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-rw-r--r--pkg/sentry/socket/netfilter/netfilter.go144
1 files changed, 53 insertions, 91 deletions
diff --git a/pkg/sentry/socket/netfilter/netfilter.go b/pkg/sentry/socket/netfilter/netfilter.go
index 6c88a50a6..b8848f08a 100644
--- a/pkg/sentry/socket/netfilter/netfilter.go
+++ b/pkg/sentry/socket/netfilter/netfilter.go
@@ -34,9 +34,16 @@ import (
// shouldn't be reached - an error has occurred if we fall through to one.
const errorTargetName = "ERROR"
-// metadata is opaque to netstack. It holds data that we need to translate
-// between Linux's and netstack's iptables representations.
-// TODO(gvisor.dev/issue/170): Use metadata to check correctness.
+const (
+ matcherNameUDP = "udp"
+)
+
+// Metadata is used to verify that we are correctly serializing and
+// deserializing iptables into structs consumable by the iptables tool. We save
+// a metadata struct when the tables are written, and when they are read out we
+// verify that certain fields are the same.
+//
+// metadata is opaque to netstack.
type metadata struct {
HookEntry [linux.NF_INET_NUMHOOKS]uint32
Underflow [linux.NF_INET_NUMHOOKS]uint32
@@ -44,10 +51,12 @@ type metadata struct {
Size uint32
}
-const enableDebugLog = true
+const enableDebug = false
+// nflog logs messages related to the writing and reading of iptables, but only
+// when enableDebug is true.
func nflog(format string, args ...interface{}) {
- if enableDebugLog {
+ if enableDebug {
log.Infof("netfilter: "+format, args...)
}
}
@@ -80,7 +89,7 @@ func GetInfo(t *kernel.Task, stack *stack.Stack, outPtr usermem.Addr) (linux.IPT
info.NumEntries = metadata.NumEntries
info.Size = metadata.Size
- nflog("GetInfo returning info: %+v", info)
+ nflog("returning info: %+v", info)
return info, nil
}
@@ -163,19 +172,19 @@ func convertNetstackToBinary(tablename string, table iptables.Table) (linux.Kern
copy(entries.Name[:], tablename)
for ruleIdx, rule := range table.Rules {
- nflog("Current offset: %d", entries.Size)
+ nflog("convert to binary: current offset: %d", entries.Size)
// Is this a chain entry point?
for hook, hookRuleIdx := range table.BuiltinChains {
if hookRuleIdx == ruleIdx {
- nflog("Found hook %d at offset %d", hook, entries.Size)
+ nflog("convert to binary: found hook %d at offset %d", hook, entries.Size)
meta.HookEntry[hook] = entries.Size
}
}
// Is this a chain underflow point?
for underflow, underflowRuleIdx := range table.Underflows {
if underflowRuleIdx == ruleIdx {
- nflog("Found underflow %d at offset %d", underflow, entries.Size)
+ nflog("convert to binary: found underflow %d at offset %d", underflow, entries.Size)
meta.Underflow[underflow] = entries.Size
}
}
@@ -195,7 +204,7 @@ func convertNetstackToBinary(tablename string, table iptables.Table) (linux.Kern
// Serialize the matcher and add it to the
// entry.
serialized := marshalMatcher(matcher)
- nflog("matcher serialized as: %v", serialized)
+ nflog("convert to binary: matcher serialized as: %v", serialized)
if len(serialized)%8 != 0 {
panic(fmt.Sprintf("matcher %T is not 64-bit aligned", matcher))
}
@@ -212,14 +221,14 @@ func convertNetstackToBinary(tablename string, table iptables.Table) (linux.Kern
entry.Elems = append(entry.Elems, serialized...)
entry.NextOffset += uint16(len(serialized))
- nflog("Adding entry: %+v", entry)
+ nflog("convert to binary: adding entry: %+v", entry)
entries.Size += uint32(entry.NextOffset)
entries.Entrytable = append(entries.Entrytable, entry)
meta.NumEntries++
}
- nflog("Finished with an marshalled size of %d", meta.Size)
+ nflog("convert to binary: finished with an marshalled size of %d", meta.Size)
meta.Size = entries.Size
return entries, meta, nil
}
@@ -237,16 +246,18 @@ func marshalMatcher(matcher iptables.Matcher) []byte {
}
func marshalUDPMatcher(matcher *iptables.UDPMatcher) []byte {
- nflog("Marshalling UDP matcher: %+v", matcher)
+ nflog("convert to binary: marshalling UDP matcher: %+v", matcher)
+
+ // We have to pad this struct size to a multiple of 8 bytes.
