linux/drivers/firmware/turris-mox-rwtm.c
Jason A. Donenfeld 16bdbae394 hwrng: core - treat default_quality as a maximum and default to 1024
Most hw_random devices return entropy which is assumed to be of full
quality, but driver authors don't bother setting the quality knob. Some
hw_random devices return less than full quality entropy, and then driver
authors set the quality knob. Therefore, the entropy crediting should be
opt-out rather than opt-in per-driver, to reflect the actual reality on
the ground.

For example, the two Raspberry Pi RNG drivers produce full entropy
randomness, and both EDK2 and U-Boot's drivers for these treat them as
such. The result is that EFI then uses these numbers and passes the to
Linux, and Linux credits them as boot, thereby initializing the RNG.
Yet, in Linux, the quality knob was never set to anything, and so on the
chance that Linux is booted without EFI, nothing is ever credited.
That's annoying.

The same pattern appears to repeat itself throughout various drivers. In
fact, very very few drivers have bothered setting quality=1024.

Looking at the git history of existing drivers and corresponding mailing
list discussion, this conclusion tracks. There's been a decent amount of
discussion about drivers that set quality < 1024 -- somebody read and
interepreted a datasheet, or made some back of the envelope calculation
somehow. But there's been very little, if any, discussion about most
drivers where the quality is just set to 1024 or unset (or set to 1000
when the authors misunderstood the API and assumed it was base-10 rather
than base-2); in both cases the intent was fairly clear of, "this is a
hardware random device; it's fine."

So let's invert this logic. A hw_random struct's quality knob now
controls the maximum quality a driver can produce, or 0 to specify 1024.
Then, the module-wide switch called "default_quality" is changed to
represent the maximum quality of any driver. By default it's 1024, and
the quality of any particular driver is then given by:

    min(default_quality, rng->quality ?: 1024);

This way, the user can still turn this off for weird reasons (and we can
replace whatever driver-specific disabling hacks existed in the past),
yet we get proper crediting for relevant RNGs.

Cc: Dominik Brodowski <linux@dominikbrodowski.net>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2022-11-18 16:59:34 +08:00

590 lines
14 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Turris Mox rWTM firmware driver
*
* Copyright (C) 2019 Marek Behún <kabel@kernel.org>
*/
#include <linux/armada-37xx-rwtm-mailbox.h>
#include <linux/completion.h>
#include <linux/debugfs.h>
#include <linux/dma-mapping.h>
#include <linux/hw_random.h>
#include <linux/mailbox_client.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#define DRIVER_NAME "turris-mox-rwtm"
/*
* The macros and constants below come from Turris Mox's rWTM firmware code.
* This firmware is open source and it's sources can be found at
* https://gitlab.labs.nic.cz/turris/mox-boot-builder/tree/master/wtmi.
*/
#define MBOX_STS_SUCCESS (0 << 30)
#define MBOX_STS_FAIL (1 << 30)
#define MBOX_STS_BADCMD (2 << 30)
#define MBOX_STS_ERROR(s) ((s) & (3 << 30))
#define MBOX_STS_VALUE(s) (((s) >> 10) & 0xfffff)
#define MBOX_STS_CMD(s) ((s) & 0x3ff)
enum mbox_cmd {
MBOX_CMD_GET_RANDOM = 1,
MBOX_CMD_BOARD_INFO = 2,
MBOX_CMD_ECDSA_PUB_KEY = 3,
MBOX_CMD_HASH = 4,
MBOX_CMD_SIGN = 5,
MBOX_CMD_VERIFY = 6,
MBOX_CMD_OTP_READ = 7,
MBOX_CMD_OTP_WRITE = 8,
};
struct mox_kobject;
struct mox_rwtm {
struct device *dev;
struct mbox_client mbox_client;
struct mbox_chan *mbox;
struct mox_kobject *kobj;
struct hwrng hwrng;
struct armada_37xx_rwtm_rx_msg reply;
void *buf;
dma_addr_t buf_phys;
struct mutex busy;
struct completion cmd_done;
/* board information */
int has_board_info;
u64 serial_number;
int board_version, ram_size;
u8 mac_address1[6], mac_address2[6];
/* public key burned in eFuse */
int has_pubkey;
u8 pubkey[135];
#ifdef CONFIG_DEBUG_FS
/*
* Signature process. This is currently done via debugfs, because it
* does not conform to the sysfs standard "one file per attribute".
