Fix unbounded resource usage in crypto and rand SQL functions (#94)

lib/src/err/mod.rs

@@ -77,7 +77,7 @@ pub enum Error {
 		message: String,
 	},
 
-	/// The wrong number of arguments was given for the specified function
+	/// The wrong quantity or magnitude of arguments was given for the specified function
 	#[error("Incorrect arguments for function {name}(). {message}")]
 	InvalidArguments {
 		name: String,

lib/src/fnc/crypto.rs

@@ -39,23 +39,72 @@ pub fn sha512(_: &Context, mut args: Vec<Value>) -> Result<Value, Error> {
 	Ok(val.into())
 }
 
+/// Allowed to cost this much more than default setting for each hash function.
+const COST_ALLOWANCE: u32 = 4;
+
+/// Like verify_password, but takes a closure to determine whether the cost of performing the
+/// operation is not too high.
+macro_rules! bounded_verify_password {
+	($algo: ident, $instance: expr, $password: expr, $hash: expr, $bound: expr) => {
+		if let (Some(salt), Some(expected_output)) = (&$hash.salt, &$hash.hash) {
+			if let Some(params) =
+				<$algo as PasswordHasher>::Params::try_from($hash).ok().filter($bound)
+			{
+				if let Ok(computed_hash) = $instance.hash_password_customized(
+					$password.as_ref(),
+					Some($hash.algorithm),
+					$hash.version,
+					params,
+					*salt,
+				) {
+					if let Some(computed_output) = &computed_hash.hash {
+						expected_output == computed_output
+					} else {
+						false
+					}
+				} else {
+					false
+				}
+			} else {
+				false
+			}
+		} else {
+			false
+		}
+	};
+
+	($algo: ident, $password: expr, $hash: expr, $bound: expr) => {
+		bounded_verify_password!($algo, $algo::default(), $password, $hash, $bound)
+	};
+}
+
 pub mod argon2 {
 
+	use super::COST_ALLOWANCE;
 	use crate::ctx::Context;
 	use crate::err::Error;
 	use crate::sql::value::Value;
 	use argon2::{
-		password_hash::{PasswordHash, PasswordHasher, PasswordVerifier, SaltString},
+		password_hash::{PasswordHash, PasswordHasher, SaltString},
 		Argon2,
 	};
 	use rand::rngs::OsRng;
 
-	pub fn cmp(_: &Context, mut args: Vec<Value>) -> Result<Value, Error> {
+	pub fn cmp(_: &Context, args: Vec<Value>) -> Result<Value, Error> {
-		let algo = Argon2::default();
+		let args: [Value; 2] = args.try_into().unwrap();
-		let hash = args.remove(0).as_string();
+		let [hash, pass] = args.map(Value::as_string);
-		let pass = args.remove(0).as_string();
+		type Params<'a> = <Argon2<'a> as PasswordHasher>::Params;
-		let test = PasswordHash::new(&hash).unwrap();
+		Ok(PasswordHash::new(&hash)
-		Ok(algo.verify_password(pass.as_ref(), &test).is_ok().into())
+			.ok()
+			.filter(|test| {
+				bounded_verify_password!(Argon2, pass, test, |params: &Params| {
+					params.m_cost() <= Params::DEFAULT_M_COST.saturating_mul(COST_ALLOWANCE)
+						&& params.t_cost() <= Params::DEFAULT_T_COST.saturating_mul(COST_ALLOWANCE)
+						&& params.p_cost() <= Params::DEFAULT_P_COST.saturating_mul(COST_ALLOWANCE)
+				})
+			})
+			.is_some()
+			.into())
 	}
 
 	pub fn gen(_: &Context, mut args: Vec<Value>) -> Result<Value, Error> {
@@ -69,20 +118,33 @@ pub mod argon2 {
 
 pub mod pbkdf2 {
 
+	use super::COST_ALLOWANCE;
 	use crate::ctx::Context;
 	use crate::err::Error;
 	use crate::sql::value::Value;
 	use pbkdf2::{
-		password_hash::{PasswordHash, PasswordHasher, PasswordVerifier, SaltString},
+		password_hash::{PasswordHash, PasswordHasher, SaltString},
 		Pbkdf2,
 	};
 	use rand::rngs::OsRng;
 
