x509-validation-1.6.9: X.509 Certificate and CRL validation

Data.X509.Validation

Description

X.509 Certificate checks and validations routines

Follows RFC5280 / RFC6818

# Documentation

type ServiceID = (HostName, ByteString) #

identification of the connection consisting of the fully qualified host name (e.g. www.example.com) and an optional suffix.

The suffix is not used by the validation process, but is used by the optional cache to identity certificate per service on a specific host. For example, one might have a different certificate on 2 differents ports (443 and 995) for the same host.

for TCP connection, it's recommended to use: :port, or :service for the suffix.

newtype Fingerprint #

Fingerprint of a certificate

Constructors

 Fingerprint ByteString

Instances

 # Methods # MethodsshowList :: [Fingerprint] -> ShowS # # MethodswithBytePtr :: Fingerprint -> (Ptr Word8 -> IO b) -> IO b #

# Failed validation types

data FailedReason #

Possible reason of certificate and chain failure.

The values InvalidName and InvalidWildcard are internal-only and are never returned by the validation functions. NameMismatch is returned instead.

Constructors

 UnknownCriticalExtension certificate contains an unknown critical extension Expired validity ends before checking time InFuture validity starts after checking time SelfSigned certificate is self signed UnknownCA unknown Certificate Authority (CA) NotAllowedToSign certificate is not allowed to sign NotAnAuthority not a CA AuthorityTooDeep Violation of the optional Basic constraint's path length NoCommonName Certificate doesn't have any common name (CN) InvalidName String Invalid name in certificate NameMismatch String connection name and certificate do not match InvalidWildcard invalid wildcard in certificate LeafKeyUsageNotAllowed the requested key usage is not compatible with the leaf certificate's key usage LeafKeyPurposeNotAllowed the requested key purpose is not compatible with the leaf certificate's extended key usage LeafNotV3 Only authorized an X509.V3 certificate as leaf certificate. EmptyChain empty chain of certificate CacheSaysNo String the cache explicitely denied this certificate InvalidSignature SignatureFailure signature failed

Instances

 # Methods # MethodsshowList :: [FailedReason] -> ShowS #

Various failure possible during signature checking

Constructors

 SignatureInvalid signature doesn't verify SignaturePubkeyMismatch algorithm and public key mismatch, cannot proceed SignatureUnimplemented unimplemented signature algorithm

Instances

 # Methods # MethodsshowList :: [SignatureFailure] -> ShowS #

# Validation configuration types

A set of checks to activate or parametrize to perform on certificates.

It's recommended to use defaultChecks to create the structure, to better cope with future changes or expansion of the structure.

Constructors

 ValidationChecks FieldscheckTimeValidity :: Boolcheck time validity of every certificate in the chain. the make sure that current time is between each validity bounds in the certificatecheckAtTime :: Maybe DateTimeThe time when the validity check happens. When set to Nothing, the current time will be usedcheckStrictOrdering :: BoolCheck that no certificate is included that shouldn't be included. unfortunately despite the specification violation, a lots of real world server serves useless and usually old certificates that are not relevant to the certificate sent, in their chain.checkCAConstraints :: BoolCheck that signing certificate got the CA basic constraint. this is absolutely not recommended to turn it off.checkExhaustive :: BoolCheck the whole certificate chain without stopping at the first failure. Allow gathering a exhaustive list of failure reasons. if this is turn off, it's absolutely not safe to ignore a failed reason even it doesn't look serious (e.g. Expired) as other more serious checks would not have been performed.checkLeafV3 :: BoolCheck that the leaf certificate is version 3. If disable, version 2 certificate is authorized in leaf position and key usage cannot be checked.checkLeafKeyUsage :: [ExtKeyUsageFlag]Check that the leaf certificate is authorized to be used for certain usage. If set to empty list no check are performed, otherwise all the flags is the list need to exists in the key usage extension. If the extension is not present, the check will pass and behave as if the certificate key is not restricted to any specific usage.checkLeafKeyPurpose :: [ExtKeyUsagePurpose]Check that the leaf certificate is authorized to be used for certain purpose. If set to empty list no check are performed, otherwise all the flags is the list need to exists in the extended key usage extension if present. If the extension is not present, then the check will pass and behave as if the certificate is not restricted to any specific purpose.checkFQHN :: BoolCheck the top certificate names matching the fully qualified hostname (FQHN). it's not recommended to turn this check off, if no other name checks are performed.

Instances

 # Methods # MethodsshowList :: [ValidationChecks] -> ShowS # # Methods

data ValidationHooks #

A set of hooks to manipulate the way the verification works.

