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Fix OpenSSL cert validation when host is an IP address (#581) #588

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Merged
bsergean merged 1 commit into from
Jun 24, 2026
Merged

Fix OpenSSL cert validation when host is an IP address (#581) #588

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17 changes: 16 additions & 1 deletion ixwebsocket/IXSocketOpenSSL.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@

#include "IXSocketOpenSSL.h"

#include "IXNetSystem.h"
#include "IXSocketConnect.h"
#include "IXUniquePtr.h"
#include <cassert>
Expand Down Expand Up @@ -768,7 +769,21 @@ namespace ix
if (!_tlsOptions.disable_hostname_validation)
{
X509_VERIFY_PARAM* param = SSL_get0_param(_ssl_connection);
X509_VERIFY_PARAM_set1_host(param, host.c_str(), host.size());

// When the host is an IP address (literal IPv4 or IPv6), it must be
// validated against the certificate's iPAddress SAN entries rather
// than the dNSName ones. X509_VERIFY_PARAM_set1_host only checks
// dNSName / CN, so it would always fail for IP literals.
struct in6_addr addr;
if (ix::inet_pton(AF_INET, host.c_str(), &addr) == 1 ||
ix::inet_pton(AF_INET6, host.c_str(), &addr) == 1)
{
X509_VERIFY_PARAM_set1_ip_asc(param, host.c_str());
}
else
{
X509_VERIFY_PARAM_set1_host(param, host.c_str(), host.size());
}
}
#endif
handshakeSuccessful = openSSLClientHandshake(host, errMsg, isCancellationRequested);
Expand Down
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