more-or-less secure way to use setuid features

2 files changed, 157 insertions, 5 deletions

diff --git a/tools/fixown.c b/tools/fixown.c
new file mode 100644
index 0000000..087e7c9
--- /dev/null
+++ b/tools/fixown.c
@@ -0,0 +1,139 @@
+#include <iostream>
+#include <iomanip>
+#include <stdlib.h>     /* for exit(), atoi() */
+#include <list>
+#include <map>
+#include <sstream>
+
+#include <sys/types.h>          /* for stat() */
+#include <sys/stat.h>           /* for stat() */
+#include <unistd.h>             /* for stat() */
+#include <pwd.h>                /* for getpwnam_r() */
+#include <grp.h>                /* for getgrnam_r() */
+
+#include "utils.h"              /* for basename() */
+
+using namespace std;
+
+class owngroup{
+public:
+  string owner;
+  string group;
+};
+
+#define x(a,b,c) make_pair(a, owngroup({b,c}))
+
+map<string,owngroup> allowed({
+  x("fixown",   "+root",   ""),
+  x("fixown2",  "+root",   ""),
+  x("skrewt",   "+qmaild", ""),
+  x("ltgrey",   "+qmaild", ""),
+  x("greylist", "+qmaild", ""),
+  x("wripper",  "",        "+daemon"),
+});
+
+pid_t mypid;
+string progname;
+string progid;
+
+int main(int _argc, char** _argv){
+  int argc(_argc);
+  char** argv(_argv);
+  {
+    progname = *argv++; argc--;
+    mypid = getpid();
+    stringstream binder;
+    binder << basename(progname) << "[" << mypid << "]";
+    progid = binder.str();
+  }
+
+  list<string> todo;
+
+  while (argc > 0) {
+    string arg = argv[0]; argc--; argv++;
+    todo.push_back(arg);
+  }
+
+  for (list<string>::const_iterator ptr = todo.begin();
+        ptr != todo.end(); ptr++){
+    string file = *ptr;
+    if (allowed.find(file) == allowed.end()){
+      cerr << progid << " not on the allowed list: " << file << endl;
+      exit(1);
+    }
+    struct stat statbuf;
+    int rslt = stat(file.c_str(), &statbuf);
+    if (rslt < 0) {
+      cerr << progid << " stat failed for "
+       << file << " : ";
+      perror(0);
+      exit(1);
+    }
+    mode_t mode = statbuf.st_mode;
+    string own = allowed[file].owner;
+    string grp = allowed[file].group;
+    if (0) cout << oct << mode
+                << " " << own
+                << " " << grp
+                << dec << endl;
+
+    if (own[0] == '+') {
+      own = own.substr(1);
+      mode |= S_ISUID;
+    }
+    if (grp[0] == '+') {
+      grp = grp.substr(1);
+      mode |= S_ISGID;
+    }
+    //xx cout << oct << mode << dec << endl << endl;
+
+    uid_t own_num = statbuf.st_uid;
+    gid_t grp_num = statbuf.st_gid;
+
+    if (own.length()){
+      struct passwd pw;
+      struct passwd* ppw;
+      long int size = sysconf(_SC_GETPW_R_SIZE_MAX);
+      char scratch[size];
+      getpwnam_r(own.c_str(), &pw,
+                   scratch, size, &ppw);
+      if (ppw == 0) {
+        cerr << progid << " user not found: " << own << endl;
+        exit(1);
+      }
+      own_num = pw.pw_uid;
+    }
+    //xxx cout << own << " --> " << own_num << endl;
+
+    if (grp.length()){
+      struct group gr;
+      struct group* pgr;
+      long int size = sysconf(_SC_GETPW_R_SIZE_MAX);
+      char scratch[size];
+      getgrnam_r(grp.c_str(), &gr,
+                   scratch, size, &pgr);
+      if (pgr == 0) {
+        cerr << progid << " user not found: " << grp << endl;
+        exit(1);
+      }
+      grp_num = gr.gr_gid;
+    }
+    //xxx cout << grp << " --> " << grp_num << endl;
+
+    rslt = chown(file.c_str(), own_num, grp_num);
+    if (rslt < 0) {
+      cerr << progid << " chown failed for "
+        << file << " : ";
+      perror(0);
+      exit(1);
+    }
+    chmod(file.c_str(), mode);
+    if (rslt < 0) {
+      cerr << progid << " chmod failed for "
+        << file << " : ";
+      perror(0);
+      exit(1);
+    }
+
+  }
+}
diff --git a/tools/makefile b/tools/makefile
index 6594ca8..723d756 100644
--- a/tools/makefile
+++ b/tools/makefile
@@ -1,5 +1,5 @@
-CC= /usr/bin/g++ -Wall -g -I $(HOME)/lib/include
-
+CC= /usr/bin/g++
+CFLAGS = -std=gnu++0x -Wall -g -I $(HOME)/lib/include
 
 #?? exhibits = checkpassword.patch hi-q.c pido.c pop3.conf smtp.conf  \
 #??    smtp.rules spamc-zap.patch spamd qmail
@@ -15,7 +15,7 @@ qmain = pido.c hi-q.c skrewt.c hi-test.c mail-scan.c greylist.c wripper.c
 qprogs = $(qmain:%.c=%)
 
 # sources for other main programs:
-moremain = wripper.c bash-c.c ltgrey.c
+moremain = wripper.c bash-c.c ltgrey.c fixown.c
 moreprogs = $(moremain:%.c=%)
 
 nonmain = libltgrey.c
@@ -32,23 +32,36 @@ beware_other = checkpassword.c spamc.c
                 | sed '\''s/\($*\)\.o[ :]*/\1.o $@ : /g'\'' > $@; \
                 [ -s $@ ] || rm -f $@'
 
-all: $(qprogs) $(moreprogs)
+all: $(qprogs) $(moreprogs) fixown2
 
 show:
 	: --- $(qprogs) +++ $(moreprogs)
 
+fixown: fixown.o utils.o
+	$(CC) $^ -o $@
+	chmod o-rwx $@
+	./fixown2 $@
+
+fixown2: fixown.o utils.o
+	$(CC) $^ -o $@
+	chmod o-rwx $@
+	./fixown $@
+
 skrewt: skrewt.o utils.o
 	$(CC) $^ -lboost_filesystem-mt -lboost_system -o $@
+	./fixown $@
 
 greylist: greylist.o utils.o
 	$(CC) $^ -lboost_filesystem-mt -lboost_system -o $@
+	./fixown $@
 
 ltgrey: ltgrey.o utils.o libltgrey.o
 	$(CC) $^ -lboost_filesystem-mt -lboost_system -o $@
+	./fixown $@
 
 wripper: wripper.o
 	$(CC) $^ -o $@
-	chgrp daemon $@ && chmod g+s $@ || true
+	./fixown $@
 
 mail-scan: mail-scan.o utils.o
 	$(CC) $^ -lboost_regex -o $@