coren has uploaded a new change for review.
https://gerrit.wikimedia.org/r/69981
Change subject: Tool Labs Tools: add take.cc
......................................................................
Tool Labs Tools: add take.cc
Change-Id: I132b56ebdedfdaee83099d1a7b34215d06441f65
---
A src/take.cc
1 file changed, 151 insertions(+), 0 deletions(-)
git pull ssh://gerrit.wikimedia.org:29418/labs/toollabs
refs/changes/81/69981/1
diff --git a/src/take.cc b/src/take.cc
new file mode 100755
index 0000000..f7c6e17
--- /dev/null
+++ b/src/take.cc
@@ -0,0 +1,151 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <dirent.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+bool refuse(const char* file, const char* why)
+{
+ fprintf(stderr, "%s: %s\n", file, why);
+ return false;
+}
+
+bool error(const char* file)
+{
+ return refuse(file, strerror(errno));
+}
+
+// This is just convenience for autoclosing files and prevent fd leaks
+struct FD {
+ int fd;
+
+ FD(int f): fd(f) { };
+ ~FD() { if(fd >= 0)
close(fd); };
+ operator int (void) const { return fd; };
+};
+
+gid_t groups[256];
+int ngroups;
+
+bool takeover(const char* path, bool trustpath)
+{
+ // We open the files and use the file descriptors exclusively
+ // to avoid trickery and race conditions
+ FD file = open(path, O_RDONLY|O_NOFOLLOW);
+
+ if(file < 0) {
+ if(errno == ELOOP)
+ return refuse(path, "will not follow or touch
symlinks");
+ return error(path);
+ }
+
+ struct stat sfile;
+
+ if(fstat(file, &sfile))
+ return error(path);
+
+ if(!trustpath) {
+ char dirname[strlen(path)+1];
+
+ strcpy(dirname, path);
+
+ if(path[0] && path[strlen(path)-1]=='/')
+ dirname[strlen(path)-1] = 0;
+
+ if(char* slash = strrchr(dirname, '/'))
+ *slash = 0;
+ else
+ strcpy(dirname, ".");
+
+ FD dir = open(dirname, O_RDONLY|O_NOFOLLOW);
+
+ if(dir < 0) {
+ if(errno == ELOOP)
+ return refuse(dirname, "will not follow or
touch symlinks");
+ return error(dirname);
+ }
+
+ struct stat sdir;
+ if(fstat(dir, &sdir))
+ return error(dirname);
+
+ if(!S_ISDIR(sdir.st_mode))
+ return refuse(dirname, "containing directory doesn't
appear to be... a directory?");
+ if(sdir.st_uid != getuid())
+ return refuse(path, "you must own the containing
directory");
+
+ // Here, we are being extremely paranoid, and check that the
file is actually in the directory.
+ if(sdir.st_dev != sfile.st_dev)
+ return refuse(path, "the file must be on the same
filesystem as its directory");
+
+ bool found = false;
+ if(DIR* df = fdopendir(dir)) {
+ while(dirent* d = readdir(df)) {
+ if(sfile.st_ino == d->d_ino) {
+ found = true;
+ break;
+ }
+ }
+ closedir(df);
+ } else
+ return error(dirname);
+
+ if(!found)
+ return refuse(path, "the file isn't in its directory?");
+ }
+
+ if(!S_ISDIR(sfile.st_mode) && sfile.st_nlink != 1)
+ return refuse(path, "will only touch files with no hardlinks");
+
+ // check that the group matches
+ bool found = false;
+ for(int i=0; i<ngroups; i++)
+ if(sfile.st_gid == groups[i]) {
+ found = true;
+ break;
+ }
+ if(!found)
+ return refuse(path, "You need to share a group with the file");
+
+ // everything checks out; do it. Do it! Doooo it!
+ if(fchown(file, getuid(), -1))
+ return error(path);
+
+ // recursion for fun and profit
+ if(S_ISDIR(sfile.st_mode)) {
+ if(DIR* df = fdopendir(file)) {
+ bool ok = true;
+
+ while(dirent* d = readdir(df)) {
+ if(d->d_name[0]=='.') {
+ if(d->d_name[1]==0)
+ continue;
+ if(d->d_name[1]=='.' && d->d_name[2]==0)
+ continue;
+ }
+ fchdir(file);
+ ok &= takeover(d->d_name, true);
+ }
+ closedir(df);
+ } else
+ return error(path);
+ }
+
+ return true;
+}
+
+
+int main(int argc, char** argv)
+{
+ ngroups = getgroups(sizeof(groups)/sizeof(groups[0]), groups);
+
+ bool ok = true;
+ for(int arg=1; arg<argc; arg++)
+ ok &= takeover(argv[arg], false);
+ return ok? 0: 1;
+}
+
--
To view, visit https://gerrit.wikimedia.org/r/69981
To unsubscribe, visit https://gerrit.wikimedia.org/r/settings
Gerrit-MessageType: newchange
Gerrit-Change-Id: I132b56ebdedfdaee83099d1a7b34215d06441f65
Gerrit-PatchSet: 1
Gerrit-Project: labs/toollabs
Gerrit-Branch: master
Gerrit-Owner: coren <[email protected]>
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