* It should be rewritten via crypto API once akcipher API is available
* from userspace.
*/
struct dentry *debugfs_root;
u32 last_sig[34];
int last_sig_done;
#endif
};
struct mox_kobject {
struct kobject kobj;
struct mox_rwtm *rwtm;
};
static inline struct kobject *rwtm_to_kobj(struct mox_rwtm *rwtm)
{
return &rwtm->kobj->kobj;
}
static inline struct mox_rwtm *to_rwtm(struct kobject *kobj)
{
return container_of(kobj, struct mox_kobject, kobj)->rwtm;
}
static void mox_kobj_release(struct kobject *kobj)
{
kfree(to_rwtm(kobj)->kobj);
}
static struct kobj_type mox_kobj_ktype = {
.release = mox_kobj_release,
.sysfs_ops = &kobj_sysfs_ops,
};
static int mox_kobj_create(struct mox_rwtm *rwtm)
{
rwtm->kobj = kzalloc(sizeof(*rwtm->kobj), GFP_KERNEL);
if (!rwtm->kobj)
return -ENOMEM;
kobject_init(rwtm_to_kobj(rwtm), &mox_kobj_ktype);
if (kobject_add(rwtm_to_kobj(rwtm), firmware_kobj, "turris-mox-rwtm")) {
kobject_put(rwtm_to_kobj(rwtm));
return -ENXIO;
}
rwtm->kobj->rwtm = rwtm;
return 0;
}
#define MOX_ATTR_RO(name, format, cat) \
static ssize_t \
name##_show(struct kobject *kobj, struct kobj_attribute *a, \
char *buf) \
{ \
struct mox_rwtm *rwtm = to_rwtm(kobj); \
if (!rwtm->has_##cat) \
return -ENODATA; \
return sprintf(buf, format, rwtm->name); \
} \
static struct kobj_attribute mox_attr_##name = __ATTR_RO(name)
MOX_ATTR_RO(serial_number, "%016llX\n", board_info);
MOX_ATTR_RO(board_version, "%i\n", board_info);
MOX_ATTR_RO(ram_size, "%i\n", board_info);
MOX_ATTR_RO(mac_address1, "%pM\n", board_info);
MOX_ATTR_RO(mac_address2, "%pM\n", board_info);
MOX_ATTR_RO(pubkey, "%s\n", pubkey);
static int mox_get_status(enum mbox_cmd cmd, u32 retval)
{
if (MBOX_STS_CMD(retval) != cmd)
return -EIO;
else if (MBOX_STS_ERROR(retval) == MBOX_STS_FAIL)
return -(int)MBOX_STS_VALUE(retval);
else if (MBOX_STS_ERROR(retval) == MBOX_STS_BADCMD)
return -ENOSYS;
else if (MBOX_STS_ERROR(retval) != MBOX_STS_SUCCESS)
return -EIO;
else
return MBOX_STS_VALUE(retval);
}
static const struct attribute *mox_rwtm_attrs[] = {
&mox_attr_serial_number.attr,
&mox_attr_board_version.attr,
&mox_attr_ram_size.attr,
&mox_attr_mac_address1.attr,
&mox_attr_mac_address2.attr,
&mox_attr_pubkey.attr,
NULL
};
static void mox_rwtm_rx_callback(struct mbox_client *cl, void *data)
{
struct mox_rwtm *rwtm = dev_get_drvdata(cl->dev);
struct armada_37xx_rwtm_rx_msg *msg = data;
rwtm->reply = *msg;
complete(&rwtm->cmd_done);
}
static void reply_to_mac_addr(u8 *mac, u32 t1, u32 t2)
{
mac[0] = t1 >> 8;
mac[1] = t1;
mac[2] = t2 >> 24;
mac[3] = t2 >> 16;
mac[4] = t2 >> 8;
mac[5] = t2;
}
static int mox_get_board_info(struct mox_rwtm *rwtm)
{
struct armada_37xx_rwtm_tx_msg msg;
