To override the hostname (to allow a certificate for one specific site
to work for another specific site,or to allow a certificate to work
when you connected to a host by its IP address),you must replace
the policy object that the trust policy uses to determine how to
interpret the certificate. To do this,first create a new TLS policy
object for the desired hostname. Then create an array containing that
policy. Finally,tell the trust object to use that array for future
evaluation of trust.

SecTrustRef changeHostForTrust(SecTrustRef trust)
{
        CFMutableArrayRef newTrustPolicies = CFArrayCreateMutable(
                kcfAllocatorDefault,&kcfTypeArrayCallBacks);

        SecPolicyRef sslPolicy = SecPolicyCreateSSL(true,CFSTR("www.example.com"));

        CFArrayAppendValue(newTrustPolicies,sslPolicy);

#ifdef MAC_BACKWARDS_COMPATIBILITY
        /* This technique works in OS X (v10.5 and later) */

        SecTrustSetPolicies(trust,newTrustPolicies);
        CFRelease(oldTrustPolicies);

        return trust;
#else
        /* This technique works in iOS 2 and later,or
           OS X v10.7 and later */

        CFMutableArrayRef certificates = CFArrayCreateMutable(
                kcfAllocatorDefault,&kcfTypeArrayCallBacks);

        /* Copy the certificates from the original trust object */
        CFIndex count = SecTrustGetCertificateCount(trust);
        CFIndex i=0;
        for (i = 0; i < count; i++) {
                SecCertificateRef item = SecTrustGetCertificateAtIndex(trust,i);
                CFArrayAppendValue(certificates,item);
        }

        /* Create a new trust object */
        SecTrustRef newtrust = NULL;
        if (SecTrustCreateWithCertificates(certificates,newTrustPolicies,&newtrust) != errSecSuccess) {
                /* Probably a good spot to log something. */

                return NULL;
        }

        return newtrust;
#endif
}

资料来源：iOS Developer Library — Overriding TLS Chain Validation Correctly — Manipulating Trust Objects

请注意,在同一页面上,您可以找到处理自签名SSL证书的其他代码段,以防您处理此类证书.

要在Swift项目中使用此功能,请将新的C文件添加到您的项目(File .. New .. File .. iOS / Source / C_File),例如mysectrust.c和相应的头mysectrust.h(如果XCode要求你创建一个桥接头,说是)

mysectrust.h

#ifndef mysectrust_h
#define mysectrust_h

#include <Security/Security.h>

SecTrustRef changeHostForTrust(SecTrustRef trust);

#endif /* mysectrust_h */

mysectrust.c

#include "mysectrust.h"

SecTrustRef changeHostForTrust(SecTrustRef trust)
{
    CFMutableArrayRef newTrustPolicies = CFArrayCreateMutable(
                                                              kcfAllocatorDefault,&kcfTypeArrayCallBacks);

    SecPolicyRef sslPolicy = SecPolicyCreateSSL(true,CFSTR("www.example.com"));

    CFArrayAppendValue(newTrustPolicies,sslPolicy);

#ifdef MAC_BACKWARDS_COMPATIBILITY
    /* This technique works in OS X (v10.5 and later) */

    SecTrustSetPolicies(trust,newTrustPolicies);
    CFRelease(oldTrustPolicies);

    return trust;
#else
    /* This technique works in iOS 2 and later,or
     OS X v10.7 and later */

    CFMutableArrayRef certificates = CFArrayCreateMutable(
                                                          kcfAllocatorDefault,&kcfTypeArrayCallBacks);

    /* Copy the certificates from the original trust object */
    CFIndex count = SecTrustGetCertificateCount(trust);
    CFIndex i=0;
    for (i = 0; i < count; i++) {
        SecCertificateRef item = SecTrustGetCertificateAtIndex(trust,i);
        CFArrayAppendValue(certificates,item);
    }

    /* Create a new trust object */
    SecTrustRef newtrust = NULL;
    if (SecTrustCreateWithCertificates(certificates,&newtrust) != errSecSuccess) {
        /* Probably a good spot to log something. */

        return NULL;
    }

    return newtrust;
#endif
}

当然,请使用您的主机名替换上述代码中的www.example.com.

然后,在Xcode项目projectname-Bridging-Header.h中找到桥接头,并附加以下行：

#import "mysectrust.h"

现在你可以从Swift调用这个函数,例如：

func whatever(trust: SecTrustRef){

    let newTrust = changeHostForTrust(trust) // call to C function
    ...
}