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-rw-r--r--libs/binder/IPCThreadState.cpp95
-rw-r--r--libs/binder/include/binder/IPCThreadState.h2
2 files changed, 91 insertions, 6 deletions
diff --git a/libs/binder/IPCThreadState.cpp b/libs/binder/IPCThreadState.cpp
index 11c8e5dcea..77703749a1 100644
--- a/libs/binder/IPCThreadState.cpp
+++ b/libs/binder/IPCThreadState.cpp
@@ -45,11 +45,11 @@
#define IF_LOG_TRANSACTIONS() if (false)
#define IF_LOG_COMMANDS() if (false)
-#define LOG_REMOTEREFS(...)
+#define LOG_REMOTEREFS(...)
#define IF_LOG_REMOTEREFS() if (false)
-#define LOG_THREADPOOL(...)
-#define LOG_ONEWAY(...)
+#define LOG_THREADPOOL(...)
+#define LOG_ONEWAY(...)
#else
@@ -394,14 +394,92 @@ void IPCThreadState::checkContextIsBinderForUse(const char* use) const {
// context, so we don't abort
}
+constexpr uint32_t encodeExplicitIdentity(bool hasExplicitIdentity, pid_t callingPid) {
+ uint32_t as_unsigned = static_cast<uint32_t>(callingPid);
+ if (hasExplicitIdentity) {
+ return as_unsigned | (1 << 30);
+ } else {
+ return as_unsigned & ~(1 << 30);
+ }
+}
+
+constexpr int64_t packCallingIdentity(bool hasExplicitIdentity, uid_t callingUid,
+ pid_t callingPid) {
+ // Calling PID is a 32-bit signed integer, but doesn't consume the entire 32 bit space.
+ // To future-proof this and because we have extra capacity, we decided to also support -1,
+ // since this constant is used to represent invalid UID in other places of the system.
+ // Thus, we pack hasExplicitIdentity into the 2nd bit from the left. This allows us to
+ // preserve the (left-most) bit for the sign while also encoding the value of
+ // hasExplicitIdentity.
+ // 32b | 1b | 1b | 30b
+ // token = [ calling uid | calling pid(sign) | has explicit identity | calling pid(rest) ]
+ uint64_t token = (static_cast<uint64_t>(callingUid) << 32) |
+ encodeExplicitIdentity(hasExplicitIdentity, callingPid);
+ return static_cast<int64_t>(token);
+}
+
+constexpr bool unpackHasExplicitIdentity(int64_t token) {
+ return static_cast<int32_t>(token) & (1 << 30);
+}
+
+constexpr uid_t unpackCallingUid(int64_t token) {
+ return static_cast<uid_t>(token >> 32);
+}
+
+constexpr pid_t unpackCallingPid(int64_t token) {
+ int32_t encodedPid = static_cast<int32_t>(token);
+ if (encodedPid & (1 << 31)) {
+ return encodedPid | (1 << 30);
+ } else {
+ return encodedPid & ~(1 << 30);
+ }
+}
+
+static_assert(unpackHasExplicitIdentity(packCallingIdentity(true, 1000, 9999)) == true,
+ "pack true hasExplicit");
+
+static_assert(unpackCallingUid(packCallingIdentity(true, 1000, 9999)) == 1000, "pack true uid");
+
+static_assert(unpackCallingPid(packCallingIdentity(true, 1000, 9999)) == 9999, "pack true pid");
+
+static_assert(unpackHasExplicitIdentity(packCallingIdentity(false, 1000, 9999)) == false,
+ "pack false hasExplicit");
+
+static_assert(unpackCallingUid(packCallingIdentity(false, 1000, 9999)) == 1000, "pack false uid");
+
+static_assert(unpackCallingPid(packCallingIdentity(false, 1000, 9999)) == 9999, "pack false pid");
+
+static_assert(unpackHasExplicitIdentity(packCallingIdentity(true, 1000, -1)) == true,
+ "pack true (negative) hasExplicit");
+
+static_assert(unpackCallingUid(packCallingIdentity(true, 1000, -1)) == 1000,
+ "pack true (negative) uid");
+
+static_assert(unpackCallingPid(packCallingIdentity(true, 1000, -1)) == -1,
+ "pack true (negative) pid");
