attrs[] = { + &attr_version.attr, + &attr_max_object_size.attr, + &attr_total_size.attr, + &attr_used_space.attr, + &attr_supported_policies.attr, + &attr_signed_update_algorithms.attr, + NULL, +}; + +static u32 get_policy(const char *name) +{ + if ((strcmp(name, "db") == 0) || + (strcmp(name, "dbx") == 0) || + (strcmp(name, "grubdb") == 0) || + (strcmp(name, "grubdbx") == 0) || + (strcmp(name, "sbat") == 0)) + return (PLPKS_WORLDREADABLE | PLPKS_SIGNEDUPDATE); + else + return PLPKS_SIGNEDUPDATE; +} + +static const char * const plpks_var_names[] = { + "PK", + "KEK", + "db", + "dbx", + "grubdb", + "grubdbx", + "sbat", + "moduledb", + "trustedcadb", + NULL, +}; + +static int plpks_get_variable(const char *key, u64 key_len, u8 *data, + u64 *data_size) +{ + struct plpks_var var = {0}; + int rc = 0; + + // We subtract 1 from key_len because we don't need to include the + // null terminator at the end of the string + var.name = kcalloc(key_len - 1, sizeof(wchar_t), GFP_KERNEL); + if (!var.name) + return -ENOMEM; + rc = utf8s_to_utf16s(key, key_len - 1, UTF16_LITTLE_ENDIAN, (wchar_t *)var.name, + key_len - 1); + if (rc < 0) + goto err; + var.namelen = rc * 2; + + var.os = PLPKS_VAR_LINUX; + if (data) { + var.data = data; + var.datalen = *data_size; + } + rc = plpks_read_os_var(&var); + + if (rc) + goto err; + + *data_size = var.datalen; + +err: + kfree(var.name); + if (rc && rc != -ENOENT) { + pr_err("Failed to read variable '%s': %d\n", key, rc); + // Return -EIO since userspace probably doesn't care about the + // specific error + rc = -EIO; + } + return rc; +} + +static int plpks_set_variable(const char *key, u64 key_len, u8 *data, + u64 data_size) +{ + struct plpks_var var = {0}; + int rc = 0; + u64 flags; + + // Secure variables need to be prefixed with 8 bytes of flags. + // We only want to perform the write if we have at least one byte of data. + if (data_size <= sizeof(flags)) + return -EINVAL; + + // We subtract 1 from key_len because we don't need to include the + // null terminator at the end of the string + var.name = kcalloc(key_len - 1, sizeof(wchar_t), GFP_KERNEL); + if (!var.name) + return -ENOMEM; + rc = utf8s_to_utf16s(key, key_len - 1, UTF16_LITTLE_ENDIAN, (wchar_t *)var.name, + key_len - 1); + if (rc < 0) + goto err; + var.namelen = rc * 2; + + // Flags are contained in the first 8 bytes of the buffer, and are always big-endian + flags = be64_to_cpup((__be64 *)data); + + var.datalen = data_size - sizeof(flags); + var.data = data + sizeof(flags); + var.os = PLPKS_VAR_LINUX; + var.policy = get_policy(key); + + // Unlike in the read case, the plpks error code can be useful to + // userspace on write, so we return it rather than just -EIO + rc = plpks_signed_update_var(&var, flags); + +err: + kfree(var.name); + return rc; +} + +// PLPKS dynamic secure boot doesn't give us a format string in the same way OPAL does. +// Instead, report the format using the SB_VERSION variable in the keystore. +// The string is made up by us, and takes the form "ibm,plpks-sb-v<n>" (or "ibm,plpks-sb-unknown" +// if the SB_VERSION variable doesn't exist). Hypervisor defines the SB_VERSION variable as a +// "1 byte unsigned integer value". +static ssize_t plpks_secvar_format(char *buf, size_t bufsize) +{ + struct plpks_var var = {0}; + ssize_t ret; + u8 version; + + var.component = NULL; + // Only the signed variables have null bytes in their names, this one doesn't + var.name = "SB_VERSION"; + var.namelen = strlen(var.name); + var.datalen = 1; + var.data = &version; + + // Unlike the other vars, SB_VERSION is owned by firmware instead of the OS + ret = plpks_read_fw_var(&var); + if (ret) { + if (ret == -ENOENT) { + ret = snprintf(buf, bufsize, "ibm,plpks-sb-unknown"); + } else { + pr_err("Error %ld reading SB_VERSION from firmware\n", ret); + ret = -EIO; + } + goto err; + } + + ret = snprintf(buf, bufsize, "ibm,plpks-sb-v%hhu", version); +err: + return ret; +} + +static int plpks_max_size(u64 *max_size) +{ + // The max object size reported by the hypervisor is accurate for the + // object itself, but we use the first 8 bytes of data on write as the + // signed update flags, so the max size a user can write is larger. + *max_size = (u64)plpks_get_maxobjectsize() + sizeof(u64); + + return 0; +} + + +static const struct secvar_operations plpks_secvar_ops = { + .get = plpks_get_variable, + .set = plpks_set_variable, + .format = plpks_secvar_format, + .max_size = plpks_max_size, + .config_attrs = config_attrs, + .var_names = plpks_var_names, +}; + +static int plpks_secvar_init(void) +{ + if (!plpks_is_available()) + return -ENODEV; + + return set_secvar_ops(&plpks_secvar_ops); +} +machine_device_initcall(pseries, plpks_secvar_init); |