+ const size = linux.SizeOfXTEntryMatch + linux.SizeOfXTUDP + 6
linuxMatcher := linux.KernelXTEntryMatch{
XTEntryMatch: linux.XTEntryMatch{
- MatchSize: linux.SizeOfXTEntryMatch + linux.SizeOfXTUDP + 6,
- // Name: "udp",
+ MatchSize: size,
},
Data: make([]byte, 0, linux.SizeOfXTUDP),
}
- copy(linuxMatcher.Name[:], "udp")
+ copy(linuxMatcher.Name[:], matcherNameUDP)
xtudp := linux.XTUDP{
SourcePortStart: matcher.Data.SourcePortStart,
@@ -255,17 +266,12 @@ func marshalUDPMatcher(matcher *iptables.UDPMatcher) []byte {
DestinationPortEnd: matcher.Data.DestinationPortEnd,
InverseFlags: matcher.Data.InverseFlags,
}
- nflog("marshalUDPMatcher: xtudp: %+v", xtudp)
linuxMatcher.Data = binary.Marshal(linuxMatcher.Data, usermem.ByteOrder, xtudp)
- nflog("marshalUDPMatcher: linuxMatcher: %+v", linuxMatcher)
- // We have to pad this struct size to a multiple of 8 bytes, so we make
- // this a little longer than it needs to be.
- buf := make([]byte, 0, linux.SizeOfXTEntryMatch+linux.SizeOfXTUDP+6)
+ buf := make([]byte, 0, size)
buf = binary.Marshal(buf, usermem.ByteOrder, linuxMatcher)
buf = append(buf, []byte{0, 0, 0, 0, 0, 0}...)
- nflog("Marshalled into matcher of size %d", len(buf))
- nflog("marshalUDPMatcher: buf is: %v", buf)
+ nflog("convert to binary: marshalled UDP matcher into %v", buf)
return buf[:]
}
@@ -283,9 +289,8 @@ func marshalTarget(target iptables.Target) []byte {
}
func marshalStandardTarget(verdict iptables.Verdict) []byte {
- nflog("Marshalling standard target with size %d", linux.SizeOfXTStandardTarget)
+ nflog("convert to binary: marshalling standard target with size %d", linux.SizeOfXTStandardTarget)
- // TODO: Must be aligned.
// The target's name will be the empty string.
target := linux.XTStandardTarget{
Target: linux.XTEntryTarget{
@@ -353,8 +358,6 @@ func translateToStandardVerdict(val int32) (iptables.Verdict, *syserr.Error) {
// SetEntries sets iptables rules for a single table. See
// net/ipv4/netfilter/ip_tables.c:translate_table for reference.
func SetEntries(stack *stack.Stack, optVal []byte) *syserr.Error {
- // printReplace(optVal)
-
// Get the basic rules data (struct ipt_replace).
if len(optVal) < linux.SizeOfIPTReplace {
log.Warningf("netfilter.SetEntries: optVal has insufficient size for replace %d", len(optVal))
@@ -375,13 +378,13 @@ func SetEntries(stack *stack.Stack, optVal []byte) *syserr.Error {
return syserr.ErrInvalidArgument
}
- nflog("Setting entries in table %q", replace.Name.String())
+ nflog("set entries: setting entries in table %q", replace.Name.String())
// Convert input into a list of rules and their offsets.
var offset uint32
var offsets []uint32
for entryIdx := uint32(0); entryIdx < replace.NumEntries; entryIdx++ {
- nflog("Processing entry at offset %d", offset)
+ nflog("set entries: processing entry at offset %d", offset)
// Get the struct ipt_entry.
if len(optVal) < linux.SizeOfIPTEntry {
@@ -406,11 +409,13 @@ func SetEntries(stack *stack.Stack, optVal []byte) *syserr.Error {
return err
}
- // TODO: Matchers (and maybe targets) can specify that they only work for certiain protocols, hooks, tables.
