macOS XPC 授权

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XPC 授权

苹果还提出了另一种验证连接进程是否具有调用公开的 XPC 方法的权限的方法。

当应用程序需要以特权用户身份执行操作时，通常不会将应用程序作为特权用户运行，而是作为根用户安装一个 HelperTool 作为 XPC 服务，应用程序可以从中调用该服务来执行这些操作。但是，调用服务的应用程序应具有足够的授权。

ShuoldAcceptNewConnection 总是 YES

在 EvenBetterAuthorizationSample 中可以找到一个示例。在 App/AppDelegate.m 中，它尝试连接到HelperTool。而在 HelperTool/HelperTool.m 中，函数**shouldAcceptNewConnection**不会检查之前提到的任何要求。它将始终返回 YES：

- (BOOL)listener:(NSXPCListener *)listener shouldAcceptNewConnection:(NSXPCConnection *)newConnection
// Called by our XPC listener when a new connection comes in.  We configure the connection
// with our protocol and ourselves as the main object.
{
assert(listener == self.listener);
#pragma unused(listener)
assert(newConnection != nil);

newConnection.exportedInterface = [NSXPCInterface interfaceWithProtocol:@protocol(HelperToolProtocol)];
newConnection.exportedObject = self;
[newConnection resume];

return YES;
}

有关如何正确配置此检查的更多信息，请参阅：

{% content-ref url="macos-xpc-connecting-process-check.md" %} macos-xpc-connecting-process-check.md {% endcontent-ref %}

应用程序权限

然而，当调用 HelperTool 的方法时，会进行一些授权操作。

App/AppDelegate.m 中的函数 applicationDidFinishLaunching 在应用程序启动后会创建一个空的授权引用。这应该总是有效的。
然后，它将尝试通过调用 setupAuthorizationRights 向该授权引用添加一些权限：

- (void)applicationDidFinishLaunching:(NSNotification *)note
{
[...]
err = AuthorizationCreate(NULL, NULL, 0, &self->_authRef);
if (err == errAuthorizationSuccess) {
err = AuthorizationMakeExternalForm(self->_authRef, &extForm);
}
if (err == errAuthorizationSuccess) {
self.authorization = [[NSData alloc] initWithBytes:&extForm length:sizeof(extForm)];
}
assert(err == errAuthorizationSuccess);

// If we successfully connected to Authorization Services, add definitions for our default
// rights (unless they're already in the database).

if (self->_authRef) {
[Common setupAuthorizationRights:self->_authRef];
}

[self.window makeKeyAndOrderFront:self];
}

Common/Common.m中的setupAuthorizationRights函数将应用程序的权限存储在/var/db/auth.db授权数据库中。请注意，它只会添加尚未存在于数据库中的权限：

+ (void)setupAuthorizationRights:(AuthorizationRef)authRef
// See comment in header.
{
assert(authRef != NULL);
[Common enumerateRightsUsingBlock:^(NSString * authRightName, id authRightDefault, NSString * authRightDesc) {
OSStatus    blockErr;

// First get the right.  If we get back errAuthorizationDenied that means there's
// no current definition, so we add our default one.

blockErr = AuthorizationRightGet([authRightName UTF8String], NULL);
if (blockErr == errAuthorizationDenied) {
blockErr = AuthorizationRightSet(
authRef,                                    // authRef
[authRightName UTF8String],                 // rightName
(__bridge CFTypeRef) authRightDefault,      // rightDefinition
(__bridge CFStringRef) authRightDesc,       // descriptionKey
NULL,                                       // bundle (NULL implies main bundle)
CFSTR("Common")                             // localeTableName
);
assert(blockErr == errAuthorizationSuccess);
} else {
// A right already exists (err == noErr) or any other error occurs, we
// assume that it has been set up in advance by the system administrator or
// this is the second time we've run.  Either way, there's nothing more for
// us to do.
}
}];
}

函数enumerateRightsUsingBlock是用于获取应用程序权限的函数，这些权限在commandInfo中定义：

static NSString * kCommandKeyAuthRightName    = @"authRightName";
static NSString * kCommandKeyAuthRightDefault = @"authRightDefault";
static NSString * kCommandKeyAuthRightDesc    = @"authRightDescription";

+ (NSDictionary *)commandInfo
{
static dispatch_once_t sOnceToken;
static NSDictionary *  sCommandInfo;

dispatch_once(&sOnceToken, ^{
sCommandInfo = @{
NSStringFromSelector(@selector(readLicenseKeyAuthorization:withReply:)) : @{
kCommandKeyAuthRightName    : @"com.example.apple-samplecode.EBAS.readLicenseKey",
kCommandKeyAuthRightDefault : @kAuthorizationRuleClassAllow,
kCommandKeyAuthRightDesc    : NSLocalizedString(
@"EBAS is trying to read its license key.",
@"prompt shown when user is required to authorize to read the license key"
)
},
NSStringFromSelector(@selector(writeLicenseKey:authorization:withReply:)) : @{
kCommandKeyAuthRightName    : @"com.example.apple-samplecode.EBAS.writeLicenseKey",
kCommandKeyAuthRightDefault : @kAuthorizationRuleAuthenticateAsAdmin,
kCommandKeyAuthRightDesc    : NSLocalizedString(
@"EBAS is trying to write its license key.",
@"prompt shown when user is required to authorize to write the license key"
)
},
NSStringFromSelector(@selector(bindToLowNumberPortAuthorization:withReply:)) : @{
kCommandKeyAuthRightName    : @"com.example.apple-samplecode.EBAS.startWebService",
kCommandKeyAuthRightDefault : @kAuthorizationRuleClassAllow,
kCommandKeyAuthRightDesc    : NSLocalizedString(
@"EBAS is trying to start its web service.",
@"prompt shown when user is required to authorize to start the web service"
)
}
};
});
return sCommandInfo;
}

