Add '--allowed-rpath-prefixes' option to '--shrink-rpath'

Fixes #97. In essence, the problem is that some packages in Nixpkgs have
RPATHs pointing to both $NIX_BUILD_TOP and $out, e.g.:

/tmp/nix-build-openldap-2.4.44.drv-0/openldap-2.4.44/libraries/libldap_r/.libs
/tmp/nix-build-openldap-2.4.44.drv-0/openldap-2.4.44/libraries/liblber/.libs
/nix/store/bfkmdxmv3a3f0g3d2q8jkdz2wam93c5z-openldap-2.4.44/lib
/nix/store/bfkmdxmv3a3f0g3d2q8jkdz2wam93c5z-openldap-2.4.44/lib64

Currently, running `patchelf --shrink-rpath` does the wrong thing by
keeping the /tmp/ paths and deleting the /nix/store ones. Now we can fix
the problem by using

patchelf --shrink-rpath --allowed-rpath-prefixes $NIX_STORE_DIR

in the Nixpkgs fixupPhase instead.

README

@@ -19,6 +19,14 @@ libraries.  In particular, it can do the following:
   an RPATH "/lib:/usr/lib:/foo/lib", and libfoo.so can only be found
   in /foo/lib, then the new RPATH will be "/foo/lib".
 
+  In addition, the '--allowed-rpath-prefixes' option can be used for
+  further rpath tuning. For instance, if an executable has an RPATH
+  "/tmp/build-foo/.libs:/foo/lib", it is probably desirable to keep
+  the "/foo/lib" reference instead of the "/tmp" entry. To accomplish
+  that, use:
+
+  $ patchelf --shrink-rpath --allowed-rpath-prefixes /usr/lib:/foo/lib my-program
+
 * Remove declared dependencies on dynamic libraries (DT_NEEDED
   entries):
 

patchelf.1

@@ -53,6 +53,12 @@ For instance, if an executable references one library libfoo.so, has
 an RPATH "/lib:/usr/lib:/foo/lib", and libfoo.so can only be found
 in /foo/lib, then the new RPATH will be "/foo/lib".
 
+.IP "--allowed-rpath-prefixes PREFIXES"
+Combined with the "--shrink-rpath" option, this can be used for
+further rpath tuning. For instance, if an executable has an RPATH
+"/tmp/build-foo/.libs:/foo/lib", it is probably desirable to keep
+the "/foo/lib" reference instead of the "/tmp" entry.
+
 .IP --print-rpath
 Prints the RPATH for an executable or library.
 

src/patchelf.cc

@@ -72,6 +72,13 @@ static vector<string> splitColonDelimitedString(const char * s){
     return parts;
 }
 
+static bool hasAllowedPrefix(const string & s, const vector<string> & allowedPrefixes){
+    for (vector<string>::const_iterator it = allowedPrefixes.begin(); it != allowedPrefixes.end(); ++it) {
+        if (!s.compare(0, it->size(), *it)) return true;
+    }
+    return false;
+}
+
 
 static unsigned int getPageSize(){
     return pageSize;
@@ -185,7 +192,7 @@ public:
 
     typedef enum { rpPrint, rpShrink, rpSet, rpRemove } RPathOp;
 
-    void modifyRPath(RPathOp op, string newRPath);
+    void modifyRPath(RPathOp op, vector<string> allowedRpathPrefixes, string newRPath);
 
     void addNeeded(set<string> libs);
 
@@ -1043,7 +1050,7 @@ static void concatToRPath(string & rpath, const string & path)
 
 
 template<ElfFileParams>
-void ElfFile<ElfFileParamNames>::modifyRPath(RPathOp op, string newRPath)
+void ElfFile<ElfFileParamNames>::modifyRPath(RPathOp op, vector<string> allowedRpathPrefixes, string newRPath)
 {
     Elf_Shdr & shdrDynamic = findSection(".dynamic");
 
@@ -1122,6 +1129,13 @@ void ElfFile<ElfFileParamNames>::modifyRPath(RPathOp op, string newRPath)
                 continue;
             }
 
+            /* If --allowed-rpath-prefixes was given, reject directories
+               not starting with any of the (colon-delimited) prefixes. */
+            if (!allowedRpathPrefixes.empty() && !hasAllowedPrefix(dirName, allowedRpathPrefixes)) {
+                debug("removing directory '%s' from RPATH because of non-allowed prefix\n", dirName.c_str());
+                continue;
+            }
+
             /* For each library that we haven't found yet, see if it
                exists in this directory. */
             bool libFound = false;
@@ -1465,6 +1479,7 @@ static bool setSoname = false;
 static string newSoname;
 static string newInterpreter;
 static bool shrinkRPath = false;
+static vector<string> allowedRpathPrefixes;
 static bool removeRPath = false;
 static bool setRPath = false;
 static bool printRPath = false;
@@ -1493,14 +1508,14 @@ static void patchElf2(ElfFile & elfFile)
         elfFile.setInterpreter(newInterpreter);
 