-	pub fn cmp(_: &Context, mut args: Vec<Value>) -> Result<Value, Error> {
+	pub fn cmp(_: &Context, args: Vec<Value>) -> Result<Value, Error> {
-		let hash = args.remove(0).as_string();
+		let args: [Value; 2] = args.try_into().unwrap();
-		let pass = args.remove(0).as_string();
+		let [hash, pass] = args.map(Value::as_string);
-		let test = PasswordHash::new(&hash).unwrap();
+		type Params = <Pbkdf2 as PasswordHasher>::Params;
-		Ok(Pbkdf2.verify_password(pass.as_ref(), &test).is_ok().into())
+		Ok(PasswordHash::new(&hash)
+			.ok()
+			.filter(|test| {
+				bounded_verify_password!(Pbkdf2, Pbkdf2, pass, test, |params: &Params| {
+					params.rounds <= Params::default().rounds.saturating_mul(COST_ALLOWANCE)
+						&& params.output_length
+							<= Params::default()
+								.output_length
+								.saturating_mul(COST_ALLOWANCE as usize)
+				})
+			})
+			.is_some()
+			.into())
 	}
 
 	pub fn gen(_: &Context, mut args: Vec<Value>) -> Result<Value, Error> {
@@ -100,15 +162,26 @@ pub mod scrypt {
 	use crate::sql::value::Value;
 	use rand::rngs::OsRng;
 	use scrypt::{
-		password_hash::{PasswordHash, PasswordHasher, PasswordVerifier, SaltString},
+		password_hash::{PasswordHash, PasswordHasher, SaltString},
 		Scrypt,
 	};
 
-	pub fn cmp(_: &Context, mut args: Vec<Value>) -> Result<Value, Error> {
+	pub fn cmp(_: &Context, args: Vec<Value>) -> Result<Value, Error> {
-		let hash = args.remove(0).as_string();
+		let args: [Value; 2] = args.try_into().unwrap();
-		let pass = args.remove(0).as_string();
+		let [hash, pass] = args.map(Value::as_string);
-		let test = PasswordHash::new(&hash).unwrap();
+		type Params = <Scrypt as PasswordHasher>::Params;
-		Ok(Scrypt.verify_password(pass.as_ref(), &test).is_ok().into())
+		Ok(PasswordHash::new(&hash)
+			.ok()
+			.filter(|test| {
+				bounded_verify_password!(Scrypt, Scrypt, pass, test, |params: &Params| {
+					// Scrypt is slow, use lower cost allowance.
+					params.log_n() <= Params::default().log_n().saturating_add(2)
+						&& params.r() <= Params::default().r().saturating_mul(2)
+						&& params.p() <= Params::default().p().saturating_mul(4)
+				})
+			})
+			.is_some()
+			.into())
 	}
 
 	pub fn gen(_: &Context, mut args: Vec<Value>) -> Result<Value, Error> {

lib/src/fnc/rand.rs

@@ -45,9 +45,18 @@ pub fn float(_: &Context, mut args: Vec<Value>) -> Result<Value, Error> {
 pub fn guid(_: &Context, mut args: Vec<Value>) -> Result<Value, Error> {
 	match args.len() {
 		1 => {
+			// Only need 53 to uniquely identify all atoms in observable universe.
+			const LIMIT: usize = 64;
 			let len = args.remove(0).as_int() as usize;
+			if len > LIMIT {
+				Err(Error::InvalidArguments {
+					name: String::from("rand::guid"),
+					message: format!("The maximum length of a GUID is {}.", LIMIT),
+				})
+			} else {
 				Ok(nanoid!(len, &ID_CHARS).into())
 			}
+		}
 		0 => Ok(nanoid!(20, &ID_CHARS).into()),
 		_ => unreachable!(),
 	}
@@ -68,33 +77,35 @@ pub fn int(_: &Context, mut args: Vec<Value>) -> Result<Value, Error> {
 }
 
