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Add a feature to show which bugs are tracking which se denials

Browse source 
The feature references a new file created by the selinux make system
that is stored on device under /system/etc/selinux/ which contains a
scontext, tcontext, tclass, and the bug they map to. logd will
reference this map every time an selinux denial comes through to see if
it's a known denial with a bug attached and then add the bug number to
the denial that's logged.

go/selinux-bug-metadata

Bug: 34997782
Test: any denial -> bug map listed in the referenced file is correcty
displayed in the selinux denials that are logged

Change-Id: I75bab59917591ed700471a0b4922b5f02f86bee9
This commit is contained in:
Max Bires 2017-08-15 11:07:49 -07:00
parent a022ea424d
commit 4214d132b3
2 changed files with 119 additions and 31 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

145
logd/LogAudit.cpp
View file

@ -25,7 +25,11 @@
#include <sys/uio.h>
#include <syslog.h>
#include <fstream>
#include <sstream>
#include <android-base/macros.h>
#include <log/log_properties.h>
#include <private/android_filesystem_config.h>
#include <private/android_logger.h>
@ -138,6 +142,71 @@ bool LogAudit::onDataAvailable(SocketClient* cli) {
return true;
}
static inline bool hasMetadata(char* str, int str_len) {
// need to check and see if str already contains bug metadata from
// possibility of stuttering if log audit crashes and then reloads kernel
// messages. Kernel denials that contain metadata will either end in
// "b/[0-9]+$" or "b/[0-9]+ duplicate messages suppressed$" which will put
// a '/' character at either 9 or 39 indices away from the end of the str.
return str_len >= 39 &&
(str[str_len - 9] == '/' || str[str_len - 39] == '/');
}
std::map<std::string, std::string> LogAudit::populateDenialMap() {
std::ifstream bug_file("/system/etc/selinux/selinux_denial_metadata");
std::string line;
// allocate a map for the static map pointer in logParse to keep track of,
// this function only runs once
std::map<std::string, std::string> denial_to_bug;
if (bug_file.good()) {
std::string scontext;
std::string tcontext;
std::string tclass;
std::string bug_num;
while (std::getline(bug_file, line)) {
std::stringstream split_line(line);
split_line >> scontext >> tcontext >> tclass >> bug_num;
denial_to_bug.emplace(scontext + tcontext + tclass, bug_num);
}
}
return denial_to_bug;
}
std::string LogAudit::denialParse(const std::string& denial, char terminator,
const std::string& search_term) {
size_t start_index = denial.find(search_term);
if (start_index != std::string::npos) {
start_index += search_term.length();
return denial.substr(
start_index, denial.find(terminator, start_index) - start_index);
}
return "";
}
void LogAudit::logParse(const std::string& string, std::string* bug_num) {
if (!__android_log_is_debuggable()) {
bug_num->assign("");
return;
}
static std::map<std::string, std::string> denial_to_bug =
populateDenialMap();
std::string scontext = denialParse(string, ':', "scontext=u:object_r:");
std::string tcontext = denialParse(string, ':', "tcontext=u:object_r:");
std::string tclass = denialParse(string, ' ', "tclass=");
if (scontext.empty()) {
scontext = denialParse(string, ':', "scontext=u:r:");
}
if (tcontext.empty()) {
tcontext = denialParse(string, ':', "tcontext=u:r:");
}
auto search = denial_to_bug.find(scontext + tcontext + tclass);
if (search != denial_to_bug.end()) {
bug_num->assign(" b/" + search->second);
} else {
bug_num->assign("");
}
}
int LogAudit::logPrint(const char* fmt, ...) {
if (fmt == NULL) {
return -EINVAL;
@ -153,7 +222,6 @@ int LogAudit::logPrint(const char* fmt, ...) {
if (rc < 0) {
return rc;
}
char* cp;
// Work around kernels missing
// https://github.com/torvalds/linux/commit/b8f89caafeb55fba75b74bea25adc4e4cd91be67
@ -165,10 +233,10 @@ int LogAudit::logPrint(const char* fmt, ...) {
while ((cp = strstr(str, " "))) {
memmove(cp, cp + 1, strlen(cp + 1) + 1);
}
bool info = strstr(str, " permissive=1") || strstr(str, " policy loaded ");
static std::string bug_metadata;
if ((fdDmesg >= 0) && initialized) {
struct iovec iov[3];
struct iovec iov[4];
static const char log_info[] = { KMSG_PRIORITY(LOG_INFO) };
static const char log_warning[] = { KMSG_PRIORITY(LOG_WARNING) };
static const char newline[] = "\n";
@ -197,19 +265,20 @@ int LogAudit::logPrint(const char* fmt, ...) {
}
if (!skip) {
static const char resume[] = " duplicate messages suppressed\n";
iov[0].iov_base = last_info ? const_cast<char*>(log_info)
: const_cast<char*>(log_warning);
iov[0].iov_len =
last_info ? sizeof(log_info) : sizeof(log_warning);
iov[1].iov_base = last_str;
iov[1].iov_len = strlen(last_str);
