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-rw-r--r--apt-pkg/acquire.cc113
1 files changed, 84 insertions, 29 deletions
diff --git a/apt-pkg/acquire.cc b/apt-pkg/acquire.cc
index 81faee5d8..fb1210750 100644
--- a/apt-pkg/acquire.cc
+++ b/apt-pkg/acquire.cc
@@ -30,6 +30,7 @@
#include <iostream>
#include <sstream>
#include <iomanip>
+#include <memory>
#include <stdio.h>
#include <stdlib.h>
@@ -76,7 +77,7 @@ void pkgAcquire::Initialize()
// chown the auth.conf file as it will be accessed by our methods
std::string const SandboxUser = _config->Find("APT::Sandbox::User");
- if (getuid() == 0 && SandboxUser.empty() == false) // if we aren't root, we can't chown, so don't try it
+ if (getuid() == 0 && SandboxUser.empty() == false && SandboxUser != "root") // if we aren't root, we can't chown, so don't try it
{
struct passwd const * const pw = getpwnam(SandboxUser.c_str());
struct group const * const gr = getgrnam("root");
@@ -102,7 +103,7 @@ static bool SetupAPTPartialDirectory(std::string const &grand, std::string const
return false;
std::string const SandboxUser = _config->Find("APT::Sandbox::User");
- if (getuid() == 0 && SandboxUser.empty() == false) // if we aren't root, we can't chown, so don't try it
+ if (getuid() == 0 && SandboxUser.empty() == false && SandboxUser != "root") // if we aren't root, we can't chown, so don't try it
{
struct passwd const * const pw = getpwnam(SandboxUser.c_str());
struct group const * const gr = getgrnam("root");
@@ -448,13 +449,50 @@ void pkgAcquire::RunFds(fd_set *RSet,fd_set *WSet)
/* This runs the queues. It manages a select loop for all of the
Worker tasks. The workers interact with the queues and items to
manage the actual fetch. */
+static bool IsAccessibleBySandboxUser(std::string const &filename, bool const ReadWrite)
+{
+ // you would think this is easily to answer with faccessat, right? Wrong!
+ // It e.g. gets groups wrong, so the only thing which works reliable is trying
+ // to open the file we want to open later on…
+ if (unlikely(filename.empty()))
+ return true;
+
+ if (ReadWrite == false)
+ {
+ errno = 0;
+ // can we read a file? Note that non-existing files are "fine"
+ int const fd = open(filename.c_str(), O_RDONLY | O_CLOEXEC);
+ if (fd == -1 && errno == EACCES)
+ return false;
+ close(fd);
+ return true;
+ }
+ else
+ {
+ // the file might not exist yet and even if it does we will fix permissions,
+ // so important is here just that the directory it is in allows that
+ std::string const dirname = flNotFile(filename);
+ if (unlikely(dirname.empty()))
+ return true;
+
+ char const * const filetag = ".apt-acquire-privs-test.XXXXXX";
+ std::string const tmpfile_tpl = flCombine(dirname, filetag);
+ std::unique_ptr<char, decltype(std::free) *> tmpfile { strdup(tmpfile_tpl.c_str()), std::free };
+ int const fd = mkstemp(tmpfile.get());
+ if (fd == -1 && errno == EACCES)
+ return false;
+ RemoveFile("IsAccessibleBySandboxUser", tmpfile.get());
+ close(fd);
+ return true;
+ }
+}
static void CheckDropPrivsMustBeDisabled(pkgAcquire const &Fetcher)
{
if(getuid() != 0)
return;
- std::string SandboxUser = _config->Find("APT::Sandbox::User");
- if (SandboxUser.empty())
+ std::string const SandboxUser = _config->Find("APT::Sandbox::User");
+ if (SandboxUser.empty() || SandboxUser == "root")
return;
struct passwd const * const pw = getpwnam(SandboxUser.c_str());
@@ -463,50 +501,67 @@ static void CheckDropPrivsMustBeDisabled(pkgAcquire const &Fetcher)