+ // TODO(gvisor.dev/issue/170): Matchers and targets can specify
+ // that they only work for certiain protocols, hooks, tables.
// Get matchers.
matchersSize := entry.TargetOffset - linux.SizeOfIPTEntry
if len(optVal) < int(matchersSize) {
log.Warningf("netfilter: entry doesn't have enough room for its matchers (only %d bytes remain)", len(optVal))
+ return syserr.ErrInvalidArgument
}
matchers, err := parseMatchers(filter, optVal[:matchersSize])
if err != nil {
@@ -423,6 +428,7 @@ func SetEntries(stack *stack.Stack, optVal []byte) *syserr.Error {
targetSize := entry.NextOffset - entry.TargetOffset
if len(optVal) < int(targetSize) {
log.Warningf("netfilter: entry doesn't have enough room for its target (only %d bytes remain)", len(optVal))
+ return syserr.ErrInvalidArgument
}
target, err := parseTarget(optVal[:targetSize])
if err != nil {
@@ -500,10 +506,11 @@ func SetEntries(stack *stack.Stack, optVal []byte) *syserr.Error {
// parseMatchers parses 0 or more matchers from optVal. optVal should contain
// only the matchers.
func parseMatchers(filter iptables.IPHeaderFilter, optVal []byte) ([]iptables.Matcher, *syserr.Error) {
- nflog("Parsing matchers of size %d", len(optVal))
+ nflog("set entries: parsing matchers of size %d", len(optVal))
var matchers []iptables.Matcher
for len(optVal) > 0 {
- nflog("parseMatchers: optVal has len %d", len(optVal))
+ nflog("set entries: optVal has len %d", len(optVal))
+
// Get the XTEntryMatch.
if len(optVal) < linux.SizeOfXTEntryMatch {
log.Warningf("netfilter: optVal has insufficient size for entry match: %d", len(optVal))
@@ -512,7 +519,7 @@ func parseMatchers(filter iptables.IPHeaderFilter, optVal []byte) ([]iptables.Ma
var match linux.XTEntryMatch
buf := optVal[:linux.SizeOfXTEntryMatch]
binary.Unmarshal(buf, usermem.ByteOrder, &match)
- nflog("parseMatchers: parsed entry match %q: %+v", match.Name.String(), match)
+ nflog("set entries: parsed entry match %q: %+v", match.Name.String(), match)
// Check some invariants.
if match.MatchSize < linux.SizeOfXTEntryMatch {
@@ -528,17 +535,17 @@ func parseMatchers(filter iptables.IPHeaderFilter, optVal []byte) ([]iptables.Ma
var matcher iptables.Matcher
var err error
switch match.Name.String() {
- case "udp":
+ case matcherNameUDP:
if len(buf) < linux.SizeOfXTUDP {
log.Warningf("netfilter: optVal has insufficient size for UDP match: %d", len(optVal))
return nil, syserr.ErrInvalidArgument
}
+ // For alignment reasons, the match's total size may
+ // exceed what's strictly necessary to hold matchData.
var matchData linux.XTUDP
- // For alignment reasons, the match's total size may exceed what's
- // strictly necessary to hold matchData.
binary.Unmarshal(buf[:linux.SizeOfXTUDP], usermem.ByteOrder, &matchData)
log.Infof("parseMatchers: parsed XTUDP: %+v", matchData)
- matcher, err = iptables.NewUDPMatcher(filter, iptables.UDPMatcherData{
+ matcher, err = iptables.NewUDPMatcher(filter, iptables.UDPMatcherParams{
SourcePortStart: matchData.SourcePortStart,
SourcePortEnd: matchData.SourcePortEnd,
DestinationPortStart: matchData.DestinationPortStart,
@@ -557,19 +564,22 @@ func parseMatchers(filter iptables.IPHeaderFilter, optVal []byte) ([]iptables.Ma
matchers = append(matchers, matcher)
- // TODO: Support revision.
