26 lines
1.0 KiB
Diff
26 lines
1.0 KiB
Diff
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diff --git a/src/crypto/x509/verify.go b/src/crypto/x509/verify.go
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index 50f4d4a..121fd1b 100644
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--- a/src/crypto/x509/verify.go
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+++ b/src/crypto/x509/verify.go
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@@ -20,6 +20,9 @@ import (
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// ignoreCN disables interpreting Common Name as a hostname. See issue 24151.
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var ignoreCN = !strings.Contains(os.Getenv("GODEBUG"), "x509ignoreCN=0")
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+// if using Common Name as a hostname is enabled via x509ignoreCN=0,
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+// warnCN enables a warning whenever Common Name is interpreted as a hostname.
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+var warnCN = strings.Contains(os.Getenv("GODEBUG"), "x509warnCN=1")
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type InvalidReason int
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@@ -1078,6 +1081,10 @@ func (c *Certificate) VerifyHostname(h string) error {
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names := c.DNSNames
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if c.commonNameAsHostname() {
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names = []string{c.Subject.CommonName}
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+ if warnCN {
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+ fmt.Fprintf(os.Stderr, "x509: Warning - certificate relies on legacy Common Name field. " +
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+ "Using CN without SAN is deprecated and will not work in future versions.\n")
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+ }
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}
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candidateName := toLowerCaseASCII(h) // Save allocations inside the loop.
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