sandbox/linux/bpf_dsl/bpf_dsl.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "sandbox/linux/bpf_dsl/bpf_dsl.h"
   6
   7 #include <errno.h>
   8
   9 #include <limits>
  10
  11 #include "base/logging.h"
  12 #include "base/memory/ref_counted.h"
  13 #include "sandbox/linux/seccomp-bpf/errorcode.h"
  14 #include "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
  15
  16 namespace sandbox {
  17 namespace bpf_dsl {
  18 namespace {
  19
  20 class AllowResultExprImpl : public internal::ResultExprImpl {
  21  public:
  22   AllowResultExprImpl() {}
  23
  24   virtual ErrorCode Compile(SandboxBPF* sb) const OVERRIDE {
  25     return ErrorCode(ErrorCode::ERR_ALLOWED);
  26   }
  27
  28  private:
  29   virtual ~AllowResultExprImpl() {}
  30
  31   DISALLOW_COPY_AND_ASSIGN(AllowResultExprImpl);
  32 };
  33
  34 class ErrorResultExprImpl : public internal::ResultExprImpl {
  35  public:
  36   explicit ErrorResultExprImpl(int err) : err_(err) {
  37     CHECK(err_ >= ErrorCode::ERR_MIN_ERRNO && err_ <= ErrorCode::ERR_MAX_ERRNO);
  38   }
  39
  40   virtual ErrorCode Compile(SandboxBPF* sb) const OVERRIDE {
  41     return ErrorCode(err_);
  42   }
  43
  44  private:
  45   virtual ~ErrorResultExprImpl() {}
  46
  47   int err_;
  48
  49   DISALLOW_COPY_AND_ASSIGN(ErrorResultExprImpl);
  50 };
  51
  52 class KillResultExprImpl : public internal::ResultExprImpl {
  53  public:
  54   explicit KillResultExprImpl(const char* msg) : msg_(msg) { DCHECK(msg_); }
  55
  56   virtual ErrorCode Compile(SandboxBPF* sb) const OVERRIDE {
  57     return sb->Kill(msg_);
  58   }
  59
  60  private:
  61   virtual ~KillResultExprImpl() {}
  62
  63   const char* msg_;
  64
  65   DISALLOW_COPY_AND_ASSIGN(KillResultExprImpl);
  66 };
  67
  68 class TraceResultExprImpl : public internal::ResultExprImpl {
  69  public:
  70   TraceResultExprImpl(uint16_t aux) : aux_(aux) {}
  71
  72   virtual ErrorCode Compile(SandboxBPF* sb) const OVERRIDE {
  73     return ErrorCode(ErrorCode::ERR_TRACE + aux_);
  74   }
  75
  76  private:
  77   virtual ~TraceResultExprImpl() {}
  78
  79   uint16_t aux_;
  80
  81   DISALLOW_COPY_AND_ASSIGN(TraceResultExprImpl);
  82 };
  83
  84 class TrapResultExprImpl : public internal::ResultExprImpl {
  85  public:
  86   TrapResultExprImpl(Trap::TrapFnc func, const void* arg)
  87       : func_(func), arg_(arg) {
  88     DCHECK(func_);
  89   }
  90
  91   virtual ErrorCode Compile(SandboxBPF* sb) const OVERRIDE {
  92     return sb->Trap(func_, arg_);
  93   }
  94
  95  private:
  96   virtual ~TrapResultExprImpl() {}
  97
  98   Trap::TrapFnc func_;
  99   const void* arg_;
 100
 101   DISALLOW_COPY_AND_ASSIGN(TrapResultExprImpl);
 102 };
 103
 104 class UnsafeTrapResultExprImpl : public internal::ResultExprImpl {
 105  public:
 106   UnsafeTrapResultExprImpl(Trap::TrapFnc func, const void* arg)
 107       : func_(func), arg_(arg) {
 108     DCHECK(func_);
 109   }
 110
 111   virtual ErrorCode Compile(SandboxBPF* sb) const OVERRIDE {
 112     return sb->UnsafeTrap(func_, arg_);
 113   }
 114
 115  private:
 116   virtual ~UnsafeTrapResultExprImpl() {}
 117
 118   Trap::TrapFnc func_;
 119   const void* arg_;
 120
 121   DISALLOW_COPY_AND_ASSIGN(UnsafeTrapResultExprImpl);
 122 };
 123
 124 class IfThenResultExprImpl : public internal::ResultExprImpl {
 125  public:
 126   IfThenResultExprImpl(const BoolExpr& cond,
 127                        const ResultExpr& then_result,
 128                        const ResultExpr& else_result)
 129       : cond_(cond), then_result_(then_result), else_result_(else_result) {}
 130
 131   virtual ErrorCode Compile(SandboxBPF* sb) const OVERRIDE {
 132     return cond_->Compile(
 133         sb, then_result_->Compile(sb), else_result_->Compile(sb));
 134   }
 135
 136  private:
 137   virtual ~IfThenResultExprImpl() {}
 138
 139   BoolExpr cond_;
