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[原创]AI静态分析 内核模块隐藏 Frida 特征 绕过linker私有结构遍历崩溃链
发表于: 6天前 2898

[原创]AI静态分析 内核模块隐藏 Frida 特征 绕过linker私有结构遍历崩溃链

6天前
2898

跟随feicong大佬学习后,对某sec.so进行了反调试分析,发现其反调试手段主要集中在:

从已有分析可以确认,这个 so 在初始化阶段会拉起多条保护链,其中与 Frida 最直接相关的一条是:

典型命中目标包括:

一旦命中,样本要么直接触发退出,要么进入更激进的异常路径,最终导致进程崩溃。

本文的重点

可以先用一张总览图把本文涉及的检测面放在一起:

详细静态分析是利用agent工具 codex + tenrec(ida的mcp)进行的,不得不感叹AI正在彻底颠覆行业。

完整的反调试机制可以先用一张图概括:

目前最准确的整理方式是:

其中:

sub_1C544 的主循环里至少包含三个检测点:

其中和本文最直接相关的是 sub_1BFAC

可以把它还原成下面这种可读伪代码:

用户态检测流程可以概括成:

这意味着,只要用户态看到的 status 内容被改写,检测就会失效。

很多人第一次分析这类检测时,会把 gum-js-loopgmain 当成“样本自己创建的线程”。
其实不是,这些线程名来自 Frida 运行时自身。

Frida 的脚本执行、消息循环、调度逻辑依赖 Gum。
在目标进程里注入 agent 后,Gum 会创建自己的事件循环线程,典型线程名就是:

这个线程基本可以视作“Frida JavaScript runtime 正在进程内运行”的直接信号。

Frida 底层依赖 GLib/GIO 事件循环。
一旦使用消息通信、异步 IO 或内部调度,GLib 相关线程也会出现,典型名就是:

原因很简单:

换句话说,线程名检测是最典型、也最容易落地的 Frida 识别手段之一。

既然样本依赖的是 /proc 输出,那最直接的思路就是:

本文使用的模块就是:

b7fK9s2c8@1M7s2y4Q4x3@1q4Q4x3V1k6Q4x3V1k6Y4K9i4c8Z5N6h3u0Q4x3X3g2U0L8$3#2Q4x3V1k6F1N6h3!0W2L8W2)9J5c8X3E0W2M7X3&6W2L8q4)9#2k6X3#2G2k6s2g2D9k6i4x3`.

hookmodule 主要做了三类事:

这三类 hook 对应三条不同检测面:

从实现层面看,hookmodule 的核心思路是把“用户态读取 /proc 的结果”前移到内核里处理:

模块支持的关键参数有:

示例加载方式:

这里的 hide_so 并不只是“隐藏 so 名字”,更准确地说是:

这是本文最核心的一部分。

用户态样本读取的 status 文本最终来自内核的 proc_pid_status()
因此最稳的方式不是去改用户态 fopen/read/fgets,而是直接在内核里拦 proc_pid_status

模块里使用了 kretprobe:

进入 proc_pid_status 时:

如果线程名命中隐藏关键字,就临时改写:

返回 proc_pid_status 后再恢复:

因为用户态样本最终看到的是:

status 文件中的线程名字段,本质上就是内核按 task_struct->comm 生成的文本。
我们在文本生成前把 task->comm 临时改成替身值,样本读到的就不再是:

而是:

等到文本生成完成,再恢复原值。
这样既能骗过检测,又不会永久破坏线程本身。

这条关键绕过链可以用时序图来表示:

用户态 hook 的问题在于:

而内核里拦 proc_pid_status 的优点是:

除了 status,模块还用 ftrace hook 了 proc_task_name

关键实现:

这个 hook 并不替代 proc_pid_status,而是补位:

对这些路径,fh_proc_task_name 可以直接把线程名输出改成:

因为有些样本并不只读 status,还会:

这时只拦 proc_pid_status 不一定够,proc_task_name 相当于多了一层兜底。

它和 proc_pid_status 的分工关系如下:

sub_1C26C 这类检测会扫 /proc/self/maps
模块里对应的处理是 hook show_map_vma

关键逻辑:

因为 /proc/<pid>/maps 的每一行最终都是内核把 vma 格式化成文本。
我们在输出层直接跳过匹配项,用户态样本看到的 maps 就不会包含:

这点需要说清楚。

show_map_vma 只能隐藏:

不能隐藏

所以它能绕过 sub_1C26C 这类 /proc/maps 检测,
但无法直接解决 sub_20BDC 那种 linker 私有结构遍历。

模块还在 proc_pid_status kretprobe 里顺手做了两件事:

