The goal of this code is to create a stack trace whenever a sigterm/sigint/sigsegv/etc is caught. In order to not rely on memory management inside of the C++ code in the case of a sigsegv, I have decided to write a bash script that will receive the PID and memory addresses in the trace array.
The Sig events are being caught.
Below is where I generate the call to the bash script
trace_size = backtrace(trace, 16);
trace[1] = (void *)ctx->rsi;
messages = backtrace_symbols(trace, trace_size);
char syscom[356] = {0};
sprintf(syscom,"bash_crash_supp.sh %d", getpid());
for (i=1; i<(trace_size-1) && i < 10; ++i)
{
sprintf(syscom,"%s %p",syscom,trace[i]);
}
Below is where my issue arises. The command in syscom is generating correctly. I can stop the code before the following popen, run the command in a terminal, and it functions correctly.
However running the script directly from the c++ code does not seem to work.
setuid(0);
FILE *bashCommand = popen(syscom,"r");
char buf[256] = {0};
while(fgets(buf,sizeof(buf),bashCommand) != 0) {
LogMessage(LOG_WARNING, "%s\n", buf);
}
pclose(bashCommand);
exit(sig);
The purpose of the bash script is to get the offset from /proc/pid/maps, and then use that to run addr2line to get the file name/line number.
strResult=$(sudo cat /proc/"$1"/maps | grep "target_file" | grep -m 1 '[0-9a-fA-F]')
offset=$( cut -d '-' -f 1 <<< "$strResult");
However offset is getting 0 when I run from the c++ code, but when I run the exact same command (that is stored in syscom in the c++ code) in a terminal, I get the expected output.
I have been trying to fix this for a while. Permissions are most likely the issue, but I've tried to work around these with every way I know of/have seen via google. The user trying to run the script (currently running the c++ code) is apache.
The fix does not need to worry about the security of the box. If something as simple as "chmod 777 /proc -r" worked, that would have been the solution (sadly the OS doesn't let me mess do such commands with /proc).
Things I've already tried:
Adding `` around the command that's stored in syscom from the c++ code
chown the script to apache
chmod 4755 on the bash_crash_supp.sh script, allowing it to always fire as root.
I have added apache to sudoers (visudo), allowing them to run sudo without using a password
I have added a sub file to sudoers.d (just in case) that does the same as above
I have looked into objdump, however it does not give me either the offset or the file/line num for an addr (from what I can see)
I have setuid(0) in the c++ code to set the current user to root
Command generated in C++
bash_crash_supp.sh 25817 0x7f4bfe600ec8 0x7f4bf28f7400 0x7f4bf28f83c6 0x7f4bf2904f02 0x7f4bfdf0fbb0 0x7f4bfdf1346e 0x7f4bfdf1eb30 0x7f4bfdf1b9a8 0x7f4bfdf176b8
Params in bash:
25817 0x7f4bfe600ec8 0x7f4bf28f7400 0x7f4bf28f83c6 0x7f4bf2904f02 0x7f4bfdf0fbb0 0x7f4bfdf1346e 0x7f4bfdf1eb30 0x7f4bfdf1b9a8 0x7f4bfdf176b8
Can anyone think of any other ways to solve this?
Long story short, almost all Unix-based systems ignore setuid on any interpreted script (anything with a shebang #!) as a security precaution.
You may use setuid on actual executables, but not the shell scripts themselves. If you're willing to take a massive security risk, you can make a wrapper executable to run the shell script and give the executable setuid.
For more information, see this question on the Unix StackExchange: https://unix.stackexchange.com/a/2910
Related
I have simple console application that prints environment variables:
int main(int argc, char **argv, char **envp)
{
printf("Scanning for LD_LIB_PATH\n");
for (char **env = envp; *env != 0; env++)
{
char *thisEnv = *env;
std::string s= *env;
if (s.find("LD_LIBRARY_PATH")!=std::string::npos)
{
printf("!!!!!!! %s\n", thisEnv);
}
printf("%s\n", thisEnv);
}
}
Before run executable I run script that sets LD_LIBRARY_PATH
export LD_LIBRARY_PATH=~/aaa/bbb/Debug:~/ccc/ddd/Debug
echo "searching:"
export | grep LD_LIBRARY
echo "done"
Script run fine with output:
exporting
searching:
declare -x LD_LIBRARY_PATH="/home/vicp/aaa/bbb/Debug:/home/vico/ccc/ddd/Debug"
done
I run executable and it finds many variables but no environment variable LD_LIB_PATH. Why?
