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Merged
kllysng merged 2 commits into from
May 19, 2026
+59 −10
Merged

Improve validation of "jku" claim (8.x) #3481

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a80bf15
Improve validation of "jku" claim
Avery-Dunn Mar 4, 2026
edcfe57
Merge branch 'dev8x' into alexholub/improve-validation-of-jku-claim-8x
kllysng May 19, 2026
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4 changes: 3 additions & 1 deletion src/Microsoft.IdentityModel.Protocols.SignedHttpRequest/SignedHttpRequestHandler.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1318,7 +1318,9 @@ private static bool IsJkuUriInListOfAllowedDomains(string jkuSetUrl, SignedHttpR
return false;

var uri = new Uri(jkuSetUrl, UriKind.RelativeOrAbsolute);
return signedHttpRequestValidationContext.SignedHttpRequestValidationParameters.AllowedDomainsForJkuRetrieval.Any(domain => uri.Host.EndsWith(domain, StringComparison.OrdinalIgnoreCase));
return signedHttpRequestValidationContext.SignedHttpRequestValidationParameters.AllowedDomainsForJkuRetrieval.Any(domain =>
uri.Host.Equals(domain, StringComparison.OrdinalIgnoreCase) ||
uri.Host.EndsWith("." + domain, StringComparison.OrdinalIgnoreCase));
}

/// <summary>
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65 changes: 56 additions & 9 deletions test/Microsoft.IdentityModel.Protocols.SignedHttpRequest.Tests/PopKeyResolvingTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -490,17 +490,11 @@ public static TheoryData<ResolvePopKeyTheoryData> ResolvePopKeyFromJkuTheoryData
},
new ResolvePopKeyTheoryData
{
CallContext = new CallContext()
{
PropertyBag = new Dictionary<string, object>()
{
// to simulate http call and satisfy test requirements
{"mockGetPopKeysFromJkuAsync_return1Key", null }
}
},
// TLD-only entries should NOT match arbitrary domains (security fix)
JkuSetUrl = "https://www.contoso.com",
SignedHttpRequestValidationParameters = { AllowResolvingPopKeyFromJku = true, AllowedDomainsForJkuRetrieval = { ".com" }},
TestId = "JkuTurnedOnTopLevelDomainMatch"
ExpectedException = new ExpectedException(typeof(SignedHttpRequestInvalidPopKeyException), string.Format(LogMessages.IDX23038, "https://www.contoso.com", ".com")),
TestId = "JkuTurnedOnTopLevelDomainNoMatch"
},
new ResolvePopKeyTheoryData
{
Expand Down Expand Up @@ -557,6 +551,59 @@ public static TheoryData<ResolvePopKeyTheoryData> ResolvePopKeyFromJkuTheoryData
JkuSetUrl = "https://localhost/keys",
SignedHttpRequestValidationParameters = { AllowResolvingPopKeyFromJku = true, AllowedDomainsForJkuRetrieval = { "localhost" }},
TestId = "JkuTurnedOnLocalUrl"
},
// Security fix: Malicious domain suffix bypass attempts should fail
new ResolvePopKeyTheoryData
{
// evilcontoso.com should NOT match allowlist entry "contoso.com"
JkuSetUrl = "https://evilcontoso.com/jwks",
SignedHttpRequestValidationParameters = { AllowResolvingPopKeyFromJku = true, AllowedDomainsForJkuRetrieval = { "contoso.com" }},
ExpectedException = new ExpectedException(typeof(SignedHttpRequestInvalidPopKeyException), string.Format(LogMessages.IDX23038, "https://evilcontoso.com/jwks", "contoso.com")),
TestId = "JkuDomainBypassAttempt_SuffixWithoutDot_ShouldFail"
},
new ResolvePopKeyTheoryData
{
// evil-contoso.com should NOT match allowlist entry "contoso.com"
JkuSetUrl = "https://evil-contoso.com/jwks",
SignedHttpRequestValidationParameters = { AllowResolvingPopKeyFromJku = true, AllowedDomainsForJkuRetrieval = { "contoso.com" }},
ExpectedException = new ExpectedException(typeof(SignedHttpRequestInvalidPopKeyException), string.Format(LogMessages.IDX23038, "https://evil-contoso.com/jwks", "contoso.com")),
TestId = "JkuDomainBypassAttempt_HyphenatedSuffix_ShouldFail"
},
new ResolvePopKeyTheoryData
{
// notcontoso.com should NOT match allowlist entry "contoso.com"
JkuSetUrl = "https://notcontoso.com/jwks",
SignedHttpRequestValidationParameters = { AllowResolvingPopKeyFromJku = true, AllowedDomainsForJkuRetrieval = { "contoso.com" }},
ExpectedException = new ExpectedException(typeof(SignedHttpRequestInvalidPopKeyException), string.Format(LogMessages.IDX23038, "https://notcontoso.com/jwks", "contoso.com")),
TestId = "JkuDomainBypassAttempt_PrefixedSuffix_ShouldFail"
},
new ResolvePopKeyTheoryData
{
CallContext = new CallContext()
{
PropertyBag = new Dictionary<string, object>()
{
{"mockGetPopKeysFromJkuAsync_return1Key", null }
}
},
// Legitimate subdomain keys.contoso.com SHOULD match allowlist entry "contoso.com"
JkuSetUrl = "https://keys.contoso.com/jwks",
SignedHttpRequestValidationParameters = { AllowResolvingPopKeyFromJku = true, AllowedDomainsForJkuRetrieval = { "contoso.com" }},
TestId = "JkuLegitimateSubdomain_ShouldPass"
},
new ResolvePopKeyTheoryData
{
CallContext = new CallContext()
{
PropertyBag = new Dictionary<string, object>()
{
{"mockGetPopKeysFromJkuAsync_return1Key", null }
}
},
// Exact domain match contoso.com SHOULD match allowlist entry "contoso.com"
JkuSetUrl = "https://contoso.com/jwks",
SignedHttpRequestValidationParameters = { AllowResolvingPopKeyFromJku = true, AllowedDomainsForJkuRetrieval = { "contoso.com" }},
TestId = "JkuExactDomainMatch_ShouldPass"
}
};
}
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