[rpcwallet] Clamp walletpassphrase value at 100M seconds

Larger values seem to trigger a bug on macos+libevent (resulting in the
rpc server stopping).

src/wallet/rpcwallet.cpp

@@ -2349,8 +2349,7 @@ UniValue walletpassphrase(const JSONRPCRequest& request)
             "This is needed prior to performing transactions related to private keys such as sending bitcoins\n"
             "\nArguments:\n"
             "1. \"passphrase\"     (string, required) The wallet passphrase\n"
-            "2. timeout            (numeric, required) The time to keep the decryption key in seconds. Limited to at most 1073741824 (2^30) seconds.\n"
-            "                                          Any value greater than 1073741824 seconds will be set to 1073741824 seconds.\n"
+            "2. timeout            (numeric, required) The time to keep the decryption key in seconds; capped at 100000000 (~3 years).\n"
             "\nNote:\n"
             "Issuing the walletpassphrase command while the wallet is already unlocked will set a new unlock\n"
             "time that overrides the old one.\n"
@@ -2383,9 +2382,10 @@ UniValue walletpassphrase(const JSONRPCRequest& request)
     if (nSleepTime < 0) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Timeout cannot be negative.");
     }
-    // Clamp timeout to 2^30 seconds
-    if (nSleepTime > (int64_t)1 << 30) {
-        nSleepTime = (int64_t)1 << 30;
+    // Clamp timeout
+    constexpr int64_t MAX_SLEEP_TIME = 100000000; // larger values trigger a macos/libevent bug?
+    if (nSleepTime > MAX_SLEEP_TIME) {
+        nSleepTime = MAX_SLEEP_TIME;
     }
 
     if (strWalletPass.length() > 0)

test/functional/wallet_encryption.py

@@ -64,14 +64,15 @@ class WalletEncryptionTest(BitcoinTestFramework):
         assert_raises_rpc_error(-8, "Timeout cannot be negative.", self.nodes[0].walletpassphrase, passphrase2, -10)
         # Check the timeout
         # Check a time less than the limit
-        expected_time = int(time.time()) + (1 << 30) - 600
-        self.nodes[0].walletpassphrase(passphrase2, (1 << 30) - 600)
+        MAX_VALUE = 100000000
+        expected_time = int(time.time()) + MAX_VALUE - 600
+        self.nodes[0].walletpassphrase(passphrase2, MAX_VALUE - 600)
         actual_time = self.nodes[0].getwalletinfo()['unlocked_until']
         assert_greater_than_or_equal(actual_time, expected_time)
         assert_greater_than(expected_time + 5, actual_time) # 5 second buffer
         # Check a time greater than the limit
-        expected_time = int(time.time()) + (1 << 30) - 1
-        self.nodes[0].walletpassphrase(passphrase2, (1 << 33))
+        expected_time = int(time.time()) + MAX_VALUE - 1
+        self.nodes[0].walletpassphrase(passphrase2, MAX_VALUE + 1000)
         actual_time = self.nodes[0].getwalletinfo()['unlocked_until']
         assert_greater_than_or_equal(actual_time, expected_time)
         assert_greater_than(expected_time + 5, actual_time) # 5 second buffer