     if (printRPath)
-        elfFile.modifyRPath(elfFile.rpPrint, "");
+        elfFile.modifyRPath(elfFile.rpPrint, vector<string>(), "");
 
     if (shrinkRPath)
-        elfFile.modifyRPath(elfFile.rpShrink, "");
+        elfFile.modifyRPath(elfFile.rpShrink, allowedRpathPrefixes, "");
     else if (removeRPath)
-        elfFile.modifyRPath(elfFile.rpRemove, "");
+        elfFile.modifyRPath(elfFile.rpRemove, vector<string>(), "");
     else if (setRPath)
-        elfFile.modifyRPath(elfFile.rpSet, newRPath);
+        elfFile.modifyRPath(elfFile.rpSet, vector<string>(), newRPath);
 
     if (printNeeded) elfFile.printNeededLibs();
 
@@ -1563,6 +1578,7 @@ void showHelp(const string & progName)
   [--set-rpath RPATH]\n\
   [--remove-rpath]\n\
   [--shrink-rpath]\n\
+  [--allowed-rpath-prefixes PREFIXES]\t\tWith '--shrink-rpath', reject rpath entries not starting with the allowed prefix\n\
   [--print-rpath]\n\
   [--force-rpath]\n\
   [--add-needed LIBRARY]\n\
@@ -1614,6 +1630,10 @@ int main(int argc, char * * argv)
         else if (arg == "--shrink-rpath") {
             shrinkRPath = true;
         }
+        else if (arg == "--allowed-rpath-prefixes") {
+            if (++i == argc) error("missing argument");
+            allowedRpathPrefixes = splitColonDelimitedString(argv[i]);
+        }
         else if (arg == "--set-rpath") {
             if (++i == argc) error("missing argument");
             setRPath = true;

tests/Makefile.am

@@ -21,7 +21,7 @@ no_rpath_arch_TESTS = \
 src_TESTS = \
   plain-fail.sh plain-run.sh shrink-rpath.sh set-interpreter-short.sh \
   set-interpreter-long.sh set-rpath.sh no-rpath.sh big-dynstr.sh \
-  set-rpath-library.sh soname.sh
+  set-rpath-library.sh soname.sh shrink-rpath-with-allowed-prefixes.sh
 
 build_TESTS = \
   $(no_rpath_arch_TESTS)

tests/shrink-rpath-with-allowed-prefixes.sh

@@ -0,0 +1,47 @@
+#! /bin/sh -e
+SCRATCH=scratch/$(basename $0 .sh)
+
+rm -rf ${SCRATCH}
+mkdir -p ${SCRATCH}
+mkdir -p ${SCRATCH}/libsA
+mkdir -p ${SCRATCH}/libsB
+
+cp main ${SCRATCH}/
+cp libfoo.so libbar.so ${SCRATCH}/libsA/
+cp libfoo.so libbar.so ${SCRATCH}/libsB/
+
+oldRPath=$(../src/patchelf --print-rpath ${SCRATCH}/main)
+if test -z "$oldRPath"; then oldRPath="/oops"; fi
+pathA="$(pwd)/${SCRATCH}/libsA"
+pathB="$(pwd)/${SCRATCH}/libsB"
+../src/patchelf --force-rpath --set-rpath $oldRPath:$pathA:$pathB ${SCRATCH}/main
+
+cp ${SCRATCH}/main ${SCRATCH}/mainA
+cp ${SCRATCH}/main ${SCRATCH}/mainB
+
+../src/patchelf --shrink-rpath ${SCRATCH}/main
+../src/patchelf --shrink-rpath --allowed-rpath-prefixes $oldRPath:$pathA ${SCRATCH}/mainA
+../src/patchelf --shrink-rpath --allowed-rpath-prefixes $oldRPath:$pathB ${SCRATCH}/mainB
+
+check() {
+    exe=$1
+    mustContain=$2
+    mustNotContain=$3
+
+    rpath=$(../src/patchelf --print-rpath $exe)
+    echo "RPATH of $exe after: $rpath"
+
+    if ! echo "$rpath" | grep -q $mustContain; then
+        echo "RPATH didn't contain '$mustContain' when it should have"
+        exit 1
+    fi
+
+    if echo "$rpath" | grep -q $mustNotContain; then
+        echo "RPATH contained '$mustNotContain' when it shouldn't have"
+        exit 1
+    fi
+}
+
+check ${SCRATCH}/main  $pathA $pathB
+check ${SCRATCH}/mainA $pathA $pathB
+check ${SCRATCH}/mainB $pathB $pathA