这可以绕过另一类典型用户态反调试:

这正对应 so 另一条链路里的:

sub_20BDC 本质上不是 /proc 检测函数,而是:

可以把它理解成一个私有版:

根据 tenrec 分析后结果,可以整理成:

sub_20BDC 的危险点有两个:

这意味着:

这也解释了为什么:

根因不是“Frida 改坏了 linker 偏移”,而是:

这条“正常环境通常不崩、Frida 环境更容易崩”的差异,可以用下面这张图概括:

从当前分析可以确认,sub_20BDC 至少有两条从初始化阶段可达的路径。

结合动态日志,当前更直接的崩溃短链是:

可以把这条崩溃链画成:

原因很简单:

也就是说:

因此,从对抗角度看:

**sec.so 的反调试并不是单点检测,而是一组层次化的保护:

本文给出的内核模块方案,核心价值在于:

这使得:

但同样需要明确边界:

因此在实战中,更合理的策略不是“只用一种手段”,而是分层处理:

这才是对抗 **sec.so 这类综合型反调试模块的更稳妥方案。

最后用一张总图收敛本文结论:

void scan_task_status_for_frida_threads(void) {
    DIR *dir = opendir("/proc/self/task");
    if (!dir)
        return;
 
    while ((de = readdir(dir)) != NULL) {
        if (!is_digits(de->d_name))
            continue;
 
        char path[0x100];
        snprintf(path, sizeof(path), "/proc/self/task/%s/status", de->d_name);
 
        char buf[0x400] = {0};
        if (!read_text_file(path, buf, sizeof(buf)))
            continue;
 
        if (strstr(buf, "gum-js-loop") || strstr(buf, "gmain")) {
            _exit(0); // 或 exit(0)
        }
    }
 
    closedir(dir);
}
void scan_task_status_for_frida_threads(void) {
    DIR *dir = opendir("/proc/self/task");
    if (!dir)
        return;
 
    while ((de = readdir(dir)) != NULL) {
        if (!is_digits(de->d_name))
            continue;
 
        char path[0x100];
        snprintf(path, sizeof(path), "/proc/self/task/%s/status", de->d_name);
 
        char buf[0x400] = {0};
        if (!read_text_file(path, buf, sizeof(buf)))
            continue;
 
        if (strstr(buf, "gum-js-loop") || strstr(buf, "gmain")) {
            _exit(0); // 或 exit(0)
        }
    }
 