UPD
As recommended I script . ./script.sh
Then double check with command:
export |grep LD_LIBRARY_PATH
Got output:
declare -x LD_LIBRARY_PATH="/home/vicp/aaa/bbb/Debug:/home/vico/ccc/ddd/Debug"
But still don't see LD_LIBRARY_PATH in my programm.
Depending on how you run the script, the env variable will only be added to the environment of the subshell running the script.
If you run the script like this:
$ ./script.sh
This will spawn a new shell wherein the script is run. The parent shell, i.e. the one you started the script from, will not be affected by what the script does. Changes to the environment will therefore not be visible (changing the working directory or similar will also not work).
If the script is intended to modify the environment of the current shell, the script needs to be sourced using the . or source commands:
$ . ./script.sh
$ source ./script.sh
From help source in bash:
Execute commands from a file in the current shell.
Then there seems to be a problem with the code:
As a commenter stated previousy, there are a lot of exclamation points in the success case printf. I presume these were meant to highlight the found variable name. Since they are outside of the opening quote of the format string, they are interpreted as logical not operators.
The result is that the format string literal (a pointer) is negated, resulting in false due to the number of operators. This usually maps to 0, which would mean the format string becomes a null pointer. What happens when handing a null pointer to printf as the format string depends, as far as I can tell, on the implementation. If it doesn't crash, it most certainly will not print anything however.
So the code may actually work, but there is no visible output due to that bug. To fix it, move the exclamation points into the format string, i.e. after the opening quote.
Look at the line printf(!!!!!!!"%s\n", thisEnv);
Change to printf("!!!! %s\n", thisEnv);
It has nothing to do with your C/C++ application.
try the following:
$ ./script.sh
$ echo $LD_LIBRARY_PATH
And you'll see that LD_LIBRARY_PATH is not set
When you launch your script, bash creates a new process with its environment inherited from the original bash process. In that newly created process, you set the process environment variable LD_LIBRARY_PATH=xxxx
When finalized your script.sh exits, and its environment dies with it.
Meaning the LD_LIBRARY_PATH is not set in your original shell.
As mentioned here above you need to run your script in the current shell
Either with . or with source.
I tested with your C/C++ and it works
I have a program that needs to run a program we'll call externalProg in parallel on our linux (CentOS) cluster - or rather, it needs to run many instances of externalProg, each on different cores. Each "thread" creates 3 files based on a few parameters - the inputs to externalProg, a command file to tell externalProg how to execute my file, and a bash script to set up the environment (calls a setup script provided by the manufacturer) and actually call externalProg with my inputs.
Since this needs to be parallel with an unknown number of concurrent threads and I don't want to risk overwriting another thread's files, I am creating temp files using
mkstemp("PREFIX_XXXXXX")
for these input files. After the external program runs, I extract the relevant data and store it, and close the temp files (therefore deleting them).
We'll call the files created (Which actually have a name based on the template above)
tmpInputs - Inputs to externalProg
tmpCommand - Input that tells externalProg how to execute tmpInputs
tmpBash - bash script to set up and call externalProg with my inputs
The file tmpBash looks something like
source /path/to/setup/script # Sets up environment variables
externalProg < /path/to/tmpCommand
where tmpCommand is just a simple text file.
The problem I'm having is actually executing the bash script. Within my program, I call
ostringstream launchcmd;
launchcmd << "bash " << path_to_tmpBash
system(launchcmd.str().c_str());
But nothing happens. No error, no warning, no 'file not found' or permission denied or anything. I have verified that the files are being created and have the correct content. The rest of the code after system() is executed successfully (Though it fails since externalProg wasn't run).
Strangely, if I go back to the terminal and type
bash /path/to/tmpBash
then externalProg is executed successfully. I have also cout'd the launchcmd string, copy and pasted that in to the terminal, which also works successfully. For some reason, this only fails when called within my program.
