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Rearrange su daemon routine

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This commit is contained in:
topjohnwu 2019-07-07 12:20:19 -07:00
parent ab90901793
commit 5fcd629f16
3 changed files with 122 additions and 133 deletions
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23
native/jni/su/su.cpp
View File

@ -94,15 +94,6 @@ static void setup_sighandlers(void (*handler)(int)) {
}
}
// Default values
su_req_base::su_req_base()
: uid(UID_ROOT), login(false), keepenv(false), mount_master(false) {}
su_request::su_request()
: shell(DEFAULT_SHELL), command("") {}
/*
* Connect daemon, send argc, argv, cwd, pts slave
*/
int su_client_main(int argc, char *argv[]) {
int c;
struct option long_opts[] = {
@ -189,18 +180,18 @@ int su_client_main(int argc, char *argv[]) {
// Tell the daemon we are su
write_int(fd, SUPERUSER);
// Wait for ack from daemon
if (read_int(fd)) {
// Fast fail
fprintf(stderr, "%s\n", strerror(EACCES));
return DENY;
}
// Send su_request
xwrite(fd, &su_req, sizeof(su_req_base));
write_string(fd, su_req.shell);
write_string(fd, su_req.command);
// Wait for ack from daemon
if (read_int(fd)) {
// Fast fail
fprintf(stderr, "%s\n", strerror(EACCES));
return EACCES;
}
// Determine which one of our streams are attached to a TTY
int atty = 0;
if (isatty(STDIN_FILENO)) atty |= ATTY_IN;

28
native/jni/su/su.h
View File

@ -2,7 +2,6 @@
#include <sys/types.h>
#include <sys/stat.h>
#include <limits.h>
#include <memory>
#include <db.h>
@ -40,18 +39,25 @@ private:
};
struct su_req_base {
unsigned uid;
bool login;
bool keepenv;
bool mount_master;
protected:
su_req_base();
unsigned uid = UID_ROOT;
bool login = false;
bool keepenv = false;
bool mount_master = false;
} __attribute__((packed));
struct su_request : public su_req_base {
const char *shell;
const char *command;
su_request();
const char *shell = DEFAULT_SHELL;
const char *command = "";
su_request(bool dyn = false) : dyn(dyn) {}
~su_request() {
if (dyn) {
free(const_cast<char*>(shell));
free(const_cast<char*>(command));
}
}
private:
bool dyn;
} __attribute__((packed));
struct su_context {
@ -60,8 +66,6 @@ struct su_context {
pid_t pid;
};
// connect.c
void app_log(const su_context &ctx);
void app_notify(const su_context &ctx);
void app_connect(const char *socket, const std::shared_ptr<su_info> &info);