    closedir(dir);
}
检测面 目标路径 模块对应处理
线程名 /proc/<pid>/task/<tid>/status proc_pid_status kretprobe
任务名显示 /proc/.../task/... 相关 seq 输出 proc_task_name ftrace
映射路径 /proc/<pid>/maps show_map_vma ftrace
static int target_pid = 0;
static int target_uid = -1;
static char *hide_so[MAX_NAMES];
static int hide_so_cnt;
static int target_pid = 0;
static int target_uid = -1;
static char *hide_so[MAX_NAMES];
static int hide_so_cnt;
insmod hookmodule.ko hide_so="frida,gum,gmain,AGENT" debug=true
insmod hookmodule.ko hide_so="frida,gum,gmain,AGENT" debug=true
static struct kretprobe_wrap my_kretprobes[] = {
    KRETPROBEHOOK(
        kretprobe_ret_handler_porc_pid_status,
        kretprobe_entry_handler_proc_pid_status,
        sizeof(struct kretprobe_data),
        "proc_pid_status",
        true),
};
static struct kretprobe_wrap my_kretprobes[] = {
    KRETPROBEHOOK(
        kretprobe_ret_handler_porc_pid_status,
        kretprobe_entry_handler_proc_pid_status,
        sizeof(struct kretprobe_data),
        "proc_pid_status",
        true),
};
task = (struct task_struct *)regs->regs[3];
get_task_struct(task);
task_lock(task);
data->task = task;
data->original_ptrace = task->ptrace;
strscpy(data->original_comm, task->comm, TASK_COMM_LEN);
data->original_state = READ_ONCE(task->__state);
task = (struct task_struct *)regs->regs[3];
get_task_struct(task);
task_lock(task);
data->task = task;
data->original_ptrace = task->ptrace;
strscpy(data->original_comm, task->comm, TASK_COMM_LEN);
data->original_state = READ_ONCE(task->__state);
for (int i = 0; i < hide_so_cnt; i++) {
    if (strstr(data->original_comm, hide_so[i])) {
        strscpy(task->comm, REPLAE_COMM, TASK_COMM_LEN);
    }
}
task->ptrace = 0;
for (int i = 0; i < hide_so_cnt; i++) {
    if (strstr(data->original_comm, hide_so[i])) {
        strscpy(task->comm, REPLAE_COMM, TASK_COMM_LEN);
    }
}
task->ptrace = 0;
task_lock(task);
task->ptrace = data->original_ptrace;
if (strcmp(task->comm, REPLAE_COMM) == 0) {
    memcpy(task->comm, data->original_comm, TASK_COMM_LEN);
}
task_unlock(task);
put_task_struct(task);
task_lock(task);
task->ptrace = data->original_ptrace;
if (strcmp(task->comm, REPLAE_COMM) == 0) {
    memcpy(task->comm, data->original_comm, TASK_COMM_LEN);
}
task_unlock(task);
put_task_struct(task);
/proc/self/task/<tid>/status
/proc/self/task/<tid>/status
static struct ftrace_hook my_hooks[] = {
    FTRACEHOOK("proc_task_name", fh_proc_task_name, &real_proc_task_name, true)
};
static struct ftrace_hook my_hooks[] = {
    FTRACEHOOK("proc_task_name", fh_proc_task_name, &real_proc_task_name, true)
};
static asmlinkage void fh_proc_task_name(struct seq_file *m,
                                         struct task_struct *p,
                                         bool escape) {
    if (!escape) {
        char tcomm[64];
        __get_task_comm(tcomm, sizeof(tcomm), p);
        for (int i = 0; i < hide_so_cnt; i++) {
            if (strstr(tcomm, hide_so[i])) {
                const char *hide_str = "hidding";
                strscpy(tcomm, hide_str, 64);
                seq_printf(m, "%.64s", tcomm);
                return;
            }
        }
    }
    real_proc_task_name(m, p, escape);
}
static asmlinkage void fh_proc_task_name(struct seq_file *m,
                                         struct task_struct *p,
                                         bool escape) {
    if (!escape) {
        char tcomm[64];
        __get_task_comm(tcomm, sizeof(tcomm), p);
        for (int i = 0; i < hide_so_cnt; i++) {
            if (strstr(tcomm, hide_so[i])) {
                const char *hide_str = "hidding";
                strscpy(tcomm, hide_str, 64);
                seq_printf(m, "%.64s", tcomm);
                return;
            }
        }
    }
    real_proc_task_name(m, p, escape);
}
static struct ftrace_hook my_hooks[] = {
    FTRACEHOOK("show_map_vma", fh_show_map_vma, &real_show_map_vma, true)
};
static struct ftrace_hook my_hooks[] = {
    FTRACEHOOK("show_map_vma", fh_show_map_vma, &real_show_map_vma, true)
};
pathname = d_path(&vma->vm_file->f_path, path_buf, sizeof(path_buf));
for (int i = 0; i < hide_so_cnt; i++) {
    if (strstr(pathname, hide_so[i])) {
        return; // 不输出这个 maps 条目
    }
}
real_show_map_vma(m, vma);
pathname = d_path(&vma->vm_file->f_path, path_buf, sizeof(path_buf));
for (int i = 0; i < hide_so_cnt; i++) {
    if (strstr(pathname, hide_so[i])) {
        return; // 不输出这个 maps 条目
    }
}
real_show_map_vma(m, vma);
if (data->original_state == TASK_TRACED) {
    WRITE_ONCE(task->__state, TASK_RUNNING);
}
 
task->ptrace = 0;
if (data->original_state == TASK_TRACED) {
    WRITE_ONCE(task->__state, TASK_RUNNING);
}
 
