Validate artifacts before calling odrefresh --compile.
Odrefresh supports partial compilation, by only re-generating the files
that are needed. This means that we need to verify already existing
artifacts before calling odrefresh, because otherwise we won't know
whether files that aren't in fs-verity have been generated by odrefresh,
or by an attacker that managed to compromise the filesystem on a
previous boot cycle.
To make this change without adding additional boot time, we need to
switch back to calling odrefresh in two phases again: first, we call
`odrefresh --check` to determine whether odrefresh needs to generate new
artifacts. In either case we will need to verify existing artifacts, but
if `odrefresh --check` said that it won't need to generate any new ones,
we can say we're done with the key after retrieving the digests, which
allows boot to continue in parallel with verification.
Bug: 206090748
Test: atest odsign_e2e_tests
Ignore-AOSP-First: Security fix
Change-Id: I347794f456b9809f25489156a2370d1be93d40cd
Merged-In: I347794f456b9809f25489156a2370d1be93d40cd
(cherry picked from commit 7bf6e0a053307a0918965da9be6560e77d6cfe59)
diff --git a/ondevice-signing/odsign_main.cpp b/ondevice-signing/odsign_main.cpp
index c443340..425776b 100644
--- a/ondevice-signing/odsign_main.cpp
+++ b/ondevice-signing/odsign_main.cpp
@@ -66,6 +66,20 @@
static const char* kStopServiceProp = "ctl.stop";
+static int removeDirectory(const std::string& directory) {
+ std::error_code ec;
+ auto num_removed = std::filesystem::remove_all(directory, ec);
+ if (ec) {
+ LOG(ERROR) << "Can't remove " << directory << ": " << ec.message();
+ return 0;
+ } else {
+ if (num_removed > 0) {
+ LOG(INFO) << "Removed " << num_removed << " entries from " << directory;
+ }
+ return num_removed;
+ }
+}
+
Result<void> verifyExistingCert(const SigningKey& key) {
if (access(kSigningKeyCert.c_str(), F_OK) < 0) {
return ErrnoError() << "Key certificate not found: " << kSigningKeyCert;
@@ -100,6 +114,13 @@
return {};
}
+art::odrefresh::ExitCode checkArtifacts() {
+ const char* const argv[] = {kOdrefreshPath, "--check"};
+ const int exit_code =
+ logwrap_fork_execvp(arraysize(argv), argv, nullptr, false, LOG_ALOG, false, nullptr);
+ return static_cast<art::odrefresh::ExitCode>(exit_code);
+}
+
art::odrefresh::ExitCode compileArtifacts(bool force) {
const char* const argv[] = {kOdrefreshPath, force ? "--force-compile" : "--compile"};
const int exit_code =
@@ -144,7 +165,7 @@
for (const auto& path_digest : digests) {
auto path = path_digest.first;
auto digest = path_digest.second;
- if ((trusted_digests.count(path) == 0)) {
+ if (trusted_digests.count(path) == 0) {
return Error() << "Couldn't find digest for " << path;
}
if (trusted_digests.at(path) != digest) {
@@ -179,7 +200,7 @@
return verifyDigests(*result, trusted_digests);
}
-Result<OdsignInfo> getOdsignInfo(const SigningKey& key) {
+Result<OdsignInfo> getAndVerifyOdsignInfo(const SigningKey& key) {
std::string persistedSignature;
OdsignInfo odsignInfo;
@@ -213,6 +234,28 @@
return odsignInfo;
}
+std::map<std::string, std::string> getTrustedDigests(const SigningKey& key) {
+ std::map<std::string, std::string> trusted_digests;
+
+ if (access(kOdsignInfo.c_str(), F_OK) != 0) {
+ // no odsign info file, which is not necessarily an error - just return
+ // an empty list of digests.
+ LOG(INFO) << kOdsignInfo << " not found.";
+ return trusted_digests;
+ }
+ auto signInfo = getAndVerifyOdsignInfo(key);
+
+ if (signInfo.ok()) {
+ trusted_digests.insert(signInfo->file_hashes().begin(), signInfo->file_hashes().end());
+ } else {
+ // This is not expected, since the file did exist. Log an error and
+ // return an empty list of digests.
+ LOG(ERROR) << "Couldn't load trusted digests: " << signInfo.error();
+ }
+
+ return trusted_digests;
+}
+
Result<void> persistDigests(const std::map<std::string, std::string>& digests,
const SigningKey& key) {
OdsignInfo signInfo;
@@ -252,23 +295,8 @@
}
}
-static Result<void> verifyArtifacts(const SigningKey& key, bool supportsFsVerity) {
- auto signInfo = getOdsignInfo(key);
- // Tell init we're done with the key; this is a boot time optimization
- // in particular for the no fs-verity case, where we need to do a
- // costly verification. If the files haven't been tampered with, which
- // should be the common path, the verification will succeed, and we won't
- // need the key anymore. If it turns out the artifacts are invalid (eg not
- // in fs-verity) or the hash doesn't match, we won't be able to generate
- // new artifacts without the key, so in those cases, remove the artifacts,
- // and use JIT zygote for the current boot. We should recover automatically
- // by the next boot.
