core: Add optional password entropy checks

Cargo.toml

@@ -58,6 +58,7 @@ thiserror = "1.0.24"
 time = "0.3.7"
 trycmd = "0.15"
 url = "2.2.2"
+zxcvbn = "3.1.0"
 
 [package]
 name = "magic-wormhole"
@@ -100,6 +101,7 @@ thiserror = { workspace = true }
 futures = { workspace = true }
 url = { workspace = true, features = ["serde"] }
 percent-encoding = { workspace = true }
+zxcvbn = { workspace = true, optional = true }
 
 # Transit dependencies
 
@@ -143,6 +145,8 @@ eyre = { workspace = true }
 
 [features]
 
+# Check the entropy of custom codes. Will fail for any weak passwords.
+entropy = ["zxcvbn"]
 transfer = ["transit", "dep:tar", "dep:rmp-serde"]
 transit = [
     "dep:noise-rust-crypto",

cli/Cargo.toml

@@ -28,7 +28,7 @@ async-std = { workspace = true, features = ["attributes", "unstable"] }
 rand = { workspace = true }
 
 # CLI specific dependencies
-magic-wormhole = { path = "..", version = "0.7", features = ["all"] }
+magic-wormhole = { path = "..", version = "0.7", features = ["all", "entropy"] }
 clap = { workspace = true, features = ["cargo", "derive", "help"] }
 clap_complete = { workspace = true }
 env_logger = { workspace = true }
@@ -39,7 +39,9 @@ color-eyre = { workspace = true }
 number_prefix = { workspace = true }
 ctrlc = { workspace = true }
 qr2term = { workspace = true }
-arboard = { workspace = true, features = ["wayland-data-control"] } # Wayland by default, fallback to X11.
+arboard = { workspace = true, features = [
+    "wayland-data-control",
+] } # Wayland by default, fallback to X11.
 
 [dev-dependencies]
 trycmd = { workspace = true }