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Serialize curl_multi_cleanup calls for OpenSSL <1.1.0 #5321

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Serialize curl_multi_cleanup calls for OpenSSL <1.1.0 #5321

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18 changes: 17 additions & 1 deletion Sources/FoundationNetworking/URLSession/libcurl/MultiHandle.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -48,6 +48,15 @@ extension URLSession {
fileprivate var timeoutSource: _TimeoutSource? = nil
private var reentrantInUpdateTimeoutTimer = false

// Only use serialization for OpenSSL < 1.1.0 which has race conditions during cleanup
private static let _needsCleanupSerialization: Bool = {
let version = CFURLSessionSSLVersionInfo()
return version.major < 1 || (version.major == 1 && version.minor < 1)
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@jrflat jrflat Dec 16, 2025

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Since curl can be built with TLS libraries other than OpenSSL, and those libraries would return {0, 0, 0} here, we'd be performing cleanup serialization that wouldn't have happened before/might not be needed. Would we want to add some way to check that SSL version parsing did succeed and is in fact OpenSSL before checking the version number?

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@clintonpi clintonpi Dec 16, 2025

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Yes! I missed adding a comment that I was thinking "if the SSL library is not known, then serialise cleanup". But true, it makes sense to not be unnecessarily defensive in this case. So I'll refactor as needed.

}()

// Process-wide cleanup lock
private static let _cleanupLock = NSLock()

init(configuration: URLSession._Configuration, workQueue: DispatchQueue) {
queue = DispatchQueue(label: "MultiHandle.isolation", target: workQueue)
setupCallbacks()
Expand All @@ -58,7 +67,14 @@ extension URLSession {
easyHandles.forEach {
try! CFURLSessionMultiHandleRemoveHandle(rawHandle, $0.rawHandle).asError()
}
try! CFURLSessionMultiHandleDeinit(rawHandle).asError()

if Self._needsCleanupSerialization {
Self._cleanupLock.lock()
try! CFURLSessionMultiHandleDeinit(rawHandle).asError()
Self._cleanupLock.unlock()
} else {
try! CFURLSessionMultiHandleDeinit(rawHandle).asError()
}
}
}
}
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16 changes: 16 additions & 0 deletions Sources/_CFURLSessionInterface/CFURLSessionInterface.c
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Expand Up @@ -676,6 +676,22 @@ CFURLSessionCurlVersion CFURLSessionCurlVersionInfo(void) {
return v;
}

CFURLSessionSSLVersion CFURLSessionSSLVersionInfo(void) {
curl_version_info_data *info = curl_version_info(CURLVERSION_NOW);
CFURLSessionSSLVersion version = {0, 0, 0};
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@jrflat jrflat Dec 16, 2025

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Related to my comment above, maybe we could add a boolean to the struct like isOpenSSL and set that to true if parsing succeeds below? An enum for different TLS libraries could be nice, but I don't think it's really needed since we're just special casing an outdated version of OpenSSL.


if (info && info->ssl_version) {
// Parse OpenSSL version string like "OpenSSL/1.0.2k-fips" or "OpenSSL/1.1.1"
const char *ssl_str = info->ssl_version;
if (strncmp(ssl_str, "OpenSSL/", 8) == 0) {
ssl_str += 8; // Skip "OpenSSL/"
sscanf(ssl_str, "%d.%d.%d", &version.major, &version.minor, &version.patch);
}
}

return version;
}


int const CFURLSessionWriteFuncPause = CURL_WRITEFUNC_PAUSE;
int const CFURLSessionReadFuncPause = CURL_READFUNC_PAUSE;
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7 changes: 7 additions & 0 deletions Sources/_CFURLSessionInterface/include/CFURLSessionInterface.h
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Expand Up @@ -580,6 +580,13 @@ typedef struct CFURLSessionCurlVersion {
} CFURLSessionCurlVersion;
CF_EXPORT CFURLSessionCurlVersion CFURLSessionCurlVersionInfo(void);

typedef struct CFURLSessionSSLVersion {
int major;
int minor;
int patch;
} CFURLSessionSSLVersion;
CF_EXPORT CFURLSessionSSLVersion CFURLSessionSSLVersionInfo(void);


CF_EXPORT int const CFURLSessionWriteFuncPause;
CF_EXPORT int const CFURLSessionReadFuncPause;
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