n_signer/src/secure_mem.c

#define _GNU_SOURCE

/* NSIGNER_HEADERLESS_DECLS_BEGIN */
#include <stddef.h>
#include <stdint.h>
#include <sys/types.h>
#include <cJSON.h>

/* from secure_mem.h */


/*
 * Secure memory buffer — mlock'd, zeroized on free.
 * Used for mnemonic phrases, private keys, and any sensitive material.
 */
typedef struct {
    void *data;       /* pointer to locked allocation */
    size_t size;      /* usable size in bytes */
    int locked;       /* 1 if mlock succeeded */
} secure_buf_t;

/* Allocate a secure buffer of `size` bytes. Returns 0 on success, -1 on failure. */
int secure_buf_alloc(secure_buf_t *buf, size_t size);

/* Zeroize and free a secure buffer. Always succeeds (idempotent). */
void secure_buf_free(secure_buf_t *buf);

/* Zeroize `len` bytes at `ptr` in a way the compiler cannot optimize away. */
void secure_memzero(void *ptr, size_t len);


/* from mnemonic.h */


/* Maximum mnemonic length: 24 words * 10 chars avg + spaces + null = 256 is safe */
#define MNEMONIC_MAX_LEN 256

/*
 * Mnemonic state — holds the loaded mnemonic in secure memory.
 * Only one mnemonic is active at a time per process.
 */
typedef struct {
    secure_buf_t buf;       /* secure storage for the mnemonic string */
    int loaded;             /* 1 if a mnemonic is currently loaded */
    int word_count;         /* 12, 15, 18, 21, or 24 */
} mnemonic_state_t;

/* Initialize mnemonic state (must be called before use). */
void mnemonic_init(mnemonic_state_t *state);

/* Load a mnemonic string into secure memory. Validates word count (12/15/18/21/24).
 * Returns 0 on success, -1 on invalid input, -2 on memory error. */
int mnemonic_load(mnemonic_state_t *state, const char *phrase);

/* Zeroize and unload the mnemonic. Idempotent. */
void mnemonic_unload(mnemonic_state_t *state);

/* Check if a mnemonic is currently loaded. */
int mnemonic_is_loaded(const mnemonic_state_t *state);

/* Get the mnemonic string (only valid while loaded). Returns NULL if not loaded. */
const char *mnemonic_get_phrase(const mnemonic_state_t *state);

/* Generate a new BIP-39 mnemonic phrase (12/15/18/21/24 words) into out.
 * Returns 0 on success, -1 on invalid arguments or generation failure. */
int mnemonic_generate(int word_count, char *out, size_t out_len);


/* from role_table.h */


/* Maximum limits */
#define ROLE_NAME_MAX 64
#define ROLE_PATH_MAX 128
#define ROLE_PURPOSE_MAX 32
#define ROLE_CURVE_MAX 16
#define ROLE_PUBKEY_HEX_MAX 66 /* 64 hex chars + null + pad */
#define ROLE_TABLE_MAX_ENTRIES 256

/* Purpose enum for fast comparison (string form kept for config/display) */
typedef enum {
    PURPOSE_NOSTR = 0,
    PURPOSE_BITCOIN,
    PURPOSE_SSH,
    PURPOSE_AGE,
    PURPOSE_FIPS,
    PURPOSE_UNKNOWN
} role_purpose_t;

/* Curve enum */
typedef enum {
    CURVE_SECP256K1 = 0,
    CURVE_ED25519,
    CURVE_X25519,
    CURVE_UNKNOWN
} role_curve_t;

/* Selector type — how this role's key is addressed */
typedef enum {
    SELECTOR_NOSTR_INDEX, /* uses nostr_index shorthand */
    SELECTOR_ROLE_PATH    /* uses explicit full path */
} role_selector_type_t;

/* A single role entry */
typedef struct {
    char name[ROLE_NAME_MAX];
    char purpose_str[ROLE_PURPOSE_MAX];
    char curve_str[ROLE_CURVE_MAX];
    role_purpose_t purpose;
    role_curve_t curve;
    role_selector_type_t selector_type;
    int nostr_index;                         /* valid if selector_type == SELECTOR_NOSTR_INDEX */
    char role_path[ROLE_PATH_MAX];           /* valid if selector_type == SELECTOR_ROLE_PATH */
    char pubkey_hex[ROLE_PUBKEY_HEX_MAX];    /* filled after derivation, empty until then */
    int derived;                             /* 1 if pubkey_hex has been populated */
} role_entry_t;

/* The role table */
typedef struct {
    role_entry_t entries[ROLE_TABLE_MAX_ENTRIES];
    int count;
} role_table_t;

