firmware: turris-mox-rwtm: Hide signature related constants behind macros

Hide signature generation related constants behind macros instead of
hardcoding the values.

Use SHA512_DIGEST_SIZE from crypto/sha2.h instead of hardcoded 64 as the
message size.

Signed-off-by: Marek Behún <kabel@kernel.org>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Link: https://lore.kernel.org/r/20240831092050.23093-5-kabel@kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

diff --git a/drivers/firmware/turris-mox-rwtm.c b/drivers/firmware/turris-mox-rwtm.c
index 8875c35f9b1932fa3b8e02b32dbd95c1f96ffd7d..cf8c605d99ef9f55ee5ed10660b0ef4c2e5baaf0 100644 (file)
--- a/drivers/firmware/turris-mox-rwtm.c
+++ b/drivers/firmware/turris-mox-rwtm.c
@@ -5,6 +5,7 @@
  * Copyright (C) 2019, 2024 Marek Behún <kabel@kernel.org>
  */
 
+#include <crypto/sha2.h>
 #include <linux/armada-37xx-rwtm-mailbox.h>
 #include <linux/completion.h>
 #include <linux/debugfs.h>
@@ -31,6 +32,11 @@
  * https://gitlab.labs.nic.cz/turris/mox-boot-builder/tree/master/wtmi.
  */
 
+#define MOX_ECC_NUMBER_WORDS   17
+#define MOX_ECC_NUMBER_LEN     (MOX_ECC_NUMBER_WORDS * sizeof(u32))
+
+#define MOX_ECC_SIGNATURE_WORDS        (2 * MOX_ECC_NUMBER_WORDS)
+
 #define MBOX_STS_SUCCESS       (0 << 30)
 #define MBOX_STS_FAIL          (1 << 30)
 #define MBOX_STS_BADCMD                (2 << 30)
@@ -85,7 +91,7 @@ struct mox_rwtm {
         * from userspace.
         */
        struct dentry *debugfs_root;
-       u32 last_sig[34];
+       u32 last_sig[MOX_ECC_SIGNATURE_WORDS];
        bool last_sig_done;
 #endif
 };
@@ -341,18 +347,18 @@ static ssize_t do_sign_read(struct file *file, char __user *buf, size_t len,
        struct mox_rwtm *rwtm = file->private_data;
        ssize_t ret;
 
-       /* only allow one read, of 136 bytes, from position 0 */
+       /* only allow one read, of whole signature, from position 0 */
        if (*ppos != 0)
                return 0;
 
-       if (len < 136)
+       if (len < sizeof(rwtm->last_sig))
                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);
+       ret = simple_read_from_buffer(buf, len, ppos, rwtm->last_sig,
+                                     sizeof(rwtm->last_sig));
        rwtm->last_sig_done = false;
 
        return ret;
@@ -367,8 +373,7 @@ static ssize_t do_sign_write(struct file *file, const char __user *buf,
        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)
+       if (len != SHA512_DIGEST_SIZE)
                return -EINVAL;
 
        /* if last result is not zero user has not read that information yet */
@@ -389,17 +394,18 @@ static ssize_t do_sign_write(struct file *file, const char __user *buf,
         *   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);
+       memset(rwtm->buf, 0, sizeof(u32));
+       ret = simple_write_to_buffer(rwtm->buf + sizeof(u32),
+                                    SHA512_DIGEST_SIZE, &dummy, buf, len);
        if (ret < 0)
                goto unlock_mutex;
-       be32_to_cpu_array(rwtm->buf, rwtm->buf, 17);
+       be32_to_cpu_array(rwtm->buf, rwtm->buf, MOX_ECC_NUMBER_WORDS);
 
        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;
+       msg.args[2] = rwtm->buf_phys + MOX_ECC_NUMBER_LEN;
+       msg.args[3] = rwtm->buf_phys + 2 * MOX_ECC_NUMBER_LEN;
        ret = mbox_send_message(rwtm->mbox, &msg);
        if (ret < 0)
                goto unlock_mutex;
@@ -417,8 +423,10 @@ static ssize_t do_sign_write(struct file *file, const char __user *buf,
         * 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);
+       memcpy(rwtm->last_sig, rwtm->buf + MOX_ECC_NUMBER_LEN,
+              sizeof(rwtm->last_sig));
+       cpu_to_be32_array(rwtm->last_sig, rwtm->last_sig,
+                         MOX_ECC_SIGNATURE_WORDS);
        rwtm->last_sig_done = true;
 
        mutex_unlock(&rwtm->busy);