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java.lang.Objectnet.i2p.crypto.SessionKeyManager
net.i2p.crypto.TransientSessionKeyManager
public class TransientSessionKeyManager
Implement the session key management, but keep everything in memory (don't write to disk). However, this being java, we cannot guarantee that the keys aren't swapped out to disk so this should not be considered secure in that sense. The outbound and inbound sides are completely independent, each with their own keys and tags. For a new session, outbound tags are not considered delivered until an ack is received. Otherwise, the loss of the first message would render all subsequent messages undecryptable. True? For an existing session, outbound tags are immediately considered delivered, and are later revoked if the ack times out. This prevents massive stream slowdown caused by repeated tag delivery after the minimum tag threshold is reached. Included tags pushes messages above the ideal 1956 size by ~2KB and causes excessive fragmentation and padding. As the tags are not seen by the streaming lib, they aren't accounted for in the window size, and one or more of a series of large messages is likely to be dropped, either due to high fragmentation or drop priorites at the tunnel OBEP. For this to work, the minimum tag threshold and tag delivery quanitity defined in GarlicMessageBuilder must be chosen with streaming lib windows sizes in mind. If a single TagSet is not delivered, there will be no stall as long as the current window size is smaller than the minimum tag threshold. Additional TagSets will be sent before the acked tags completely run out. See below. all subsequent messages will fail to decrypt. See ConnectionOptions in streaming for more information. There are large inefficiencies caused by the repeated delivery of tags in a new session. With an initial streaming window size of 6 and 40 tags per delivery, a web server would deliver up to 240 tags (7680 bytes, not including bundled leaseset, etc.) in the first volley of the response. Could the two directions be linked somehow, such that the initial request could contain a key or tags for the response? Should the tag threshold and quantity be adaptive? Todo: Switch to ConcurrentHashMaps and ReadWriteLocks, only get write lock during cleanup
Field Summary | |
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protected I2PAppContext |
_context
|
static int |
DEFAULT_TAGS
This was 100 since 0.6.1.10 (50 before that). |
static int |
LOW_THRESHOLD
ditto |
static int |
MAX_INBOUND_SESSION_TAGS
a few MB? how about 16MB! This is the max size of _inboundTagSets. |
Constructor Summary | |
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TransientSessionKeyManager(I2PAppContext context)
The session key manager should only be constructed and accessed through the application context. |
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TransientSessionKeyManager(I2PAppContext context,
int tagsToSend,
int lowThreshold)
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Method Summary | |
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SessionTag |
consumeNextAvailableTag(PublicKey target,
SessionKey key)
Retrieve the next available session tag for identifying the use of the given key when communicating with the target. |
SessionKey |
consumeTag(SessionTag tag)
Determine if we have received a session key associated with the given session tag, and if so, discard it (but keep track for frequent dups) and return the decryption key it was received with (via tagsReceived(...)). |
void |
createSession(PublicKey target,
SessionKey key)
Associate a new session key with the specified target. |
void |
failTags(PublicKey target)
Deprecated. unused and rather drastic |
void |
failTags(PublicKey target,
SessionKey key,
TagSetHandle ts)
Mark these tags as invalid, since the peer has failed to ack them in time. |
int |
getAvailableTags(PublicKey target,
SessionKey key)
Determine (approximately) how many available session tags for the current target have been confirmed and are available |
long |
getAvailableTimeLeft(PublicKey target,
SessionKey key)
Determine how long the available tags will be available for before expiring, in milliseconds |
SessionKey |
getCurrentKey(PublicKey target)
Retrieve the session key currently associated with encryption to the target, or null if a new session key should be generated. |
SessionKey |
getCurrentOrNewKey(PublicKey target)
Retrieve the session key currently associated with encryption to the target. |
int |
getLowThreshold()
|
int |
getTagsToSend()
How many to send, IF we need to. |
void |
renderStatusHTML(Writer out)
