Certora Prover CLI Options

The certoraRun utility invokes the Solidity compiler and afterwards sends the job to Certora’s servers.

The most commonly used command is:

certoraRun contractFile:contractName --verify contractName:specFile

If contractFile is named contractName.sol, the run command can be simplified to

certoraRun contractFile --verify contractName:specFile

A short summary of these options can be seen by invoking certoraRun --help

Overview

Modes of operation

The Certora Prover has three modes of operation. The modes are mutually exclusive - you cannot run the tool with more than one mode at a time.

--verify

What does it do?
It runs formal verification of properties specified in a .spec file on a given contract. Each contract must have been declared in the input files or have the same name as the source code file it is in.

When to use it?
When you wish to prove properties on the source code. This is by far the most common mode of the tool.

Example
If we have a Solidity file Bank.sol, with a contract named Bank inside it, and a specification file called Bank.spec, the run command would be:
certoraRun Bank.sol --verify Bank:Bank.spec

--assert_contracts

What does it do?
Replaces all EVM instructions that cause a non-benign revert in the smart contract with an assertion. Non-benign reverts include division by 0, bad dereference of an array, throw command, and more.
Each contract must have been declared in the input files or have the same name as the source code file it is in.

When to use it?
When you want to see if a suspect instruction can fail in the code, without writing a .spec file.

Example
If we have a solidity file Bank.sol, with a contract named Investor inside it which we want to assert, we write:
certoraRun Bank.sol:Investor --assert_contracts Investor

Most frequently used options

--msg <description>

What does it do? Adds a message description to your run, similar to a commit message. This message will appear in the title of the completion email sent to you. Note that you need to wrap your message in quotes if it contains spaces.

When to use it?
Adding a message makes it easier to track several runs. It is very useful if you are running many verifications simultaneously. It is also helpful to keep track of a single file verification status over time, so we recommend always providing an informative message.

Example
To create the message above, we used
certoraRun Bank.sol --verify Bank:Bank.spec --msg 'Removed an assertion'

--rule <rule name> ...

What does it do?
Formally verifies one or more given properties instead of the whole specification file. An invariant can also be selected.

When to use it?
This option saves a lot of run time. Use it whenever you care about only a specific subset of a specification’s properties. The most common case is when you add a new rule to an existing specification. The other is when code changes cause a specific rule to fail; in the process of fixing the code, updating the rule, and understanding counterexamples, you likely want to verify only that specific rule.

Example
If Bank.spec includes the following properties:
invariant address_zero_cannot_become_an_account()

rule withdraw_succeeds() rule withdraw_fails()

If we want to verify only withdraw_succeeds, we run
certoraRun Bank.sol --verify Bank:Bank.spec --rule withdraw_succeeds

If we want to verify both withdraw_succeeds and withdraw_fails, we run
certoraRun Bank.sol --verify Bank:Bank.spec --rule withdraw_succeeds withdraw_fails

--method <method_signature>

What does it do? Only uses functions with the given method signature when instantiating parametric rules and invariants. The method signature consists of the name of a method and the types of its arguments.

You may provide multiple method signatures, in which case the Prover will run on each of the listed methods.

When to use it? This option is useful when focusing on a specific counterexample; running on a specific contract method saves time.

Example Suppose we are verifying an ERC20 contract, and we have the following parametric rule:

rule r {
    method f; env e; calldataarg args;
    address owner; address spender;

    mathint allowance_before = allowance(owner, spender);
    f(e,args);
    mathint allowance_after  = allowance(owner, spender);

    assert allowance_after > allowance_before => e.msg.sender == owner; 
}

If we discover a counterexample in the method deposit(uint), and wish to change the contract or the spec to rerun, we can just rerun on the deposit method:

certoraRun --method 'deposit(uint)'

Note that many shells will interpret the ( and ) characters specially, so the method signature argument will usually need to be quoted as in the example.

--parametric_contracts <contract_name> ...

New in version 5.0: Prior to version 5, method variables and invariants were only instantiated with methods of Special variables and fields.

