# Security - First Steps

Let's imagine that you have your **backend** API in some domain.

And you have a **frontend** in another domain or in a different path of the same domain (or in a mobile application).

And you want to have a way for the frontend to authenticate with the backend, using a **username** and **password**.

We can use **OAuth2** to build that with **FastAPI**.

        buildList {
            firScope.simpleImports.values.forEach { imports ->
                imports.forEach { import ->
                    val importedClassId = import.importedName?.let { importedName ->
                        val importedClassId =
                            import.resolvedParentClassId?.createNestedClassId(importedName) ?: ClassId(import.packageFqName, importedName)

## Let's Encrypt

Avant Let's Encrypt, ces certificats HTTPS étaient vendus par des tiers de confiance.

Le processus d'acquisition d'un de ces certificats était auparavant lourd, nécessitait pas mal de paperasses et les certificats étaient assez chers.

Mais ensuite, <a href="https://letsencrypt.org/" class="external-link" target="_blank">Let's Encrypt</a> a été créé.

        Pair(
            (node as? NodeWithJavadoc<*>)?.javadoc?.orElse(null)?.let { findVersionFromJavadoc(it) }
                // This is needed to find the JavaDoc of a package declaration in 'package-info.java'
                ?: (node as? PackageDeclaration)?.parentNode?.get()?.childNodes?.filterIsInstance<JavadocComment>()?.singleOrNull()?.parse()?.let { findVersionFromJavadoc(it) }
                ?: versionNotFound,

# https://github.com/apache/lucene-solr/blob/master/lucene/analysis/common/src/resources/org/apache/lucene/analysis/snowball/finnish_stop.txt
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            type.isDouble -> KtConstantValue.KtDoubleConstantValue((value as Number).toDouble(), expression)
            else -> null
        }

        return constantValue?.let { KtConstantAnnotationValue(it, analysisSession.token) }
    }

    private fun Collection<FirExpression>.convertVarargsExpression(
        builder: KtSymbolByFirBuilder,
    ): Pair<Collection<KtAnnotationValue>, KtElement?> {

    parameters.gradleVersion = moduleIdentity.version.map { it.version }
    parameters.homeDir = intTestHomeDir
}

fun Gradle.rootBuild(): Gradle = parent.let { it?.rootBuild() ?: this }

tasks.withType<DistributionTest>().configureEach {
    shouldRunAfter("test")

    setJvmArgsOfTestJvm()
    setSystemPropertiesOfTestJVM("default")
    configureGradleTestEnvironment()

private
fun hasFunctionFlags(functionsSupplier: Supplier<MutableList<KmFunction>>, jvmSignature: String, predicate: FlagsPredicate) =
    functionsSupplier.get().firstOrNull {
        jvmSignature == it.signature?.asString()
    }?.flags?.let { predicate(it) } ?: false


private

   * see calls in Google code that pass a null `dir` to a FilenameFilter.... So let's declare the
   * parameter as non-nullable (since passing null to a FilenameFilter is unsafe in general), but if
   * someone still manages to pass null, let's continue to have the method work.
   *
   * (PatternFilenameFilter is of course one of those classes that shouldn't be a publicly visible

    (this as? FirResolvedNamedReference)?.resolvedSymbol

internal fun FirReference.getResolvedKtSymbolOfNameReference(builder: KtSymbolByFirBuilder): KtSymbol? =
    getResolvedSymbolOfNameReference()?.fir?.let(builder::buildSymbol)

internal fun FirErrorNamedReference.getCandidateSymbols(): Collection<FirBasedSymbol<*>> =
    diagnostic.getCandidateSymbols()