| // Copyright 2019 The Chromium OS Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| use std::cmp::min; |
| use std::fmt; |
| use std::mem::size_of; |
| use std::result::Result; |
| |
| use rand_core::{Error, ErrorKind, RngCore}; |
| |
| /// A random number generator that uses fuzzer input as the source of its |
| /// randomness. When run on the same input, it provides the same output, as |
| /// long as its methods are called in the same order and with the same |
| /// arguments. |
| pub struct FuzzRng<'a> { |
| buf: &'a [u8], |
| } |
| |
| impl<'a> FuzzRng<'a> { |
| /// Creates a new `FuzzRng` from `buf`, which should be part or all of an |
| /// input buffer provided by a fuzzing library. |
| pub fn new(buf: &'a [u8]) -> FuzzRng<'a> { |
| FuzzRng { buf: buf } |
| } |
| |
| /// Consumes `self` and returns the inner slice. |
| pub fn into_inner(self) -> &'a [u8] { |
| let FuzzRng { buf } = self; |
| buf |
| } |
| } |
| |
| impl<'a> RngCore for FuzzRng<'a> { |
| fn next_u32(&mut self) -> u32 { |
| let mut buf = [0u8; size_of::<u32>()]; |
| self.fill_bytes(&mut buf); |
| |
| u32::from_ne_bytes(buf) |
| } |
| |
| fn next_u64(&mut self) -> u64 { |
| let mut buf = [0u8; size_of::<u64>()]; |
| self.fill_bytes(&mut buf); |
| |
| u64::from_ne_bytes(buf) |
| } |
| |
| fn fill_bytes(&mut self, dest: &mut [u8]) { |
| let amt = min(self.buf.len(), dest.len()); |
| let (a, b) = self.buf.split_at(amt); |
| dest[..amt].copy_from_slice(a); |
| self.buf = b; |
| |
| if amt < dest.len() { |
| // We didn't have enough data to fill the whole buffer. Fill the rest |
| // with zeroes. The compiler is smart enough to turn this into a memset. |
| for b in &mut dest[amt..] { |
| *b = 0; |
| } |
| } |
| } |
| |
| fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> { |
| if self.buf.len() >= dest.len() { |
| Ok(self.fill_bytes(dest)) |
| } else { |
| Err(Error::new( |
| ErrorKind::Unavailable, |
| "not enough data in fuzzer input", |
| )) |
| } |
| } |
| } |
| |
| impl<'a> fmt::Debug for FuzzRng<'a> { |
| fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { |
| write!(f, "FuzzRng {{ {} bytes }}", self.buf.len()) |
| } |
| } |
| |
| #[cfg(test)] |
| mod tests { |
| use super::*; |
| |
| #[test] |
| fn gen_u32() { |
| let val = 0xc2a744u32; |
| let buf = val.to_ne_bytes(); |
| let mut rng = FuzzRng::new(&buf); |
| |
| assert_eq!(rng.next_u32(), val); |
| assert_eq!(rng.next_u32(), 0); |
| } |
| |
| #[test] |
| fn gen_u64() { |
| let val = 0xac75689deeu64; |
| let buf = val.to_ne_bytes(); |
| let mut rng = FuzzRng::new(&buf); |
| |
| assert_eq!(rng.next_u64(), val); |
| assert_eq!(rng.next_u64(), 0); |
| } |
| |
| #[test] |
