Add a --master-key option

This lets the user override the default location for the master key
when used with --keygen

Part of 16769.

changes/feature16769

@@ -1,3 +1,7 @@
   o Minor features (ed25519):
     - Add a --newpass option to allow changing or removing the
-      passphrase of an encrypted key.
+      passphrase of an encrypted key with tor --keygen. Implements
+      part of ticket 16769.
+    - Add a --master-key option to allow overriding the location of
+      the master key when running tor --keygen.  Implements part of
+      ticket 16769.

src/or/config.c

@@ -762,6 +762,7 @@ or_options_free(or_options_t *options)
   }
   tor_free(options->BridgePassword_AuthDigest_);
   tor_free(options->command_arg);
+  tor_free(options->master_key_fname);
   config_free(&options_format, options);
 }
 
@@ -1919,6 +1920,7 @@ static const struct {
   { "--list-fingerprint",     TAKES_NO_ARGUMENT },
   { "--keygen",               TAKES_NO_ARGUMENT },
   { "--newpass",              TAKES_NO_ARGUMENT },
+  { "--master-key",           ARGUMENT_NECESSARY },
   { "--no-passphrase",        TAKES_NO_ARGUMENT },
   { "--passphrase-fd",        ARGUMENT_NECESSARY },
   { "--verify-config",        TAKES_NO_ARGUMENT },
@@ -4547,6 +4549,19 @@ options_init_from_torrc(int argc, char **argv)
     }
   }
 
+  {
+    const config_line_t *key_line = config_line_find(cmdline_only_options,
+                                                     "--master-key");
+    if (key_line) {
+      if (command != CMD_KEYGEN) {
+        log_err(LD_CONFIG, "--master-key without --keygen!");
+        exit(1);
+      } else {
+        get_options_mutable()->master_key_fname = tor_strdup(key_line->value);
+      }
+    }
+  }
+
  err:
 
   tor_free(cf);

src/or/or.h

@@ -4303,6 +4303,7 @@ typedef struct {
   int use_keygen_passphrase_fd;
   int keygen_passphrase_fd;
   int change_key_passphrase;
+  char *master_key_fname;
 } or_options_t;
 
 /** Persistent state for an onion router, as saved to disk. */

src/or/routerkeys.c

@@ -258,6 +258,9 @@ write_secret_key(const ed25519_secret_key_t *key, int encrypted,
  *
  * If INIT_ED_KEY_SUGGEST_KEYGEN is set, have log messages about failures
  * refer to the --keygen option.
+ *
+ * If INIT_ED_KEY_EXPLICIT_FNAME is set, use the provided file name for the
+ * secret key file, encrypted or not.
  */
 ed25519_keypair_t *
 ed_key_init_from_file(const char *fname, uint32_t flags,
@@ -279,6 +282,7 @@ ed_key_init_from_file(const char *fname, uint32_t flags,
   const int norepair = !! (flags & INIT_ED_KEY_NO_REPAIR);
   const int split = !! (flags & INIT_ED_KEY_SPLIT);
   const int omit_secret = !! (flags &  INIT_ED_KEY_OMIT_SECRET);
+  const int explicit_fname = !! (flags & INIT_ED_KEY_EXPLICIT_FNAME);
 
   /* we don't support setting both of these flags at once. */
   tor_assert((flags & (INIT_ED_KEY_NO_REPAIR|INIT_ED_KEY_NEEDCERT)) !=
@@ -291,8 +295,13 @@ ed_key_init_from_file(const char *fname, uint32_t flags,
   char *got_tag = NULL;
   ed25519_keypair_t *keypair = tor_malloc_zero(sizeof(ed25519_keypair_t));
 
-  tor_asprintf(&secret_fname, "%s_secret_key", fname);
-  tor_asprintf(&encrypted_secret_fname, "%s_secret_key_encrypted", fname);
+  if (explicit_fname) {
+    secret_fname = tor_strdup(fname);
+    encrypted_secret_fname = tor_strdup(fname);
+  } else {
+    tor_asprintf(&secret_fname, "%s_secret_key", fname);
+    tor_asprintf(&encrypted_secret_fname, "%s_secret_key_encrypted", fname);
+  }
   tor_asprintf(&public_fname, "%s_public_key", fname);
   tor_asprintf(&cert_fname, "%s_cert", fname);
 
@@ -729,7 +738,12 @@ load_ed_keys(const or_options_t *options, time_t now)
       goto err;
     }
     tor_free(fname);
-    fname = options_get_datadir_fname2(options, "keys", "ed25519_master_id");
+    if (options->master_key_fname) {
+      fname = tor_strdup(options->master_key_fname);
+      flags |= INIT_ED_KEY_EXPLICIT_FNAME;
+    } else {
+      fname = options_get_datadir_fname2(options, "keys", "ed25519_master_id");
+    }
     id = ed_key_init_from_file(
              fname,
              flags,

src/or/routerkeys.h

@@ -17,6 +17,7 @@
 #define INIT_ED_KEY_TRY_ENCRYPTED               (1u<<8)
 #define INIT_ED_KEY_NO_REPAIR                   (1u<<9)
 #define INIT_ED_KEY_SUGGEST_KEYGEN              (1u<<10)
+#define INIT_ED_KEY_EXPLICIT_FNAME              (1u<<11)
 
 struct tor_cert_st;
 ed25519_keypair_t *ed_key_init_from_file(const char *fname, uint32_t flags,