- // TODO: Support proto -- matchers usually specify which proto(s) they work with.
+ // TODO(gvisor.dev/issue/170): Check the revision field.
optVal = optVal[match.MatchSize:]
}
- // TODO: Check that optVal is exhausted.
+ if len(optVal) != 0 {
+ log.Warningf("netfilter: optVal should be exhausted after parsing matchers")
+ return nil, syserr.ErrInvalidArgument
+ }
+
return matchers, nil
}
// parseTarget parses a target from optVal. optVal should contain only the
// target.
func parseTarget(optVal []byte) (iptables.Target, *syserr.Error) {
- nflog("Parsing target of size %d", len(optVal))
+ nflog("set entries: parsing target of size %d", len(optVal))
if len(optVal) < linux.SizeOfXTEntryTarget {
log.Warningf("netfilter: optVal has insufficient size for entry target %d", len(optVal))
return nil, syserr.ErrInvalidArgument
@@ -598,7 +608,8 @@ func parseTarget(optVal []byte) (iptables.Target, *syserr.Error) {
case iptables.Drop:
return iptables.UnconditionalDropTarget{}, nil
default:
- panic(fmt.Sprintf("Unknown verdict: %v", verdict))
+ log.Warningf("Unknown verdict: %v", verdict)
+ return nil, syserr.ErrInvalidArgument
}
case errorTargetName:
@@ -673,52 +684,3 @@ func hookFromLinux(hook int) iptables.Hook {
}
panic(fmt.Sprintf("Unknown hook %d does not correspond to a builtin chain", hook))
}
-
-// printReplace prints information about the struct ipt_replace in optVal. It
-// is only for debugging.
-func printReplace(optVal []byte) {
- // Basic replace info.
- var replace linux.IPTReplace
- replaceBuf := optVal[:linux.SizeOfIPTReplace]
- optVal = optVal[linux.SizeOfIPTReplace:]
- binary.Unmarshal(replaceBuf, usermem.ByteOrder, &replace)
- log.Infof("Replacing table %q: %+v", replace.Name.String(), replace)
-
- // Read in the list of entries at the end of replace.
- var totalOffset uint16
- for entryIdx := uint32(0); entryIdx < replace.NumEntries; entryIdx++ {
- var entry linux.IPTEntry
- entryBuf := optVal[:linux.SizeOfIPTEntry]
- binary.Unmarshal(entryBuf, usermem.ByteOrder, &entry)
- log.Infof("Entry %d (total offset %d): %+v", entryIdx, totalOffset, entry)
-
- totalOffset += entry.NextOffset
- if entry.TargetOffset == linux.SizeOfIPTEntry {
- log.Infof("Entry has no matches.")
- } else {
- log.Infof("Entry has matches.")
- }
-
- var target linux.XTEntryTarget
- targetBuf := optVal[entry.TargetOffset : entry.TargetOffset+linux.SizeOfXTEntryTarget]
- binary.Unmarshal(targetBuf, usermem.ByteOrder, &target)
- log.Infof("Target named %q: %+v", target.Name.String(), target)
-
- switch target.Name.String() {
- case "":
- var standardTarget linux.XTStandardTarget
- stBuf := optVal[entry.TargetOffset : entry.TargetOffset+linux.SizeOfXTStandardTarget]
- binary.Unmarshal(stBuf, usermem.ByteOrder, &standardTarget)
- log.Infof("Standard target with verdict %q (%d).", linux.VerdictStrings[standardTarget.Verdict], standardTarget.Verdict)
- case errorTargetName:
- var errorTarget linux.XTErrorTarget
- etBuf := optVal[entry.TargetOffset : entry.TargetOffset+linux.SizeOfXTErrorTarget]
- binary.Unmarshal(etBuf, usermem.ByteOrder, &errorTarget)
- log.Infof("Error target with name %q.", errorTarget.Name.String())
- default:
- log.Infof("Unknown target type.")
- }
-
- optVal = optVal[entry.NextOffset:]
- }
-}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-17 03:46:45 +0000