task->ptrace = 0;
[ 7621.344945] hookmodule: Modified TracerPid for process 2055 to 0
[ 7621.345031] hookmodule: [SEQ:358] KRETPROBE HANDLER :proc_pid_status return (entry was SEQ:357)
[ 7621.345050] hookmodule: [SEQ:358] Restored TracerPid for process 2055 to 0
[ 7621.346354] hookmodule: orig getdents64 address is 00000000191697cc
[ 7621.346528] hookmodule: orig getdents64 address is 00000000191697cc
[ 7623.020180] hookmodule: [SEQ:359] KREPROBE ENTRY_HANDLER:proc_pid_status entry
[ 7623.020255] hookmodule: Modified TracerPid for process 13612 to 0
[ 7623.020571] hookmodule: [SEQ:360] KRETPROBE HANDLER :proc_pid_status return (entry was SEQ:359)
[ 7623.020614] hookmodule: [SEQ:360] Restored TracerPid for process 13612 to 0
[ 7623.020859] hookmodule: orig getdents64 address is 00000000191697cc
[ 7623.030068] hookmodule: orig getdents64 address is 00000000191697cc
[ 7624.322863] hookmodule: orig getdents64 address is 00000000191697cc
[ 7624.323171] hookmodule: orig getdents64 address is 00000000191697cc
[ 7624.342313] hookmodule: Hiding target library frida form PID 13646 maps
[ 7624.342400] hookmodule: Hiding target library frida form PID 13646 maps
[ 7624.342441] hookmodule: Hiding target library frida form PID 13646 maps
[ 7624.342486] hookmodule: Hiding target library frida form PID 13646 maps
[ 7624.420313] hookmodule: Hiding target library frida form PID 13646 maps
[ 7624.420355] hookmodule: Hiding target library frida form PID 13646 maps
[ 7624.420376] hookmodule: Hiding target library frida form PID 13646 maps
[ 7624.420396] hookmodule: Hiding target library frida form PID 13646 maps
[ 7625.677320] hookmodule: orig getdents64 address is 00000000191697cc
[ 7625.694435] hookmodule: orig getdents64 address is 00000000191697cc
[ 7629.417787] hookmodule: [SEQ:361] KREPROBE ENTRY_HANDLER:proc_pid_status entry
[ 7629.417859] hookmodule: Modified TracerPid for process 4725 to 0
[ 7629.418097] hookmodule: [SEQ:362] KREPROBE ENTRY_HANDLER:proc_pid_status entry
[ 7629.418108] hookmodule: [SEQ:363] KRETPROBE HANDLER :proc_pid_status return (entry was SEQ:361)
[ 7629.418160] hookmodule: [SEQ:363] Restored TracerPid for process 4725 to 0
[ 7629.418190] hookmodule: Modified TracerPid for process 4725 to 0
[ 7629.418328] hookmodule: [SEQ:364] KRETPROBE HANDLER :proc_pid_status return (entry was SEQ:362)
[ 7629.418367] hookmodule: [SEQ:364] Restored TracerPid for process 4725 to 0
[ 7629.422463] hookmodule: [SEQ:365] KREPROBE ENTRY_HANDLER:proc_pid_status entry
[ 7629.422506] hookmodule: Modified TracerPid for process 4725 to 0
[ 7629.422785] hookmodule: [SEQ:366] KRETPROBE HANDLER :proc_pid_status return (entry was SEQ:365)
[ 7629.422818] hookmodule: [SEQ:366] Restored TracerPid for process 4725 to 0
[ 7621.344945] hookmodule: Modified TracerPid for process 2055 to 0
[ 7621.345031] hookmodule: [SEQ:358] KRETPROBE HANDLER :proc_pid_status return (entry was SEQ:357)
[ 7621.345050] hookmodule: [SEQ:358] Restored TracerPid for process 2055 to 0
[ 7621.346354] hookmodule: orig getdents64 address is 00000000191697cc
[ 7621.346528] hookmodule: orig getdents64 address is 00000000191697cc
[ 7623.020180] hookmodule: [SEQ:359] KREPROBE ENTRY_HANDLER:proc_pid_status entry
[ 7623.020255] hookmodule: Modified TracerPid for process 13612 to 0
[ 7623.020571] hookmodule: [SEQ:360] KRETPROBE HANDLER :proc_pid_status return (entry was SEQ:359)
[ 7623.020614] hookmodule: [SEQ:360] Restored TracerPid for process 13612 to 0
[ 7623.020859] hookmodule: orig getdents64 address is 00000000191697cc
[ 7623.030068] hookmodule: orig getdents64 address is 00000000191697cc
[ 7624.322863] hookmodule: orig getdents64 address is 00000000191697cc
[ 7624.323171] hookmodule: orig getdents64 address is 00000000191697cc
[ 7624.342313] hookmodule: Hiding target library frida form PID 13646 maps
[ 7624.342400] hookmodule: Hiding target library frida form PID 13646 maps
[ 7624.342441] hookmodule: Hiding target library frida form PID 13646 maps
[ 7624.342486] hookmodule: Hiding target library frida form PID 13646 maps
[ 7624.420313] hookmodule: Hiding target library frida form PID 13646 maps
[ 7624.420355] hookmodule: Hiding target library frida form PID 13646 maps
[ 7624.420376] hookmodule: Hiding target library frida form PID 13646 maps
[ 7624.420396] hookmodule: Hiding target library frida form PID 13646 maps
[ 7625.677320] hookmodule: orig getdents64 address is 00000000191697cc
[ 7625.694435] hookmodule: orig getdents64 address is 00000000191697cc
[ 7629.417787] hookmodule: [SEQ:361] KREPROBE ENTRY_HANDLER:proc_pid_status entry
[ 7629.417859] hookmodule: Modified TracerPid for process 4725 to 0
[ 7629.418097] hookmodule: [SEQ:362] KREPROBE ENTRY_HANDLER:proc_pid_status entry
[ 7629.418108] hookmodule: [SEQ:363] KRETPROBE HANDLER :proc_pid_status return (entry was SEQ:361)
[ 7629.418160] hookmodule: [SEQ:363] Restored TracerPid for process 4725 to 0
[ 7629.418190] hookmodule: Modified TracerPid for process 4725 to 0
[ 7629.418328] hookmodule: [SEQ:364] KRETPROBE HANDLER :proc_pid_status return (entry was SEQ:362)
[ 7629.418367] hookmodule: [SEQ:364] Restored TracerPid for process 4725 to 0
[ 7629.422463] hookmodule: [SEQ:365] KREPROBE ENTRY_HANDLER:proc_pid_status entry
[ 7629.422506] hookmodule: Modified TracerPid for process 4725 to 0
[ 7629.422785] hookmodule: [SEQ:366] KRETPROBE HANDLER :proc_pid_status return (entry was SEQ:365)
[ 7629.422818] hookmodule: [SEQ:366] Restored TracerPid for process 4725 to 0
void *find_loaded_module_by_name_via_solist(const char *name);
void *find_loaded_module_by_name_via_solist(const char *name);
void *find_loaded_module_by_name_via_solist(const char *name) {
    if (!guard_initialized)
        solist_head = get_linker_solist_head();   // sub_2082C()
 
