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fix HMAC_DRBG edge case #3165

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merged 2 commits into from
Aug 11, 2020
Merged

fix HMAC_DRBG edge case #3165

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b4f65c1
Fix HMAC_DRBG edge case
Aug 4, 2020
383608c
.gitlint: Also ignore URLs with hash fragments
Aug 11, 2020
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10 changes: 10 additions & 0 deletions .changelog/3165.bugfix.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
go/common/crypto/drbg: Also consider empty slices as Null values

The wrong handling of an edge case in the HMAC_DRBG implementation has been
corrected. An update with empty `additional_data` now behaves the same as an
update with nil additional data. While the spec is not 100% clear around how
this is to be treated, supplemental documentation suggests that this is the
correct way to handle it.

Oasis code never uses HMAC_DRNG with a non-nil empty `additional_data`
parameter, so nothing changes for Oasis users.
2 changes: 1 addition & 1 deletion .gitlint-rules/urls.py
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@
gitlint.rule_finder.assert_valid_rule_class = lambda *_: True

# URL regular expression.
URL_RE_RAW = r'http[s]?://(?:[a-zA-Z]|[0-9]|[$-_@.&+]|[!*\(\),]|(?:%[0-9a-fA-F][0-9a-fA-F]))+'
URL_RE_RAW = r'http[s]?://(?:[a-zA-Z]|[0-9]|[#-_@.&+]|[!*\(\),]|(?:%[0-9a-fA-F][0-9a-fA-F]))+'
URL_RE = re.compile(URL_RE_RAW, re.IGNORECASE)
LINE_MATCH_RE = re.compile(r'.*' + URL_RE_RAW + r'$')

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4 changes: 2 additions & 2 deletions go/common/crypto/drbg/hmac_drbg.go
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Original file line number Diff line number Diff line change
Expand Up @@ -87,7 +87,7 @@ func (r *Drbg) generate(requestedNumberOfBytes int, additionalInput []byte) ([]b

// 2. If additional_input != Null, then (Key, V) = HMAC_DRBG_Update
// (additional_input, Key, V).
if additionalInput != nil {
if len(additionalInput) != 0 {
r.update(additionalInput)
}

Expand Down Expand Up @@ -130,7 +130,7 @@ func (r *Drbg) update(providedData []byte) {
v := updateV(r.hash, k, r.v)

// 3. If (provided_data = Null), then return K and V.
if providedData == nil {
if len(providedData) == 0 {
r.v, r.k = v, k
return
}
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46 changes: 45 additions & 1 deletion go/common/crypto/drbg/hmac_drbg_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,51 @@ func toHexUpper(b []byte) string {
return strings.ToUpper(hex.EncodeToString(b))
}

func TestDrbgNISTExample1(t *testing.T) {
func TestDrbgNISTExampleZeroLength(t *testing.T) {
const readSz = 1024 / 8

entropyInput, _ := hex.DecodeString("000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F303132333435363738393A3B3C3D3E3F404142434445464748494A4B4C4D4E4F505152535455565758595A5B5C5D5E5F606162636465666768696A6B6C6D6E")
nonce, _ := hex.DecodeString("202122232425262728292A2B2C2D2E2F")

// HMAC_DRBG_Instantiate_algorithm
drbg, err := New(crypto.SHA512, entropyInput, nonce, nil)
require.NoError(t, err, "HMAC_DRBG_Instantiate_algorithm (ctor)")
require.Equal(
t,
"A7E118A531DEF956DCFF94BB3D801F775DC68F91696A434CC25E270E639044E1A7240266D3AA202D46C1054B610247535007DF12CFC8DA45982A587FC81C47D5",
toHexUpper(drbg.k),
"HMAC_DRBG_Instantiate_algorithm (K)",
)
require.Equal(
t,
"110793EAA60DC9DBCD4208104088A23DAECC1226EAF1D03BBA9D83A69599916571907346B15A0439362B9C8EE330E52DEACC639B98E8030A95780CD7C24B04D5",
toHexUpper(drbg.v),
"HMAC_DRBG_Instantiate_algorithm (V)",
)

// HMAC_DRBG_Generate
v, err := drbg.generate(readSz, []byte{})
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require.NoError(t, err, "HMAC_DRBG_Generate")
require.Equal(
t,
"A463395AA79F237A22E5BD24462BD303E1BE5103BA37299BED170E10713EE9CDA62FABD5171231E1F6D82629BC521D41178D002D92918F397824E449004E9AE1851F7BFA11CD616EF519A9E2A05951D9108AB38959CA7E9E80B18ADFCC622389495795CBFB7D39AF6C8571DDCE035CA6890C7A1AF80861F0629EF1B6952BA206",
toHexUpper(v),
"HMAC_DRBG_Generate",
)

// HMAC_DRBG_Generate, io.Reader edition.
n, err := drbg.Read(v)
require.NoError(t, err, "HMAC_DRBG_Generate (io.Reader)")
require.Equal(t, readSz, n, "HMAC_DRBG_Generate (io.Reader")
require.Equal(
t,
"FB5BD98D2CB25EC4955CD15204D68C497281CA0CE2201DACA5E412DDFDEBAF98D724D21662E45ABA9AE200D941C4CF76039808F29A8000346A6CC97D44417737A89F90472AC6088B45C666C561686F191745228F11ED556A519DA9AA1646D15B901382D87726D17DC5139FDEE1E8BDB0F328D4B105865BD1D815641E6B1DBA23",
toHexUpper(v),
"HMAC_DRBG_Generate (io.Reader)",
)
}

func TestDrbgNISTExampleNil(t *testing.T) {
const readSz = 1024 / 8

entropyInput, _ := hex.DecodeString("000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F303132333435363738393A3B3C3D3E3F404142434445464748494A4B4C4D4E4F505152535455565758595A5B5C5D5E5F606162636465666768696A6B6C6D6E")
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