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Fix string.well_known_regex to reject comma in header names #528

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Merged
timostamm merged 1 commit into from
Sep 3, 2026
Merged

Fix string.well_known_regex to reject comma in header names #528

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2 changes: 1 addition & 1 deletion proto/protovalidate/buf/validate/validate.proto
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Original file line number Diff line number Diff line change
Expand Up @@ -3828,7 +3828,7 @@ message StringRules {
message: "must be a valid HTTP header name"
expression:
"rules.well_known_regex != 1 || this == '' || this.matches(!has(rules.strict) || rules.strict ?"
"'^:?[0-9a-zA-Z!#$%&\\'*+-.^_|~\\x60]+$' :"
"'^:?[0-9a-zA-Z!#$%&\\'*+.^_|~\\x60-]+$' :"

@timostamm timostamm Sep 3, 2026 •
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The cause of the bug was +-. in the character class. It's a range that expands to +,-..

The most direct fix is to quote the hyphen, but it would need to be \\\\- in validate.proto because of the two layers of escaping (prototext and CEL).

Moving the hyphen to the end has the same effect (no longer a range) but doesn't require escaping.

Reproduction:

header/v1/header.proto:

syntax = "proto3";
package header.v1;
import "buf/validate/validate.proto";

message Header {
  // The regular expression in `string.well_known_regex.header_name`
  string name = 1 [(buf.validate.field).cel = {
    // original, broken:
    //expression: "this.matches('^:?[0-9a-zA-Z!#$%&\\'*+-.^_|~\\x60]+$')"

    // fixed:
    expression: "this.matches('^:?[0-9a-zA-Z!#$%&\\'*+.^_|~\\x60-]+$')"
  }];
}

main.go:

package main

import (
	headerv1 "example/internal/gen/header/v1"
	"fmt"

	"buf.build/go/protovalidate"
)

func main() {
	h := &headerv1.Header{Name: ","}
	err := protovalidate.Validate(h)
	fmt.Printf("%q %t\n", h.GetName(), err == nil)
}

The output is "," true with the original, "," false with the fixed expression.

"'^[^\\u0000\\u000A\\u000D]+$')"
},
(predefined).cel = {
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2 changes: 1 addition & 1 deletion tools/internal/gen/buf/validate/validate.pb.go
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14 changes: 14 additions & 0 deletions tools/protovalidate-conformance/internal/cases/cases_strings.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1528,6 +1528,10 @@ func stringSuite() suites.Suite {
Message: &cases.StringHttpHeaderName{Val: ":authority"},
Expected: results.Success(true),
},
"well_known_regex/header_name/strict/valid/all_chars": {
Message: &cases.StringHttpHeaderName{Val: "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!#$%&'*+-.^_|~`"},
Expected: results.Success(true),
},
"well_known_regex/header_name/strict/valid/numbers": {
Message: &cases.StringHttpHeaderName{Val: "abc-123"},
Expected: results.Success(true),
Expand Down Expand Up @@ -1570,6 +1574,16 @@ func stringSuite() suites.Suite {
},
),
},
"well_known_regex/header_name/strict/invalid/comma": {
Message: &cases.StringHttpHeaderName{Val: "foo,bar"},
Expected: results.Violations(
&validate.Violation{
Field: results.FieldPath("val"),
Rule: results.FieldPath("string.well_known_regex"),
RuleId: proto.String("string.well_known_regex.header_name"),
},
),
},
"well_known_regex/header_name/strict/invalid/space": {
Message: &cases.StringHttpHeaderName{Val: "foo bar"},
Expected: results.Violations(
Expand Down
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