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Current File : //proc/thread-self/root/usr/local/lib/node_modules/mediasoup/worker/src/RTC/StunPacket.cpp
#define MS_CLASS "RTC::StunPacket"
// #define MS_LOG_DEV_LEVEL 3
#include "RTC/StunPacket.hpp"
#include "Logger.hpp"
#include "Utils.hpp"
#include <cstdio> // std::snprintf()
#include <cstring> // std::memcmp(), std::memcpy()
namespace RTC
{
/* Class variables. */
const uint8_t StunPacket::magicCookie[] = { 0x21, 0x12, 0xA4, 0x42 };
/* Class methods. */
StunPacket* StunPacket::Parse(const uint8_t* data, size_t len)
{
MS_TRACE();
if (!StunPacket::IsStun(data, len))
return nullptr;
/*
The message type field is decomposed further into the following
structure:
0 1
2 3 4 5 6 7 8 9 0 1 2 3 4 5
+--+--+-+-+-+-+-+-+-+-+-+-+-+-+
|M |M |M|M|M|C|M|M|M|C|M|M|M|M|
|11|10|9|8|7|1|6|5|4|0|3|2|1|0|
+--+--+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Format of STUN Message Type Field
Here the bits in the message type field are shown as most significant
(M11) through least significant (M0). M11 through M0 represent a 12-
bit encoding of the method. C1 and C0 represent a 2-bit encoding of
the class.
*/
// Get type field.
uint16_t msgType = Utils::Byte::Get2Bytes(data, 0);
// Get length field.
uint16_t msgLength = Utils::Byte::Get2Bytes(data, 2);
// length field must be total size minus header's 20 bytes, and must be multiple of 4 Bytes.
if ((static_cast<size_t>(msgLength) != len - 20) || ((msgLength & 0x03) != 0))
{
MS_WARN_TAG(
ice,
"length field + 20 does not match total size (or it is not multiple of 4 bytes), "
"packet discarded");
return nullptr;
}
// Get STUN method.
uint16_t msgMethod = (msgType & 0x000f) | ((msgType & 0x00e0) >> 1) | ((msgType & 0x3E00) >> 2);
// Get STUN class.
uint16_t msgClass = ((data[0] & 0x01) << 1) | ((data[1] & 0x10) >> 4);
// Create a new StunPacket (data + 8 points to the received TransactionID field).
auto* packet = new StunPacket(
static_cast<Class>(msgClass), static_cast<Method>(msgMethod), data + 8, data, len);
/*
STUN Attributes
After the STUN header are zero or more attributes. Each attribute
MUST be TLV encoded, with a 16-bit type, 16-bit length, and value.
Each STUN attribute MUST end on a 32-bit boundary. As mentioned
above, all fields in an attribute are transmitted most significant
bit first.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value (variable) ....
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*/
// Start looking for attributes after STUN header (Byte #20).
size_t pos{ 20 };
// Flags (positions) for special MESSAGE-INTEGRITY and FINGERPRINT attributes.
bool hasMessageIntegrity{ false };
bool hasFingerprint{ false };
size_t fingerprintAttrPos; // Will point to the beginning of the attribute.
uint32_t fingerprint; // Holds the value of the FINGERPRINT attribute.
// Ensure there are at least 4 remaining bytes (attribute with 0 length).
while (pos + 4 <= len)
{
// Get the attribute type.
auto attrType = static_cast<Attribute>(Utils::Byte::Get2Bytes(data, pos));
// Get the attribute length.
uint16_t attrLength = Utils::Byte::Get2Bytes(data, pos + 2);
// Ensure the attribute length is not greater than the remaining size.
if ((pos + 4 + attrLength) > len)
{
MS_WARN_TAG(ice, "the attribute length exceeds the remaining size, packet discarded");
delete packet;
return nullptr;
}
// FINGERPRINT must be the last attribute.
if (hasFingerprint)
{
MS_WARN_TAG(ice, "attribute after FINGERPRINT is not allowed, packet discarded");
delete packet;
return nullptr;
}
// After a MESSAGE-INTEGRITY attribute just FINGERPRINT is allowed.