struct armada_37xx_rwtm_rx_msg *reply = &rwtm->reply;
int ret;
msg.command = MBOX_CMD_BOARD_INFO;
ret = mbox_send_message(rwtm->mbox, &msg);
if (ret < 0)
return ret;
ret = wait_for_completion_timeout(&rwtm->cmd_done, HZ / 2);
if (ret < 0)
return ret;
ret = mox_get_status(MBOX_CMD_BOARD_INFO, reply->retval);
if (ret == -ENODATA) {
dev_warn(rwtm->dev,
"Board does not have manufacturing information burned!\n");
} else if (ret == -ENOSYS) {
dev_notice(rwtm->dev,
"Firmware does not support the BOARD_INFO command\n");
} else if (ret < 0) {
return ret;
} else {
rwtm->serial_number = reply->status[1];
rwtm->serial_number <<= 32;
rwtm->serial_number |= reply->status[0];
rwtm->board_version = reply->status[2];
rwtm->ram_size = reply->status[3];
reply_to_mac_addr(rwtm->mac_address1, reply->status[4],
reply->status[5]);
reply_to_mac_addr(rwtm->mac_address2, reply->status[6],
reply->status[7]);
rwtm->has_board_info = 1;
pr_info("Turris Mox serial number %016llX\n",
rwtm->serial_number);
pr_info(" board version %i\n", rwtm->board_version);
pr_info(" burned RAM size %i MiB\n", rwtm->ram_size);
}
msg.command = MBOX_CMD_ECDSA_PUB_KEY;
ret = mbox_send_message(rwtm->mbox, &msg);
if (ret < 0)
return ret;
ret = wait_for_completion_timeout(&rwtm->cmd_done, HZ / 2);
if (ret < 0)
return ret;
ret = mox_get_status(MBOX_CMD_ECDSA_PUB_KEY, reply->retval);
if (ret == -ENODATA) {
dev_warn(rwtm->dev, "Board has no public key burned!\n");
} else if (ret == -ENOSYS) {
dev_notice(rwtm->dev,
"Firmware does not support the ECDSA_PUB_KEY command\n");
} else if (ret < 0) {
return ret;
} else {
u32 *s = reply->status;
rwtm->has_pubkey = 1;
sprintf(rwtm->pubkey,
"%06x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x%08x",
ret, s[0], s[1], s[2], s[3], s[4], s[5], s[6], s[7],
s[8], s[9], s[10], s[11], s[12], s[13], s[14], s[15]);
}
return 0;
}
static int check_get_random_support(struct mox_rwtm *rwtm)
{
struct armada_37xx_rwtm_tx_msg msg;
int ret;
msg.command = MBOX_CMD_GET_RANDOM;
msg.args[0] = 1;
msg.args[1] = rwtm->buf_phys;
msg.args[2] = 4;
ret = mbox_send_message(rwtm->mbox, &msg);
if (ret < 0)
return ret;
ret = wait_for_completion_timeout(&rwtm->cmd_done, HZ / 2);
if (ret < 0)
return ret;
return mox_get_status(MBOX_CMD_GET_RANDOM, rwtm->reply.retval);
}
static int mox_hwrng_read(struct hwrng *rng, void *data, size_t max, bool wait)
{
struct mox_rwtm *rwtm = (struct mox_rwtm *) rng->priv;
struct armada_37xx_rwtm_tx_msg msg;
int ret;
if (max > 4096)
max = 4096;
msg.command = MBOX_CMD_GET_RANDOM;
msg.args[0] = 1;
msg.args[1] = rwtm->buf_phys;
msg.args[2] = (max + 3) & ~3;
if (!wait) {
if (!mutex_trylock(&rwtm->busy))
return -EBUSY;
} else {
mutex_lock(&rwtm->busy);
}