gid_t const old_euid = geteuid();
gid_t const old_egid = getegid();
+
+ long const ngroups_max = sysconf(_SC_NGROUPS_MAX);
+ std::unique_ptr<gid_t[]> old_gidlist(new gid_t[ngroups_max]);
+ if (unlikely(old_gidlist == NULL))
+ return;
+ ssize_t old_gidlist_nr;
+ if ((old_gidlist_nr = getgroups(ngroups_max, old_gidlist.get())) < 0)
+ {
+ _error->FatalE("getgroups", "getgroups %lu failed", ngroups_max);
+ old_gidlist[0] = 0;
+ old_gidlist_nr = 1;
+ }
+ if (setgroups(1, &pw->pw_gid))
+ _error->FatalE("setgroups", "setgroups %u failed", pw->pw_gid);
+
if (setegid(pw->pw_gid) != 0)
- _error->Errno("setegid", "setegid %u failed", pw->pw_gid);
+ _error->FatalE("setegid", "setegid %u failed", pw->pw_gid);
if (seteuid(pw->pw_uid) != 0)
- _error->Errno("seteuid", "seteuid %u failed", pw->pw_uid);
+ _error->FatalE("seteuid", "seteuid %u failed", pw->pw_uid);
for (pkgAcquire::ItemCIterator I = Fetcher.ItemsBegin();
I != Fetcher.ItemsEnd(); ++I)
{
- std::string filename = (*I)->DestFile;
- if (filename.empty())
- continue;
-
// no need to drop privileges for a complete file
if ((*I)->Complete == true)
continue;
- // we check directory instead of file as the file might or might not
- // exist already as a link or not which complicates everything…
- std::string dirname = flNotFile(filename);
- if (unlikely(dirname.empty()))
- continue;
- // translate relative to absolute for DirectoryExists
- // FIXME: What about ../ and ./../ ?
- if (dirname.substr(0,2) == "./")
- dirname = SafeGetCWD() + dirname.substr(2);
-
- if (DirectoryExists(dirname))
- ;
- else
- continue; // assume it is created correctly by the acquire system
-
- if (faccessat(-1, dirname.c_str(), R_OK | W_OK | X_OK, AT_EACCESS | AT_SYMLINK_NOFOLLOW) != 0)
+ // if destination file is inaccessible all hope is lost for privilege dropping
+ if (IsAccessibleBySandboxUser((*I)->DestFile, true) == false)
{
_error->WarningE("pkgAcquire::Run", _("Can't drop privileges for downloading as file '%s' couldn't be accessed by user '%s'."),
- filename.c_str(), SandboxUser.c_str());
+ (*I)->DestFile.c_str(), SandboxUser.c_str());
_config->Set("APT::Sandbox::User", "");
break;
}
+
+ // if its the source file (e.g. local sources) we might be lucky
+ // by dropping the dropping only for some methods.
+ URI const source = (*I)->DescURI();
+ if (source.Access == "file" || source.Access == "copy")
+ {
+ std::string const conf = "Binary::" + source.Access + "::APT::Sandbox::User";
+ if (_config->Exists(conf) == true)
+ continue;
+
+ if (IsAccessibleBySandboxUser(source.Path, false) == false)
+ {
+ _error->NoticeE("pkgAcquire::Run", _("Can't drop privileges for downloading as file '%s' couldn't be accessed by user '%s'."),
+ source.Path.c_str(), SandboxUser.c_str());
+ _config->CndSet("Binary::file::APT::Sandbox::User", "root");
+ _config->CndSet("Binary::copy::APT::Sandbox::User", "root");
+ }
+ }
}
if (seteuid(old_euid) != 0)
- _error->Errno("seteuid", "seteuid %u failed", old_euid);
+ _error->FatalE("seteuid", "seteuid %u failed", old_euid);
if (setegid(old_egid) != 0)
- _error->Errno("setegid", "setegid %u failed", old_egid);
+ _error->FatalE("setegid", "setegid %u failed", old_egid);
+ if (setgroups(old_gidlist_nr, old_gidlist.get()))
+ _error->FatalE("setgroups", "setgroups %u failed", 0);
}
pkgAcquire::RunResult pkgAcquire::Run(int PulseIntervall)
{
generated by cgit v1.2.3 (git 2.25.1) at 2024-05-25 14:23:48 +0000