/* Initialize an empty role table */
void role_table_init(role_table_t *table);

/* Add a role entry. Returns 0 on success, -1 if table full, -2 if name duplicate. */
int role_table_add(role_table_t *table, const role_entry_t *entry);

/* Find a role by name. Returns pointer to entry or NULL. */
role_entry_t *role_table_find_by_name(role_table_t *table, const char *name);

/* Find a role by nostr_index. Returns pointer or NULL. */
role_entry_t *role_table_find_by_nostr_index(role_table_t *table, int index);

/* Find a role by role_path. Returns pointer or NULL. */
role_entry_t *role_table_find_by_path(role_table_t *table, const char *path);

/* Get the default role (named "main"). Returns pointer or NULL if no "main" role. */
role_entry_t *role_table_get_default(role_table_t *table);

/* Parse purpose string to enum */
role_purpose_t role_purpose_from_str(const char *s);

/* Parse curve string to enum */
role_curve_t role_curve_from_str(const char *s);

/* Purpose enum to string */
const char *role_purpose_to_str(role_purpose_t p);

/* Curve enum to string */
const char *role_curve_to_str(role_curve_t c);


/* from selector.h */


/* Error codes for selector resolution */
#define SELECTOR_OK                 0
#define SELECTOR_ERR_AMBIGUOUS     -1   /* multiple selectors specified */
#define SELECTOR_ERR_NOT_FOUND     -2   /* no matching role in table */
#define SELECTOR_ERR_NO_DEFAULT    -3   /* no selector given and no "main" role exists */

/* Parsed selector from a request's options object */
typedef struct {
    int has_role;          /* 1 if "role" field was present */
    char role_name[ROLE_NAME_MAX];

    int has_nostr_index;   /* 1 if "nostr_index" field was present */
    int nostr_index;

    int has_role_path;     /* 1 if "role_path" field was present */
    char role_path[ROLE_PATH_MAX];
} selector_request_t;

/* Initialize a selector request (all fields zeroed/unset) */
void selector_request_init(selector_request_t *req);

/*
 * Resolve a selector request against the role table.
 * On success (returns SELECTOR_OK), *out points to the matched role_entry_t.
 * On failure, returns one of the SELECTOR_ERR_* codes and *out is NULL.
 */
int selector_resolve(const selector_request_t *req, role_table_t *table, role_entry_t **out);

/*
 * Return a human-readable error string for a selector error code.
 */
const char *selector_strerror(int err);


/* from enforcement.h */


/* Error codes */
#define ENFORCE_OK                0
#define ENFORCE_ERR_PURPOSE      -1 /* purpose mismatch */
#define ENFORCE_ERR_CURVE        -2 /* curve mismatch */
#define ENFORCE_ERR_UNKNOWN_VERB -3 /* verb not recognized */

/* Known verbs */
#define VERB_SIGN_EVENT     "sign_event"
#define VERB_GET_PUBLIC_KEY "get_public_key"
#define VERB_NIP44_ENCRYPT  "nip44_encrypt"
#define VERB_NIP44_DECRYPT  "nip44_decrypt"
#define VERB_NIP04_ENCRYPT  "nip04_encrypt"
#define VERB_NIP04_DECRYPT  "nip04_decrypt"

/*
 * Check whether `verb` is allowed to execute against `role`.
 * Returns ENFORCE_OK if allowed, or an ENFORCE_ERR_* code.
 *
 * The enforcement rules are:
 *   - All nostr verbs (sign_event, get_public_key, nip44_*, nip04_*) require:
 *     purpose == PURPOSE_NOSTR and curve == CURVE_SECP256K1
 *   - Unknown verbs return ENFORCE_ERR_UNKNOWN_VERB (fail-closed).
 */
int enforce_verb_role(const char *verb, const role_entry_t *role);

/*
 * Return a human-readable error string for an enforcement error code.
 */
const char *enforce_strerror(int err);


/* from policy.h */


#define POLICY_MAX_ENTRIES    32
#define POLICY_MAX_VERBS      16
#define POLICY_MAX_ROLES      16
#define POLICY_MAX_PURPOSES   8
#define POLICY_VERB_MAX_LEN   32
#define POLICY_CALLER_MAX_LEN 160

/* Prompt behavior */
typedef enum {
    PROMPT_NEVER = 0,
    PROMPT_FIRST_PER_BOOT,
    PROMPT_EVERY_REQUEST,
    PROMPT_DENY
} prompt_mode_t;

typedef enum {
    POLICY_SOURCE_DEFAULT = 0,   /* the catch-all entry */
    POLICY_SOURCE_PREAPPROVE,    /* from --preapprove CLI flag */
    POLICY_SOURCE_SESSION_GRANT  /* from prompt [a] during session */
} policy_source_t;

