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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this file,
#include "SandboxBrokerClient.h"
#include "SandboxInfo.h"
#include "SandboxLogging.h"
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/un.h>
#include <unistd.h>
#include "mozilla/Assertions.h"
#include "base/strings/safe_sprintf.h"
namespace mozilla {
SandboxBrokerClient::SandboxBrokerClient(int aFd) : mFileDesc(aFd) {}
SandboxBrokerClient::~SandboxBrokerClient() { close(mFileDesc); }
int SandboxBrokerClient::DoCall(const Request* aReq, const char* aPath,
const char* aPath2, void* aResponseBuff,
bool expectFd) {
// Remap /proc/self to the actual pid, so that the broker can open
// it. This happens here instead of in the broker to follow the
// principle of least privilege and keep the broker as simple as
// possible. (Note: when pid namespaces happen, this will also need
// to remap the inner pid to the outer pid.)
// We only remap the first path.
static const char kProcSelf[] = "/proc/self/";
static const size_t kProcSelfLen = sizeof(kProcSelf) - 1;
const char* path = aPath;
// This buffer just needs to be large enough for any such path that
// the policy would actually allow. sizeof("/proc/2147483647/") == 18.
char rewrittenPath[64];
if (strncmp(aPath, kProcSelf, kProcSelfLen) == 0) {
ssize_t len = base::strings::SafeSPrintf(rewrittenPath, "/proc/%d/%s",
getpid(), aPath + kProcSelfLen);
if (static_cast<size_t>(len) < sizeof(rewrittenPath)) {
if (SandboxInfo::Get().Test(SandboxInfo::kVerbose)) {
SANDBOX_LOG("rewriting %s -> %s", aPath, rewrittenPath);
}
path = rewrittenPath;
} else {
SANDBOX_LOG("not rewriting unexpectedly long path %s", aPath);
}
}
struct iovec ios[3];
int respFds[2];
// Set up iovecs for request + path.
ios[0].iov_base = const_cast<Request*>(aReq);
ios[0].iov_len = sizeof(*aReq);
ios[1].iov_base = const_cast<char*>(path);
ios[1].iov_len = strlen(path) + 1;
if (aPath2 != nullptr) {
ios[2].iov_base = const_cast<char*>(aPath2);
ios[2].iov_len = strlen(aPath2) + 1;
} else {
ios[2].iov_base = nullptr;
ios[2].iov_len = 0;
}
if (ios[1].iov_len > kMaxPathLen) {
return -ENAMETOOLONG;
}
if (ios[2].iov_len > kMaxPathLen) {
return -ENAMETOOLONG;
}
// Create response socket and send request.
if (socketpair(AF_UNIX, SOCK_SEQPACKET, 0, respFds) < 0) {
return -errno;
}
const ssize_t sent = SendWithFd(mFileDesc, ios, 3, respFds[1]);
const int sendErrno = errno;
MOZ_ASSERT(sent < 0 || static_cast<size_t>(sent) ==
ios[0].iov_len + ios[1].iov_len + ios[2].iov_len);
close(respFds[1]);
if (sent < 0) {
close(respFds[0]);
return -sendErrno;
}
// Set up iovecs for response.
Response resp;
ios[0].iov_base = &resp;
ios[0].iov_len = sizeof(resp);
if (aResponseBuff) {
ios[1].iov_base = aResponseBuff;
ios[1].iov_len = aReq->mBufSize;
} else {
ios[1].iov_base = nullptr;
ios[1].iov_len = 0;
}
// Wait for response and return appropriately.
int openedFd = -1;
const ssize_t recvd = RecvWithFd(respFds[0], ios, aResponseBuff ? 2 : 1,
expectFd ? &openedFd : nullptr);
const int recvErrno = errno;
close(respFds[0]);
if (recvd < 0) {
return -recvErrno;
}
if (recvd == 0) {
SANDBOX_LOG("Unexpected EOF, op %d flags 0%o path %s", aReq->mOp,
aReq->mFlags, path);
return -EIO;
}
MOZ_ASSERT(static_cast<size_t>(recvd) <= ios[0].iov_len + ios[1].iov_len);
// Some calls such as readlink return a size if successful
if (resp.mError >= 0) {
// Success!
if (expectFd) {
MOZ_ASSERT(openedFd >= 0);
return openedFd;
}
return resp.mError;
}
if (SandboxInfo::Get().Test(SandboxInfo::kVerbose)) {
// Keep in mind that "rejected" files can include ones that don't
// actually exist, if it's something that's optional or part of a
// search path (e.g., shared libraries). In those cases, this
// error message is expected.