if (hasMessageIntegrity && attrType != Attribute::FINGERPRINT)
{
MS_WARN_TAG(
ice,
"attribute after MESSAGE-INTEGRITY other than FINGERPRINT is not allowed, "
"packet discarded");
delete packet;
return nullptr;
}
const uint8_t* attrValuePos = data + pos + 4;
switch (attrType)
{
case Attribute::USERNAME:
{
packet->SetUsername(
reinterpret_cast<const char*>(attrValuePos), static_cast<size_t>(attrLength));
break;
}
case Attribute::PRIORITY:
{
// Ensure attribute length is 4 bytes.
if (attrLength != 4)
{
MS_WARN_TAG(ice, "attribute PRIORITY must be 4 bytes length, packet discarded");
delete packet;
return nullptr;
}
packet->SetPriority(Utils::Byte::Get4Bytes(attrValuePos, 0));
break;
}
case Attribute::ICE_CONTROLLING:
{
// Ensure attribute length is 8 bytes.
if (attrLength != 8)
{
MS_WARN_TAG(ice, "attribute ICE-CONTROLLING must be 8 bytes length, packet discarded");
delete packet;
return nullptr;
}
packet->SetIceControlling(Utils::Byte::Get8Bytes(attrValuePos, 0));
break;
}
case Attribute::ICE_CONTROLLED:
{
// Ensure attribute length is 8 bytes.
if (attrLength != 8)
{
MS_WARN_TAG(ice, "attribute ICE-CONTROLLED must be 8 bytes length, packet discarded");
delete packet;
return nullptr;
}
packet->SetIceControlled(Utils::Byte::Get8Bytes(attrValuePos, 0));
break;
}
case Attribute::USE_CANDIDATE:
{
// Ensure attribute length is 0 bytes.
if (attrLength != 0)
{
MS_WARN_TAG(ice, "attribute USE-CANDIDATE must be 0 bytes length, packet discarded");
delete packet;
return nullptr;
}
packet->SetUseCandidate();
break;
}
case Attribute::MESSAGE_INTEGRITY:
{
// Ensure attribute length is 20 bytes.
if (attrLength != 20)
{
MS_WARN_TAG(ice, "attribute MESSAGE-INTEGRITY must be 20 bytes length, packet discarded");
delete packet;
return nullptr;
}
hasMessageIntegrity = true;
packet->SetMessageIntegrity(attrValuePos);
break;
}
case Attribute::FINGERPRINT:
{
// Ensure attribute length is 4 bytes.
if (attrLength != 4)
{
MS_WARN_TAG(ice, "attribute FINGERPRINT must be 4 bytes length, packet discarded");
delete packet;
return nullptr;
}
hasFingerprint = true;
fingerprintAttrPos = pos;
fingerprint = Utils::Byte::Get4Bytes(attrValuePos, 0);
packet->SetFingerprint();
break;
}
case Attribute::ERROR_CODE:
{
// Ensure attribute length >= 4bytes.
if (attrLength < 4)
{
MS_WARN_TAG(ice, "attribute ERROR-CODE must be >= 4bytes length, packet discarded");
delete packet;
return nullptr;
}
uint8_t errorClass = Utils::Byte::Get1Byte(attrValuePos, 2);
uint8_t errorNumber = Utils::Byte::Get1Byte(attrValuePos, 3);
auto errorCode = static_cast<uint16_t>(errorClass * 100 + errorNumber);
packet->SetErrorCode(errorCode);
break;
}
default:;
}
// Set next attribute position.
pos =
static_cast<size_t>(Utils::Byte::PadTo4Bytes(static_cast<uint16_t>(pos + 4 + attrLength)));
}
// Ensure current position matches the total length.
if (pos != len)
{
MS_WARN_TAG(ice, "computed packet size does not match total size, packet discarded");
delete packet;
return nullptr;
}
// If it has FINGERPRINT attribute then verify it.
if (hasFingerprint)
{
// Compute the CRC32 of the received packet up to (but excluding) the
// FINGERPRINT attribute and XOR it with 0x5354554e.
uint32_t computedFingerprint = Utils::Crypto::GetCRC32(data, fingerprintAttrPos) ^ 0x5354554e;
// Compare with the FINGERPRINT value in the packet.