/* A single policy entry */
typedef struct {
    char caller[POLICY_CALLER_MAX_LEN];   /* e.g. "uid:1000" or "*" for any */
    char verbs[POLICY_MAX_VERBS][POLICY_VERB_MAX_LEN];
    int verb_count;
    char roles[POLICY_MAX_ROLES][ROLE_NAME_MAX];
    int role_count;
    char purposes[POLICY_MAX_PURPOSES][ROLE_PURPOSE_MAX];
    int purpose_count;
    prompt_mode_t prompt;
    policy_source_t source;
} policy_entry_t;

/* Policy table */
typedef struct {
    policy_entry_t entries[POLICY_MAX_ENTRIES];
    int count;
} policy_table_t;

/* Policy check result */
#define POLICY_ALLOW     0
#define POLICY_DENY     -1
#define POLICY_PROMPT   -2   /* would need user confirmation */
#define POLICY_NO_MATCH -3   /* no policy entry matched (fail-closed = deny) */

/* Initialize policy table */
void policy_table_init(policy_table_t *table);

/* Initialize default policy: allow same-uid, deny others */
void policy_init_default(policy_table_t *table, uid_t owner_uid);

/* Add a policy entry. Returns 0 on success, -1 if full. */
int policy_table_add(policy_table_t *table, const policy_entry_t *entry);

/*
 * Check whether caller_id is allowed to invoke `verb` on `role_name` with given `purpose`.
 * Returns POLICY_ALLOW, POLICY_DENY, POLICY_PROMPT, or POLICY_NO_MATCH.
 */
int policy_check(const policy_table_t *table, const char *caller_id,
                 const char *verb, const char *role_name, const char *purpose,
                 policy_source_t *out_source);

/* Parse prompt mode from string */
prompt_mode_t prompt_mode_from_str(const char *s);

/* Prompt mode to string */
const char *prompt_mode_to_str(prompt_mode_t m);


/* from crypto.h */


/* Per-role derived key material (stored in secure memory) */
typedef struct {
    secure_buf_t private_key;  /* 32 bytes, mlock'd */
    unsigned char public_key[32];
    char pubkey_hex[65];       /* 64 hex chars + null */
    char npub[128];            /* bech32 npub */
    int valid;
} derived_key_t;

/* Key store — holds derived keys for all roles */
typedef struct {
    derived_key_t keys[ROLE_TABLE_MAX_ENTRIES];
    int count;
} key_store_t;

/* Derive keys for all roles in the table using the loaded mnemonic.
 * Populates key_store and sets role->pubkey_hex and role->derived for each role.
 * Only derives for roles with purpose=nostr and curve=secp256k1 (for now).
 * Returns number of keys derived, or -1 on error. */
int crypto_derive_all(key_store_t *store, role_table_t *table, const mnemonic_state_t *mnemonic);

/* Get the derived private key for a role (by table index). Returns NULL if not derived. */
const unsigned char *crypto_get_private_key(const key_store_t *store, int role_index);

/* Get the derived public key hex for a role. Returns NULL if not derived. */
const char *crypto_get_pubkey_hex(const key_store_t *store, int role_index);

/* Sign a Nostr event. event_json is the unsigned event JSON string.
 * Returns a newly-allocated string containing the signed event JSON, or NULL on error.
 * Caller must free() the returned string. */
char *crypto_sign_event(const key_store_t *store, int role_index, const char *event_json);

/* Zeroize all derived keys in the store. */
void crypto_wipe(key_store_t *store);


/* from dispatcher.h */


/* Dispatcher context — holds references to shared state */
typedef struct {
    role_table_t *role_table;
    mnemonic_state_t *mnemonic;
    key_store_t *key_store;
} dispatcher_ctx_t;

/* Initialize dispatcher context */
void dispatcher_init(dispatcher_ctx_t *ctx, role_table_t *table, mnemonic_state_t *mnemonic, key_store_t *key_store);

/*
 * Process a JSON-RPC request string and produce a JSON-RPC response string.
 *
 * The caller owns the returned string and must free() it.
 * Returns NULL only on catastrophic allocation failure.
 *
 * Response format on success:
 *   { "id": "...", "result": "..." }
 *
 * Response format on error:
 *   { "id": "...", "error": { "code": <int>, "message": "..." } }
 *
 * Error codes:
 *   -32700  Parse error (invalid JSON)
 *   -32600  Invalid request (missing id/method/params)
 *   -32601  Method not found (unknown verb after enforcement)
 *   -32602  Invalid params
 *   1001    ambiguous_role_selector
 *   1002    role_not_found
 *   1003    no_default_role
 *   1004    purpose_mismatch
 *   1005    curve_mismatch
 *   1006    mnemonic_not_loaded
 */
char *dispatcher_handle_request(dispatcher_ctx_t *ctx, const char *json_request);


