[release-branch.go1.23] crypto/x509: properly check for IPv6 hosts in URIs

When checking URI constraints, use netip.ParseAddr, which understands
zones, unlike net.ParseIP which chokes on them. This prevents zone IDs
from mistakenly satisfying URI constraints.

Thanks to Juho Forsén of Mattermost for reporting this issue.

For #71156
Fixes #71208
Fixes CVE-2024-45341

Change-Id: Iecac2529f3605382d257996e0fb6d6983547e400
Reviewed-on: https://go-internal-review.googlesource.com/c/go/+/1700
Reviewed-by: Tatiana Bradley <tatianabradley@google.com>
Reviewed-by: Damien Neil <dneil@google.com>
(cherry picked from commit 22ca55d396ba801e6ae9b2bd67a059fcb30562fd)
Reviewed-on: https://go-internal-review.googlesource.com/c/go/+/1762
Reviewed-by: Roland Shoemaker <bracewell@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/643103
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>

diff --git a/src/crypto/x509/name_constraints_test.go b/src/crypto/x509/name_constraints_test.go
index 008c7028f4e4c44acc8dd3d6afa5b43dad736d7e..a5851845164d1021f417e937d08aef9e943fa346 100644 (file)
--- a/src/crypto/x509/name_constraints_test.go
+++ b/src/crypto/x509/name_constraints_test.go
@@ -1607,6 +1607,23 @@ var nameConstraintsTests = []nameConstraintsTest{
                leaf:          leafSpec{sans: []string{"dns:.example.com"}},
                expectedError: "cannot parse dnsName \".example.com\"",
        },
+       // #86: URIs with IPv6 addresses with zones and ports are rejected
+       {
+               roots: []constraintsSpec{
+                       {
+                               ok: []string{"uri:example.com"},
+                       },
+               },
+               intermediates: [][]constraintsSpec{
+                       {
+                               {},
+                       },
+               },
+               leaf: leafSpec{
+                       sans: []string{"uri:http://[2006:abcd::1%25.example.com]:16/"},
+               },
+               expectedError: "URI with IP",
+       },
 }
 
 func makeConstraintsCACert(constraints constraintsSpec, name string, key *ecdsa.PrivateKey, parent *Certificate, parentKey *ecdsa.PrivateKey) (*Certificate, error) {

diff --git a/src/crypto/x509/verify.go b/src/crypto/x509/verify.go
index 7170087287644e76f9180993637d855fcce74d84..bbccfce57742c018a7bcde27b2a198b0ff2df787 100644 (file)
--- a/src/crypto/x509/verify.go
+++ b/src/crypto/x509/verify.go
@@ -11,6 +11,7 @@ import (
        "errors"
        "fmt"
        "net"
+       "net/netip"
        "net/url"
        "reflect"
        "runtime"
@@ -434,8 +435,10 @@ func matchURIConstraint(uri *url.URL, constraint string) (bool, error) {
                }
        }
 
-       if strings.HasPrefix(host, "[") && strings.HasSuffix(host, "]") ||
-               net.ParseIP(host) != nil {
+       // netip.ParseAddr will reject the URI IPv6 literal form "[...]", so we
+       // check if _either_ the string parses as an IP, or if it is enclosed in
+       // square brackets.
+       if _, err := netip.ParseAddr(host); err == nil || (strings.HasPrefix(host, "[") && strings.HasSuffix(host, "]")) {
                return false, fmt.Errorf("URI with IP (%q) cannot be matched against constraints", uri.String())
        }