| fn fill_bytes() { |
| let buf = &[ |
| 0xed, 0x90, 0xf3, 0xa4, 0x8f, 0xbf, 0x6e, 0xdb, 0x68, 0xb9, 0x1f, 0x9a, 0x13, 0xfc, |
| 0x9f, 0xc8, 0x9e, 0xfa, 0x4a, 0x02, 0x5e, 0xc8, 0xb1, 0xe5, 0x2d, 0x59, 0x22, 0x89, |
| 0x10, 0x23, 0xc3, 0x31, 0x6c, 0x42, 0x40, 0xce, 0xfe, 0x6e, 0x5c, 0x3d, 0x10, 0xba, |
| 0x0d, 0x11, 0xbc, 0x6a, 0x1f, 0x21, 0xc9, 0x72, 0x37, 0xba, 0xfa, 0x00, 0xb2, 0xa8, |
| 0x51, 0x6d, 0xb2, 0x94, 0xf2, 0x34, 0xf8, 0x3c, 0x21, 0xc9, 0x59, 0x24, 0xd8, 0x77, |
| 0x51, 0x3f, 0x64, 0xde, 0x19, 0xc8, 0xb3, 0x03, 0x26, 0x81, 0x85, 0x4c, 0xef, 0xb0, |
| 0xd5, 0xd8, 0x65, 0xe1, 0x89, 0x8f, 0xb7, 0x14, 0x9b, 0x0d, 0xd9, 0xcb, 0xda, 0x35, |
| 0xb2, 0xff, 0xd5, 0xd1, 0xae, 0x38, 0x55, 0xd5, 0x65, 0xba, 0xdc, 0xa1, 0x82, 0x62, |
| 0xbf, 0xe6, 0x3d, 0x7a, 0x8f, 0x13, 0x65, 0x2f, 0x4b, 0xdc, 0xcb, 0xee, 0xd8, 0x99, |
| 0x2c, 0x21, 0x97, 0xc8, 0x6e, 0x8e, 0x09, 0x0f, 0xf1, 0x4b, 0x85, 0xb5, 0x0f, 0x52, |
| 0x82, 0x7f, 0xe0, 0x23, 0xc5, 0x9a, 0x6a, 0x7c, 0xf1, 0x46, 0x7d, 0xbf, 0x3f, 0x14, |
| 0x0d, 0x41, 0x09, 0xd5, 0x63, 0x70, 0xa1, 0x0e, 0x04, 0x3c, 0x06, 0x0a, 0x0b, 0x5c, |
| 0x95, 0xaf, 0xbd, 0xf5, 0x4b, 0x7f, 0xbe, 0x8d, 0xe2, 0x09, 0xce, 0xa2, 0xf6, 0x1e, |
| 0x58, 0xd8, 0xda, 0xd4, 0x56, 0x56, 0xe1, 0x32, 0x30, 0xef, 0x0f, 0x2e, 0xed, 0xb9, |
| 0x14, 0x57, 0xa8, 0x8a, 0x9c, 0xd8, 0x58, 0x7f, 0xd9, 0x4f, 0x11, 0xb2, 0x7a, 0xcf, |
| 0xc0, 0xef, 0xf3, 0xc7, 0xc1, 0xc5, 0x1e, 0x86, 0x47, 0xc6, 0x42, 0x71, 0x15, 0xc8, |
| 0x25, 0x1d, 0x94, 0x00, 0x8d, 0x04, 0x37, 0xe7, 0xfe, 0xf6, 0x10, 0x28, 0xe5, 0xb2, |
| 0xef, 0x95, 0xa6, 0x53, 0x20, 0xf8, 0x51, 0xdb, 0x54, 0x99, 0x40, 0x4a, 0x7c, 0xd6, |
| 0x90, 0x4a, 0x55, 0xdc, 0x37, 0xb8, 0xbc, 0x0b, 0xc4, 0x54, 0xd1, 0x9b, 0xb3, 0x8c, |
| 0x09, 0x55, 0x77, 0xf5, 0x1b, 0xa7, 0x36, 0x06, 0x29, 0x4c, 0xa3, 0x26, 0x35, 0x1b, |
| 0x29, 0xa3, 0xa3, 0x45, 0x74, 0xee, 0x0b, 0x78, 0xf8, 0x69, 0x70, 0xa4, 0x1d, 0x11, |
| 0x7a, 0x91, 0xca, 0x4c, 0x83, 0xb3, 0xbf, 0xf6, 0x7f, 0x54, 0xca, 0xdb, 0x1f, 0xc4, |
| 0xd2, 0xb2, 0x23, 0xfa, 0xc0, 0x24, 0x77, 0x74, 0x61, 0x9e, 0x0b, 0x77, 0x49, 0x29, |
| 0xf1, 0xd9, 0xbf, 0xf0, 0x5e, 0x99, 0xa6, 0xf1, 0x00, 0xa4, 0x7f, 0xa0, 0xb1, 0x6b, |
| 0xd8, 0xbe, 0xef, 0xa0, 0xa1, 0xa5, 0x33, 0x9c, 0xc3, 0x95, 0xaa, 0x9f, |
| ]; |
| |
| let mut rng = FuzzRng::new(&buf[..]); |
| let mut dest = Vec::with_capacity(buf.len()); |
| for chunk in buf.chunks(11) { |
| dest.resize(chunk.len(), 0); |
| rng.fill_bytes(&mut dest); |
| |
| assert_eq!(chunk, &*dest); |
| } |
| |
| dest.resize(97, 0x2c); |
| rng.fill_bytes(&mut dest); |
| |
| let mut zero_buf = Vec::with_capacity(dest.len()); |
| zero_buf.resize(dest.len(), 0); |
| |
| assert_eq!(zero_buf, dest); |
