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Commit c4e4823b authored by Mark Salyzyn's avatar Mark Salyzyn
Browse files

logd: validate and fill in socket credentials 

- android::pidToUid() additional checking.  Make sure if we have to
  convert a PID to an UID that the parse of /proc/<pid>/status
  requires a trailing space after the number
- android::tidToPid() added, in the same vein as android::pidToUid().
- stats.tidToPid() added
- If no credentials, set PID to 0 and UID to DEFAULT_OVERFLOWUID
- If credentialed PID is 0, use stats.tidToPid()
- If credentialed UID is DEFAULT_OVERFLOWUID, use stats.pidToUid()

Test: remove +passcred from logd.rc for daemon and confirm very few
      UID=65534 or PID=0 cases actually show up
Bug: 37985222
Change-Id: I7d20506e70e67beb3043d1537cf9450ab58dc278
parent 46bb1ffa

logd/LogBuffer.h

+4 −1
Original line number Diff line number Diff line
@@ -159,9 +159,12 @@ class LogBuffer : public LogBufferInterface { 
    const char* pidToName(pid_t pid) {

        return stats.pidToName(pid);

    }

    uid_t pidToUid(pid_t pid) {

    virtual uid_t pidToUid(pid_t pid) override {

        return stats.pidToUid(pid);

    }

    virtual pid_t tidToPid(pid_t tid) override {

        return stats.tidToPid(tid);

    }

    const char* uidToName(uid_t uid) {

        return stats.uidToName(uid);

    }

logd/LogBufferInterface.cpp

+8 −1
Original line number Diff line number Diff line
@@ -15,8 +15,15 @@ 
 */



#include "LogBufferInterface.h"

#include "LogUtils.h"



LogBufferInterface::LogBufferInterface() {

}

LogBufferInterface::~LogBufferInterface() {

}

uid_t LogBufferInterface::pidToUid(pid_t pid) {

    return android::pidToUid(pid);

}

pid_t LogBufferInterface::tidToPid(pid_t tid) {

    return android::tidToPid(tid);

}

logd/LogBufferInterface.h

+3 −0
Original line number Diff line number Diff line
@@ -33,6 +33,9 @@ class LogBufferInterface { 
    virtual int log(log_id_t log_id, log_time realtime, uid_t uid, pid_t pid,

                    pid_t tid, const char* msg, unsigned short len) = 0;



    virtual uid_t pidToUid(pid_t pid);

    virtual pid_t tidToPid(pid_t tid);



   private:

    DISALLOW_COPY_AND_ASSIGN(LogBufferInterface);

};

logd/LogListener.cpp

+27 −1
Original line number Diff line number Diff line
@@ -14,7 +14,9 @@ 
 * limitations under the License.

 */



#include <ctype.h>

#include <limits.h>

#include <stdio.h>

#include <sys/cdefs.h>

#include <sys/prctl.h>

#include <sys/socket.h>
@@ -72,8 +74,11 @@ bool LogListener::onDataAvailable(SocketClient* cli) { 
        cmsg = CMSG_NXTHDR(&hdr, cmsg);

    }



    struct ucred fake_cred;

    if (cred == NULL) {

        return false;

        cred = &fake_cred;

        cred->pid = 0;

        cred->uid = DEFAULT_OVERFLOWUID;

    }



    if (cred->uid == AID_LOGD) {
@@ -96,6 +101,27 @@ bool LogListener::onDataAvailable(SocketClient* cli) { 
        return false;

    }



    // Check credential validity, acquire corrected details if not supplied.

    if (cred->pid == 0) {

        cred->pid = logbuf ? logbuf->tidToPid(header->tid)

                           : android::tidToPid(header->tid);

        if (cred->pid == getpid()) {

            // We expect that /proc/<tid>/ is accessible to self even without

            // readproc group, so that we will always drop messages that come

            // from any of our logd threads and their library calls.

            return false;  // ignore self

        }

    }

    if (cred->uid == DEFAULT_OVERFLOWUID) {

        uid_t uid =

            logbuf ? logbuf->pidToUid(cred->pid) : android::pidToUid(cred->pid);

        if (uid == AID_LOGD) {

            uid = logbuf ? logbuf->pidToUid(header->tid)

                         : android::pidToUid(cred->pid);

        }

        if (uid != AID_LOGD) cred->uid = uid;

    }



    char* msg = ((char*)buffer) + sizeof(android_log_header_t);

    n -= sizeof(android_log_header_t);

logd/LogListener.h

+10 −0
Original line number Diff line number Diff line
@@ -20,6 +20,16 @@ 
#include <sysutils/SocketListener.h>

#include "LogReader.h"



// DEFAULT_OVERFLOWUID is defined in linux/highuid.h, which is not part of

// the uapi headers for userspace to use.  This value is filled in on the

// out-of-band socket credentials if the OS fails to find one available.

// One of the causes of this is if SO_PASSCRED is set, all the packets before

// that point will have this value.  We also use it in a fake credential if

// no socket credentials are supplied.

#ifndef DEFAULT_OVERFLOWUID

#define DEFAULT_OVERFLOWUID 65534

#endif



class LogListener : public SocketListener {

    LogBufferInterface* logbuf;

    LogReader* reader;