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bpo-32185: Don't send IP in SNI TLS extension #4938

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bpo-32185: Don't send IP in SNI TLS extension #4938

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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2017-12-20-09-25-10.bpo-32185.IL0cMt.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
The SSL module no longer sends IP addresses in SNI TLS extension on
platforms with OpenSSL 1.0.2+ or inet_pton.
42 changes: 40 additions & 2 deletions Modules/_ssl.c
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,11 @@ static PySocketModule_APIObject PySocketModule;
#include <sys/poll.h>
#endif

#ifndef MS_WINDOWS
/* inet_pton */
#include <arpa/inet.h>
#endif

/* Don't warn about deprecated functions */
#ifdef __GNUC__
#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
Expand Down Expand Up @@ -755,8 +760,41 @@ newPySSLSocket(PySSLContext *sslctx, PySocketSockObject *sock,
SSL_set_mode(self->ssl, mode);

#if HAVE_SNI
if (server_hostname != NULL)
SSL_set_tlsext_host_name(self->ssl, server_hostname);
if (server_hostname != NULL) {
/* Don't send SNI for IP addresses. We cannot simply use inet_aton() and
* inet_pton() here. inet_aton() may be linked weakly and inet_pton() isn't
* available on all platforms. Use OpenSSL's IP address parser. It's
* available since 1.0.2 and LibreSSL since at least 2.3.0. */
int send_sni = 1;
#if OPENSSL_VERSION_NUMBER >= 0x10200000L
ASN1_OCTET_STRING *ip = a2i_IPADDRESS(server_hostname);
if (ip == NULL) {
send_sni = 1;
ERR_clear_error();
} else {
send_sni = 0;
ASN1_OCTET_STRING_free(ip);
}
#elif defined(HAVE_INET_PTON)
#ifdef ENABLE_IPV6
char packed[Py_MAX(sizeof(struct in_addr), sizeof(struct in6_addr))];
#else
char packed[sizeof(struct in_addr)];
#endif /* ENABLE_IPV6 */
if (inet_pton(AF_INET, server_hostname, packed)) {
send_sni = 0;
#ifdef ENABLE_IPV6
} else if(inet_pton(AF_INET6, server_hostname, packed)) {
send_sni = 0;
#endif /* ENABLE_IPV6 */
} else {
send_sni = 1;
}
#endif /* HAVE_INET_PTON */
if (send_sni) {
SSL_set_tlsext_host_name(self->ssl, server_hostname);
}
}
#endif
/* If the socket is in non-blocking mode or timeout mode, set the BIO
* to non-blocking mode (blocking is the default)
Expand Down