net/netip: allow only valid prefix digits in ParsePrefix

The prefix bits for a call to ParsePrefix are passed raw to
strconv.Atoi, this means that it can accept +- signs as well as leading
zeroes, which are not allowed prefix values following RFC 4632 Section
3.1 and RFC 4291 Section 2.3.

Validate non-digit characters as well as leading zeroes and return an
error accordingly.

Fixes #63850

Change-Id: I412a7e1cecc6ee9ea1582d4b04cb40d79ee714f1
GitHub-Last-Rev: 462d97fc5f412e18376356dbc10b63711c084144
GitHub-Pull-Request: golang/go#63859
Reviewed-on: https://go-review.googlesource.com/c/go/+/538860
Reviewed-by: Heschi Kreinick <heschi@google.com>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

diff --git a/src/net/netip/netip.go b/src/net/netip/netip.go
index 99cb754fae87762b22c42b2014d6989558ee8019..46f466c076b3414d86a875bc9fbefb6daa9857e7 100644 (file)
--- a/src/net/netip/netip.go
+++ b/src/net/netip/netip.go
@@ -1309,6 +1309,12 @@ func ParsePrefix(s string) (Prefix, error) {
        }
 
        bitsStr := s[i+1:]
+
+       // strconv.Atoi accepts a leading sign and leading zeroes, but we don't want that.
+       if len(bitsStr) > 1 && (bitsStr[0] < '1' || bitsStr[0] > '9') {
+               return Prefix{}, errors.New("netip.ParsePrefix(" + strconv.Quote(s) + "): bad bits after slash: " + strconv.Quote(bitsStr))
+       }
+
        bits, err := strconv.Atoi(bitsStr)
        if err != nil {
                return Prefix{}, errors.New("netip.ParsePrefix(" + strconv.Quote(s) + "): bad bits after slash: " + strconv.Quote(bitsStr))

diff --git a/src/net/netip/netip_test.go b/src/net/netip/netip_test.go
index 39893e0f6df5567bde7207fa459b2159a9cd0e4c..36e57ce17147faad141f0ef28a495c68a05d649a 100644 (file)
--- a/src/net/netip/netip_test.go
+++ b/src/net/netip/netip_test.go
@@ -1456,7 +1456,7 @@ func TestParsePrefixError(t *testing.T) {
                },
                {
                        prefix: "1.1.1.0/-1",
-                       errstr: "out of range",
+                       errstr: "bad bits",
                },
                {
                        prefix: "1.1.1.0/33",
@@ -1475,6 +1475,22 @@ func TestParsePrefixError(t *testing.T) {
                        prefix: "2001:db8::%a/32",
                        errstr: "zones cannot be present",
                },
+               {
+                       prefix: "1.1.1.0/+32",
+                       errstr: "bad bits",
+               },
+               {
+                       prefix: "1.1.1.0/-32",
+                       errstr: "bad bits",
+               },
+               {
+                       prefix: "1.1.1.0/032",
+                       errstr: "bad bits",
+               },
+               {
+                       prefix: "1.1.1.0/0032",
+                       errstr: "bad bits",
+               },
        }
        for _, test := range tests {
                t.Run(test.prefix, func(t *testing.T) {