diff options
| -rw-r--r-- | Documentation/ABI/testing/debugfs-turris-mox-rwtm | 9 | ||||
| -rw-r--r-- | drivers/firmware/turris-mox-rwtm.c | 166 |
2 files changed, 175 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/debugfs-turris-mox-rwtm b/Documentation/ABI/testing/debugfs-turris-mox-rwtm new file mode 100644 index 000000000000..2b3255ee68fd --- /dev/null +++ b/Documentation/ABI/testing/debugfs-turris-mox-rwtm @@ -0,0 +1,9 @@ +What: /sys/kernel/debug/turris-mox-rwtm/do_sign +Date: Jun 2020 +KernelVersion: 5.8 +Contact: Marek Behún <marek.behun@nic.cz> +Description: (W) Message to sign with the ECDSA private key stored in + device's OTP. The message must be exactly 64 bytes (since + this is intended for SHA-512 hashes). + (R) The resulting signature, 136 bytes. This contains the R and + S values of the ECDSA signature, both in big-endian format. diff --git a/drivers/firmware/turris-mox-rwtm.c b/drivers/firmware/turris-mox-rwtm.c index e27f68437b56..50bb2a6d6ccf 100644 --- a/drivers/firmware/turris-mox-rwtm.c +++ b/drivers/firmware/turris-mox-rwtm.c @@ -7,6 +7,7 @@ #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> @@ -69,6 +70,18 @@ struct mox_rwtm { /* 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 { @@ -279,6 +292,152 @@ unlock_mutex: 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; @@ -340,6 +499,12 @@ static int turris_mox_rwtm_probe(struct platform_device *pdev) goto free_channel; } + ret = rwtm_register_debugfs(rwtm); + if (ret < 0) { + dev_err(dev, "Failed creating debugfs entries: %i\n", ret); + goto free_channel; + } + return 0; free_channel: @@ -355,6 +520,7 @@ 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); |