What does it do? Only uses methods on the specified contract when instantiating parametric rules or invariants. The contract name must be one of the contracts included in the scene.

When to use it? As with the --rule <rule name> ... and --method <method_signature> options, this option is used to avoid rerunning the entire verification

Example Suppose you are working on a multicontract verification and wish to debug a counterexample in a method of the Underlying contract defined in the file Example.sol:

certoraRun Main:Example.sol Underlying:Example.sol --verify Main:Example.spec \
    --parametric_contracts Underlying

--send_only

What does it do? Causes the CLI to exit immediately when the job is submitted, rather than waiting for it to complete.

When to use it? When you want to run many jobs concurrently in a script, or otherwise want the CLI to not block the terminal.

Example

certoraRun Example.sol --verify Example:Example.spec --send_only

Options affecting the type of verification run

--multi_assert_check

What does it do? This mode checks each assertion statement that occurs in a rule, separately. The check is done by decomposing each rule into multiple sub-rules, each of which checks one assertion, while it assumes all preceding assertions. In addition, all assertions that originate from the Solidity code (as opposed to those from the specification), are checked together by a designated, single sub-rule.

As an illustrative example, consider the following rule R that has two assertions:

…
assert a1
…
assert a2
…

The multi_assert_check mode would generate and check two sub-rules: R1 where a1 is proved while a2 is removed, and R2 where a1 is assumed (i.e., transformed into a requirement statement), and a2 is proved.

R passes if and only if, R1 and R2 both pass. In particular, in case R1 (resp. R2) fails, the counter-example shows a violation of a1 (resp. a2).

Caution

We suggest using this mode carefully. In general, as this mode generates and checks more rules, it may lead to worse running-time performance. Please see indications for use below.

When to use it? When you have a rule with multiple assertions:

  1. As a timeout mitigation strategy: checking each assertion separately may, in some cases, perform better than checking all the assertions together and consequently solve timeouts.

  2. If you wish to get multiple counter-examples in a single run of the tool, where each counter-example violates a different assertion in the rule.

Example certoraRun Bank.sol --verify Bank:Bank.spec --multi_assert_check

--rule_sanity

What does it do? This option enables sanity checking for rules. The --rule_sanity option may be followed by one of none, basic, or advanced; See Rule Sanity Checks for more information about sanity checks.

When to use it?
We suggest using this option routinely while developing rules. It is also a useful check if you notice rules passing surprisingly quickly or easily.

Example certoraRun Bank.sol --verify Bank:Bank.spec --rule_sanity basic

--short_output

What does it do?
Reduces the verbosity of the tool.

When to use it?
When we do not care much for the output. It is recommended when running the tool in continuous integration.

Example certoraRun Bank.sol --verify Bank:Bank.spec --short_output

Options that control the Solidity compiler

--solc

What does it do?
Use this option to provide a path to the Solidity compiler executable file. We check in all directories in the $PATH environment variable for an executable with this name. If --solc is not used, we look for an executable called solc, or solc.exe on windows platforms.

When to use it?
Whenever you want to use a Solidity compiler executable with a non-default name. This is usually used when you have several Solidity compiler executable versions you switch between.

Example
certoraRun Bank.sol --verify Bank:Bank.spec --solc solc8.1

--solc_map

What does it do?
Compiles every smart contract with a different Solidity compiler executable. All used contracts must be listed.

When to use it?
When different contracts have to be compiled for different Solidity versions.

Example
certoraRun Bank.sol Exchange.sol --verify Bank:Bank.spec --solc_map Bank=solc4.25,Exchange=solc6.7

--solc_optimize

What does it do?
Passes the value of this option to the solidity compiler’s option --solc_optimize.

When to use it?
When we want to select the Solidity compiler EVM version

Example certoraRun Bank.sol --verify Bank:Bank.spec --solc_evm_version Istanbul

--solc_optimize

What does it do?
Passes the value of this option as is to the solidity compiler’s option --optimize and --optimize-runs.

