common: trivial changes from review.

diff --git a/common/hsm_secret.c b/common/hsm_secret.c
index b24b1f9a..62348627 100644
--- a/common/hsm_secret.c
+++ b/common/hsm_secret.c
@@ -107,9 +107,13 @@ enum hsm_secret_type detect_hsm_secret_type(const u8 *hsm_secret, size_t len)
 	/* Legacy 73-byte encrypted format */
 	if (len == ENCRYPTED_HSM_SECRET_LEN)
 		return HSM_SECRET_ENCRYPTED;
-	assert(len > sizeof(struct sha256));
-	/* Check if it starts with our type bytes (mnemonic formats) */
-	if (memeqzero(hsm_secret, 32))
+
+	/* Since HSM_SECRET_PLAIN_SIZE == 32, this must be true! */
+	assert(len >= sizeof(struct sha256));
+
+	/* First 32 bytes are the hash of the resulting seed: all 0
+	 * for "no passphrase" */
+	if (memeqzero(hsm_secret, sizeof(struct sha256)))
 		return HSM_SECRET_MNEMONIC_NO_PASS;
 	else
 		return HSM_SECRET_MNEMONIC_WITH_PASS;
@@ -200,8 +204,6 @@ const char *hsm_secret_error_str(enum hsm_secret_error err)
 		return "Invalid hsm_secret format";
 	case HSM_SECRET_ERR_TERMINAL:
 		return "Terminal error";
-	case HSM_SECRET_ERR_MEMORY:
-		return "Memory error";
 	}
 	return "Unknown error";
 }
@@ -403,7 +405,7 @@ static void restore_echo(const struct termios *saved_term)
 }
 
 /* Read line from stdin (uses tal allocation) */
-static char *read_line(const tal_t *ctx)
+static const char *read_line(const tal_t *ctx)
 {
 	char *line = NULL;
 	size_t size = 0;
@@ -433,7 +435,7 @@ const char *read_stdin_pass(const tal_t *ctx, enum hsm_secret_error *err)
 		return NULL;
 	}
 
-	char *input = read_line(ctx);
+	const char *input = read_line(ctx);
 	if (!input) {
 		if (echo_disabled)
 			restore_echo(&saved_term);
@@ -455,7 +457,7 @@ const char *read_stdin_mnemonic(const tal_t *ctx, enum hsm_secret_error *err)
 	printf("Introduce your BIP39 word list separated by space (at least 12 words):\n");
 	fflush(stdout);
 
-	char *line = read_line(ctx);
+	const char *line = read_line(ctx);
 	if (!line) {
 		*err = HSM_SECRET_ERR_INVALID_FORMAT;
 		return NULL;
diff --git a/common/hsm_secret.h b/common/hsm_secret.h
index 4ec44c9a..740f2ebc 100644
--- a/common/hsm_secret.h
+++ b/common/hsm_secret.h
@@ -32,7 +32,6 @@ enum hsm_secret_error {
 	HSM_SECRET_ERR_SEED_DERIVATION_FAILED,
 	HSM_SECRET_ERR_INVALID_FORMAT,
 	HSM_SECRET_ERR_TERMINAL,
-	HSM_SECRET_ERR_MEMORY
 };
 
 /**
@@ -40,7 +39,7 @@ enum hsm_secret_error {
  */
 struct hsm_secret {
 	enum hsm_secret_type type;
-	u8 *secret_data;          /* Variable length: 32 bytes (legacy) or 64 bytes (mnemonic) */
+	const u8 *secret_data;          /* Variable length: 32 bytes (legacy) or 64 bytes (mnemonic) */
 	const char *mnemonic;           /* NULL if not derived from mnemonic */
 };
 
@@ -71,7 +70,7 @@ bool hsm_secret_needs_passphrase(const u8 *hsm_secret, size_t len);
  * @hsm_secret - raw file contents
  * @len - length of file
  * @passphrase - passphrase, or NULL if not needed
- * @err - optional pointer to set error code on failure
+ * @err - pointer to set error code on failure
  *
  * Returns parsed `struct hsm_secret` or NULL on error.
  */
@@ -100,8 +99,8 @@ struct secret *get_encryption_key(const tal_t *ctx, const char *passphrase);
  * Returns true on success.
  */
 bool encrypt_legacy_hsm_secret(const struct secret *encryption_key,
-			const struct secret *hsm_secret,
-			u8 *output);
+			       const struct secret *hsm_secret,
+			       u8 *output);
 
 /**
  * Reads a passphrase from stdin, disabling terminal echo.
diff --git a/hsmd/hsmd.c b/hsmd/hsmd.c
index 957e5e84..7266b4f1 100644
--- a/hsmd/hsmd.c
+++ b/hsmd/hsmd.c
@@ -301,7 +301,6 @@ static void hsmd_send_init_reply_failure(enum hsm_secret_error error_code, enum
 static void create_hsm(int fd, const char *passphrase)
 {
 	u8 *hsm_secret_data;
-	size_t hsm_secret_len;
 	int ret;
 	/* Always create a mnemonic-based hsm_secret */
 	u8 entropy[BIP39_ENTROPY_LEN_128];
@@ -313,7 +312,6 @@ static void create_hsm(int fd, const char *passphrase)
 	/* Generate random entropy for new mnemonic */
 	randombytes_buf(entropy, sizeof(entropy));
 