iov[2].iov_base = const_cast<char*>(bug_metadata.c_str());
iov[2].iov_len = bug_metadata.length();
if (count > 1) {
iov[2].iov_base = const_cast<char*>(resume);
iov[2].iov_len = strlen(resume);
iov[3].iov_base = const_cast<char*>(resume);
iov[3].iov_len = strlen(resume);
} else {
iov[2].iov_base = const_cast<char*>(newline);
iov[2].iov_len = strlen(newline);
iov[3].iov_base = const_cast<char*>(newline);
iov[3].iov_len = strlen(newline);
}
writev(fdDmesg, iov, arraysize(iov));
@ -223,13 +292,16 @@ int LogAudit::logPrint(const char* fmt, ...) {
last_info = info;
}
if (count == 0) {
logParse(str, &bug_metadata);
iov[0].iov_base = info ? const_cast<char*>(log_info)
: const_cast<char*>(log_warning);
iov[0].iov_len = info ? sizeof(log_info) : sizeof(log_warning);
iov[1].iov_base = str;
iov[1].iov_len = strlen(str);
iov[2].iov_base = const_cast<char*>(newline);
iov[2].iov_len = strlen(newline);
iov[2].iov_base = const_cast<char*>(bug_metadata.c_str());
iov[2].iov_len = bug_metadata.length();
iov[3].iov_base = const_cast<char*>(newline);
iov[3].iov_len = strlen(newline);
writev(fdDmesg, iov, arraysize(iov));
}
@ -285,24 +357,32 @@ int LogAudit::logPrint(const char* fmt, ...) {
// log to events
size_t l = strnlen(str, LOGGER_ENTRY_MAX_PAYLOAD);
size_t n = l + sizeof(android_log_event_string_t);
size_t str_len = strnlen(str, LOGGER_ENTRY_MAX_PAYLOAD);
if (((fdDmesg < 0) || !initialized) && !hasMetadata(str, str_len))
logParse(str, &bug_metadata);
str_len = (str_len + bug_metadata.length() <= LOGGER_ENTRY_MAX_PAYLOAD)
? str_len + bug_metadata.length()
: LOGGER_ENTRY_MAX_PAYLOAD;
size_t message_len = str_len + sizeof(android_log_event_string_t);
bool notify = false;
if (events) { // begin scope for event buffer
uint32_t buffer[(n + sizeof(uint32_t) - 1) / sizeof(uint32_t)];
uint32_t buffer[(message_len + sizeof(uint32_t) - 1) / sizeof(uint32_t)];
android_log_event_string_t* event =
reinterpret_cast<android_log_event_string_t*>(buffer);
event->header.tag = htole32(AUDITD_LOG_TAG);
event->type = EVENT_TYPE_STRING;
event->length = htole32(l);
memcpy(event->data, str, l);
event->length = htole32(message_len);
memcpy(event->data, str, str_len - bug_metadata.length());
memcpy(event->data + str_len - bug_metadata.length(),
bug_metadata.c_str(), bug_metadata.length());
rc = logbuf->log(LOG_ID_EVENTS, now, uid, pid, tid,
reinterpret_cast<char*>(event),
(n <= USHRT_MAX) ? (unsigned short)n : USHRT_MAX);
rc = logbuf->log(
LOG_ID_EVENTS, now, uid, pid, tid, reinterpret_cast<char*>(event),
(message_len <= USHRT_MAX) ? (unsigned short)message_len
: USHRT_MAX);
if (rc >= 0) {
notify = true;
}
@ -333,28 +413,31 @@ int LogAudit::logPrint(const char* fmt, ...) {
const char* ecomm = strchr(comm, '"');
if (ecomm) {
++ecomm;
l = ecomm - comm;
str_len = ecomm - comm;
} else {
l = strlen(comm) + 1;
str_len = strlen(comm) + 1;
ecomm = "";
}
size_t b = estr - str;
if (b > LOGGER_ENTRY_MAX_PAYLOAD) {
b = LOGGER_ENTRY_MAX_PAYLOAD;
size_t prefix_len = estr - str;
if (prefix_len > LOGGER_ENTRY_MAX_PAYLOAD) {
prefix_len = LOGGER_ENTRY_MAX_PAYLOAD;
}
size_t e = strnlen(ecomm, LOGGER_ENTRY_MAX_PAYLOAD - b);
n = b + e + l + 2;
size_t suffix_len = strnlen(ecomm, LOGGER_ENTRY_MAX_PAYLOAD - prefix_len);
message_len = str_len + prefix_len + suffix_len + bug_metadata.length() + 2;
if (main) { // begin scope for main buffer
char newstr[n];
char newstr[message_len];
*newstr = info ? ANDROID_LOG_INFO : ANDROID_LOG_WARN;
strlcpy(newstr + 1, comm, l);
strncpy(newstr + 1 + l, str, b);
strncpy(newstr + 1 + l + b, ecomm, e);
strlcpy(newstr + 1, comm, str_len);
strncpy(newstr + 1 + str_len, str, prefix_len);
strncpy(newstr + 1 + str_len + prefix_len, ecomm, suffix_len);
strncpy(newstr + 1 + str_len + prefix_len + suffix_len,
bug_metadata.c_str(), bug_metadata.length());
rc = logbuf->log(LOG_ID_MAIN, now, uid, pid, tid, newstr,
(n <= USHRT_MAX) ? (unsigned short)n : USHRT_MAX);
(message_len <= USHRT_MAX) ? (unsigned short)message_len
: USHRT_MAX);
if (rc >= 0) {
notify = true;
@ -368,7 +451,7 @@ int LogAudit::logPrint(const char* fmt, ...) {
if (notify) {
reader->notifyNewLog();
if (rc < 0) {
rc = n;
rc = message_len;
}
}

5
logd/LogAudit.h
View file

@ -17,6 +17,7 @@
#ifndef _LOGD_LOG_AUDIT_H__
#define _LOGD_LOG_AUDIT_H__
#include <map>
#include <queue>
#include <sysutils/SocketListener.h>
@ -50,6 +51,10 @@ class LogAudit : public SocketListener {
private:
static int getLogSocket();
std::map<std::string, std::string> populateDenialMap();
std::string denialParse(const std::string& denial, char terminator,
const std::string& search_term);
void logParse(const std::string& string, std::string* bug_num);
int logPrint(const char* fmt, ...)
__attribute__((__format__(__printf__, 2, 3)));
};