When to use it?
When we want to activate in the solidity compiler the opcode-based optimizer for the generated bytecode and control the number of times the optimizer will be activated (if no value is set, the compiler’s default is 200 runs)

Example certoraRun Bank.sol --verify Bank:Bank.spec --solc_optimize 300

--solc_via_ir

What does it do?
Passes the value of this option to the solidity compiler’s option --via-ir.

When to use it?
When we want to enable the IR-based code generator

Example certoraRun Bank.sol --verify Bank:Bank.spec --solc_via_ir

--solc_evm_version

What does it do?
Passes the value of this option to the solidity compiler’s option --evm-version.

When to use it?
When we want to select the Solidity compiler EVM version

Example certoraRun Bank.sol --verify Bank:Bank.spec --solc_evm_version Istanbul

--solc_allow_path

What does it do?
Passes the value of this option as is to the solidity compiler’s option --allow-paths. See –allow-path specification

When to use it?
When we want to add an additional location the Solidity compiler to load sources from

Example certoraRun Bank.sol --verify Bank:Bank.spec --solc_allow_path ~/Projects/Bank

--packages_path

What does it do?
Gets the path to a directory including the Solidity packages.

When to use it?
By default, we look for the packages in $NODE_PATH. If the packages are in any other directory, you must use --packages_path.

Example
certoraRun Bank.sol --verify Bank:Bank.spec --packages_path Solidity/packages

--packages

What does it do?
For each package, gets the path to a directory including that Solidity package.

When to use it?
By default we look for the packages in $NODE_PATH. If there are packages are in several different directories, use --packages.

Example
certoraRun Bank.sol --verify Bank:Bank.spec --packages ds-stop=$PWD/lib/ds-token/lib/ds-stop/src ds-note=$PWD/lib/ds-token/lib/ds-stop/lib/ds-note/src

Options regarding source code loops

--optimistic_loop

What does it do? The Certora Prover unrolls loops - if the loop should be executed three times, it will copy the code inside the loop three times. After we finish the loop’s iterations, we add an assertion to verify we have actually finished running the loop. For example, in a while (a < b) loop, after the loop’s unrolling, we add assert a >= b. We call this assertion the loop unwind condition.
This option changes the assertions of the loop unwind condition to requirements (in the case above require a >= b). That means, we ignore all the cases where the loop unwind condition does not hold, instead of considering them as a failure.

When to use it?
When you have loops in your code and are getting a counterexample labeled loop unwind condition. In general, you need this flag whenever the number of loop iterations varies. It is usually a necessity if using --loop_iter. Note that --optimistic_loop could cause vacuous rules.

Example

certoraRun Bank.sol --verify Bank:Bank.spec --optimistic_loop

--loop_iter

What does it do? Sets the maximal number of loop iterations we verify for. The way the Certora Prover handles loops is by unrolling them - if the loop should be executed three times, it will copy the code inside the loop three times. This option sets the number of unrolls. Be aware that the run time grows exponentially by the number of loop iterations.

When to use it?
The default number of loop iterations we unroll is one. However, in many cases, bugs only occur when there are several iterations. Common scenarios include iteration over list elements. Two, or in some cases three, is usually the most you will ever need to uncover bugs.

Example

certoraRun Bank.sol --verify Bank:Bank.spec --loop_iter 2

Options regarding hashing of unbounded data

--optimistic_hashing

What does it do?

When hashing data of potentially unbounded length (including unbounded arrays, like bytes, uint[], etc.), assume that its length is bounded by the value set through the --hashing_length_bound option. If this is not set, and the length can be exceeded by the input program, the Prover reports an assertion violation. I.e., when this option is set, the boundedness of the hashed data assumed checked by the Prover, when this option is set that boundedness is assumed instead.

See Modeling of Hashing in the Prover for more details.

When to use it?

When the assertion regarding unbounded hashing is thrown, but it is acceptable for the Prover to ignore cases where the length hashed values exceeds the current bound.

Example

certoraRun Bank.sol --verify Bank:Bank.spec --optimistic_hashing

--hashing_length_bound

What does it do?

Constraint on the maximal length of otherwise unbounded data chunks that are being hashed. This constraint is either assumed or checked by the Prover, depending on whether --optimistic_hashing has been set. The bound is specified as a number of bytes.