SANDBOX_LOG("Failed errno %d op %s flags 0%o path %s", resp.mError,
OperationDescription[aReq->mOp], aReq->mFlags, path);
}
if (openedFd >= 0) {
close(openedFd);
}
return resp.mError;
}
int SandboxBrokerClient::Open(const char* aPath, int aFlags) {
Request req = {SANDBOX_FILE_OPEN, aFlags, 0};
int maybeFd = DoCall(&req, aPath, nullptr, nullptr, true);
if (maybeFd >= 0) {
// NSPR has opinions about file flags. Fix O_CLOEXEC.
if ((aFlags & O_CLOEXEC) == 0) {
fcntl(maybeFd, F_SETFD, 0);
}
}
return maybeFd;
}
int SandboxBrokerClient::Access(const char* aPath, int aMode) {
Request req = {SANDBOX_FILE_ACCESS, aMode, 0};
return DoCall(&req, aPath, nullptr, nullptr, false);
}
int SandboxBrokerClient::Stat(const char* aPath, statstruct* aStat) {
if (!aPath || !aStat) {
return -EFAULT;
}
Request req = {SANDBOX_FILE_STAT, 0, sizeof(statstruct)};
return DoCall(&req, aPath, nullptr, (void*)aStat, false);
}
int SandboxBrokerClient::LStat(const char* aPath, statstruct* aStat) {
if (!aPath || !aStat) {
return -EFAULT;
}
Request req = {SANDBOX_FILE_STAT, O_NOFOLLOW, sizeof(statstruct)};
return DoCall(&req, aPath, nullptr, (void*)aStat, false);
}
int SandboxBrokerClient::Chmod(const char* aPath, int aMode) {
Request req = {SANDBOX_FILE_CHMOD, aMode, 0};
return DoCall(&req, aPath, nullptr, nullptr, false);
}
int SandboxBrokerClient::Link(const char* aOldPath, const char* aNewPath) {
Request req = {SANDBOX_FILE_LINK, 0, 0};
return DoCall(&req, aOldPath, aNewPath, nullptr, false);
}
int SandboxBrokerClient::Symlink(const char* aOldPath, const char* aNewPath) {
Request req = {SANDBOX_FILE_SYMLINK, 0, 0};
return DoCall(&req, aOldPath, aNewPath, nullptr, false);
}
int SandboxBrokerClient::Rename(const char* aOldPath, const char* aNewPath) {
Request req = {SANDBOX_FILE_RENAME, 0, 0};
return DoCall(&req, aOldPath, aNewPath, nullptr, false);
}
int SandboxBrokerClient::Mkdir(const char* aPath, int aMode) {
Request req = {SANDBOX_FILE_MKDIR, aMode, 0};
return DoCall(&req, aPath, nullptr, nullptr, false);
}
int SandboxBrokerClient::Unlink(const char* aPath) {
Request req = {SANDBOX_FILE_UNLINK, 0, 0};
return DoCall(&req, aPath, nullptr, nullptr, false);
}
int SandboxBrokerClient::Rmdir(const char* aPath) {
Request req = {SANDBOX_FILE_RMDIR, 0, 0};
return DoCall(&req, aPath, nullptr, nullptr, false);
}
int SandboxBrokerClient::Readlink(const char* aPath, void* aBuff,
size_t aSize) {
Request req = {SANDBOX_FILE_READLINK, 0, aSize};
return DoCall(&req, aPath, nullptr, aBuff, false);
}
int SandboxBrokerClient::Connect(const sockaddr_un* aAddr, size_t aLen,
int aType) {
static constexpr size_t maxLen = sizeof(aAddr->sun_path);
const char* path = aAddr->sun_path;
const auto addrEnd = reinterpret_cast<const char*>(aAddr) + aLen;
// Ensure that the length isn't impossibly small.
if (addrEnd <= path) {
return -EINVAL;
}
// Unix domain only
if (aAddr->sun_family != AF_UNIX) {
return -EAFNOSUPPORT;
}
// How much of sun_path may be accessed?
auto bufLen = static_cast<size_t>(addrEnd - path);
if (bufLen > maxLen) {
bufLen = maxLen;
}
// Try to handle abstract addresses where the address (the part
// after the leading null byte) resembles a pathname: a leading
// slash and no embedded nulls.
//
// `DoCall` expects null-terminated strings, but in this case the
// "path" is terminated by the sockaddr length (without a null), so
// we need to make a copy.
if (bufLen >= 2 && path[0] == '\0' && path[1] == '/' &&
!memchr(path + 1, '\0', bufLen - 1)) {
char tmpBuf[maxLen];
MOZ_RELEASE_ASSERT(bufLen - 1 < maxLen);
memcpy(tmpBuf, path + 1, bufLen - 1);
tmpBuf[bufLen - 1] = '\0';
const Request req = {SANDBOX_SOCKET_CONNECT_ABSTRACT, aType, 0};
return DoCall(&req, tmpBuf, nullptr, nullptr, true);
}
// Require null-termination. (Linux doesn't require it, but
// applications usually null-terminate for portability, and not
// handling unterminated strings means we don't have to copy the path.)
const size_t pathLen = strnlen(path, bufLen);
if (pathLen == bufLen) {
return -ENAMETOOLONG;
}
// Abstract addresses are handled only in some specific case, error in others
if (pathLen == 0) {
return -ENETUNREACH;
}
const Request req = {SANDBOX_SOCKET_CONNECT, aType, 0};
return DoCall(&req, path, nullptr, nullptr, true);
}
} // namespace mozilla