C++ – How to give ‘Everybody’ full rights to a file (programmatically)

cfile-permissionswindows-vista

I'm modifying an old C++ program to run on Vista. It does not require Admin privileges.

I've changed the code to put logfiles in \ProgramData\MyApp\. These logfiles are written with the stdio functions (fopen, fprintf, fclose).

Here's the problem:

UserA runs the program first, it creates \ProgramData\MyApp\MyLogFile.txt using CreateFile()
UserB runs the program next, it tries to append to MyLogFile.txt and gets access denied.

I tried creating a null SECURITY_DESCRIPTOR and passing that to CreateFile(). That does create a file with "no permissions assigned", but it seems as if the first user to write to the file takes ownership and afterwards all the other non-admin users are out of luck.

It's important that all users share the same logfiles, but it's also important that I change as little code as possible.

Edited to add:

\ProgramData\MyApp is created by a standard Visual Studio installer. (I don't see any place to set directory security.) When it creates \MyApp it grants Users these permissions:

Read & execute  
List folder contents
Read
Special permissions

Under Advanced I see that Special permissions includes:

Create files / write data
Create folders / append data
Write attributes
Write extended attributes

Best Answer

+1 to everyone for trying, but eventually I found the answer here:

how to change the ACLs from c++?

I did have to change one line of that solution, from this:

ea[0].grfAccessMode = DENY_ACCESS;

to this:

ea[0].grfAccessMode = GRANT_ACCESS;

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C++ – How to list the symbols in a .so file

The standard tool for listing symbols is nm, you can use it simply like this:

nm -gD yourLib.so

If you want to see symbols of a C++ library, add the "-C" option which demangle the symbols (it's far more readable demangled).

nm -gDC yourLib.so

If your .so file is in elf format, you have two options:

Either objdump (-C is also useful for demangling C++):

$ objdump -TC libz.so

libz.so:     file format elf64-x86-64

DYNAMIC SYMBOL TABLE:
0000000000002010 l    d  .init  0000000000000000              .init
0000000000000000      DF *UND*  0000000000000000  GLIBC_2.2.5 free
0000000000000000      DF *UND*  0000000000000000  GLIBC_2.2.5 __errno_location
0000000000000000  w   D  *UND*  0000000000000000              _ITM_deregisterTMCloneTable

Or use readelf:

$ readelf -Ws libz.so
Symbol table '.dynsym' contains 112 entries:
   Num:    Value          Size Type    Bind   Vis      Ndx Name
     0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND
     1: 0000000000002010     0 SECTION LOCAL  DEFAULT   10
     2: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND free@GLIBC_2.2.5 (14)
     3: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND __errno_location@GLIBC_2.2.5 (14)
     4: 0000000000000000     0 NOTYPE  WEAK   DEFAULT  UND _ITM_deregisterTMCloneTable

C++ – How to print the full value of a long string in gdb

set print elements 0

From the GDB manual:

set print elements number-of-elements

Set a limit on how many elements of an array GDB will print. If GDB is printing a large array, it stops printing after it has printed the number of elements set by the set print elements command. This limit also applies to the display of strings. When GDB starts, this limit is set to 200. Setting number-of-elements to zero means that the printing is unlimited.

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