Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Add check for maximum signature length in ecdsa.ParseDERSignature #2135

Merged
merged 1 commit into from
Mar 18, 2024
Merged

Add check for maximum signature length in ecdsa.ParseDERSignature #2135

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
26 changes: 21 additions & 5 deletions btcec/ecdsa/signature.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -37,10 +37,20 @@ var (
oneInitializer = []byte{0x01}
)

// MinSigLen is the minimum length of a DER encoded signature and is when both R
// and S are 1 byte each.
// 0x30 + <1-byte> + 0x02 + 0x01 + <byte> + 0x2 + 0x01 + <byte>
const MinSigLen = 8
const (
// MinSigLen is the minimum length of a DER encoded signature and is when both R
// and S are 1 byte each.
// 0x30 + <1-byte> + 0x02 + 0x01 + <byte> + 0x2 + 0x01 + <byte>
MinSigLen = 8

// MaxSigLen is the maximum length of a DER encoded signature and is
// when both R and S are 33 bytes each. It is 33 bytes because a
// 256-bit integer requires 32 bytes and an additional leading null byte
// might be required if the high bit is set in the value.
//
// 0x30 + <1-byte> + 0x02 + 0x21 + <33 bytes> + 0x2 + 0x21 + <33 bytes>
MaxSigLen = 72
)

// canonicalPadding checks whether a big-endian encoded integer could
// possibly be misinterpreted as a negative number (even though OpenSSL
Expand Down Expand Up @@ -68,9 +78,15 @@ func parseSig(sigStr []byte, der bool) (*Signature, error) {
// 0x30 <length of whole message> <0x02> <length of R> <R> 0x2
// <length of S> <S>.

if len(sigStr) < MinSigLen {
// The signature must adhere to the minimum and maximum allowed length.
totalSigLen := len(sigStr)
if totalSigLen < MinSigLen {
return nil, errors.New("malformed signature: too short")
}
if der && totalSigLen > MaxSigLen {
return nil, errors.New("malformed signature: too long")
}

// 0x30
index := 0
if sigStr[index] != 0x30 {
Expand Down
15 changes: 15 additions & 0 deletions btcec/ecdsa/signature_test.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -333,6 +333,21 @@ var signatureTests = []signatureTest{
der: false,
isValid: false,
},
{
name: "Long signature.",
sig: []byte{0x30, 0x44, 0x02, 0x20, 0x4e, 0x45, 0xe1, 0x69,
0x32, 0xb8, 0xaf, 0x51, 0x49, 0x61, 0xa1, 0xd3, 0xa1,
0xa2, 0x5f, 0xdf, 0x3f, 0x4f, 0x77, 0x32, 0xe9, 0xd6,
0x24, 0xc6, 0xc6, 0x15, 0x48, 0xab, 0x5f, 0xb8, 0xcd,
0x41, 0x02, 0x20, 0x18, 0x15, 0x22, 0xec, 0x8e, 0xca,
0x07, 0xde, 0x48, 0x60, 0xa4, 0xac, 0xdd, 0x12, 0x90,
0x9d, 0x83, 0x1c, 0xc5, 0x6c, 0xbb, 0xac, 0x46, 0x22,
0x08, 0x22, 0x21, 0xa8, 0x76, 0x8d, 0x1d, 0x09, 0x91,
0x17, 0x90, 0xda, 0x42, 0xca, 0xaf, 0x19, 0x7d, 0xb4,
},
der: true,
isValid: false,
},
}

func TestSignatures(t *testing.T) {
Expand Down
Loading