Re: How to get all shared libs of a path?

A note on running ldd, quoting the man page:

Security

In the usual case, ldd invokes the standard dynamic linker (see ld.so(8)) with the LD_TRACE_LOADED_OBJECTS environment variable set to 1, which causes the linker to display the library dependencies. Be aware, however, that in some circumstances, some versions of ldd may attempt to obtain the dependency information by directly executing the program. Thus, you should never employ ldd on an untrusted executable, since this may result in the execution of arbitrary code. A safer alternative when dealing with untrusted executables is:
$ objdump -p /path/to/program | grep NEEDED
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A note on dependencies: Make the distribution-provided package manager (apt/dpkg, rpm, yum, whatever) resolve dependencies. Put the executables into distribution-specific packages (see distribution documentation for details), hand out the packages instead of bare executables, have the IT department install the packages instead of the bare executables. https://serverfault.com/questions/18620/how-to-create-an-rpm-for-suse may help creating SuSE packages.

(Yes, I know my favorite distribution Slackware is an exception to the rule: You are expected to resolve dependencies by hand, or simply install ALL packages. But most other distributions do an excellent job at managing dependencies.)

Alexander

--
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)

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Re^2: How to get all shared libs of a path? by ovedpo15 (Pilgrim) on Jun 20, 2021 at 18:56 UTC
Hi, thank you for your reply. This actually helps a lot. I want to find the shared libs in order to find the rpm packages related to the path. I'm using zypper and rpm. I use the following command to find the related packages: `rpm -qf --queryformat "[%{NAME}]" path` [download] In the path section I also insert the shared libs to find their related packages. It works with the code I provided but is there a better way of doing it without parsing the output of ldd and puting each lib path into the command above?	[reply] [d/l]
Re^3: How to get all shared libs of a path? by afoken (Chancellor) on Jun 20, 2021 at 20:33 UTC
I want to find the shared libs in order to find the rpm packages related to the path. That information should also be found in the Makefile (or the tool that generates it), at least the basic library name. Also, as documented in the ldd man page, `objdump -p` can be used to extract the names of shared libraries from the binary, without risking to accidentally executing it. What you get is a list of library names. Search CPAN, I would be surprised if no one has written a module to extract that information from an ELF file without running `objdump`. Now that you got a list of library names, read the ld.so man page to find out how to create a list of possible file names from each library. ld.so reads /etc/ld.so.cache, which is binary noise containing a list of directories to search and an ordered list of candidate libraries. It is generated by ldconfig, which also has a man page. ldconfig reads /etc/ld.so.conf, the format of that file is documented in the ldconfig man page. Assuming that ld.so.conf was not changed after the last run of ldconfig, you don't need to read ld.so.cache at all, and can simply read ld.so.conf. That, combined with the rules and the substitued tokens explained in the ld.so man page, is all you need to re-implement in perl. Essentially, just a little bit of string operations and some calls to stat (in form of `-f -x $candidate`). And now, the really bad news: That's not sufficient. Nor is ldd. Programms can load libraries at runtime. And they do, often without telling you. You don't really want to know what happens when Name Service Switch (see man 5 nss) or PAM (see man 8 pam) start doing their jobs. But the worst part: You can not extract that information from the binary, because it is not (always) contained in the binary. NSS and PAM highly depend on the system configuration. And NSS and PAM are just two examples. Perl loads libraries at runtime every time you use an XS module. Alexander -- Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)	[reply] [d/l] [select]