From d3c5951bb4552185b5a0766a38cc30ffbf857036 Mon Sep 17 00:00:00 2001
From: Evgeny Zinoviev <me@ch1p.io>
Date: Sun, 16 Jun 2019 18:22:01 +0300
Subject: rewrite

---
 Makefile      |   4 +--
 README.md     |   4 ++-
 sketch.sh     |   1 -
 sketchtrial.c | 103 ----------------------------------------------------------
 sketchtrial.m |  28 ++++++++++++++++
 5 files changed, 33 insertions(+), 107 deletions(-)
 delete mode 100644 sketchtrial.c
 create mode 100644 sketchtrial.m

diff --git a/Makefile b/Makefile
index 9c717ea..21116b5 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,7 @@
-CFLAGS = -dynamiclib -lpthread
+CFLAGS = -dynamiclib -framework AppKit -framework Foundation
 
 all:
-	$(CC) $(CFLAGS) sketchtrial.c -o libsketchtrial.dylib
+	$(CC) $(CFLAGS) sketchtrial.m -o libsketchtrial.dylib
 
 clean:
 	rm -rf *.o libsketchtrial.dylib
diff --git a/README.md b/README.md
index c7b608f..995367f 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,8 @@
 # sketchtrial
 
-To bypass Sketch trial verification process you just need to spoof a couple of NSDate calls when the app starts. This repository contains a shared library code that can be inserted (using `DYLD_INSERT_LIBRARIES`) to the Sketch process that spoofs the right `gettimeofday` calls.
+This is a shared library that spoofs some ObjC method calls to disable Sketch license verification.
+
+Tested on Sketch 55.2.
 
 ## Building
 ```
diff --git a/sketch.sh b/sketch.sh
index 73dcdfc..f9d9dad 100755
--- a/sketch.sh
+++ b/sketch.sh
@@ -1,5 +1,4 @@
 #!/bin/bash
 DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"
-export DYLD_FORCE_FLAT_NAMESPACE=1 
 export DYLD_INSERT_LIBRARIES=$DIR/libsketchtrial.dylib
 /Applications/Sketch.app/Contents/MacOS/Sketch
diff --git a/sketchtrial.c b/sketchtrial.c
deleted file mode 100644
index 388f8ab..0000000
--- a/sketchtrial.c
+++ /dev/null
@@ -1,103 +0,0 @@
-#include <stdio.h>
-#include <stdlib.h>
-#include <stdbool.h>
-#include <string.h>
-#include <sys/time.h>
-#include <unistd.h>
-#include <execinfo.h>
-#include <dlfcn.h>
-#include <pthread.h>
-
-static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
-static int calls_left = 9;
-static bool done = false;
-static char buf[32];
-static long days = -5000;
-
-// pointer to the original function
-int (*orig_gettimeofday) (struct timeval *restrict tp, void *restrict tzp) = NULL;
-
-void parse_bt_source(char* src, char* dst, int len) {
-    int pos = 0;
-    int state = 0;
-    for (char *c = src; *c != '\0' && pos < len-1; c++) {
-        if (!state) {
-            if (*c == ' ') {
-                state = 1;
-            }
-            continue;
-        }
-        if (state == 1) {
-            if (*c != ' ') {
-                state = 2;
-            }
-        }
-        if (state == 2) {
-            if (*c != ' ') {
-                dst[pos++] = *c;
-            } else {
-                dst[pos] = '\0';
-                break;
-            }
-        }
-    }
-}
-
-int gettimeofday(struct timeval *restrict tp, void *restrict tzp) {
-    if (!orig_gettimeofday) {
-        orig_gettimeofday = dlsym(RTLD_NEXT, "gettimeofday");
-    }
-
-    int result = orig_gettimeofday(tp, tzp);
-    if (result != 0 || done) {
-        return result;
-    }
-
-    pthread_mutex_lock(&mutex);
-    if (!calls_left) {
-        goto end;
-    }
-
-    void *callstack[128];
-    int frames = backtrace(callstack, 128);
-    char **strs = backtrace_symbols(callstack, frames);
-    int i;
-    bool call_sketch = false;
-    bool call_nsdate = false;
-
-    for (i = 0; i < frames; ++i) {
-        parse_bt_source(strs[i], buf, 32);
-        if (strstr(strs[i], "NSNotification") != NULL || !strcmp(buf, "CFNetwork")) {
-            call_sketch = false;
-            break;
-        }
-        if (!call_nsdate && strstr(strs[i], "NSDate") != NULL) {
-            call_nsdate = true;
-        }
-        if (!call_sketch && !strcmp(buf, "Sketch")) {
-            call_sketch = true;
-        }
-    }
-
-    if (call_sketch && call_nsdate) {
-        tp->tv_sec += days * 86400;
-        tp->tv_usec = tp->tv_sec * 1000000;
-        calls_left--;
-
-        printf("spoofed time on call stack:\n");
-        for (i = 0; i < frames; i++) {
-            printf("    %s\n", strs[i]);
-        }
-        printf("\n");
-    }
-
-    free(strs);
-    if (!calls_left) {
-        done = true;
-    }
-
-end:
-    pthread_mutex_unlock(&mutex);
-
-    return result;
-}
diff --git a/sketchtrial.m b/sketchtrial.m
new file mode 100644
index 0000000..26875d6
--- /dev/null
+++ b/sketchtrial.m
@@ -0,0 +1,28 @@
+#import <objc/runtime.h>
+#import <Foundation/Foundation.h>
+#include <AppKit/AppKit.h>
+
+
+//
+// BCRegularLicense
+//
+
+@interface BCRegularLicensePatched : NSObject
+- (bool)isExpired;
+@end
+
+@implementation BCRegularLicensePatched
+
++(void)load {
+Class origClass = NSClassFromString(@"BCRegularLicense");
+    Method origMethod = class_getInstanceMethod(origClass, @selector(isExpired));
+    Method replMethod = class_getInstanceMethod(NSClassFromString(@"BCRegularLicensePatched"), @selector(isExpired));
+    
+    method_exchangeImplementations(origMethod, replMethod);
+}
+
+-(bool)isExpired {
+    return false;
+}
+
+@end
-- 
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