204
native/jni/su/su_daemon.cpp
View File

@ -101,27 +101,38 @@ static shared_ptr<su_info> get_su_info(unsigned uid) {
// Lock before the policy is determined
info->lock();
RunFinally unlock([&] {
info->unlock();
});
if (info->access.policy == QUERY) {
// Not cached, get data from database
database_check(info);
// If it's root or the manager, allow it silently
if (info->uid == UID_ROOT || (info->uid % 100000) == (info->mgr_st.st_uid % 100000)) {
info->access = SILENT_SU_ACCESS;
return info;
}
// Check su access settings
switch (info->cfg[ROOT_ACCESS]) {
case ROOT_ACCESS_DISABLED:
LOGW("Root access is disabled!\n");
info->access = NO_SU_ACCESS;
break;
return info;
case ROOT_ACCESS_ADB_ONLY:
if (info->uid != UID_SHELL) {
LOGW("Root access limited to ADB only!\n");
info->access = NO_SU_ACCESS;
return info;
}
break;
case ROOT_ACCESS_APPS_ONLY:
if (info->uid == UID_SHELL) {
LOGW("Root access is disabled for ADB!\n");
info->access = NO_SU_ACCESS;
return info;
}
break;
case ROOT_ACCESS_APPS_AND_ADB:
@ -129,41 +140,32 @@ static shared_ptr<su_info> get_su_info(unsigned uid) {
break;
}
// If it's the manager, allow it silently
if ((info->uid % 100000) == (info->mgr_st.st_uid % 100000))
info->access = SILENT_SU_ACCESS;
// Allow if it's root
if (info->uid == UID_ROOT)
info->access = SILENT_SU_ACCESS;
if (info->access.policy != QUERY)
return info;
// If still not determined, check if manager exists
if (info->access.policy == QUERY && info->str[SU_MANAGER][0] == '\0')
if (info->str[SU_MANAGER][0] == '\0') {
info->access = NO_SU_ACCESS;
return info;
}
}
// If still not determined, ask manager
if (info->access.policy == QUERY) {
// Create random socket
struct sockaddr_un addr;
int sockfd = create_rand_socket(&addr);
struct sockaddr_un addr;
int sockfd = create_rand_socket(&addr);
// Connect manager
app_connect(addr.sun_path + 1, info);
int fd = socket_accept(sockfd, 60);
if (fd < 0) {
info->access.policy = DENY;
} else {
socket_send_request(fd, info);
int ret = read_int_be(fd);
info->access.policy = ret < 0 ? DENY : static_cast<policy_t>(ret);
close(fd);
}
close(sockfd);
// Connect manager
app_connect(addr.sun_path + 1, info);
int fd = socket_accept(sockfd, 60);
if (fd < 0) {
info->access.policy = DENY;
} else {
socket_send_request(fd, info);
int ret = read_int_be(fd);
info->access.policy = ret < 0 ? DENY : static_cast<policy_t>(ret);
close(fd);
}
// Unlock
info->unlock();
close(sockfd);
return info;
}
@ -187,24 +189,31 @@ static void set_identity(unsigned uid) {
void su_daemon_handler(int client, struct ucred *credential) {
LOGD("su: request from pid=[%d], client=[%d]\n", credential->pid, client);
auto info = get_su_info(credential->uid);
su_context ctx = {
.info = get_su_info(credential->uid),
.req = su_request(true),
.pid = credential->pid
};
// Read su_request
xxread(client, &ctx.req, sizeof(su_req_base));
ctx.req.shell = read_string(client);
ctx.req.command = read_string(client);
if (ctx.info->access.log)
app_log(ctx);
else if (ctx.info->access.notify)
app_notify(ctx);
// Fail fast
if (info->access.policy == DENY && info->str[SU_MANAGER][0] == '\0') {
LOGD("su: fast deny\n");
if (ctx.info->access.policy == DENY) {
LOGW("su: request rejected (%u)", ctx.info->uid);
ctx.info.reset();
write_int(client, DENY);
close(client);
return;
}
/* Fork a new process, the child process will need to setsid,
* open a pseudo-terminal if needed, and will eventually run exec
* The parent process will wait for the result and
* send the return code back to our client
*/
int child = xfork();
if (child) {
info.reset();
} else if (int child = xfork(); child) {
ctx.info.reset();
// Wait result
LOGD("su: waiting child pid=[%d]\n", child);
@ -221,27 +230,23 @@ void su_daemon_handler(int client, struct ucred *credential) {