if (fingerprint != computedFingerprint)
{
MS_WARN_TAG(
ice,
"computed FINGERPRINT value does not match the value in the packet, "
"packet discarded");
delete packet;
return nullptr;
}
}
return packet;
}
/* Instance methods. */
StunPacket::StunPacket(
Class klass, Method method, const uint8_t* transactionId, const uint8_t* data, size_t size)
: klass(klass), method(method), transactionId(transactionId), data(const_cast<uint8_t*>(data)),
size(size)
{
MS_TRACE();
}
StunPacket::~StunPacket()
{
MS_TRACE();
}
void StunPacket::Dump() const
{
MS_TRACE();
MS_DUMP("<StunPacket>");
std::string klass;
switch (this->klass)
{
case Class::REQUEST:
klass = "Request";
break;
case Class::INDICATION:
klass = "Indication";
break;
case Class::SUCCESS_RESPONSE:
klass = "SuccessResponse";
break;
case Class::ERROR_RESPONSE:
klass = "ErrorResponse";
break;
}
if (this->method == Method::BINDING)
{
MS_DUMP(" Binding %s", klass.c_str());
}
else
{
// This prints the unknown method number. Example: TURN Allocate => 0x003.
MS_DUMP(" %s with unknown method %#.3x", klass.c_str(), static_cast<uint16_t>(this->method));
}
MS_DUMP(" size: %zu bytes", this->size);
static char transactionId[25];
for (int i{ 0 }; i < 12; ++i)
{
// NOTE: n must be 3 because snprintf adds a \0 after printed chars.
std::snprintf(transactionId + (i * 2), 3, "%.2x", this->transactionId[i]);
}
MS_DUMP(" transactionId: %s", transactionId);
if (this->errorCode != 0u)
MS_DUMP(" errorCode: %" PRIu16, this->errorCode);
if (!this->username.empty())
MS_DUMP(" username: %s", this->username.c_str());
if (this->priority != 0u)
MS_DUMP(" priority: %" PRIu32, this->priority);
if (this->iceControlling != 0u)
MS_DUMP(" iceControlling: %" PRIu64, this->iceControlling);
if (this->iceControlled != 0u)
MS_DUMP(" iceControlled: %" PRIu64, this->iceControlled);
if (this->hasUseCandidate)
MS_DUMP(" useCandidate");
if (this->xorMappedAddress != nullptr)
{
int family;
uint16_t port;
std::string ip;
Utils::IP::GetAddressInfo(this->xorMappedAddress, family, ip, port);
MS_DUMP(" xorMappedAddress: %s : %" PRIu16, ip.c_str(), port);
}
if (this->messageIntegrity != nullptr)
{
static char messageIntegrity[41];
for (int i{ 0 }; i < 20; ++i)
{
std::snprintf(messageIntegrity + (i * 2), 3, "%.2x", this->messageIntegrity[i]);
}
MS_DUMP(" messageIntegrity: %s", messageIntegrity);
}
if (this->hasFingerprint)
MS_DUMP(" has fingerprint");
MS_DUMP("</StunPacket>");
}
StunPacket::Authentication StunPacket::CheckAuthentication(
const std::string& localUsername, const std::string& localPassword)
{
MS_TRACE();
switch (this->klass)
{
case Class::REQUEST:
case Class::INDICATION:
{
// Both USERNAME and MESSAGE-INTEGRITY must be present.
if (!this->messageIntegrity || this->username.empty())
return Authentication::BAD_REQUEST;
// Check that USERNAME attribute begins with our local username plus ":".
size_t localUsernameLen = localUsername.length();
if (
this->username.length() <= localUsernameLen || this->username.at(localUsernameLen) != ':' ||
(this->username.compare(0, localUsernameLen, localUsername) != 0))
{
return Authentication::UNAUTHORIZED;
}
break;
}
// This method cannot check authentication in received responses (as we
// are ICE-Lite and don't generate requests).
case Class::SUCCESS_RESPONSE:
case Class::ERROR_RESPONSE:
{
MS_ERROR("cannot check authentication for a STUN response");
return Authentication::BAD_REQUEST;
}
}
// If there is FINGERPRINT it must be discarded for MESSAGE-INTEGRITY calculation,
// so the header length field must be modified (and later restored).
if (this->hasFingerprint)
// Set the header length field: full size - header length (20) - FINGERPRINT length (8).