|
boolean |
shouldSendTags(PublicKey target,
SessionKey key,
int lowThreshold)
|
void |
shutdown()
Called when the system is closing down, instructing the session key manager to take whatever precautions are necessary (saving state, etc) |
void |
tagsAcked(PublicKey target,
SessionKey key,
TagSetHandle ts)
Mark these tags as acked, start to use them (if we haven't already) |
TagSetHandle |
tagsDelivered(PublicKey target,
SessionKey key,
Set<SessionTag> sessionTags)
Take note of the fact that the given sessionTags associated with the key for encryption to the target have been sent. |
void |
tagsReceived(SessionKey key,
Set<SessionTag> sessionTags)
Accept the given tags and associate them with the given key for decryption |
Methods inherited from class net.i2p.crypto.SessionKeyManager |
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createSession, shouldSendTags |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Field Detail |
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protected final I2PAppContext _context
public static final int MAX_INBOUND_SESSION_TAGS
public static final int DEFAULT_TAGS
- Tags are 32 bytes. So it previously added 3200 bytes to an initial message. - Too many tags adds a huge overhead to short-duration connections (like http, datagrams, etc.) - Large messages have a much higher chance of being dropped due to one of their 1KB fragments being discarded by a tunnel participant. - This reduces the effective maximum datagram size because the client doesn't know when tags will be bundled, so the tag size must be subtracted from the maximum I2NP size or transport limit.Issues with too small a value:
- When tags are sent, a reply leaseset (~1KB) is always bundled. Maybe don't need to bundle more than every minute or so rather than every time? - Does the number of tags (and the threshold of 20) limit the effective streaming lib window size? Should the threshold and the number of sent tags be variable based on the message rate?We have to be very careful if we implement an adaptive scheme, since the key manager is per-router, not per-local-dest. Or maybe that's a bad idea, and we need to move to a per-dest manager. This needs further investigation. So a value somewhat higher than the low threshold seems appropriate. Use care when adjusting these values. See ConnectionOptions in streaming, and TransientSessionKeyManager in crypto, for more information.
public static final int LOW_THRESHOLD
Constructor Detail |
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public TransientSessionKeyManager(I2PAppContext context)
public TransientSessionKeyManager(I2PAppContext context, int tagsToSend, int lowThreshold)
tagsToSend
- how many to send at a time, may be lower or higher than lowThreshold. 1-128lowThreshold
- below this, send more. 1-128Method Detail |
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public void shutdown()
SessionKeyManager
shutdown
in class SessionKeyManager
public SessionKey getCurrentKey(PublicKey target)
getCurrentKey
in class SessionKeyManager
public SessionKey getCurrentOrNewKey(PublicKey target)
getCurrentOrNewKey
in class SessionKeyManager
public void createSession(PublicKey target, SessionKey key)
createSession
in class SessionKeyManager
public SessionTag consumeNextAvailableTag(PublicKey target, SessionKey key)
consumeNextAvailableTag
in class SessionKeyManager
public int getTagsToSend()
getTagsToSend
in class SessionKeyManager
public int getLowThreshold()
getLowThreshold
in class SessionKeyManager
public boolean shouldSendTags(PublicKey target, SessionKey key, int lowThreshold)
shouldSendTags
in class SessionKeyManager
public int getAvailableTags(PublicKey target, SessionKey key)
getAvailableTags
in class SessionKeyManager
public long getAvailableTimeLeft(PublicKey target, SessionKey key)
getAvailableTimeLeft
in class SessionKeyManager
public TagSetHandle tagsDelivered(PublicKey target, SessionKey key, Set<SessionTag> sessionTags)
tagsDelivered
in class SessionKeyManager
public void failTags(PublicKey target)
failTags
in class SessionKeyManager
public void failTags(PublicKey target, SessionKey key, TagSetHandle ts)
failTags
in class SessionKeyManager
public void tagsAcked(PublicKey target, SessionKey key, TagSetHandle ts)
tagsAcked
in class SessionKeyManager
public void tagsReceived(SessionKey key, Set<SessionTag> sessionTags)
tagsReceived
in class SessionKeyManager
public SessionKey consumeTag(SessionTag tag)
consumeTag
in class SessionKeyManager
public void renderStatusHTML(Writer out) throws IOException
renderStatusHTML
in class SessionKeyManager
IOException
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