Attachment 257114 Details for Bug 142980 – Patch

[patch] Patch

bug-142980-20150720140154.patch (text/plain), 6.74 KB, created by Michael Catanzaro on 2015-07-20 12:03:07 PDT

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Creator: Michael Catanzaro

Created: 2015-07-20 12:03:07 PDT

Size: 6.74 KB

patch

obsolete

>Subversion Revision: 187015
>diff --git a/Source/WebKit2/ChangeLog b/Source/WebKit2/ChangeLog
>index 6c506a0938feb4325f1f587d499bf564cc00c25f..554e5230901f11eb5df297593a12c31ae4e90900 100644
>--- a/Source/WebKit2/ChangeLog
>+++ b/Source/WebKit2/ChangeLog
>@@ -1,3 +1,25 @@
>+2015-07-20  Michael Catanzaro  <mcatanzaro@igalia.com>
>+
>+        [Seccomp] Should be easier to debug blocked syscalls
>+        https://bugs.webkit.org/show_bug.cgi?id=142980
>+
>+        These should be printed even when not running in debug mode. There is no
>+        value in hiding errors from release build users.
>+
>+        Reviewed by NOBODY (OOPS!).
>+
>+        * Shared/linux/SeccompFilters/SeccompBroker.cpp:
>+        (WebKit::SeccompBroker::runLoop): Don't close stderr et. al. in release builds.
>+        * Shared/linux/SeccompFilters/Syscall.cpp:
>+        (WebKit::write_uint): Added.
>+        (WebKit::reportUnexpectedSyscall): Added.
>+        (WebKit::Syscall::createFromContext): Call reportUnexpectedSyscall. Also, no need to crash
>+        here in release builds.
>+        * Shared/linux/SeccompFilters/SyscallPolicy.cpp:
>+        (WebKit::SyscallPolicy::hasPermissionForPath): Print a warning when access is denied.
>+        (WebKit::SyscallPolicy::permissionToString): Added.
>+        * Shared/linux/SeccompFilters/SyscallPolicy.h: Add permissionToString.
>+
> 2015-07-19  Michael Catanzaro  <mcatanzaro@igalia.com>
> 
>         Unreviewed, placate -Wmismatched-tags after r187011
>diff --git a/Source/WebKit2/Shared/linux/SeccompFilters/SeccompBroker.cpp b/Source/WebKit2/Shared/linux/SeccompFilters/SeccompBroker.cpp
>index 591f089a7b11366f6b5b71ad73dac8e9491eb3a8..162049d14b4bab9070f570b5f8a7836f63eee35d 100644
>--- a/Source/WebKit2/Shared/linux/SeccompFilters/SeccompBroker.cpp
>+++ b/Source/WebKit2/Shared/linux/SeccompFilters/SeccompBroker.cpp
>@@ -320,16 +320,11 @@ void SeccompBroker::initialize()
> 
> NO_RETURN void SeccompBroker::runLoop(int socket)
> {
>-#ifndef NDEBUG
>-    int i = STDERR_FILENO + 1;
>-#else
>-    int i = 0;
>-#endif
>-    // Close all inherited file descriptors other
>-    // than the socket to the sandboxed process.
>-    for (; i < FD_SETSIZE; ++i)
>+    // Close unnecessary inherited file descriptors.
>+    for (int i = STDERR_FILENO + 1; i < FD_SETSIZE; ++i) {
>         if (i != socket)
>             close(i);
>+    }
> 
>     while (true) {
>         char buffer[messageMaxSize];
>diff --git a/Source/WebKit2/Shared/linux/SeccompFilters/Syscall.cpp b/Source/WebKit2/Shared/linux/SeccompFilters/Syscall.cpp
>index 0d4afd0dd22309d90ebefa3ee67b46138334a5e7..de97d31714fb87e2a6d4690f351adb816ea3370f 100644
>--- a/Source/WebKit2/Shared/linux/SeccompFilters/Syscall.cpp
>+++ b/Source/WebKit2/Shared/linux/SeccompFilters/Syscall.cpp
>@@ -1,5 +1,6 @@
> /*
>  * Copyright (C) 2013 Intel Corporation. All rights reserved.
>+ * Copyright (C) 2015 Igalia S.L.
>  *
>  * Redistribution and use in source and binary forms, with or without
>  * modification, are permitted provided that the following conditions
>@@ -32,10 +33,47 @@
> #include "OpenSyscall.h"
> #include "SigactionSyscall.h"
> #include "SigprocmaskSyscall.h"
>+#include <limits>
> #include <seccomp.h>
>+#include <string.h>
>+#include <unistd.h>
> 
> namespace WebKit {
> 
>+// The redundant "constexpr const" is to placate Clang's -Wwritable-strings.
>+static constexpr const char* const message = "Blocked unexpected syscall: ";
>+
