solana-with-rpc-optimizations/programs/bpf_loader/src/bpf_verifier.rs

use crate::BPFError;
use solana_rbpf::ebpf;
use thiserror::Error;

#[derive(Debug, Error)]
pub enum VerifierError {
    #[error("program length must be a multiple of {} octets", ebpf::INSN_SIZE)]
    ProgramLengthNotMultiple,
    #[error("program too big, max {}, is {}", ebpf::PROG_MAX_INSNS, .0)]
    ProgramTooLarge(usize),
    #[error("no program set, call prog_set() to load one")]
    NoProgram,
    #[error("division by 0 (insn #{0})")]
    DivisionByZero(usize),
    #[error("unsupported argument for LE/BE (insn #{0})")]
    UnsupportedLEBEArgument(usize),
    #[error("LD_DW instruction cannot be last in program")]
    LDDWCannotBeLast,
    #[error("incomplete LD_DW instruction (insn #{0})")]
    IncompleteLDDW(usize),
    #[error("infinite loop (insn #{0})")]
    InfiniteLoop(usize),
    #[error("jump out of code to #{0} (insn #{1})")]
    JumpOutOfCode(usize, usize),
    #[error("jump to middle of LD_DW at #{0} (insn #{1})")]
    JumpToMiddleOfLDDW(usize, usize),
    #[error("invalid source register (insn #{0})")]
    InvalidSourceRegister(usize),
    #[error("cannot write into register r10 (insn #{0})")]
    CannotWriteR10(usize),
    #[error("invalid destination register (insn #{0})")]
    InvalidDestinationRegister(usize),
    #[error("unknown eBPF opcode {0:#2x} (insn #{1:?})")]
    UnknownOpCode(u8, usize),
}

fn check_prog_len(prog: &[u8]) -> Result<(), BPFError> {
    if prog.len() % ebpf::INSN_SIZE != 0 {
        return Err(VerifierError::ProgramLengthNotMultiple.into());
    }
    if prog.len() > ebpf::PROG_MAX_SIZE {
        return Err(VerifierError::ProgramTooLarge(prog.len() / ebpf::INSN_SIZE).into());
    }

    if prog.is_empty() {
        return Err(VerifierError::NoProgram.into());
    }
    Ok(())
}

fn check_imm_nonzero(insn: &ebpf::Insn, insn_ptr: usize) -> Result<(), BPFError> {
    if insn.imm == 0 {
        return Err(VerifierError::DivisionByZero(insn_ptr).into());
    }
    Ok(())
}

fn check_imm_endian(insn: &ebpf::Insn, insn_ptr: usize) -> Result<(), BPFError> {
    match insn.imm {
        16 | 32 | 64 => Ok(()),
        _ => Err(VerifierError::UnsupportedLEBEArgument(insn_ptr).into()),
    }
}

fn check_load_dw(prog: &[u8], insn_ptr: usize) -> Result<(), BPFError> {
    if insn_ptr >= (prog.len() / ebpf::INSN_SIZE) {
        // Last instruction cannot be LD_DW because there would be no 2nd DW
        return Err(VerifierError::LDDWCannotBeLast.into());
    }
    let next_insn = ebpf::get_insn(prog, insn_ptr + 1);
    if next_insn.opc != 0 {
        return Err(VerifierError::IncompleteLDDW(insn_ptr).into());
    }
    Ok(())
}

fn check_jmp_offset(prog: &[u8], insn_ptr: usize) -> Result<(), BPFError> {
    let insn = ebpf::get_insn(prog, insn_ptr);
    if insn.off == -1 {
        return Err(VerifierError::InfiniteLoop(insn_ptr).into());
    }

    let dst_insn_ptr = insn_ptr as isize + 1 + insn.off as isize;
    if dst_insn_ptr < 0 || dst_insn_ptr as usize >= (prog.len() / ebpf::INSN_SIZE) {
        return Err(VerifierError::JumpOutOfCode(dst_insn_ptr as usize, insn_ptr).into());
    }
    let dst_insn = ebpf::get_insn(prog, dst_insn_ptr as usize);
    if dst_insn.opc == 0 {
        return Err(VerifierError::JumpToMiddleOfLDDW(dst_insn_ptr as usize, insn_ptr).into());
    }
    Ok(())
}

fn check_registers(insn: &ebpf::Insn, store: bool, insn_ptr: usize) -> Result<(), BPFError> {
    if insn.src > 10 {
        return Err(VerifierError::InvalidSourceRegister(insn_ptr).into());
    }
    match (insn.dst, store) {
        (0..=9, _) | (10, true) => Ok(()),
        (10, false) => Err(VerifierError::CannotWriteR10(insn_ptr).into()),
        (_, _) => Err(VerifierError::InvalidDestinationRegister(insn_ptr).into()),
    }
}

pub fn check(prog: &[u8]) -> Result<(), BPFError> {
    check_prog_len(prog)?;

    let mut insn_ptr: usize = 0;
    while insn_ptr * ebpf::INSN_SIZE < prog.len() {
        let insn = ebpf::get_insn(prog, insn_ptr);
        let mut store = false;

        match insn.opc {
            // BPF_LD class
            ebpf::LD_ABS_B => {}
            ebpf::LD_ABS_H => {}
            ebpf::LD_ABS_W => {}
            ebpf::LD_ABS_DW => {}
            ebpf::LD_IND_B => {}
            ebpf::LD_IND_H => {}
            ebpf::LD_IND_W => {}
            ebpf::LD_IND_DW => {}

            ebpf::LD_DW_IMM => {
                store = true;
                check_load_dw(prog, insn_ptr)?;
                insn_ptr += 1;
            }