Utils::Byte::Set2Bytes(this->data, 2, static_cast<uint16_t>(this->size - 20 - 8));
// Calculate the HMAC-SHA1 of the message according to MESSAGE-INTEGRITY rules.
const uint8_t* computedMessageIntegrity = Utils::Crypto::GetHmacShA1(
localPassword, this->data, (this->messageIntegrity - 4) - this->data);
Authentication result;
// Compare the computed HMAC-SHA1 with the MESSAGE-INTEGRITY in the packet.
if (std::memcmp(this->messageIntegrity, computedMessageIntegrity, 20) == 0)
result = Authentication::OK;
else
result = Authentication::UNAUTHORIZED;
// Restore the header length field.
if (this->hasFingerprint)
Utils::Byte::Set2Bytes(this->data, 2, static_cast<uint16_t>(this->size - 20));
return result;
}
StunPacket* StunPacket::CreateSuccessResponse()
{
MS_TRACE();
MS_ASSERT(
this->klass == Class::REQUEST,
"attempt to create a success response for a non Request STUN packet");
return new StunPacket(Class::SUCCESS_RESPONSE, this->method, this->transactionId, nullptr, 0);
}
StunPacket* StunPacket::CreateErrorResponse(uint16_t errorCode)
{
MS_TRACE();
MS_ASSERT(
this->klass == Class::REQUEST,
"attempt to create an error response for a non Request STUN packet");
auto* response =
new StunPacket(Class::ERROR_RESPONSE, this->method, this->transactionId, nullptr, 0);
response->SetErrorCode(errorCode);
return response;
}
void StunPacket::Authenticate(const std::string& password)
{
// Just for Request, Indication and SuccessResponse messages.
if (this->klass == Class::ERROR_RESPONSE)
{
MS_ERROR("cannot set password for ErrorResponse messages");
return;
}
this->password = password;
}
void StunPacket::Serialize(uint8_t* buffer)
{
MS_TRACE();
// Some useful variables.
uint16_t usernamePaddedLen{ 0 };
uint16_t xorMappedAddressPaddedLen{ 0 };
bool addXorMappedAddress =
((this->xorMappedAddress != nullptr) && this->method == StunPacket::Method::BINDING &&
this->klass == Class::SUCCESS_RESPONSE);
bool addErrorCode = ((this->errorCode != 0u) && this->klass == Class::ERROR_RESPONSE);
bool addMessageIntegrity = (this->klass != Class::ERROR_RESPONSE && !this->password.empty());
bool addFingerprint{ true }; // Do always.
// Update data pointer.
this->data = buffer;
// First calculate the total required size for the entire packet.
this->size = 20; // Header.
if (!this->username.empty())
{
usernamePaddedLen = Utils::Byte::PadTo4Bytes(static_cast<uint16_t>(this->username.length()));
this->size += 4 + usernamePaddedLen;
}
if (this->priority != 0u)
this->size += 4 + 4;
if (this->iceControlling != 0u)
this->size += 4 + 8;
if (this->iceControlled != 0u)
this->size += 4 + 8;
if (this->hasUseCandidate)
this->size += 4;
if (addXorMappedAddress)
{
switch (this->xorMappedAddress->sa_family)
{
case AF_INET:
{
xorMappedAddressPaddedLen = 8;
this->size += 4 + 8;
break;
}
case AF_INET6:
{
xorMappedAddressPaddedLen = 20;
this->size += 4 + 20;
break;
}
default:
{
MS_ERROR("invalid inet family in XOR-MAPPED-ADDRESS attribute");
addXorMappedAddress = false;
}
}
}
if (addErrorCode)
this->size += 4 + 4;
if (addMessageIntegrity)
this->size += 4 + 20;
if (addFingerprint)
this->size += 4 + 4;
// Merge class and method fields into type.
uint16_t typeField = (static_cast<uint16_t>(this->method) & 0x0f80) << 2;
typeField |= (static_cast<uint16_t>(this->method) & 0x0070) << 1;
typeField |= (static_cast<uint16_t>(this->method) & 0x000f);
typeField |= (static_cast<uint16_t>(this->klass) & 0x02) << 7;
typeField |= (static_cast<uint16_t>(this->klass) & 0x01) << 4;
// Set type field.