| } |
| |
| #[test] |
| fn try_fill_bytes() { |
| let buf = &[ |
| 0xdb, 0x35, 0xad, 0x4e, 0x9d, 0xf5, 0x2d, 0xf6, 0x0d, 0xc5, 0xd2, 0xfc, 0x9f, 0x4c, |
| 0xb5, 0x12, 0xe3, 0x78, 0x40, 0x8d, 0x8b, 0xa1, 0x5c, 0xfe, 0x66, 0x49, 0xa9, 0xc0, |
| 0x43, 0xa0, 0x95, 0xae, 0x31, 0x99, 0xd2, 0xaa, 0xbc, 0x85, 0x9e, 0x4b, 0x08, 0xca, |
| 0x59, 0x21, 0x2b, 0x66, 0x37, 0x6a, 0xb9, 0xb2, 0xd8, 0x71, 0x84, 0xdd, 0xf6, 0x47, |
| 0xa5, 0xb9, 0x87, 0x9f, 0x24, 0x97, 0x01, 0x65, 0x15, 0x38, 0x01, 0xd6, 0xb6, 0xf2, |
| 0x80, |
| ]; |
| let mut rng = FuzzRng::new(&buf[..]); |
| let mut dest = Vec::with_capacity(buf.len()); |
| for chunk in buf.chunks(13) { |
| dest.resize(chunk.len(), 0); |
| rng.try_fill_bytes(&mut dest) |
| .expect("failed to fill bytes while data is remaining"); |
| |
| assert_eq!(chunk, &*dest); |
| } |
| |
| dest.resize(buf.len(), 0); |
| rng.try_fill_bytes(&mut dest) |
| .expect_err("successfully filled bytes when no data is remaining"); |
| } |
| |
| #[test] |
| fn try_fill_bytes_partial() { |
| let buf = &[ |
| 0x8b, 0xe3, 0x20, 0x8d, 0xe0, 0x0b, 0xbe, 0x51, 0xa6, 0xec, 0x8a, 0xb5, 0xd6, 0x17, |
| 0x04, 0x3f, 0x87, 0xae, 0xc8, 0xe8, 0xf8, 0xe7, 0xd4, 0xbd, 0xf3, 0x4e, 0x74, 0xcf, |
| 0xbf, 0x0e, 0x9d, 0xe5, 0x78, 0xc3, 0xe6, 0x44, 0xb8, 0xd1, 0x40, 0xda, 0x63, 0x9f, |
| 0x48, 0xf4, 0x09, 0x9c, 0x5c, 0x5f, 0x36, 0x0b, 0x0d, 0x2b, 0xe3, 0xc7, 0xcc, 0x3e, |
| 0x9a, 0xb9, 0x0a, 0xca, 0x6d, 0x90, 0x77, 0x3b, 0x7a, 0x50, 0x16, 0x13, 0x5d, 0x20, |
| 0x70, 0xc0, 0x88, 0x04, 0x9c, 0xac, 0x2b, 0xd6, 0x61, 0xa0, 0xbe, 0xa4, 0xff, 0xbd, |
| 0xac, 0x9c, 0xa1, 0xb2, 0x95, 0x26, 0xeb, 0x99, 0x46, 0x67, 0xe4, 0xcd, 0x88, 0x7b, |
| 0x20, 0x4d, 0xb2, 0x92, 0x40, 0x9f, 0x1c, 0xbd, 0xba, 0x22, 0xff, 0xca, 0x89, 0x3c, |
| 0x3b, |
| ]; |
| |
| let mut rng = FuzzRng::new(&buf[..]); |
| let mut dest = Vec::with_capacity(buf.len()); |
| dest.resize((buf.len() / 2) + 1, 0); |
| |
| // The first time should be successful because there is enough data left |
| // in the buffer. |
| rng.try_fill_bytes(&mut dest).expect("failed to fill bytes"); |
| assert_eq!(&buf[..dest.len()], &*dest); |
| |
| // The second time should fail because while there is data in the buffer it |
| // is not enough to fill `dest`. |
| rng.try_fill_bytes(&mut dest) |
| .expect_err("filled bytes with insufficient data in buffer"); |
| |
| // This should succeed because `dest` is exactly big enough to hold all the remaining |
| // data in the buffer. |
| dest.resize(buf.len() - dest.len(), 0); |
| rng.try_fill_bytes(&mut dest) |
| .expect("failed to fill bytes with exact-sized buffer"); |
| assert_eq!(&buf[buf.len() - dest.len()..], &*dest); |
| } |
| } |