ret = mbox_send_message(rwtm->mbox, &msg);
if (ret < 0)
goto unlock_mutex;
ret = wait_for_completion_interruptible(&rwtm->cmd_done);
if (ret < 0)
goto unlock_mutex;
ret = mox_get_status(MBOX_CMD_GET_RANDOM, rwtm->reply.retval);
if (ret < 0)
goto unlock_mutex;
memcpy(data, rwtm->buf, max);
ret = max;
unlock_mutex:
mutex_unlock(&rwtm->busy);
return ret;
}
#ifdef CONFIG_DEBUG_FS
static int rwtm_debug_open(struct inode *inode, struct file *file)
{
file->private_data = inode->i_private;
return nonseekable_open(inode, file);
}
static ssize_t do_sign_read(struct file *file, char __user *buf, size_t len,
loff_t *ppos)
{
struct mox_rwtm *rwtm = file->private_data;
ssize_t ret;
/* only allow one read, of 136 bytes, from position 0 */
if (*ppos != 0)
return 0;
if (len < 136)
return -EINVAL;
if (!rwtm->last_sig_done)
return -ENODATA;
/* 2 arrays of 17 32-bit words are 136 bytes */
ret = simple_read_from_buffer(buf, len, ppos, rwtm->last_sig, 136);
rwtm->last_sig_done = 0;
return ret;
}
static ssize_t do_sign_write(struct file *file, const char __user *buf,
size_t len, loff_t *ppos)
{
struct mox_rwtm *rwtm = file->private_data;
struct armada_37xx_rwtm_rx_msg *reply = &rwtm->reply;
struct armada_37xx_rwtm_tx_msg msg;
loff_t dummy = 0;
ssize_t ret;
/* the input is a SHA-512 hash, so exactly 64 bytes have to be read */
if (len != 64)
return -EINVAL;
/* if last result is not zero user has not read that information yet */
if (rwtm->last_sig_done)
return -EBUSY;
if (!mutex_trylock(&rwtm->busy))
return -EBUSY;
/*
* Here we have to send:
* 1. Address of the input to sign.
* The input is an array of 17 32-bit words, the first (most
* significat) is 0, the rest 16 words are copied from the SHA-512
* hash given by the user and converted from BE to LE.
* 2. Address of the buffer where ECDSA signature value R shall be
* stored by the rWTM firmware.
* 3. Address of the buffer where ECDSA signature value S shall be
* stored by the rWTM firmware.
*/
memset(rwtm->buf, 0, 4);
ret = simple_write_to_buffer(rwtm->buf + 4, 64, &dummy, buf, len);
if (ret < 0)
goto unlock_mutex;
be32_to_cpu_array(rwtm->buf, rwtm->buf, 17);
msg.command = MBOX_CMD_SIGN;
msg.args[0] = 1;
msg.args[1] = rwtm->buf_phys;
msg.args[2] = rwtm->buf_phys + 68;
msg.args[3] = rwtm->buf_phys + 2 * 68;
ret = mbox_send_message(rwtm->mbox, &msg);
if (ret < 0)
goto unlock_mutex;
ret = wait_for_completion_interruptible(&rwtm->cmd_done);
if (ret < 0)
goto unlock_mutex;
ret = MBOX_STS_VALUE(reply->retval);
if (MBOX_STS_ERROR(reply->retval) != MBOX_STS_SUCCESS)
goto unlock_mutex;
/*
* Here we read the R and S values of the ECDSA signature
* computed by the rWTM firmware and convert their words from
* LE to BE.