/* from server.h */


#define SERVER_SOCKET_NAME_MAX 108
#define SERVER_MAX_MSG_SIZE    65536

/* Caller identity */
typedef struct {
    uid_t uid;
    gid_t gid;
    pid_t pid;
    char caller_id[POLICY_CALLER_MAX_LEN];  /* "uid:<n>" */
} caller_identity_t;

/* Server context */
typedef struct {
    char socket_name[SERVER_SOCKET_NAME_MAX]; /* abstract namespace name (without \0 prefix) */
    char last_error[256];
    int listen_fd;
    int running;
    dispatcher_ctx_t *dispatcher;
    policy_table_t *policy;
    int socket_name_explicit;
} server_ctx_t;

/* Initialize server context. socket_name is the abstract namespace name (e.g. "nsigner").
 * socket_name_explicit should be non-zero when provided via --socket-name override. */
void server_init(server_ctx_t *ctx, const char *socket_name, int socket_name_explicit,
                 dispatcher_ctx_t *dispatcher, policy_table_t *policy);

/* Start listening. Returns 0 on success, -1 on error. */
int server_start(server_ctx_t *ctx);

/* Get human-readable description of last server error. */
const char *server_last_error(const server_ctx_t *ctx);

/* Handle one pending connection (non-blocking). Returns 1 if handled, 0 if nothing pending, -1 on error.
 * activity_cb is called with a description string for the TUI activity log. */
typedef void (*server_activity_cb)(const char *message, void *user_data);
int server_handle_one(server_ctx_t *ctx, server_activity_cb cb, void *cb_data);

/* Stop server and close socket */
void server_stop(server_ctx_t *ctx);

/* Extract caller identity from connected fd */
int server_get_caller(int fd, caller_identity_t *out);


/* from socket_name.h */


/*
 * Generate random socket name in format: nsigner_<word1>_<word2>
 * Returns 0 on success, -1 on error.
 */
int socket_name_random(char *out, size_t out_len);


/* from main.h */
/*
 * nsigner main header - version information
 *
 * Version macros are auto-updated by increment_and_push.sh.
 */


/* Version information (auto-updated by build/version tooling) */
#define NSIGNER_VERSION_MAJOR 0
#define NSIGNER_VERSION_MINOR 0
#define NSIGNER_VERSION_PATCH 2
#define NSIGNER_VERSION "v0.0.2"


/* NSIGNER_HEADERLESS_DECLS_END */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>

/*
 * Zeroize memory in a way the compiler cannot optimize out.
 * Uses explicit_bzero when available, with a volatile fallback.
 */
void secure_memzero(void *ptr, size_t len) {
    if (ptr == NULL || len == 0) {
        return;
    }

#if defined(__GLIBC__) || defined(__linux__)
    explicit_bzero(ptr, len);
#else
    size_t i;
    volatile unsigned char *p = (volatile unsigned char *)ptr;

    for (i = 0; i < len; ++i) {
        p[i] = 0;
    }
#endif
}

/*
 * Allocate secure memory and attempt to lock it in RAM.
 * Returns 0 on success, -1 on allocation/argument failure.
 */
int secure_buf_alloc(secure_buf_t *buf, size_t size) {
    if (buf == NULL || size == 0) {
        return -1;
    }

    buf->data = malloc(size);
    if (buf->data == NULL) {
        buf->size = 0;
        buf->locked = 0;
        return -1;
    }

    buf->size = size;
    buf->locked = 0;

    if (mlock(buf->data, buf->size) == 0) {
        buf->locked = 1;
    } else {
        fprintf(stderr, "warning: secure_buf_alloc: mlock failed; continuing unlocked\n");
    }

    memset(buf->data, 0, buf->size);
    return 0;
}

/*
 * Zeroize and release secure memory.
 * Safe to call multiple times.
 */
void secure_buf_free(secure_buf_t *buf) {
    if (buf == NULL) {
        return;
    }

    if (buf->data != NULL && buf->size > 0) {
        secure_memzero(buf->data, buf->size);

        if (buf->locked) {
            (void)munlock(buf->data, buf->size);
        }

        free(buf->data);
    }

    buf->data = NULL;
    buf->size = 0;
    buf->locked = 0;
}