Utils::Byte::Set2Bytes(buffer, 0, typeField);
// Set length field.
Utils::Byte::Set2Bytes(buffer, 2, static_cast<uint16_t>(this->size) - 20);
// Set magic cookie.
std::memcpy(buffer + 4, StunPacket::magicCookie, 4);
// Set TransactionId field.
std::memcpy(buffer + 8, this->transactionId, 12);
// Update the transaction ID pointer.
this->transactionId = buffer + 8;
// Add atributes.
size_t pos{ 20 };
// Add USERNAME.
if (usernamePaddedLen != 0u)
{
Utils::Byte::Set2Bytes(buffer, pos, static_cast<uint16_t>(Attribute::USERNAME));
Utils::Byte::Set2Bytes(buffer, pos + 2, static_cast<uint16_t>(this->username.length()));
std::memcpy(buffer + pos + 4, this->username.c_str(), this->username.length());
pos += 4 + usernamePaddedLen;
}
// Add PRIORITY.
if (this->priority != 0u)
{
Utils::Byte::Set2Bytes(buffer, pos, static_cast<uint16_t>(Attribute::PRIORITY));
Utils::Byte::Set2Bytes(buffer, pos + 2, 4);
Utils::Byte::Set4Bytes(buffer, pos + 4, this->priority);
pos += 4 + 4;
}
// Add ICE-CONTROLLING.
if (this->iceControlling != 0u)
{
Utils::Byte::Set2Bytes(buffer, pos, static_cast<uint16_t>(Attribute::ICE_CONTROLLING));
Utils::Byte::Set2Bytes(buffer, pos + 2, 8);
Utils::Byte::Set8Bytes(buffer, pos + 4, this->iceControlling);
pos += 4 + 8;
}
// Add ICE-CONTROLLED.
if (this->iceControlled != 0u)
{
Utils::Byte::Set2Bytes(buffer, pos, static_cast<uint16_t>(Attribute::ICE_CONTROLLED));
Utils::Byte::Set2Bytes(buffer, pos + 2, 8);
Utils::Byte::Set8Bytes(buffer, pos + 4, this->iceControlled);
pos += 4 + 8;
}
// Add USE-CANDIDATE.
if (this->hasUseCandidate)
{
Utils::Byte::Set2Bytes(buffer, pos, static_cast<uint16_t>(Attribute::USE_CANDIDATE));
Utils::Byte::Set2Bytes(buffer, pos + 2, 0);
pos += 4;
}
// Add XOR-MAPPED-ADDRESS
if (addXorMappedAddress)
{
Utils::Byte::Set2Bytes(buffer, pos, static_cast<uint16_t>(Attribute::XOR_MAPPED_ADDRESS));
Utils::Byte::Set2Bytes(buffer, pos + 2, xorMappedAddressPaddedLen);
uint8_t* attrValue = buffer + pos + 4;
switch (this->xorMappedAddress->sa_family)
{
case AF_INET:
{
// Set first byte to 0.
attrValue[0] = 0;
// Set inet family.
attrValue[1] = 0x01;
// Set port and XOR it.
std::memcpy(
attrValue + 2,
&(reinterpret_cast<const sockaddr_in*>(this->xorMappedAddress))->sin_port,
2);
attrValue[2] ^= StunPacket::magicCookie[0];
attrValue[3] ^= StunPacket::magicCookie[1];
// Set address and XOR it.
std::memcpy(
attrValue + 4,
&(reinterpret_cast<const sockaddr_in*>(this->xorMappedAddress))->sin_addr.s_addr,
4);
attrValue[4] ^= StunPacket::magicCookie[0];
attrValue[5] ^= StunPacket::magicCookie[1];
attrValue[6] ^= StunPacket::magicCookie[2];
attrValue[7] ^= StunPacket::magicCookie[3];
pos += 4 + 8;
break;
}
case AF_INET6:
{
// Set first byte to 0.
