iPhone get SSID without private library

Here's the cleaned up ARC version, based on @elsurudo's code:

- (id)fetchSSIDInfo {
     NSArray *ifs = (__bridge_transfer NSArray *)CNCopySupportedInterfaces();
     NSLog(@"Supported interfaces: %@", ifs);
     NSDictionary *info;
     for (NSString *ifnam in ifs) {
         info = (__bridge_transfer NSDictionary *)CNCopyCurrentNetworkInfo((__bridge CFStringRef)ifnam);
         NSLog(@"%@ => %@", ifnam, info);
         if (info && [info count]) { break; }
     }
     return info;
}

As of iOS 7 or 8, you can do this (need Entitlement for iOS 12+ as shown below):

@import SystemConfiguration.CaptiveNetwork;

/** Returns first non-empty SSID network info dictionary.
 *  @see CNCopyCurrentNetworkInfo */
- (NSDictionary *)fetchSSIDInfo {
    NSArray *interfaceNames = CFBridgingRelease(CNCopySupportedInterfaces());
    NSLog(@"%s: Supported interfaces: %@", __func__, interfaceNames);

    NSDictionary *SSIDInfo;
    for (NSString *interfaceName in interfaceNames) {
        SSIDInfo = CFBridgingRelease(
            CNCopyCurrentNetworkInfo((__bridge CFStringRef)interfaceName));
        NSLog(@"%s: %@ => %@", __func__, interfaceName, SSIDInfo);

        BOOL isNotEmpty = (SSIDInfo.count > 0);
        if (isNotEmpty) {
            break;
        }
    }
    return SSIDInfo;
}

Example output:

2011-03-04 15:32:00.669 ShowSSID[4857:307] -[ShowSSIDAppDelegate fetchSSIDInfo]: Supported interfaces: (
    en0
)
2011-03-04 15:32:00.693 ShowSSID[4857:307] -[ShowSSIDAppDelegate fetchSSIDInfo]: en0 => {
    BSSID = "ca:fe:ca:fe:ca:fe";
    SSID = XXXX;
    SSIDDATA = <01234567 01234567 01234567>;
}

Note that no ifs are supported on the simulator. Test on your device.

iOS 12

You must enable access wifi info from capabilities.

Important To use this function in iOS 12 and later, enable the Access WiFi Information capability for your app in Xcode. When you enable this capability, Xcode automatically adds the Access WiFi Information entitlement to your entitlements file and App ID. Documentation link

Swift 4.2

func getConnectedWifiInfo() -> [AnyHashable: Any]? {

    if let ifs = CFBridgingRetain( CNCopySupportedInterfaces()) as? [String],
        let ifName = ifs.first as CFString?,
        let info = CFBridgingRetain( CNCopyCurrentNetworkInfo((ifName))) as? [AnyHashable: Any] {

        return info
    }
    return nil

}

UPDATE FOR iOS 10 and up

CNCopySupportedInterfaces is no longer deprecated in iOS 10. (API Reference)

You need to import SystemConfiguration/CaptiveNetwork.h and add SystemConfiguration.framework to your target's Linked Libraries (under build phases).

Here is a code snippet in swift (RikiRiocma's Answer):

import Foundation
import SystemConfiguration.CaptiveNetwork

public class SSID {
    class func fetchSSIDInfo() -> String {
        var currentSSID = ""
        if let interfaces = CNCopySupportedInterfaces() {
            for i in 0..<CFArrayGetCount(interfaces) {
                let interfaceName: UnsafePointer<Void> = CFArrayGetValueAtIndex(interfaces, i)
                let rec = unsafeBitCast(interfaceName, AnyObject.self)
                let unsafeInterfaceData = CNCopyCurrentNetworkInfo("\(rec)")
                if unsafeInterfaceData != nil {
                    let interfaceData = unsafeInterfaceData! as Dictionary!
                    currentSSID = interfaceData["SSID"] as! String
                }
            }
        }
        return currentSSID
    }
}

(Important: CNCopySupportedInterfaces returns nil on simulator.)

For Objective-c, see Esad's answer here and below

+ (NSString *)GetCurrentWifiHotSpotName {    
    NSString *wifiName = nil;
    NSArray *ifs = (__bridge_transfer id)CNCopySupportedInterfaces();
    for (NSString *ifnam in ifs) {
        NSDictionary *info = (__bridge_transfer id)CNCopyCurrentNetworkInfo((__bridge CFStringRef)ifnam);
        if (info[@"SSID"]) {
            wifiName = info[@"SSID"];
        }
    }
    return wifiName;
}

UPDATE FOR iOS 9

As of iOS 9 Captive Network is deprecated*. (source)

*No longer deprecated in iOS 10, see above.

It's recommended you use NEHotspotHelper (source)

You will need to email apple at [email protected] and request entitlements. (source)

Sample Code (Not my code. See Pablo A's answer):

for(NEHotspotNetwork *hotspotNetwork in [NEHotspotHelper supportedNetworkInterfaces]) {
    NSString *ssid = hotspotNetwork.SSID;
    NSString *bssid = hotspotNetwork.BSSID;
    BOOL secure = hotspotNetwork.secure;
    BOOL autoJoined = hotspotNetwork.autoJoined;
    double signalStrength = hotspotNetwork.signalStrength;
}

Side note: Yup, they deprecated CNCopySupportedInterfaces in iOS 9 and reversed their position in iOS 10. I spoke with an Apple networking engineer and the reversal came after so many people filed Radars and spoke out about the issue on the Apple Developer forums.