 140   ResultExpr then_result_;
 141   ResultExpr else_result_;
 142
 143   DISALLOW_COPY_AND_ASSIGN(IfThenResultExprImpl);
 144 };
 145
 146 class ConstBoolExprImpl : public internal::BoolExprImpl {
 147  public:
 148   ConstBoolExprImpl(bool value) : value_(value) {}
 149
 150   virtual ErrorCode Compile(SandboxBPF* sb,
 151                             ErrorCode true_ec,
 152                             ErrorCode false_ec) const OVERRIDE {
 153     return value_ ? true_ec : false_ec;
 154   }
 155
 156  private:
 157   virtual ~ConstBoolExprImpl() {}
 158
 159   bool value_;
 160
 161   DISALLOW_COPY_AND_ASSIGN(ConstBoolExprImpl);
 162 };
 163
 164 class PrimitiveBoolExprImpl : public internal::BoolExprImpl {
 165  public:
 166   PrimitiveBoolExprImpl(int argno,
 167                         ErrorCode::ArgType is_32bit,
 168                         uint64_t mask,
 169                         uint64_t value)
 170       : argno_(argno), is_32bit_(is_32bit), mask_(mask), value_(value) {}
 171
 172   virtual ErrorCode Compile(SandboxBPF* sb,
 173                             ErrorCode true_ec,
 174                             ErrorCode false_ec) const OVERRIDE {
 175     return sb->CondMaskedEqual(
 176         argno_, is_32bit_, mask_, value_, true_ec, false_ec);
 177   }
 178
 179  private:
 180   virtual ~PrimitiveBoolExprImpl() {}
 181
 182   int argno_;
 183   ErrorCode::ArgType is_32bit_;
 184   uint64_t mask_;
 185   uint64_t value_;
 186
 187   DISALLOW_COPY_AND_ASSIGN(PrimitiveBoolExprImpl);
 188 };
 189
 190 class NegateBoolExprImpl : public internal::BoolExprImpl {
 191  public:
 192   explicit NegateBoolExprImpl(const BoolExpr& cond) : cond_(cond) {}
 193
 194   virtual ErrorCode Compile(SandboxBPF* sb,
 195                             ErrorCode true_ec,
 196                             ErrorCode false_ec) const OVERRIDE {
 197     return cond_->Compile(sb, false_ec, true_ec);
 198   }
 199
 200  private:
 201   virtual ~NegateBoolExprImpl() {}
 202
 203   BoolExpr cond_;
 204
 205   DISALLOW_COPY_AND_ASSIGN(NegateBoolExprImpl);
 206 };
 207
 208 class AndBoolExprImpl : public internal::BoolExprImpl {
 209  public:
 210   AndBoolExprImpl(const BoolExpr& lhs, const BoolExpr& rhs)
 211       : lhs_(lhs), rhs_(rhs) {}
 212
 213   virtual ErrorCode Compile(SandboxBPF* sb,
 214                             ErrorCode true_ec,
 215                             ErrorCode false_ec) const OVERRIDE {
 216     return lhs_->Compile(sb, rhs_->Compile(sb, true_ec, false_ec), false_ec);
 217   }
 218
 219  private:
 220   virtual ~AndBoolExprImpl() {}
 221
 222   BoolExpr lhs_;
 223   BoolExpr rhs_;
 224
 225   DISALLOW_COPY_AND_ASSIGN(AndBoolExprImpl);
 226 };
 227
 228 class OrBoolExprImpl : public internal::BoolExprImpl {
 229  public:
 230   OrBoolExprImpl(const BoolExpr& lhs, const BoolExpr& rhs)
 231       : lhs_(lhs), rhs_(rhs) {}
 232
 233   virtual ErrorCode Compile(SandboxBPF* sb,
 234                             ErrorCode true_ec,
 235                             ErrorCode false_ec) const OVERRIDE {
 236     return lhs_->Compile(sb, true_ec, rhs_->Compile(sb, true_ec, false_ec));
 237   }
 238
 239  private:
 240   virtual ~OrBoolExprImpl() {}
 241
 242   BoolExpr lhs_;
 243   BoolExpr rhs_;
 244
 245   DISALLOW_COPY_AND_ASSIGN(OrBoolExprImpl);
 246 };
 247
 248 }  // namespace
 249
 250 namespace internal {
 251
 252 uint64_t DefaultMask(size_t size) {
 253   switch (size) {
 254     case 4:
 255       return std::numeric_limits<uint32_t>::max();
 256     case 8:
 257       return std::numeric_limits<uint64_t>::max();
 258     default:
 259       CHECK(false) << "Unimplemented DefaultMask case";
 260       return 0;
 261   }
 262 }
 263
 264 BoolExpr ArgEq(int num, size_t size, uint64_t mask, uint64_t val) {
 265   CHECK(size == 4 || size == 8);
 266
 267   // TODO(mdempsky): Should we just always use TP_64BIT?