+
+static_assert(unpackHasExplicitIdentity(packCallingIdentity(false, 1000, -1)) == false,
+ "pack false (negative) hasExplicit");
+
+static_assert(unpackCallingUid(packCallingIdentity(false, 1000, -1)) == 1000,
+ "pack false (negative) uid");
+
+static_assert(unpackCallingPid(packCallingIdentity(false, 1000, -1)) == -1,
+ "pack false (negative) pid");
+
int64_t IPCThreadState::clearCallingIdentity()
{
// ignore mCallingSid for legacy reasons
- int64_t token = ((int64_t)mCallingUid<<32) | mCallingPid;
+ int64_t token = packCallingIdentity(mHasExplicitIdentity, mCallingUid, mCallingPid);
clearCaller();
+ mHasExplicitIdentity = true;
return token;
}
+bool IPCThreadState::hasExplicitIdentity() {
+ return mHasExplicitIdentity;
+}
+
void IPCThreadState::setStrictModePolicy(int32_t policy)
{
mStrictModePolicy = policy;
@@ -474,9 +552,10 @@ ProcessState::CallRestriction IPCThreadState::getCallRestriction() const {
void IPCThreadState::restoreCallingIdentity(int64_t token)
{
- mCallingUid = (int)(token>>32);
+ mCallingUid = unpackCallingUid(token);
mCallingSid = nullptr; // not enough data to restore
- mCallingPid = (int)token;
+ mCallingPid = unpackCallingPid(token);
+ mHasExplicitIdentity = unpackHasExplicitIdentity(token);
}
void IPCThreadState::clearCaller()
@@ -889,6 +968,7 @@ IPCThreadState::IPCThreadState()
mCallRestriction(mProcess->mCallRestriction) {
pthread_setspecific(gTLS, this);
clearCaller();
+ mHasExplicitIdentity = false;
mIn.setDataCapacity(256);
mOut.setDataCapacity(256);
}
@@ -1279,6 +1359,7 @@ status_t IPCThreadState::executeCommand(int32_t cmd)
const pid_t origPid = mCallingPid;
const char* origSid = mCallingSid;
const uid_t origUid = mCallingUid;
+ const bool origHasExplicitIdentity = mHasExplicitIdentity;
const int32_t origStrictModePolicy = mStrictModePolicy;
const int32_t origTransactionBinderFlags = mLastTransactionBinderFlags;
const int32_t origWorkSource = mWorkSource;
@@ -1292,6 +1373,7 @@ status_t IPCThreadState::executeCommand(int32_t cmd)
mCallingPid = tr.sender_pid;
mCallingSid = reinterpret_cast<const char*>(tr_secctx.secctx);
mCallingUid = tr.sender_euid;
+ mHasExplicitIdentity = false;
mLastTransactionBinderFlags = tr.flags;
// ALOGI(">>>> TRANSACT from pid %d sid %s uid %d\n", mCallingPid,
@@ -1367,6 +1449,7 @@ status_t IPCThreadState::executeCommand(int32_t cmd)
mCallingPid = origPid;
mCallingSid = origSid;
mCallingUid = origUid;
+ mHasExplicitIdentity = origHasExplicitIdentity;
mStrictModePolicy = origStrictModePolicy;
mLastTransactionBinderFlags = origTransactionBinderFlags;
mWorkSource = origWorkSource;
diff --git a/libs/binder/include/binder/IPCThreadState.h b/libs/binder/include/binder/IPCThreadState.h
index c01e92f043..65b77c6736 100644
--- a/libs/binder/include/binder/IPCThreadState.h
+++ b/libs/binder/include/binder/IPCThreadState.h
@@ -139,6 +139,7 @@ public:
int64_t clearCallingIdentity();
// Restores PID/UID (not SID)
void restoreCallingIdentity(int64_t token);
+ bool hasExplicitIdentity();
status_t setupPolling(int* fd);
status_t handlePolledCommands();
@@ -241,6 +242,7 @@ private:
bool mPropagateWorkSource;
bool mIsLooper;
bool mIsFlushing;
+ bool mHasExplicitIdentity;
int32_t mStrictModePolicy;
int32_t mLastTransactionBinderFlags;
CallRestriction mCallRestriction;
generated by cgit v1.2.3-59-g8ed1b (git 2.39.0) at 2025-12-10 12:09:56 +0000