- SetProperty(kOdsignKeyDoneProp, "1");
- if (!signInfo.ok()) {
- return Error() << signInfo.error().message();
- }
- std::map<std::string, std::string> trusted_digests(signInfo->file_hashes().begin(),
- signInfo->file_hashes().end());
+static Result<void> verifyArtifacts(const std::map<std::string, std::string>& trusted_digests,
+ bool supportsFsVerity) {
Result<void> integrityStatus;
if (supportsFsVerity) {
@@ -337,22 +365,57 @@
}
}
- art::odrefresh::ExitCode odrefresh_status = compileArtifacts(kForceCompilation);
- if (odrefresh_status == art::odrefresh::ExitCode::kOkay) {
- LOG(INFO) << "odrefresh said artifacts are VALID";
- // A post-condition of validating artifacts is that if the ones on /system
- // are used, kArtArtifactsDir is removed. Conversely, if kArtArtifactsDir
- // exists, those are artifacts that will be used, and we should verify them.
- int err = access(kArtArtifactsDir.c_str(), F_OK);
- // If we receive any error other than ENOENT, be suspicious
- bool artifactsPresent = (err == 0) || (err < 0 && errno != ENOENT);
- if (artifactsPresent) {
- auto verificationResult = verifyArtifacts(*key, supportsFsVerity);
- if (!verificationResult.ok()) {
- LOG(ERROR) << verificationResult.error().message();
+ art::odrefresh::ExitCode odrefresh_status = checkArtifacts();
+
+ // The artifacts dir doesn't necessarily need to exist; if the existing
+ // artifacts on the system partition are valid, those can be used.
+ int err = access(kArtArtifactsDir.c_str(), F_OK);
+ // If we receive any error other than ENOENT, be suspicious
+ bool artifactsPresent = (err == 0) || (err < 0 && errno != ENOENT);
+
+ if (artifactsPresent && (odrefresh_status == art::odrefresh::ExitCode::kOkay ||
+ odrefresh_status == art::odrefresh::ExitCode::kCompilationRequired)) {
+ // If we haven't verified the digests yet, we need to validate them. We
+ // need to do this both in case the existing artifacts are okay, but
+ // also if odrefresh said that a recompile is required. In the latter
+ // case, odrefresh may use partial compilation, and leave some
+ // artifacts unchanged.
+ auto trusted_digests = getTrustedDigests(*key);
+
+ if (odrefresh_status == art::odrefresh::ExitCode::kOkay) {
+ // Tell init we're done with the key; this is a boot time optimization
+ // in particular for the no fs-verity case, where we need to do a
+ // costly verification. If the files haven't been tampered with, which
+ // should be the common path, the verification will succeed, and we won't
+ // need the key anymore. If it turns out the artifacts are invalid (eg not
+ // in fs-verity) or the hash doesn't match, we won't be able to generate
+ // new artifacts without the key, so in those cases, remove the artifacts,
+ // and use JIT zygote for the current boot. We should recover automatically
+ // by the next boot.
+ SetProperty(kOdsignKeyDoneProp, "1");
+ }
+
+ auto verificationResult = verifyArtifacts(trusted_digests, supportsFsVerity);
+ if (!verificationResult.ok()) {
+ int num_removed = removeDirectory(kArtArtifactsDir);
+ if (num_removed == 0) {
+ // If we can't remove the bad artifacts, we shouldn't continue, and
+ // instead prevent Zygote from using them (which is taken care of
+ // in the exit handler).
+ LOG(ERROR) << "Failed to remove unknown artifacts.";
return -1;
}
}
+ }
+
+ // Now that we verified existing artifacts, compile if we need to.
+ if (odrefresh_status == art::odrefresh::ExitCode::kCompilationRequired) {
+ odrefresh_status = compileArtifacts(kForceCompilation);
+ }
+
+ if (odrefresh_status == art::odrefresh::ExitCode::kOkay) {
+ // No new artifacts generated, and we verified existing ones above, nothing left to do.
+ LOG(INFO) << "odrefresh said artifacts are VALID";
} else if (odrefresh_status == art::odrefresh::ExitCode::kCompilationSuccess ||
odrefresh_status == art::odrefresh::ExitCode::kCompilationFailed) {
const bool compiled_all = odrefresh_status == art::odrefresh::ExitCode::kCompilationSuccess;