After a bit of experimentation, I've determined that system() calls /bin/sh on our cluster. If I change launchcmd to look like
/path/to/tmpBash
(So that the full command should look like /bin/sh /path/to/tmpBash), I get a permission denied error, which is no surprise. The problem is that I can't chmod +x the tmpBash file while it's still open, and if I close the file, it gets deleted - so I'm not sure how to address that.
Is there something obviously wrong I'm doing, or does system() have some nuance that I'm missing?
edit: I wanted to add that I can successfully call things like
system("echo $PATH")
and get the expected results (in this case, my default $PATH).
Two separate ideas:
Change your SHELL environment variable to be /bin/bash, then call system(),
or:
Use execve directly `execve('/bin/bash', ['/path/to/tmpBash'], environ)
I have a c++ program that run a command and pass some arguments to it. The code is as follow:
int RunApplication(fs::path applicationPathName,std::string arguments)
{
std::string applicationShortPath=GetShortFileName(applicationPathName);
std::string cmd="\""+applicationShortPath +"\" "+ arguments+" >>log.txt 2>&1 \"";
std::cout<<cmd<<std::endl;
int result=std::system(cmd.c_str());
return result;
}
When I run system command, the cmd window appears shortly and then closes, but the result is 1 and the cmd was not run (the command should generate output which is not generated).
To check that the cmd is correct, I stopped the application just before system line and copy/ paste cmd content to a cmd window and it worked.
I am wondering how can I find why application is not run in system()?
the cmd has this value just before running it:
"D:/DEVELO~3/x64/Debug/enfuse.exe" -w --hard-mask --exposure-weight=1 --saturation-weight=0.328 --contrast-weight=0.164 -o "C:/Users/m/AppData/Local/Temp/1.tif" "C:/Users/m/AppData/Local/Temp/1.jpg" "C:/Users/m/AppData/Local/Temp/2.jpg" >>log.txt 2>&1 "
How can I find why it is not working?
Is there any way that I set the system so it doesn't close cmd window so I can inspect it?
is there any better way to run a command on OS?
Does Boost has any solution for this?
Edit
After running it with cmd /k, I get this error message:
The input line is too long.
How can I fix it other than reducing cmd line?
There are two different things here: if you have to start a suprocess, "system" is not the best way of doing it (better to use the proper API, like CreateProcess, or a multiplatform wrapper, but avoid to go through the command interpreter, to avoid to open to potential malware injection).
But in this case system() is probably the right way to go since you in fact need the command interpreter (you cannot manage things like >>log.txt 2>&1 with only a process creation.)
The problem looks like a failure in the called program: may be the path is not correct or some of the files it has to work with are not existent or accessible with appropriate-permission and so on.
One of the firt thing to do: open a command prompt and paste the string you posted, in there. Does it run? Does it say something about any error?
Another thing to check is how escape sequence are used in C++ literals: to get a '\', you need '\\' since the first is the escape for the second (like \n, or \t etc.). Although it seems not the case, here, it is one of the most common mistakes.
Use cmd /k to keep the terminal: http://ss64.com/nt/cmd.html
Or just spawn cmd.exe instead and inspect the environment, permissions, etc. You can manually paste that command to see whether it would work from that shell. If it does, you know that paths, permssions and environment are ok, so you have some other issue on your hands (argument escaping, character encoding issues)
Check here How to execute a command and get output of command within C++ using POSIX?
Boost.Process is not official yet http://www.highscore.de/boost/process/
I wrote a c++ program to check if a process is running or not . this process is independently launched at background . my program works fine when I run it on foreground but when I time schedule it, it do not work .
int PID= ReadCommanOutput("pidof /root/test/testProg1"); /// also tested with pidof -m
I made a script in /etc/cron.d/myscript to time schedule it as follows :-
45 15 * * * root /root/ProgramMonitor/./testBkg > /root/ProgramMonitor/OutPut.txt
what could be the reason for this ?
string ReadCommanOutput(string command)
{
string output="";
int its=system((command+" > /root/ProgramMonitor/macinfo.txt").c_str());
if(its==0)
{
ifstream reader1("/root/ProgramMonitor/macinfo.txt",fstream::in);
if(!reader1.fail())
{
while(!reader1.eof())
{
string line;
getline(reader1,line);
if(reader1.fail())// for last read
break;
if(!line.empty())
{
stringstream ss(line.c_str());
ss>>output;
cout<<command<<" output = ["<<output<<"]"<<endl;
break;
}
}
reader1.close();
remove("/root/ProgramMonitor/macinfo.txt");
}
else
cout<<"/root/ProgramMonitor/macinfo.txt not found !"<<endl;
}
else
cout<<"ERROR: code = "<<its<<endl;
return output;
}
its output coming as "ERROR: code = 256"
thanks in advacee .