attrValue[0] = 0;
// Set inet family.
attrValue[1] = 0x02;
// Set port and XOR it.
std::memcpy(
attrValue + 2,
&(reinterpret_cast<const sockaddr_in6*>(this->xorMappedAddress))->sin6_port,
2);
attrValue[2] ^= StunPacket::magicCookie[0];
attrValue[3] ^= StunPacket::magicCookie[1];
// Set address and XOR it.
std::memcpy(
attrValue + 4,
&(reinterpret_cast<const sockaddr_in6*>(this->xorMappedAddress))->sin6_addr.s6_addr,
16);
attrValue[4] ^= StunPacket::magicCookie[0];
attrValue[5] ^= StunPacket::magicCookie[1];
attrValue[6] ^= StunPacket::magicCookie[2];
attrValue[7] ^= StunPacket::magicCookie[3];
attrValue[8] ^= this->transactionId[0];
attrValue[9] ^= this->transactionId[1];
attrValue[10] ^= this->transactionId[2];
attrValue[11] ^= this->transactionId[3];
attrValue[12] ^= this->transactionId[4];
attrValue[13] ^= this->transactionId[5];
attrValue[14] ^= this->transactionId[6];
attrValue[15] ^= this->transactionId[7];
attrValue[16] ^= this->transactionId[8];
attrValue[17] ^= this->transactionId[9];
attrValue[18] ^= this->transactionId[10];
attrValue[19] ^= this->transactionId[11];
pos += 4 + 20;
break;
}
}
}
// Add ERROR-CODE.
if (addErrorCode)
{
Utils::Byte::Set2Bytes(buffer, pos, static_cast<uint16_t>(Attribute::ERROR_CODE));
Utils::Byte::Set2Bytes(buffer, pos + 2, 4);
auto codeClass = static_cast<uint8_t>(this->errorCode / 100);
uint8_t codeNumber = static_cast<uint8_t>(this->errorCode) - (codeClass * 100);
Utils::Byte::Set2Bytes(buffer, pos + 4, 0);
Utils::Byte::Set1Byte(buffer, pos + 6, codeClass);
Utils::Byte::Set1Byte(buffer, pos + 7, codeNumber);
pos += 4 + 4;
}
// Add MESSAGE-INTEGRITY.
if (addMessageIntegrity)
{
// Ignore FINGERPRINT.
if (addFingerprint)
Utils::Byte::Set2Bytes(buffer, 2, static_cast<uint16_t>(this->size - 20 - 8));
// Calculate the HMAC-SHA1 of the packet according to MESSAGE-INTEGRITY rules.
const uint8_t* computedMessageIntegrity =
Utils::Crypto::GetHmacShA1(this->password, buffer, pos);
Utils::Byte::Set2Bytes(buffer, pos, static_cast<uint16_t>(Attribute::MESSAGE_INTEGRITY));
Utils::Byte::Set2Bytes(buffer, pos + 2, 20);
std::memcpy(buffer + pos + 4, computedMessageIntegrity, 20);
// Update the pointer.
this->messageIntegrity = buffer + pos + 4;
pos += 4 + 20;
// Restore length field.
if (addFingerprint)
Utils::Byte::Set2Bytes(buffer, 2, static_cast<uint16_t>(this->size - 20));
}
else
{
// Unset the pointer (if it was set).
this->messageIntegrity = nullptr;
}
// Add FINGERPRINT.
if (addFingerprint)
{
// Compute the CRC32 of the packet up to (but excluding) the FINGERPRINT
// attribute and XOR it with 0x5354554e.
uint32_t computedFingerprint = Utils::Crypto::GetCRC32(buffer, pos) ^ 0x5354554e;
Utils::Byte::Set2Bytes(buffer, pos, static_cast<uint16_t>(Attribute::FINGERPRINT));
Utils::Byte::Set2Bytes(buffer, pos + 2, 4);
Utils::Byte::Set4Bytes(buffer, pos + 4, computedFingerprint);
pos += 4 + 4;
// Set flag.
this->hasFingerprint = true;
}
else
{
this->hasFingerprint = false;
}
MS_ASSERT(pos == this->size, "pos != this->size");
}
} // namespace RTC
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