The default value of this option is 224 (224 bytes correspond to 7 EVM machine words as 7 * 32 == 224).

When to use it?
Reason to lower this value:

Lowering potentially improves SMT performance, especially if there are many occurrences of unbounded hashing in the program.

Reasons to raise this value:

  • when --optimistic_hashing is not set: avoid the assertion being violated when the hashed values are actually bounded, but by a bound that is higher than the default value (in case of --optimistic_hashing being not set)

  • when --optimistic_hashing is set: find bugs that rely on a hashed array being at least of that length. (Optimistic hashing excludes all cases from the scope of verification where something being hashed is longer than this bound.)

Example

certoraRun Bank.sol --verify Bank:Bank.spec --hashing_length_bound 128

Options that help reduce the running time

--method

What does it do? Parametric rules will only verify the method with the given signature, instead of all public and external methods of the contract. Note that you will need to wrap the method’s signature with quotes, as the shell doesn’t interpret parenthesis correctly otherwise.

When to use it?
When you are trying to solve/understand a counterexample of a parametric rule on a specific method.

Example
certoraRun Bank.sol --verify Bank:Bank.spec --method 'withdraw(uint256,bool)'

--cache

What does it do?
A cache in the cloud for optimizing the analysis before running the SMT solvers. The cache used is the argument this option gets. If a cache with this name does not exist, it creates one with this name.

When to use it?
By default, we do not use a cache. If you want to use a cache to speed up the building process, use this option.

Example
certoraRun Bank.sol --verify Bank:Bank.spec --cache bank_regulation

--smt_timeout <seconds>

What does it do?
Sets the maximal timeout for all the SMT solvers. Gets an integer input, which represents seconds.

The Certora Prover generates a logical formula from the specification and source code. Then, it passes it on to an array of SMT solvers. The time it can take for the SMT solvers to solve the equation is highly variable, and could potentially be infinite. This is why they must be limited in run time.

Note that the SMT timeout applies separately to each individual rule (or each method for parametric rules). To set the global timeout, see --prover_args '-globalTimeout <seconds>'.

When to use it?
The default time out for the solvers is 300 seconds. There are two use cases for this option.
One is to decrease the timeout. This is useful for simple rules, that are solved quickly by the SMT solvers. Here, it is beneficial to reduce the timeout, so that when a new code breaks the specification, the tool will fail quickly. This is the more common use case.
The second use is when the solvers can prove the property, they just need more time. Usually, if the rule isn’t solved in 600 seconds, it will not be solved in 2,000 either. It is better to concentrate your efforts on simplifying the rule, the source code, add more summaries, or use other time-saving options. The prime causes for an increase of --smt_timeout are rules that are solved quickly, but time out when you add a small change, such as a requirement, or changing a strict inequality to a weak inequality.

Example
certoraRun Bank.sol --verify Bank:Bank.spec --smt_timeout 300

--global_timeout <seconds>

Sets the maximal timeout for the Prover. Gets an integer input, which represents seconds.

The Certora Prover is bound to run a maximal time of 2 hours (7200 seconds). Users may opt to set this number lower to facilitate faster iteration on specifications.

When to use it? When running on just a few rules, or when willing to make faster iterations on specs without waiting too long for the entire set of rules to complete. Note that even if in the shorter running time not all rules were processed, a second run may pull some results from cache, and therefore more results will be available.

Example certoraRun Bank.sol --verify Bank:Bank.spec --global_timeout 60

Options for controlling contract creation

--dynamic_bound <n>

What does it do? If set to zero (the default), contract creation (via the new statement or the create/create2 instructions) will result in a havoc, like any other unresolved external call. If non-zero, then dynamic contract creation will be modeled with cloning, where each contract will be cloned at most n times.

When to use it? When you wish to model contract creation, that is, simulating the actual creation of the contract. Without it, create and create2 commands simply return a fresh address; the Prover does not model their storage, code, constructors, immutables, etc. Any interaction with these generated addresses is modeled imprecisely with conservative havoc.