            // BPF_LDX class
            ebpf::LD_B_REG => {}
            ebpf::LD_H_REG => {}
            ebpf::LD_W_REG => {}
            ebpf::LD_DW_REG => {}

            // BPF_ST class
            ebpf::ST_B_IMM => store = true,
            ebpf::ST_H_IMM => store = true,
            ebpf::ST_W_IMM => store = true,
            ebpf::ST_DW_IMM => store = true,

            // BPF_STX class
            ebpf::ST_B_REG => store = true,
            ebpf::ST_H_REG => store = true,
            ebpf::ST_W_REG => store = true,
            ebpf::ST_DW_REG => store = true,
            ebpf::ST_W_XADD => {
                unimplemented!();
            }
            ebpf::ST_DW_XADD => {
                unimplemented!();
            }

            // BPF_ALU class
            ebpf::ADD32_IMM => {}
            ebpf::ADD32_REG => {}
            ebpf::SUB32_IMM => {}
            ebpf::SUB32_REG => {}
            ebpf::MUL32_IMM => {}
            ebpf::MUL32_REG => {}
            ebpf::DIV32_IMM => {
                check_imm_nonzero(&insn, insn_ptr)?;
            }
            ebpf::DIV32_REG => {}
            ebpf::OR32_IMM => {}
            ebpf::OR32_REG => {}
            ebpf::AND32_IMM => {}
            ebpf::AND32_REG => {}
            ebpf::LSH32_IMM => {}
            ebpf::LSH32_REG => {}
            ebpf::RSH32_IMM => {}
            ebpf::RSH32_REG => {}
            ebpf::NEG32 => {}
            ebpf::MOD32_IMM => {
                check_imm_nonzero(&insn, insn_ptr)?;
            }
            ebpf::MOD32_REG => {}
            ebpf::XOR32_IMM => {}
            ebpf::XOR32_REG => {}
            ebpf::MOV32_IMM => {}
            ebpf::MOV32_REG => {}
            ebpf::ARSH32_IMM => {}
            ebpf::ARSH32_REG => {}
            ebpf::LE => {
                check_imm_endian(&insn, insn_ptr)?;
            }
            ebpf::BE => {
                check_imm_endian(&insn, insn_ptr)?;
            }

            // BPF_ALU64 class
            ebpf::ADD64_IMM => {}
            ebpf::ADD64_REG => {}
            ebpf::SUB64_IMM => {}
            ebpf::SUB64_REG => {}
            ebpf::MUL64_IMM => {
                check_imm_nonzero(&insn, insn_ptr)?;
            }
            ebpf::MUL64_REG => {}
            ebpf::DIV64_IMM => {
                check_imm_nonzero(&insn, insn_ptr)?;
            }
            ebpf::DIV64_REG => {}
            ebpf::OR64_IMM => {}
            ebpf::OR64_REG => {}
            ebpf::AND64_IMM => {}
            ebpf::AND64_REG => {}
            ebpf::LSH64_IMM => {}
            ebpf::LSH64_REG => {}
            ebpf::RSH64_IMM => {}
            ebpf::RSH64_REG => {}
            ebpf::NEG64 => {}
            ebpf::MOD64_IMM => {}
            ebpf::MOD64_REG => {}
            ebpf::XOR64_IMM => {}
            ebpf::XOR64_REG => {}
            ebpf::MOV64_IMM => {}
            ebpf::MOV64_REG => {}
            ebpf::ARSH64_IMM => {}
            ebpf::ARSH64_REG => {}

            // BPF_JMP class
            ebpf::JA => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JEQ_IMM => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JEQ_REG => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JGT_IMM => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JGT_REG => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JGE_IMM => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JGE_REG => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JLT_IMM => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JLT_REG => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JLE_IMM => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JLE_REG => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JSET_IMM => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JSET_REG => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JNE_IMM => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JNE_REG => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JSGT_IMM => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JSGT_REG => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JSGE_IMM => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JSGE_REG => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JSLT_IMM => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JSLT_REG => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JSLE_IMM => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::JSLE_REG => {
                check_jmp_offset(prog, insn_ptr)?;
            }
            ebpf::CALL_IMM => {}
            ebpf::CALL_REG => {}
            ebpf::EXIT => {}

            _ => {
                return Err(VerifierError::UnknownOpCode(insn.opc, insn_ptr).into());
            }
        }

        check_registers(&insn, store, insn_ptr)?;

        insn_ptr += 1;
    }

    // insn_ptr should now be equal to number of instructions.
    if insn_ptr != prog.len() / ebpf::INSN_SIZE {
        return Err(VerifierError::JumpOutOfCode(insn_ptr, insn_ptr).into());
    }

    Ok(())
}