 pub fn string(_: &Context, mut args: Vec<Value>) -> Result<Value, Error> {
+	// Limit how much time and bandwidth is spent.
+	const LIMIT: i64 = 2i64.pow(16);
 	match args.len() {
 		2 => match args.remove(0).as_int() {
-			min if min >= 0 => match args.remove(0).as_int() {
+			min if (0..=LIMIT).contains(&min) => match args.remove(0).as_int() {
-				max if max >= 0 && max < min => Ok(rand::thread_rng()
+				max if min <= max && max <= LIMIT => Ok(rand::thread_rng()
-					.sample_iter(&Alphanumeric)
-					.take(rand::thread_rng().gen_range(max as usize..=min as usize))
-					.map(char::from)
-					.collect::<String>()
-					.into()),
-				max if max >= 0 => Ok(rand::thread_rng()
 					.sample_iter(&Alphanumeric)
 					.take(rand::thread_rng().gen_range(min as usize..=max as usize))
 					.map(char::from)
 					.collect::<String>()
 					.into()),
+				max if max >= 0 && max <= min => Ok(rand::thread_rng()
+					.sample_iter(&Alphanumeric)
+					.take(rand::thread_rng().gen_range(max as usize..=min as usize))
+					.map(char::from)
+					.collect::<String>()
+					.into()),
 				_ => Err(Error::InvalidArguments {
 					name: String::from("rand::string"),
-					message: String::from("To generate a string of between X and Y characters in length, the 2 arguments must be positive numbers."),
+					message: format!("To generate a string of between X and Y characters in length, the 2 arguments must be positive numbers and no higher than {}.", LIMIT),
 				}),
 			},
 			_ => Err(Error::InvalidArguments {
 				name: String::from("rand::string"),
-				message: String::from("To generate a string of between X and Y characters in length, the 2 arguments must be positive numbers."),
+				message: format!("To generate a string of between X and Y characters in length, the 2 arguments must be positive numbers and no higher than {}.", LIMIT),
 			}),
 		},
 		1 => match args.remove(0).as_int() {
-			x if x >= 0 => Ok(rand::thread_rng()
+			x if (0..=LIMIT).contains(&x) => Ok(rand::thread_rng()
 				.sample_iter(&Alphanumeric)
 				.take(x as usize)
 				.map(char::from)
@@ -102,7 +113,7 @@ pub fn string(_: &Context, mut args: Vec<Value>) -> Result<Value, Error> {
 				.into()),
 			_ => Err(Error::InvalidArguments {
 				name: String::from("rand::string"),
-				message: String::from("To generate a string of X characters in length, the argument must be a positive number."),
+				message: format!("To generate a string of X characters in length, the argument must be a positive number and no higher than {}.", LIMIT),
 			}),
 		},
 		0 => Ok(rand::thread_rng()

lib/src/fnc/string.rs

@@ -36,7 +36,15 @@ pub fn repeat(_: &Context, args: Vec<Value>) -> Result<Value, Error> {
 	let [val_arg, num_arg]: [Value; 2] = args.try_into().unwrap();
 	let val = val_arg.as_string();
 	let num = num_arg.as_int() as usize;
+	const LIMIT: usize = 2usize.pow(20);
+	if val.len().saturating_mul(num) > LIMIT {
+		Err(Error::InvalidArguments {
+			name: String::from("string::repeat"),
+			message: format!("Output must not exceed {} bytes.", LIMIT),
+		})
+	} else {
 		Ok(val.repeat(num).into())
+	}
 }
 
 pub fn replace(_: &Context, args: Vec<Value>) -> Result<Value, Error> {