bool clientHasLogCredentials(uid_t uid, gid_t gid, pid_t pid) {
if ((uid == AID_ROOT) || (uid == AID_SYSTEM) || (uid == AID_LOG)) {
return true;
}
if ((gid == AID_ROOT) || (gid == AID_SYSTEM) || (gid == AID_LOG)) {
return true;
}
// FYI We will typically be here for 'adb logcat'
char filename[256];
snprintf(filename, sizeof(filename), "/proc/%u/status", pid);
bool ret;
bool foundLog = false;
bool foundGid = false;
bool foundUid = false;
//
// Reading /proc/<pid>/status is rife with race conditions. All of /proc
// suffers from this and its use should be minimized. However, we have no
// choice.
//
// Notably the content from one 4KB page to the next 4KB page can be from a
// change in shape even if we are gracious enough to attempt to read
// atomically. getline can not even guarantee a page read is not split up
// and in effect can read from different vintages of the content.
//
// We are finding out in the field that a 'logcat -c' via adb occasionally
// is returned with permission denied when we did only one pass and thus
// breaking scripts. For security we still err on denying access if in
// doubt, but we expect the falses should be reduced significantly as
// three times is a charm.
//
for (int retry = 3; !(ret = foundGid && foundUid && foundLog) && retry;
--retry) {
FILE* file = fopen(filename, "r");
if (!file) {
continue;
}
char* line = nullptr;
size_t len = 0;
while (getline(&line, &len, file) > 0) {
static const char groups_string[] = "Groups:\t";
static const char uid_string[] = "Uid:\t";
static const char gid_string[] = "Gid:\t";
if (strncmp(groups_string, line, sizeof(groups_string) - 1) == 0) {
if (groupIsLog(line + sizeof(groups_string) - 1)) {
foundLog = true;
}
} else if (strncmp(uid_string, line, sizeof(uid_string) - 1) == 0) {
uid_t u[4] = { (uid_t)-1, (uid_t)-1, (uid_t)-1, (uid_t)-1 };
sscanf(line + sizeof(uid_string) - 1, "%u\t%u\t%u\t%u", &u[0],
&u[1], &u[2], &u[3]);
// Protect against PID reuse by checking that UID is the same
if ((uid == u[0]) && (uid == u[1]) && (uid == u[2]) &&
(uid == u[3])) {
foundUid = true;
}
} else if (strncmp(gid_string, line, sizeof(gid_string) - 1) == 0) {
gid_t g[4] = { (gid_t)-1, (gid_t)-1, (gid_t)-1, (gid_t)-1 };
sscanf(line + sizeof(gid_string) - 1, "%u\t%u\t%u\t%u", &g[0],
&g[1], &g[2], &g[3]);
// Protect against PID reuse by checking that GID is the same
if ((gid == g[0]) && (gid == g[1]) && (gid == g[2]) &&
(gid == g[3])) {
foundGid = true;
}
}
}
free(line);
fclose(file);
}
return ret;
}
bool clientHasLogCredentials(SocketClient * cli) {
uid_t uid = cli->getUid();
if (uid == AID_ROOT) {
return true;
}
gid_t gid = cli->getGid();
if ((gid == AID_ROOT) || (gid == AID_SYSTEM) || (gid == AID_LOG)) {
return true;
}
// FYI We will typically be here for 'adb logcat'
bool ret = false;
char filename[1024];
snprintf(filename, sizeof(filename), "/proc/%d/status", cli->getPid());
FILE *file = fopen(filename, "r");
if (!file) {
return ret;
}
bool foundGid = false;
bool foundUid = false;
char line[1024];
while (fgets(line, sizeof(line), file)) {
static const char groups_string[] = "Groups:\t";
static const char uid_string[] = "Uid:\t";
static const char gid_string[] = "Gid:\t";
if (strncmp(groups_string, line, strlen(groups_string)) == 0) {
ret = groupIsLog(line + strlen(groups_string));
if (!ret) {
break;
}
} else if (strncmp(uid_string, line, strlen(uid_string)) == 0) {
uid_t u[4] = { (uid_t) -1, (uid_t) -1, (uid_t) -1, (uid_t) -1};
sscanf(line + strlen(uid_string), "%u\t%u\t%u\t%u",
&u[0], &u[1], &u[2], &u[3]);
// Protect against PID reuse by checking that the UID is the same
if ((uid != u[0]) || (uid != u[1]) || (uid != u[2]) || (uid != u[3])) {
ret = false;
break;
}
foundUid = true;
} else if (strncmp(gid_string, line, strlen(gid_string)) == 0) {
gid_t g[4] = { (gid_t) -1, (gid_t) -1, (gid_t) -1, (gid_t) -1};
sscanf(line + strlen(gid_string), "%u\t%u\t%u\t%u",
&g[0], &g[1], &g[2], &g[3]);
// Protect against PID reuse by checking that the GID is the same
if ((gid != g[0]) || (gid != g[1]) || (gid != g[2]) || (gid != g[3])) {
ret = false;
break;
}
foundGid = true;
}
}
fclose(file);
if (!foundGid || !foundUid) {
ret = false;
}
return ret;
}