+ (NSString *)authorizationRightForCommand:(SEL)command
// See comment in header.
{
return [self commandInfo][NSStringFromSelector(command)][kCommandKeyAuthRightName];
}

+ (void)enumerateRightsUsingBlock:(void (^)(NSString * authRightName, id authRightDefault, NSString * authRightDesc))block
// Calls the supplied block with information about each known authorization right..
{
[self.commandInfo enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
#pragma unused(key)
#pragma unused(stop)
NSDictionary *  commandDict;
NSString *      authRightName;
id              authRightDefault;
NSString *      authRightDesc;

// If any of the following asserts fire it's likely that you've got a bug
// in sCommandInfo.

commandDict = (NSDictionary *) obj;
assert([commandDict isKindOfClass:[NSDictionary class]]);

authRightName = [commandDict objectForKey:kCommandKeyAuthRightName];
assert([authRightName isKindOfClass:[NSString class]]);

authRightDefault = [commandDict objectForKey:kCommandKeyAuthRightDefault];
assert(authRightDefault != nil);

authRightDesc = [commandDict objectForKey:kCommandKeyAuthRightDesc];
assert([authRightDesc isKindOfClass:[NSString class]]);

block(authRightName, authRightDefault, authRightDesc);
}];
}

这意味着在此过程结束时，commandInfo中声明的权限将存储在/var/db/auth.db中。请注意，您可以在其中找到每个需要身份验证的方法的权限名称和**kCommandKeyAuthRightDefault。后者指示谁可以获得此权限**。

有不同的范围来指示谁可以访问权限。其中一些在AuthorizationDB.h中定义（您可以在此处找到所有内容），但总结如下：

名称	值	描述
kAuthorizationRuleClassAllow	allow	任何人
kAuthorizationRuleClassDeny	deny	无人
kAuthorizationRuleIsAdmin	is-admin	当前用户需要是管理员（在管理员组内）
kAuthorizationRuleAuthenticateAsSessionUser	authenticate-session-owner	要求用户进行身份验证。
kAuthorizationRuleAuthenticateAsAdmin	authenticate-admin	要求用户进行身份验证。他需要是管理员（在管理员组内）
kAuthorizationRightRule	rule	指定规则
kAuthorizationComment	comment	在权限上指定一些额外的注释

权限验证

在HelperTool/HelperTool.m中，函数**readLicenseKeyAuthorization检查调用者是否被授权执行此方法**，调用函数**checkAuthorization。此函数将检查调用进程发送的authData是否具有正确的格式**，然后将检查获取权限所需的内容以调用特定方法。如果一切顺利，返回的error将为nil：

- (NSError *)checkAuthorization:(NSData *)authData command:(SEL)command
{
[...]

// First check that authData looks reasonable.

error = nil;
if ( (authData == nil) || ([authData length] != sizeof(AuthorizationExternalForm)) ) {
error = [NSError errorWithDomain:NSOSStatusErrorDomain code:paramErr userInfo:nil];
}

// Create an authorization ref from that the external form data contained within.

if (error == nil) {
err = AuthorizationCreateFromExternalForm([authData bytes], &authRef);

// Authorize the right associated with the command.

if (err == errAuthorizationSuccess) {
AuthorizationItem   oneRight = { NULL, 0, NULL, 0 };
AuthorizationRights rights   = { 1, &oneRight };

oneRight.name = [[Common authorizationRightForCommand:command] UTF8String];
assert(oneRight.name != NULL);

err = AuthorizationCopyRights(
authRef,
&rights,
NULL,
kAuthorizationFlagExtendRights | kAuthorizationFlagInteractionAllowed,
NULL
);
}
if (err != errAuthorizationSuccess) {
error = [NSError errorWithDomain:NSOSStatusErrorDomain code:err userInfo:nil];
}
}

if (authRef != NULL) {
junk = AuthorizationFree(authRef, 0);
assert(junk == errAuthorizationSuccess);
}

return error;
}

请注意，要检查调用该方法的权限，函数authorizationRightForCommand将仅检查先前的注释对象commandInfo。然后，它将调用AuthorizationCopyRights来检查是否有权调用该函数（请注意，标志允许与用户交互）。

在这种情况下，要调用函数readLicenseKeyAuthorization，kCommandKeyAuthRightDefault被定义为@kAuthorizationRuleClassAllow。因此，任何人都可以调用它。

数据库信息

提到这些信息存储在/var/db/auth.db中。您可以使用以下命令列出所有存储的规则：

sudo sqlite3 /var/db/auth.db
SELECT name FROM rules;
SELECT name FROM rules WHERE name LIKE '%safari%';

然后，您可以使用以下命令查看谁可以访问权限：

security authorizationdb read com.apple.safaridriver.allow

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你在一家 网络安全公司 工作吗？想要在 HackTricks 中 宣传你的公司 吗？或者你想要获得 PEASS 的最新版本或下载 HackTricks 的 PDF 吗？请查看 订阅计划！
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