*/
memcpy(rwtm->last_sig, rwtm->buf + 68, 136);
cpu_to_be32_array(rwtm->last_sig, rwtm->last_sig, 34);
rwtm->last_sig_done = 1;
mutex_unlock(&rwtm->busy);
return len;
unlock_mutex:
mutex_unlock(&rwtm->busy);
return ret;
}
static const struct file_operations do_sign_fops = {
.owner = THIS_MODULE,
.open = rwtm_debug_open,
.read = do_sign_read,
.write = do_sign_write,
.llseek = no_llseek,
};
static int rwtm_register_debugfs(struct mox_rwtm *rwtm)
{
struct dentry *root, *entry;
root = debugfs_create_dir("turris-mox-rwtm", NULL);
if (IS_ERR(root))
return PTR_ERR(root);
entry = debugfs_create_file_unsafe("do_sign", 0600, root, rwtm,
&do_sign_fops);
if (IS_ERR(entry))
goto err_remove;
rwtm->debugfs_root = root;
return 0;
err_remove:
debugfs_remove_recursive(root);
return PTR_ERR(entry);
}
static void rwtm_unregister_debugfs(struct mox_rwtm *rwtm)
{
debugfs_remove_recursive(rwtm->debugfs_root);
}
#else
static inline int rwtm_register_debugfs(struct mox_rwtm *rwtm)
{
return 0;
}
static inline void rwtm_unregister_debugfs(struct mox_rwtm *rwtm)
{
}
#endif
static int turris_mox_rwtm_probe(struct platform_device *pdev)
{
struct mox_rwtm *rwtm;
struct device *dev = &pdev->dev;
int ret;
rwtm = devm_kzalloc(dev, sizeof(*rwtm), GFP_KERNEL);
if (!rwtm)
return -ENOMEM;
rwtm->dev = dev;
rwtm->buf = dmam_alloc_coherent(dev, PAGE_SIZE, &rwtm->buf_phys,
GFP_KERNEL);
if (!rwtm->buf)
return -ENOMEM;
ret = mox_kobj_create(rwtm);
if (ret < 0) {
dev_err(dev, "Cannot create turris-mox-rwtm kobject!\n");
return ret;
}
ret = sysfs_create_files(rwtm_to_kobj(rwtm), mox_rwtm_attrs);
if (ret < 0) {
dev_err(dev, "Cannot create sysfs files!\n");
goto put_kobj;
}
platform_set_drvdata(pdev, rwtm);
mutex_init(&rwtm->busy);
rwtm->mbox_client.dev = dev;
rwtm->mbox_client.rx_callback = mox_rwtm_rx_callback;
rwtm->mbox = mbox_request_channel(&rwtm->mbox_client, 0);
if (IS_ERR(rwtm->mbox)) {
ret = PTR_ERR(rwtm->mbox);
if (ret != -EPROBE_DEFER)
dev_err(dev, "Cannot request mailbox channel: %i\n",
ret);
goto remove_files;
}
init_completion(&rwtm->cmd_done);
ret = mox_get_board_info(rwtm);
if (ret < 0)
dev_warn(dev, "Cannot read board information: %i\n", ret);
ret = check_get_random_support(rwtm);
if (ret < 0) {
dev_notice(dev,
"Firmware does not support the GET_RANDOM command\n");
goto free_channel;
}
rwtm->hwrng.name = DRIVER_NAME "_hwrng";
rwtm->hwrng.read = mox_hwrng_read;
rwtm->hwrng.priv = (unsigned long) rwtm;
ret = devm_hwrng_register(dev, &rwtm->hwrng);
if (ret < 0) {
dev_err(dev, "Cannot register HWRNG: %i\n", ret);
goto free_channel;
}
ret = rwtm_register_debugfs(rwtm);
if (ret < 0) {
dev_err(dev, "Failed creating debugfs entries: %i\n", ret);
goto free_channel;
}
dev_info(dev, "HWRNG successfully registered\n");
return 0;
free_channel:
mbox_free_channel(rwtm->mbox);
remove_files:
sysfs_remove_files(rwtm_to_kobj(rwtm), mox_rwtm_attrs);
put_kobj:
kobject_put(rwtm_to_kobj(rwtm));
return ret;
}
static int turris_mox_rwtm_remove(struct platform_device *pdev)
{
struct mox_rwtm *rwtm = platform_get_drvdata(pdev);
rwtm_unregister_debugfs(rwtm);
sysfs_remove_files(rwtm_to_kobj(rwtm), mox_rwtm_attrs);
kobject_put(rwtm_to_kobj(rwtm));
mbox_free_channel(rwtm->mbox);
return 0;
}
static const struct of_device_id turris_mox_rwtm_match[] = {
{ .compatible = "cznic,turris-mox-rwtm", },
{ .compatible = "marvell,armada-3700-rwtm-firmware", },
{ },
};
MODULE_DEVICE_TABLE(of, turris_mox_rwtm_match);
static struct platform_driver turris_mox_rwtm_driver = {
.probe = turris_mox_rwtm_probe,
.remove = turris_mox_rwtm_remove,
.driver = {
.name = DRIVER_NAME,
.of_match_table = turris_mox_rwtm_match,
},
};
module_platform_driver(turris_mox_rwtm_driver);
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("Turris Mox rWTM firmware driver");
MODULE_AUTHOR("Marek Behun <kabel@kernel.org>");