    cur = solist_head;
    if (!cur)
        return 0;
 
    found = 0;
    sdk = *off_47FB8;
 
    if (sdk <= 22) {
        do {
            if (strlen((char *)cur) <= 0x7F && strstr((char *)cur, name))
                found = cur;
            cur = *(void **)(cur + 176);
        } while (cur);
        return found;
    }
 
    if (sdk <= 25) {
        do {
            soname = *(const char **)(cur + 416);
            if (soname && strstr(soname, name))
                found = cur;
            cur = *(void **)(cur + 48);
        } while (cur);
        return found;
    }
 
    if (sdk == 31) {
        while (cur) {
            if ((*(uint8_t *)(cur + 408) & 1) != 0)
                soname = *(const char **)(cur + 424);
            else
                soname = (const char *)(cur + 409);
 
            if (soname && strstr(soname, name))
                found = cur;
 
            cur = *(void **)(cur + 40);
        }
        return found;
    }
 
    if (sdk > 31) {
        while (cur) {
            if ((*(uint8_t *)(cur + 392) & 1) != 0)
                soname = *(const char **)(cur + 408);
            else
                soname = (const char *)(cur + 393);
 
            if (soname && strstr(soname, name))
                found = cur;
 
            cur = *(void **)(cur + 40);
        }
        return found;
    }
 
    do {
        soname = *(const char **)(cur + 408);
        if (soname && strstr(soname, name))
            found = cur;
        cur = *(void **)(cur + 40);
    } while (cur);
 
    return found;
}
void *find_loaded_module_by_name_via_solist(const char *name) {
    if (!guard_initialized)
        solist_head = get_linker_solist_head();   // sub_2082C()
 
    cur = solist_head;
    if (!cur)
        return 0;
 
    found = 0;
    sdk = *off_47FB8;
 
    if (sdk <= 22) {
        do {
            if (strlen((char *)cur) <= 0x7F && strstr((char *)cur, name))
                found = cur;
            cur = *(void **)(cur + 176);
        } while (cur);
        return found;
    }
 
    if (sdk <= 25) {
        do {
            soname = *(const char **)(cur + 416);
            if (soname && strstr(soname, name))
                found = cur;
            cur = *(void **)(cur + 48);
        } while (cur);
        return found;
    }
 
    if (sdk == 31) {
        while (cur) {
            if ((*(uint8_t *)(cur + 408) & 1) != 0)
                soname = *(const char **)(cur + 424);
            else
                soname = (const char *)(cur + 409);
 
            if (soname && strstr(soname, name))

传播安全知识、拓宽行业人脉——看雪讲师团队等你加入!

最后于 6天前 被nuoen编辑 ,原因:
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写的很好
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好文章,干货
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