 268   const ErrorCode::ArgType arg_type =
 269       (size == 4) ? ErrorCode::TP_32BIT : ErrorCode::TP_64BIT;
 270
 271   return BoolExpr(new const PrimitiveBoolExprImpl(num, arg_type, mask, val));
 272 }
 273
 274 }  // namespace internal
 275
 276 ResultExpr Allow() {
 277   return ResultExpr(new const AllowResultExprImpl());
 278 }
 279
 280 ResultExpr Error(int err) {
 281   return ResultExpr(new const ErrorResultExprImpl(err));
 282 }
 283
 284 ResultExpr Kill(const char* msg) {
 285   return ResultExpr(new const KillResultExprImpl(msg));
 286 }
 287
 288 ResultExpr Trace(uint16_t aux) {
 289   return ResultExpr(new const TraceResultExprImpl(aux));
 290 }
 291
 292 ResultExpr Trap(Trap::TrapFnc trap_func, const void* aux) {
 293   return ResultExpr(new const TrapResultExprImpl(trap_func, aux));
 294 }
 295
 296 ResultExpr UnsafeTrap(Trap::TrapFnc trap_func, const void* aux) {
 297   return ResultExpr(new const UnsafeTrapResultExprImpl(trap_func, aux));
 298 }
 299
 300 BoolExpr BoolConst(bool value) {
 301   return BoolExpr(new const ConstBoolExprImpl(value));
 302 }
 303
 304 BoolExpr operator!(const BoolExpr& cond) {
 305   return BoolExpr(new const NegateBoolExprImpl(cond));
 306 }
 307
 308 BoolExpr operator&&(const BoolExpr& lhs, const BoolExpr& rhs) {
 309   return BoolExpr(new const AndBoolExprImpl(lhs, rhs));
 310 }
 311
 312 BoolExpr operator||(const BoolExpr& lhs, const BoolExpr& rhs) {
 313   return BoolExpr(new const OrBoolExprImpl(lhs, rhs));
 314 }
 315
 316 Elser If(const BoolExpr& cond, const ResultExpr& then_result) {
 317   return Elser(Cons<Elser::Clause>::List()).ElseIf(cond, then_result);
 318 }
 319
 320 Elser::Elser(Cons<Clause>::List clause_list) : clause_list_(clause_list) {
 321 }
 322
 323 Elser::Elser(const Elser& elser) : clause_list_(elser.clause_list_) {
 324 }
 325
 326 Elser::~Elser() {
 327 }
 328
 329 Elser Elser::ElseIf(const BoolExpr& cond, const ResultExpr& then_result) const {
 330   return Elser(
 331       Cons<Clause>::Make(std::make_pair(cond, then_result), clause_list_));
 332 }
 333
 334 ResultExpr Elser::Else(const ResultExpr& else_result) const {
 335   // We finally have the default result expression for this
 336   // if/then/else sequence.  Also, we've already accumulated all
 337   // if/then pairs into a list of reverse order (i.e., lower priority
 338   // conditions are listed before higher priority ones).  E.g., an
 339   // expression like
 340   //
 341   //    If(b1, e1).ElseIf(b2, e2).ElseIf(b3, e3).Else(e4)
 342   //
 343   // will have built up a list like
 344   //
 345   //    [(b3, e3), (b2, e2), (b1, e1)].
 346   //
 347   // Now that we have e4, we can walk the list and create a ResultExpr
 348   // tree like:
 349   //
 350   //    expr = e4
 351   //    expr = (b3 ? e3 : expr) = (b3 ? e3 : e4)
 352   //    expr = (b2 ? e2 : expr) = (b2 ? e2 : (b3 ? e3 : e4))
 353   //    expr = (b1 ? e1 : expr) = (b1 ? e1 : (b2 ? e2 : (b3 ? e3 : e4)))
 354   //
 355   // and end up with an appropriately chained tree.
 356
 357   ResultExpr expr = else_result;
 358   for (Cons<Clause>::List it = clause_list_; it.get(); it = it->tail()) {
 359     Clause clause = it->head();
 360     expr = ResultExpr(
 361         new const IfThenResultExprImpl(clause.first, clause.second, expr));
 362   }
 363   return expr;
 364 }
 365
 366 ResultExpr SandboxBPFDSLPolicy::InvalidSyscall() const {
 367   return Error(ENOSYS);
 368 }
 369
 370 ErrorCode SandboxBPFDSLPolicy::EvaluateSyscall(SandboxBPF* sb,
 371                                                int sysno) const {
 372   return EvaluateSyscall(sysno)->Compile(sb);
 373 }
 374
 375 ErrorCode SandboxBPFDSLPolicy::InvalidSyscall(SandboxBPF* sb) const {
 376   return InvalidSyscall()->Compile(sb);
 377 }
 378
 379 ResultExpr SandboxBPFDSLPolicy::Trap(Trap::TrapFnc trap_func, const void* aux) {
 380   return bpf_dsl::Trap(trap_func, aux);
 381 }
 382
 383 }  // namespace bpf_dsl
 384 }  // namespace sandbox