>+// Since "sprintf" is not signal-safe, reimplement %d here. Based on code from
>+// http://outflux.net/teach-seccomp by Will Drewry and Kees Cook, released under
>+// the Chromium BSD license.
>+static void writeUnsignedInt(char* buf, unsigned val)
>+{
>+    int width = 0;
>+    unsigned tens;
>+
>+    if (!val) {
>+        strcpy(buf, "0");
>+        return;
>+    }
>+    for (tens = val; tens; tens /= 10)
>+        ++width;
>+    buf[width] = '\0';
>+    for (tens = val; tens; tens /= 10)
>+        buf[--width] = '0' + (tens % 10);
>+}
>+
>+static void reportUnexpectedSyscall(int syscall)
>+{
>+    char buf[128];
>+#if defined(__has_builtin) && __has_builtin(__builtin_strlen)
>+    static_assert(__builtin_strlen(message) + std::numeric_limits<int>::digits10 + 1 < sizeof(buf), "Buffer too small");
>+#endif
>+    strcpy(buf, message);
>+    writeUnsignedInt(buf + strlen(buf), syscall);
>+    strcat(buf, "\n");
>+    write(STDERR_FILENO, buf, strlen(buf));
>+}
>+
> std::unique_ptr<Syscall> Syscall::createFromContext(ucontext_t* ucontext)
> {
>     mcontext_t* mcontext = &ucontext->uc_mcontext;
>@@ -54,7 +92,8 @@ std::unique_ptr<Syscall> Syscall::createFromContext(ucontext_t* ucontext)
>     case __NR_rt_sigaction:
>         return SigactionSyscall::createFromContext(mcontext);
>     default:
>-        CRASH();
>+        reportUnexpectedSyscall(mcontext->gregs[REG_SYSCALL]);
>+        ASSERT_NOT_REACHED();
>     }
> 
>     return nullptr;
>diff --git a/Source/WebKit2/Shared/linux/SeccompFilters/SyscallPolicy.cpp b/Source/WebKit2/Shared/linux/SeccompFilters/SyscallPolicy.cpp
>index 1ef946cb5f9175fb3bc8de4bd67346bb4ff203d7..60983198caf7c428ddc188f38da727572cd370ec 100644
>--- a/Source/WebKit2/Shared/linux/SeccompFilters/SyscallPolicy.cpp
>+++ b/Source/WebKit2/Shared/linux/SeccompFilters/SyscallPolicy.cpp
>@@ -97,7 +97,13 @@ bool SyscallPolicy::hasPermissionForPath(const char* path, Permission permission
>     free(basePath);
>     free(canonicalPath);
> 
>-    return (permission & policy->value) == permission;
>+    if ((permission & policy->value) == permission)
>+        return true;
>+
>+    // Don't warn if the file doesn't exist at all.
>+    if (!access(path, F_OK) || errno != ENOENT)
>+        fprintf(stderr, "Blocked impermissible %s access to %s\n", SyscallPolicy::permissionToString(permission), path);
>+    return false;
> }
> 
> void SyscallPolicy::addFilePermission(const String& path, Permission permission)
>@@ -256,6 +262,23 @@ void SyscallPolicy::addDefaultWebProcessPolicy(const WebProcessCreationParameter
> #endif
> }
> 
>+const char* SyscallPolicy::permissionToString(Permission permission)
>+{
>+    switch (permission) {
>+    case Read:
>+        return "read";
>+    case Write:
>+        return "write";
>+    case ReadAndWrite:
>+        return "read/write";
>+    case NotAllowed:
>+        return "disallowed";
>+    }
>+
>+    ASSERT_NOT_REACHED();
>+    return "";
>+}
>+
> } // namespace WebKit
> 
> #endif // ENABLE(SECCOMP_FILTERS)
>diff --git a/Source/WebKit2/Shared/linux/SeccompFilters/SyscallPolicy.h b/Source/WebKit2/Shared/linux/SeccompFilters/SyscallPolicy.h
>index 54a6e91362308f398a262cc4a3c374d7a05e76ba..b2680dc9ab08811428e8d968d0852e757311f792 100644
>--- a/Source/WebKit2/Shared/linux/SeccompFilters/SyscallPolicy.h
>+++ b/Source/WebKit2/Shared/linux/SeccompFilters/SyscallPolicy.h
>@@ -52,6 +52,8 @@ public:
> 
>     void addDefaultWebProcessPolicy(const WebProcessCreationParameters&);
> 
>+    static const char* permissionToString(Permission);
>+
> private:
>     typedef HashMap<String, int> PermissionMap;
>     PermissionMap m_filePermission;

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zan: review+

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Attachments on bug 142980: 249264 | 249265 | 249274 | 257067 | 257114