If you really wanted to pipe(2), fork(2), execve(2) then read the output of a pidof command, you should at least use popen(3) since ReadCommandOutput is not in the Posix API; at the very least
pid_t thepid = 0;
FILE* fpidof = popen("pidof /root/test/testProg1");
if (fpidof) {
int p=0;
if (fscanf(fpidof, "%d", &p)>0 && p>0)
thepid = (pid_t)p;
pclose(fpidof);
}
BTW, you did not specify what should happen if several processes (or none) are running the testProg1....; you also need to check the result of pclose
But you don't need to; actually you'll want to build, perhaps using snprintf, the pidof command (and you should be scared of code injection into that command, so quote arguments appropriately). You could simply find your command by accessing the proc(5) file system: you would opendir(3) on "/proc/", then loop on readdir(3) and for every entry which has a numerical name like 1234 (starts with a digit) readlink(2) its exe entry like e.g. /proc/1234/exe ...). Don't forget the closedir and test every syscall.
Please read Advanced Linux Programming
Notice that libraries like Poco or toolkits like Qt (which has a layer QCore without any GUI, and providing QProcess ....) could be useful to you.
As to why your pidof is failing, we can't guess (perhaps a permission issue, or perhaps there is no more any process like you want). Try to run it as root in another terminal at least. Test its exit code, and display both its stdout & stderr at least for debugging purposes.
Also, a better way (assuming that testProg1 is some kind of a server application, to be run in at most one single process) might be to define different conventions. Your testProg1 might start by writing its own pid into /var/run/testProg1.pid and your current application might then read the pid from that file and check, with kill(2) and a 0 signal number, that the process is still existing.
BTW, you could also improve your crontab(5) entry. You could make it run some shell script which uses logger(1) and (for debugging) runs pidof with its output redirected elsewhere. You might also read the mail perhaps sent to root by cron.
Finally I solved this problem by using su command
I have used
ReadCommanOutput("su -c 'pidof /root/test/testProg1' - root");
insteadof
ReadCommanOutput("pidof /root/test/testProg1");
I'm trying to create a new dir via SSH with a python script. When i try my commands by using the Python command line it just works. But when I try to do the same by a script it does not create the new 'test' folder (I even copy/paste the commands in the script into the Python cmd to verify they are right and there they work). So any ideas why it does not work by script?
The used code:
child = pexpect.spawn('ssh 192.168.56.101 -oStrictHostKeyChecking=no')
child.expect=('password:')
child.sendline('MyPwd')
child.sendline('mkdir /home/myUser/Desktop/test')
Seems to work when I just add another line
for example
child.sendline('\n')
so the entire script is
child = pexpect.spawn('ssh 192.168.56.101 -oStrictHostKeyChecking=no')
child.expect=('password:')
child.sendline('MyPwd')
child.sendline('mkdir /home/myUser/Desktop/test')
child.sendline('\n')
What I usually do to solve this issue is sync-ing with host machine. After I send something to the machine, I expect an answer, which usually translates in the machine's prompt. So, in your case, I would go for something like this:
child = pexpect.spawn('ssh 192.168.56.101 -oStrictHostKeyChecking=no')
child.expect('password:')
child.sendline('MyPwd')
child.expect('YourPromptHere')
child.sendline('mkdir /home/myUser/Desktop/test')
child.expect('YourPromptHere')
You can just replace YourPromptHere with the prompt of the machine, if you are running the script on a single target, or with a regular expression (eg. "(\$ )|(# )|(> )").
tl;dr : To summarize what I said, you need to wait until the previous action was finished until sending a new one.