Example Suppose a contract C creates a new instance of a contract Foo, and you wish to inline the constructor of Foo at the creation site. certoraRun C.sol Foo.sol --dynamic_bound 1

--dynamic_dispatch

What does it do? If false (the default), then all contract method invocations on newly created instances will be unresolved. The user must explicitly write `DISPATCHER` summaries for all methods called on newly created instances. If true, the Prover will, on a best-effort basis, automatically apply the DISPATCHER summary for call sites that must be with a newly created contract as a receiver.

Importantly, this option is only applicable to cases where the Prover can prove that the callee is a created contract. For example, in the below example, the bar function will be unresolved:

MyFoo f;
if(*) {
   f = new MyFoo(...);
} else {
  f = storageStruct.myFoo;
}
f.bar();

When to use it? When you prefer not to add explicit DISPATCHER summaries to methods invoked by the created contract.

Example Suppose a contract C creates a new instance of a contract Foo, and you wish to inline the constructor of Foo at the creation site, and Foo calls some method m() which you wish to automatically link to the newly created contract. Note that you must add a --dynamic_bound argument as well. certoraRun C.sol Foo.sol --dynamic_bound 1 --dynamic_dispatch true

--prototype <hex string>=<contract>

What does it do? Instructs the Prover to use a specific contract type for the return value from a call to create or create2 on the given hexadecimal string as a prefix. The hexadecimal string represents proxy code that forwards calls to another contract. As we are using the prototype flag to skip calls to the proxy, no constructor code is being simulated for these contract creation resolutions.

When to use it? If you are verifying a contract creation that uses low level calls to create or create2 for contract creation.

Example Suppose you have a contract C that creates another contract Foo like this:

assembly {
     let ptr := mload(0x40)
     mstore(ptr, 0x3d602d80600a3d3981f3363d3d373d3d3d363d73000000000000000000000000)
     mstore(add(ptr, 0x14), shl(0x60, implementation))
     mstore(add(ptr, 0x28), 0x5af43d82803e903d91602b57fd5bf30000000000000000000000000000000000)
     instance := create(0, ptr, 0x37)
}

Then you can set the string 3d602d80600a3d3981f3363d3d373d3d3d363d73 appearing in the first mstore after the 0x prefix as a “prototype” for Foo. The Prover will then be able to create a new instance of Foo at the point where the code creates it: certoraRun C.sol Foo.sol --prototype 3d602d80600a3d3981f3363d3d373d3d3d363d73=Foo --dynamic_bound 1 Note: this argument has no effect if the dynamic bound is zero.

Also note that the hex string must be:

  • a strict prefix of the memory region passed to the create command

  • must be unique within each invocation of the tool

  • must not contain gaps, e.g., 3d602d80600a3d3981f3363d3d373d3d3d363d730000 in the above example will not work (those last four bytes will be overwritten) but 3d602d80600a3d3981f3363d3d373d3d3d363d will

Version options

--version

What does it do?
Shows the version of the local installation of the tool you have.

When to use it?
When you suspect you have an old installation. To install the newest version, use pip install --upgrade certora-cli.
Example

certoraRun --version

Advanced options

--java_args

What does it do?

Allows setting configuring the underlying JVM.

When to use it?

Upon instruction from the Certora team.

Example

--java_args '"-Dcvt.default.parallelism=2"' - will set the number of “tasks” that can run in parallel to 2.

--prover_args

The --prover_args option allows you to provide fine-grained tuning options to the Prover. --prover_args receives a string containing Prover-specific options, and will be sent as-is to the Prover. --prover_args cannot set Prover options that are set by standalone certoraRun options (e.g. the Prover option --t is set by --smt_timeout therefore cannot appear in --prover_args). --prover_args value must be quoted

--prover_args '-optimisticReturnsize'

This option determines whether havoc summaries assume that the called method returns the correct number of return values.

--prover_args '-showInternalFunctions'

A single occurrence of --prover_args can set multiple values --prover_args '-showInternalFunctions -optimisticReturnsize'

What does it do?

This option causes the Prover to output a list of all the potentially summarizable internal function calls on the command line. The output is also visible in the log file that you can download from the report.

