clmTypes.ts

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/**
 * PowerShell Constrained Language Mode allowed types.
 *
 * Microsoft's CLM restricts .NET type usage to this allowlist when PS runs
 * under AppLocker/WDAC system lockdown. Any type NOT in this set is considered
 * unsafe for untrusted code execution.
 *
 * We invert this: type literals not in this set → ask. One canonical check
 * replaces enumerating individual dangerous types (named pipes, reflection,
 * process spawning, P/Invoke marshaling, etc.). Microsoft maintains the list.
 *
 * Source: https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_language_modes
 *
 * Normalization: entries stored lowercase, short AND full names where both
 * exist (PS resolves type accelerators like [int] → System.Int32 at runtime;
 * we match against what the AST emits, which is the literal text).
 */
export const CLM_ALLOWED_TYPES: ReadonlySet<string> = new Set(
  [
    // Type accelerators (short names as they appear in AST TypeName.Name)
    // SECURITY: 'adsi' and 'adsisearcher' REMOVED. Both are Active Directory
    // Service Interface types that perform NETWORK BINDS when cast:
    //   [adsi]'LDAP://evil.com/...' → connects to LDAP server
    //   [adsisearcher]'(objectClass=user)' → binds to AD and queries
    // Microsoft's CLM allows these because it's for Windows admins in trusted
    // domains; we block them since the target isn't validated.
    'alias',
    'allowemptycollection',
    'allowemptystring',
    'allownull',
    'argumentcompleter',
    'argumentcompletions',
    'array',
    'bigint',
    'bool',
    'byte',
    'char',
    'cimclass',
    'cimconverter',
    'ciminstance',
    // 'cimsession' REMOVED — see wmi/adsi comment below
    'cimtype',
    'cmdletbinding',
    'cultureinfo',
    'datetime',
    'decimal',
    'double',
    'dsclocalconfigurationmanager',
    'dscproperty',
    'dscresource',
    'experimentaction',
    'experimental',
    'experimentalfeature',
    'float',
    'guid',
    'hashtable',
    'int',
    'int16',
    'int32',
    'int64',
    'ipaddress',
    'ipendpoint',
    'long',
    'mailaddress',
    'norunspaceaffinity',
    'nullstring',
    'objectsecurity',
    'ordered',
    'outputtype',
    'parameter',
    'physicaladdress',
    'pscredential',
    'pscustomobject',
    'psdefaultvalue',
    'pslistmodifier',
    'psobject',
    'psprimitivedictionary',
    'pstypenameattribute',
    'ref',
    'regex',
    'sbyte',
    'securestring',
    'semver',
    'short',
    'single',
    'string',
    'supportswildcards',
    'switch',
    'timespan',
    'uint',
    'uint16',
    'uint32',
    'uint64',
    'ulong',
    'uri',
    'ushort',
    'validatecount',
    'validatedrive',
    'validatelength',
    'validatenotnull',
    'validatenotnullorempty',
    'validatenotnullorwhitespace',
    'validatepattern',
    'validaterange',
    'validatescript',
    'validateset',
    'validatetrusteddata',
    'validateuserdrive',
    'version',
    'void',
    'wildcardpattern',
    // SECURITY: 'wmi', 'wmiclass', 'wmisearcher', 'cimsession' REMOVED.
    // WMI type casts perform WMI queries which can target remote computers
    // (network request) and access dangerous classes like Win32_Process.
    // cimsession creates a CIM session (network connection to remote host).
    //   [wmi]'\\evil-host\root\cimv2:Win32_Process.Handle="1"' → remote WMI
    //   [wmisearcher]'SELECT * FROM Win32_Process' → runs WQL query
    // Same rationale as adsi/adsisearcher removal above.
    'x500distinguishedname',
    'x509certificate',
    'xml',
    // Full names for accelerators that resolve to System.* (AST may emit either)
    'system.array',
    'system.boolean',
    'system.byte',
    'system.char',
    'system.datetime',
    'system.decimal',
    'system.double',
    'system.guid',
    'system.int16',
    'system.int32',
    'system.int64',
    'system.numerics.biginteger',
    'system.sbyte',
    'system.single',
    'system.string',
    'system.timespan',
    'system.uint16',
    'system.uint32',
    'system.uint64',
    'system.uri',
    'system.version',
    'system.void',
    'system.collections.hashtable',
    'system.text.regularexpressions.regex',
    'system.globalization.cultureinfo',
    'system.net.ipaddress',
    'system.net.ipendpoint',
    'system.net.mail.mailaddress',
    'system.net.networkinformation.physicaladdress',
    'system.security.securestring',
    'system.security.cryptography.x509certificates.x509certificate',
    'system.security.cryptography.x509certificates.x500distinguishedname',
    'system.xml.xmldocument',
    // System.Management.Automation.* — FQ equivalents of PS-specific accelerators
    'system.management.automation.pscredential',
    'system.management.automation.pscustomobject',
    'system.management.automation.pslistmodifier',
    'system.management.automation.psobject',
    'system.management.automation.psprimitivedictionary',
    'system.management.automation.psreference',
    'system.management.automation.semanticversion',
    'system.management.automation.switchparameter',
    'system.management.automation.wildcardpattern',
    'system.management.automation.language.nullstring',
    // Microsoft.Management.Infrastructure.* — FQ equivalents of CIM accelerators
    // SECURITY: cimsession FQ REMOVED — same network-bind hazard as short name
    // (creates a CIM session to a remote host).
    'microsoft.management.infrastructure.cimclass',
    'microsoft.management.infrastructure.cimconverter',
    'microsoft.management.infrastructure.ciminstance',
    'microsoft.management.infrastructure.cimtype',
    // FQ equivalents of remaining short-name accelerators
    // SECURITY: DirectoryEntry/DirectorySearcher/ManagementObject/
    // ManagementClass/ManagementObjectSearcher FQ REMOVED — same network-bind
    // hazard as short names adsi/adsisearcher/wmi/wmiclass/wmisearcher
    // (LDAP bind, remote WMI). See short-name removal comments above.
    'system.collections.specialized.ordereddictionary',
    'system.security.accesscontrol.objectsecurity',
    // Arrays of allowed types are allowed (e.g. [string[]])
    // normalizeTypeName strips [] before lookup, so store the base name
    'object',
    'system.object',
    // ModuleSpecification — full qualified name
    'microsoft.powershell.commands.modulespecification',
  ].map(t => t.toLowerCase()),
)

/**
 * Normalize a type name from AST TypeName.FullName or TypeName.Name.
 * Handles array suffix ([]) and generic brackets.
 */
export function normalizeTypeName(name: string): string {
  // Strip array suffix: "String[]" → "string" (arrays of allowed types are allowed)
  // Strip generic args: "List[int]" → "list" (conservative — the generic wrapper
  // might be unsafe even if the type arg is safe, so we check the outer type)
  return name
    .toLowerCase()
    .replace(/\[\]$/, '')
    .replace(/\[.*\]$/, '')
    .trim()
}

/**
 * True if typeName (from AST) is in Microsoft's CLM allowlist.
 * Types NOT in this set trigger ask — they access system APIs CLM blocks.
 */
export function isClmAllowedType(typeName: string): boolean {
  return CLM_ALLOWED_TYPES.has(normalizeTypeName(typeName))
}