-
 	/* Generate mnemonic from entropy */
 	tal_wally_start();
 	ret = bip39_mnemonic_from_bytes(NULL, entropy, sizeof(entropy), &mnemonic);
@@ -322,27 +320,26 @@ static void create_hsm(int fd, const char *passphrase)
 	if (ret != WALLY_OK) {
 		unlink_noerr("hsm_secret");
 		hsmd_send_init_reply_failure(HSM_SECRET_ERR_SEED_DERIVATION_FAILED, STATUS_FAIL_INTERNAL_ERROR,
-			                        "Failed to generate mnemonic from entropy");
+					     "Failed to generate mnemonic from entropy");
 	}
 
 	if (!mnemonic) {
 		unlink_noerr("hsm_secret");
 		hsmd_send_init_reply_failure(HSM_SECRET_ERR_SEED_DERIVATION_FAILED, STATUS_FAIL_INTERNAL_ERROR,
-			                        "Failed to get generated mnemonic");
+					     "Failed to get generated mnemonic");
 	}
 
 	/* Derive seed hash from mnemonic + passphrase (or zero if no passphrase) */
 	if (!derive_seed_hash(mnemonic, passphrase, &seed_hash)) {
 		unlink_noerr("hsm_secret");
 		hsmd_send_init_reply_failure(HSM_SECRET_ERR_SEED_DERIVATION_FAILED, STATUS_FAIL_INTERNAL_ERROR,
-			                        "Failed to derive seed hash from mnemonic");
+					     "Failed to derive seed hash from mnemonic");
 	}
 
 	/* Create hsm_secret format: seed_hash (32 bytes) + mnemonic */
 	hsm_secret_data = tal_arr(tmpctx, u8, 0);
 	towire_sha256(&hsm_secret_data, &seed_hash);
 	towire(&hsm_secret_data, mnemonic, strlen(mnemonic));
-	hsm_secret_len = tal_count(hsm_secret_data);
 
 	/* Derive the actual secret from mnemonic + passphrase for our global hsm_secret */
 	u8 bip32_seed[BIP39_SEED_LEN_512];
@@ -358,7 +355,7 @@ static void create_hsm(int fd, const char *passphrase)
 	}
 
 	/* Write the hsm_secret data to file */
-	if (!write_all(fd, hsm_secret_data, hsm_secret_len)) {
+	if (!write_all(fd, hsm_secret_data, tal_count(hsm_secret_data))) {
 		unlink_noerr("hsm_secret");
 		status_failed(STATUS_FAIL_INTERNAL_ERROR,
 		              "writing: %s", strerror(errno));
@@ -494,7 +491,7 @@ static struct io_plan *init_hsm(struct io_conn *conn,
 	u32 minversion, maxversion;
 	struct tlv_hsmd_init_tlvs *tlvs;
 	const u32 our_minversion = 4, our_maxversion = 6;
-	const char *hsm_passphrase = NULL;  /* Initialize to NULL */
+	const char *hsm_passphrase;
 
 	/* This must be lightningd. */
 	assert(is_lightningd(c));
@@ -531,6 +528,8 @@ static struct io_plan *init_hsm(struct io_conn *conn,
 	 * never sets that anymore), and we use the TLV instead. */
 	if (tlvs->hsm_passphrase)
 		hsm_passphrase = tlvs->hsm_passphrase;
+	else
+		hsm_passphrase = NULL;
 
 	if (!developer) {
 		assert(!dev_force_privkey);
@@ -637,6 +636,7 @@ static struct io_plan *handle_memleak(struct io_conn *conn,
 
 	memleak_ptr(memtable, dev_force_privkey);
 	memleak_ptr(memtable, dev_force_bip32_seed);
+
 	found_leak = dump_memleak(memtable, memleak_status_broken, NULL);
 	reply = towire_hsmd_dev_memleak_reply(NULL, found_leak);
 	return req_reply(conn, c, take(reply));
@@ -768,15 +768,16 @@ static struct io_plan *handle_client(struct io_conn *conn, struct client *c)
 	case WIRE_HSMD_CLIENT_HSMFD:
 		return pass_client_hsmfd(conn, c, c->msg_in);
 
-	case WIRE_HSMD_DEV_MEMLEAK:
-		if (developer)
-			return handle_memleak(conn, c, c->msg_in);
-		/* fall thru */
-
 	case WIRE_HSMD_DERIVE_BIP86_KEY:
 		return handle_derive_bip86_key(conn, c, c->msg_in);
 	case WIRE_HSMD_CHECK_BIP86_PUBKEY:
 		return handle_check_bip86_pubkey(conn, c, c->msg_in);
+
+	case WIRE_HSMD_DEV_MEMLEAK:
+		if (!developer)
+			break;
+		return handle_memleak(conn, c, c->msg_in);
+
 	case WIRE_HSMD_NEW_CHANNEL:
 	case WIRE_HSMD_SETUP_CHANNEL:
  	case WIRE_HSMD_CHECK_OUTPOINT: