OSS-Fuzz: OSS-Fuzz fuzzing integration

Signed-off-by: Arthur Chan <[email protected]>

Cargo.toml

@@ -7,6 +7,7 @@ members = [
     "password-auth",
     "pbkdf2",
     "scrypt",
+    "scrypt/fuzz",
     "sha-crypt",
     "yescrypt"
 ]

scrypt/fuzz/.gitignore

@@ -0,0 +1,4 @@
+target
+corpus
+artifacts
+coverage

scrypt/fuzz/Cargo.toml

@@ -0,0 +1,32 @@
+[package]
+name = "scrypt-fuzz"
+version = "0.0.0"
+publish = false
+edition = "2018"
+
+[package.metadata]
+cargo-fuzz = true
+
+[dependencies]
+libfuzzer-sys = "0.4"
+pbkdf2 = { version = "=0.13.0-pre.1", path = "../../pbkdf2" }
+salsa20 = { version = "=0.11.0-pre.2", default-features = false }
+sha2 = { version = "=0.11.0-pre.4", default-features = false }
+password-hash = { version = "0.6.0-rc.0", default-features = false, features = ["rand_core"], optional = true }
+hex = "0.4"
+base64 = "0.22.1"
+
+[features]
+default = ["simple", "std"]
+simple = ["password-hash"]
+std = ["password-hash/std"]
+
+[dependencies.scrypt]
+path = ".."
+
+[[bin]]
+name = "scrypt_fuzzer"
+path = "fuzz_targets/scrypt_fuzzer.rs"
+test = false
+doc = false
+bench = false

scrypt/fuzz/fuzz_targets/scrypt_fuzzer.rs

@@ -0,0 +1,138 @@
+// Copyright 2024 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#![no_main]
+
+use libfuzzer_sys::fuzz_target;
+use scrypt::{scrypt, Params};
+
+#[cfg(feature = "simple")]
+use {
+    password_hash::{PasswordHash, PasswordHasher, PasswordVerifier, SaltString},
+    scrypt::Scrypt,
+    password_hash::Ident,
+};
+
+#[cfg(feature = "simple")]
+const SAMPLE_HASH: &str =
+    "$scrypt$ln=16,r=8,p=1$aM15713r3Xsvxbi31lqr1Q$nFNh2CVHVjNldFVKDHDlm4CbdRSCdEBsjjJxD+iCs5E";
+
+// Generate random params
+fn fuzzed_params(data: &[u8]) -> Option<Params> {
+    if data.len() >= 4 {
+        let log_n = data[0] % 16; // Cap log_n to 16
+        let r = u32::from_le_bytes([data[1], data[2], data[3], 0]) % 32; // Cap r to a reasonable value like 32
+        let p = if data.len() > 4 { u32::from_le_bytes([data[4], data[5], data[6], 0]) % 16 } else { 1 };
+        let len = if data.len() > 7 { data[7] as usize % 65 } else { 32 };
+
+        Params::new(log_n, r, p, len).ok()
+    } else {
+        None
+    }
+}
+
+// Generate random salt value
+#[cfg(feature = "simple")]
+fn fuzzed_salt(data: &[u8]) -> Option<SaltString> {
+    let salt_data = if data.len() >= 16 {
+        &data[..16]
+    } else {
+        &data
+    };
+    SaltString::encode_b64(salt_data).ok()
+}
+
+// Validate the salt string
+fn validate_salt(salt_str: &str) -> bool {
+    // Check length
+    let length = salt_str.len();
+    if length < 4 || length > 64 {
+        return false;
+    }
+
+    for char in salt_str.chars() {
+        if !matches!(char, 'a'..='z' | 'A'..='Z' | '0'..='9' | '/' | '+' | '.' | '-') {
+            return false;
+        }
+    }
+
+    true
+}
+
+// Prepare random data by splitting random data
+fn split_fuzz_data<'a>(data: &'a [u8], splits: &[usize]) -> Vec<&'a [u8]> {
+    let mut result = Vec::new();
+    let mut start = 0;
+
+    for &split in splits {
+        if start + split <= data.len() {
+            result.push(&data[start..start + split]);
+            start += split;
+        } else {
+            result.push(&data[start..]);
+            break; 
+        }
+    }
+
+    result
+}
+
+fuzz_target!(|data: &[u8]| {
+    let params = fuzzed_params(data).unwrap_or_else(|| Params::new(16, 8, 1, 64).unwrap());
+    let splits = split_fuzz_data(data, &[32, 32, 32]);
+    let password = splits.get(0).unwrap_or(&data);
+    let salt = splits.get(1).unwrap_or(&data);
+    let mut result = vec![0u8; 256];
+
+    #[cfg(feature = "simple")]
+    if let Some(salt_string) = fuzzed_salt(salt) {
+        if !validate_salt(salt_string.as_str()) {
+            return;
+        }
+
+        let salt_value = salt_string.as_salt(); // Safe to use now
+
+        let formatted_hash = format!("$scrypt$ln=16,r=8,p=1${}$invalid$", hex::encode(password));
+
+        if let Ok(hash) = PasswordHash::new(SAMPLE_HASH).or_else(|_| PasswordHash::new(formatted_hash.as_str())) {
+            // Randomly choose the fuzz target function
+            let target_selector = if !data.is_empty() { data[0] % 5 } else { 0 };
+            match target_selector {
+                0 => {
+                    let _ = scrypt(password, salt, &params, &mut result);
+                },
+                1 => {
+                    let _ = Scrypt.verify_password(password, &hash).is_err();
+                },
+                2 => {
+                    let _ = Scrypt.hash_password_customized(password, Some(Ident::new_unwrap("scrypt")), None, params, salt_value);
+                },
+                3 => {
+                    if let Some(random_params) = fuzzed_params(password) {
+                        let _ = scrypt(password, salt, &random_params, &mut result);
+                    }
+                },
+                4 => {
+                    let _ = PasswordHash::new(SAMPLE_HASH).is_ok();
+                },
+                _ => {
+                    let _ = scrypt(password, salt, &params, &mut result);
+                },
+            }
+        }
+    } else {
+        // Skip this iteration if the salt is invalid
+        return;
+    }
+});