Add support for mnemonics in hsm_secret #8400
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rustyrussell
requested changes
Jul 8, 2025
common/hsm_secret.c
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| #include <ccan/tal/str/str.h> | ||
| #include <ccan/tal/tal.h> | ||
| #include <common/errcode.h> | ||
| #include <common/utils.h> | ||
| #include <common/hsm_secret.h> | ||
| #include <errno.h> | ||
| #include <termios.h> | ||
| #include <unistd.h> | ||
| #include <ccan/crypto/sha256/sha256.h> | ||
| #include <ccan/mem/mem.h> | ||
| #include <sodium.h> | ||
| #include <wally_bip39.h> | ||
| #include <sys/stat.h> | ||
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These need to be in alphabetical order!
common/hsm_secret.c
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| case HSM_SECRET_INVALID: | ||
| return false; | ||
| } | ||
| return false; |
common/hsm_secret.c
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| return HSM_SECRET_ENCRYPTED; | ||
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| /* Check if it starts with our type bytes (mnemonic formats) */ | ||
| if (len > 32) { |
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if (len < 32)
return HSM_SECRET_INVALID;
common/hsm_secret.c
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| static void hash_passphrase(const char *passphrase, u8 hash[PASSPHRASE_HASH_LEN]) | ||
| { | ||
| struct sha256 sha; | ||
| sha256(&sha, passphrase, strlen(passphrase)); | ||
| memcpy(hash, sha.u.u8, PASSPHRASE_HASH_LEN); | ||
| } |
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We have a sha256 type for a reason, let's use it, not convert to u8[]
common/hsm_secret.c
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| /* First 32 bytes are the stored passphrase hash */ | ||
| const u8 *stored_hash = hsm_secret; | ||
| u8 computed_hash[32]; | ||
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| hash_passphrase(passphrase, computed_hash); | ||
| return memcmp(stored_hash, computed_hash, 32) == 0; | ||
| } | ||
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struct sha256 actual, expected;
/* First 32 bytes are the stored passphrase hash */
memcpy(&expected, hsm_secret, sizeof(struct sha256));
sha256(&actual, passphrase, strlen(passphrase));
return sha256_eq(&expected, &actual);
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| if (strlen(passphrase) == 0) { | ||
| passphrase = NULL; |
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Mildly prefer if (streq(passphrase, "")) ?
| if (bip39_mnemonic_to_seed(mnemonic, passphrase, bip32_seed, sizeof(bip32_seed), &bip32_seed_len) != WALLY_OK) | ||
| errx(ERROR_LIBWALLY, "Unable to derive BIP32 seed from BIP39 mnemonic"); | ||
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| /* Write to file using your new mnemonic format */ | ||
| int fd = open(hsm_secret_path, O_CREAT|O_EXCL|O_WRONLY, 0400); | ||
| if (fd < 0) { | ||
| errx(ERROR_USAGE, "Unable to create hsm_secret file"); |
tools/hsmtool.c
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| sha256(&sha, passphrase, strlen(passphrase)); | ||
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| if (!write_all(fd, sha.u.u8, PASSPHRASE_HASH_LEN)) | ||
| errx(ERROR_USAGE, "Error writing passphrase hash to hsm_secret file"); |
tools/hsmtool.c
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| if (passphrase) { | ||
| /* Write passphrase hash (32 bytes) + mnemonic for protected format */ | ||
| struct sha256 sha; | ||
| sha256(&sha, passphrase, strlen(passphrase)); |
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This should be hash of the final seed. This is a bit trickier: we need hsm_secret to expose that "calculate seed from mnemonic and passphrase" function (or opencode it with libwally?)
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| u8 bip32_seed[BIP39_SEED_LEN_512]; | ||
| size_t bip32_seed_len; | ||
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| if (bip39_mnemonic_to_seed(mnemonic, passphrase, bip32_seed, sizeof(bip32_seed), &bip32_seed_len) != WALLY_OK) | ||
| errx(ERROR_LIBWALLY, "Unable to derive BIP32 seed from BIP39 mnemonic"); |
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We still need this for below.,
sangbida
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This is a newer API to replace hsm_encryption.c and hsm_encryption.c, this tidies up the API to be used and also cleans things up to support our new formts. Our hsm_secret formats now include: - Legacy 32-byte plain format - Legacy 73-byte encrypted format - New mnemonic format without passphrase (32 zero bytes + mnemonic) - New mnemonic format with passphrase (32-byte hash + mnemonic) This commit includes support to detect the format based on the file size and content structure. The hsm will store mnemonics in the hsm_secret file as: `passphraseHash`mnemonic`
Changelog-Added: `hsmtool` now supports hsm_secret files using a 12-word mnemonic.
In preparation for BIP-39, we need to hand the passphrase (if any) to HSMD. So we extend the hsmd wire protocol to allow that.
Changelog-Changed: hsmd: New nodes will now be created with a BIP-39 12-word phrase as their root secret.
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Important
25.09 FREEZE July 28TH: Non-bugfix PRs not ready by this date will wait for 25.12.
RC1 is scheduled on August 11th
The final release is scheduled for September 1st.
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