BEWARE, it's easy to change behavior leading to compromised security.

Constructors

 ValidationHooks FieldshookMatchSubjectIssuer :: DistinguishedName -> Certificate -> Boolcheck whether a given issuer DistinguishedName matches the subject DistinguishedName of a candidate issuer certificate.hookValidateTime :: DateTime -> Certificate -> [FailedReason]check whether the certificate in the second argument is valid at the time provided in the first argument. Return an empty list for success or else one or more failure reasons.hookValidateName :: HostName -> Certificate -> [FailedReason]validate the certificate leaf name with the DNS named used to connecthookFilterReason :: [FailedReason] -> [FailedReason]user filter to modify the list of failure reasons

Instances

 # Methods

Default checks to perform

The default checks are: * Each certificate time is valid * CA constraints is enforced for signing certificate * Leaf certificate is X.509 v3 * Check that the FQHN match

Default hooks in the validation process

# Validation

Arguments

 :: HashALG the hash algorithm we want to use for hashing the leaf certificate -> ValidationHooks Hooks to use -> ValidationChecks Checks to do -> CertificateStore The trusted certificate store for CA -> ValidationCache the validation cache callbacks -> ServiceID identification of the connection -> CertificateChain the certificate chain we want to validate -> IO [FailedReason] the return failed reasons (empty list is no failure)

X509 validation

the function first interrogate the cache and if the validation fail, proper verification is done. If the verification pass, the add to cache callback is called.

Arguments

 :: CertificateStore The trusted certificate store for CA -> ValidationCache the validation cache callbacks -> ServiceID identification of the connection -> CertificateChain the certificate chain we want to validate -> IO [FailedReason] the return failed reasons (empty list is no failure)

Validate using the default hooks and checks and the SHA256 mechanism as hashing mechanism

Arguments

 :: (Show a, Eq a, ASN1Object a) => SignedExact a object to fingerprint -> HashALG algorithm to compute the fingerprint -> Fingerprint fingerprint in binary form

Get the fingerprint of the whole signed object using the hashing algorithm specified

# Cache for validation

The result of a cache query

Constructors

 ValidationCachePass cache allow this fingerprint to go through ValidationCacheDenied String cache denied this fingerprint for further validation ValidationCacheUnknown unknown fingerprint in cache

Instances

 # Methods # Methods

Arguments

 = ServiceID connection's identification -> Fingerprint fingerprint of the leaf certificate -> Certificate leaf certificate -> IO ValidationCacheResult return if the operation is succesful or not

Validation cache query callback type

Arguments

 = ServiceID connection's identification -> Fingerprint fingerprint of the leaf certificate -> Certificate leaf certificate -> IO ()

Validation cache callback type

data ValidationCache #

All the callbacks needed for querying and adding to the cache.

Constructors

Instances

 # Methods

# Simple instances of cache mechanism

create a simple constant cache that list exceptions to the certification validation. Typically this is use to allow self-signed certificates for specific use, with out-of-bounds user checks.

No fingerprints will be added after the instance is created.

The underlying structure for the check is kept as a list, as usually the exception list will be short, but when the list go above a dozen exceptions it's recommended to use another cache mechanism with a faster lookup mechanism (hashtable, map, etc).

Note that only one fingerprint is allowed per ServiceID, for other use, another cache mechanism need to be use.

Arguments

 :: [(ServiceID, Fingerprint)] a list of exceptions -> IO ValidationCache

Trust on first use (TOFU) cache with an optional list of exceptions

this is similar to the exceptionCache, except that after each succesfull validation it does add the fingerprint to the database. This prevent any further modification of the fingerprint for the remaining

# Signature verification

verifySignedSignature :: (Show a, Eq a, ASN1Object a) => SignedExact a -> PubKey -> SignatureVerification #

Verify a Signed object against a specified public key

Arguments

 :: SignatureALG Signature algorithm used -> PubKey Public key to use for verify -> ByteString Certificate data that need to be verified -> ByteString Signature to verify -> SignatureVerification

verify signature using parameter

A set of possible return from signature verification.

When SignatureFailed is return, the signature shouldn't be accepted.

Other values are only useful to differentiate the failure reason, but are all equivalent to failure.

Constructors

 SignaturePass verification succeeded SignatureFailed SignatureFailure verification failed

Instances

 # Methods # Methods

Various failure possible during signature checking

Constructors

 SignatureInvalid signature doesn't verify SignaturePubkeyMismatch algorithm and public key mismatch, cannot proceed SignatureUnimplemented unimplemented signature algorithm

Instances

 # Methods # MethodsshowList :: [SignatureFailure] -> ShowS #