When to use it?

In some cases the Prover is unable to locate all internal function calls, and so summaries may not be applied. This option can be useful to determine whether summary is applied or not.

The Prover’s ability to locate a summarizable call depends on the call site, rather than the method declaration. In particular, it is possible that the same internal function is called from two different contract functions, but only one of those calls is summarizable.

The list that is output by this setting is grouped under the public and external methods of the contract. If an external method f calls an internal method g which in turn calls another internal method h, then both g and h will be reported under the entry for f.

Example

certoraRun Bank.sol --verify Bank:bank.spec --prover_args '-showInternalFunctions'

--prover_args '-globalTimeout <seconds>'

This option sets the global timeout in seconds. By default, the global timeout is two hours. Values larger than two hours (7200 seconds) are ignored.

The global timeout is different from the --smt_timeout <seconds> option: the --smt_timeout flag constrains the amount of time allocated to the processing of each individual rule, while the -globalTimeout flag constrains the processing of the entire job, including static analysis and other preprocessing.

Jobs that exceed the global timeout will simply be terminated, so the result reports may not be generated.

--prover_args '-solver <solver spec>'

By default, a portfolio of SMT solvers using various configurations is used within the Prover. It can be useful to specify only a subset of these to save on computation time. In rare cases, solver specific options can improve performance as well. Setting -solver <solver spec> filters the predefined portfolio to only use those configuration that match the given solver specification.

The solver spec can be a single solver (-solver z3:def), or a list of solver configurations (-solver [z3:def,cvc5:def]), where each such solver can be further modified. For example, cvc5 (as in -solver cvc5) refers to the set of pre-configured configurations of cvc5 whereas cvc5:nonlin is a specific configuration used for nonlinear problems. Additional options can be set via z3{randomSeed=17}.

With -smt_overrideSolvers true, the portfolio can be replaced instead of filtered. For example, in conjunction with -solver [cvc5:def,z3:def], the portfolio is replaced with the default configurations of cvc5 and z3, irrespective of their presence in the predefined portfolio. For even better control of which solvers are used in which situation, solver specification for certain logics can be given via -smt_LIASolvers <solver spec>, -smt_NIASolvers <solver spec>, and -smt_BVSolvers<solver spec> for linear, non-linear and bit-vector formulas.

--prover_args '-smt_useBV true'

This option models bitwise operations exactly instead of using the default overapproximations. It is useful when the Prover reports a counterexample caused by incorrect modeling of bitwise operations, but can dramatically increase the time taken for verification.

The disadvantage of this encoding is that it does not model mathint precisely: the maximum supported integer value is :math:2^256-1 in this case, effectively restricting a mathint to a uint256. We currently do not have a setting or encoding that models precisely both bitwise operations and mathint.

--prover_args '-maxNumberOfReachChecksBasedOnDomination <n>'

This option sets the number of program points to test with the deepSanity built-in rule. See Thorough complexity checks — deepSanity.

–allow_solidity_calls_in_quantifiers

What does it do?

Instructs the Prover to permit contract method calls in quantified expression bodies.

When to use it?

Upon instruction from the Certora team.

Example

--allow_solidity_calls_in_quantifiers instructs the Prover to not generate an error on encountering contract method calls in quantified expression bodies.

Advanced options that control control flow splitting

See here for an explanation of control flow splitting.

--prover_args '-mediumTimeout <seconds>'

The “medium timeout” determines how much time is given to checking a split at not max-depth before we split again.

--prover_args '-dontStopAtFirstSplitTimeout <true/false>'

We can tell the Certora Prover to not stop when the first split has had a maximum-depth timeout. Note that this is only useful for SAT results, since for an overall UNSAT results, all splits need to be UNSAT, while for a SAT result it is enough that one split is UNSAT.

--prover_args '-smt_initialSplitDepth <number>'

Splitting can be configured to skip the checks at low splitting levels, thus generating sub-splits up to a given depth immediately. Note that the number of splits generated here is equal to 2^n where n is the initial splitting depth (unless the program has less than n branchings, which will be rare in practice).