return;
}
/* The child process will need to setsid, open a pseudo-terminal
* if needed, and will eventually run exec.
* The parent process will wait for the result and
* send the return code back to our client
*/
LOGD("su: fork handler\n");
// Abort upon any error occurred
log_cb.ex = exit;
su_context ctx = {
.info = info,
.pid = credential->pid
};
// ack
write_int(client, 0);
// Become session leader
xsetsid();
// Read su_request
xxread(client, &ctx.req, sizeof(su_req_base));
ctx.req.shell = read_string(client);
ctx.req.command = read_string(client);
// Get pts_slave
char *pts_slave = read_string(client);
@ -257,7 +262,7 @@ void su_daemon_handler(int client, struct ucred *credential) {
xstat(pts_slave, &st);
// If caller is not root, ensure the owner of pts_slave is the caller
if(st.st_uid != info->uid && info->uid != 0)
if(st.st_uid != ctx.info->uid && ctx.info->uid != 0)
LOGE("su: Wrong permission of pts_slave");
// Opening the TTY has to occur after the
@ -292,8 +297,8 @@ void su_daemon_handler(int client, struct ucred *credential) {
// Handle namespaces
if (ctx.req.mount_master)
info->cfg[SU_MNT_NS] = NAMESPACE_MODE_GLOBAL;
switch (info->cfg[SU_MNT_NS]) {
ctx.info->cfg[SU_MNT_NS] = NAMESPACE_MODE_GLOBAL;
switch (ctx.info->cfg[SU_MNT_NS]) {
case NAMESPACE_MODE_GLOBAL:
LOGD("su: use global namespace\n");
break;
@ -309,58 +314,47 @@ void su_daemon_handler(int client, struct ucred *credential) {
break;
}
if (info->access.log)
app_log(ctx);
else if (info->access.notify)
app_notify(ctx);
const char *argv[] = { nullptr, nullptr, nullptr, nullptr };
if (info->access.policy == ALLOW) {
const char *argv[] = { nullptr, nullptr, nullptr, nullptr };
argv[0] = ctx.req.login ? "-" : ctx.req.shell;
argv[0] = ctx.req.login ? "-" : ctx.req.shell;
if (ctx.req.command[0]) {
argv[1] = "-c";
argv[2] = ctx.req.command;
}
// Setup environment
umask(022);
char path[32], buf[4096];
snprintf(path, sizeof(path), "/proc/%d/cwd", ctx.pid);
xreadlink(path, buf, sizeof(buf));
chdir(buf);
snprintf(path, sizeof(path), "/proc/%d/environ", ctx.pid);
memset(buf, 0, sizeof(buf));
int fd = open(path, O_RDONLY);
read(fd, buf, sizeof(buf));
close(fd);
clearenv();
for (size_t pos = 0; buf[pos];) {
putenv(buf + pos);
pos += strlen(buf + pos) + 1;
}
if (!ctx.req.keepenv) {
struct passwd *pw;
pw = getpwuid(ctx.req.uid);
if (pw) {
setenv("HOME", pw->pw_dir, 1);
if (ctx.req.login || ctx.req.uid) {
setenv("USER", pw->pw_name, 1);
setenv("LOGNAME", pw->pw_name, 1);
}
setenv("SHELL", ctx.req.shell, 1);
}
}
set_identity(ctx.req.uid);
execvp(ctx.req.shell, (char **) argv);
fprintf(stderr, "Cannot execute %s: %s\n", ctx.req.shell, strerror(errno));
PLOGE("exec");
exit(EXIT_FAILURE);
} else {
LOGW("su: request rejected (%u->%u)", info->uid, ctx.req.uid);
fprintf(stderr, "%s\n", strerror(EACCES));
exit(EXIT_FAILURE);
if (ctx.req.command[0]) {
argv[1] = "-c";
argv[2] = ctx.req.command;
}
// Setup environment
umask(022);
char path[32], buf[4096];
snprintf(path, sizeof(path), "/proc/%d/cwd", ctx.pid);
xreadlink(path, buf, sizeof(buf));
chdir(buf);
snprintf(path, sizeof(path), "/proc/%d/environ", ctx.pid);
memset(buf, 0, sizeof(buf));
int fd = open(path, O_RDONLY);
read(fd, buf, sizeof(buf));
close(fd);
clearenv();
for (size_t pos = 0; buf[pos];) {
putenv(buf + pos);
pos += strlen(buf + pos) + 1;
}
if (!ctx.req.keepenv) {
struct passwd *pw;
pw = getpwuid(ctx.req.uid);
if (pw) {
setenv("HOME", pw->pw_dir, 1);
if (ctx.req.login || ctx.req.uid) {
setenv("USER", pw->pw_name, 1);
setenv("LOGNAME", pw->pw_name, 1);
}
setenv("SHELL", ctx.req.shell, 1);
}
}
set_identity(ctx.req.uid);
execvp(ctx.req.shell, (char **) argv);
fprintf(stderr, "Cannot execute %s: %s\n", ctx.req.shell, strerror(errno));
PLOGE("exec");
exit(EXIT_FAILURE);
}