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Fixed packEcCoordinatesFromEcPoint having variable-sized output, prevent reconstruction of public key

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This commit is contained in:
Craig Gidney 2014-08-18 23:42:40 -04:00 committed by Frederic Jacobs
parent 4cd30f32ed
commit 5d31f76f3e
2 changed files with 47 additions and 34 deletions
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56
Signal/src/network/rtp/zrtp/agreement/EvpKeyAgreement.m
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@ -250,39 +250,41 @@ enum KeyAgreementType {
}
-(NSData*) packEcCoordinatesFromEcPoint:(const EC_POINT*) ec_point withEcGroup:(const EC_GROUP*) ec_group {
BIGNUM *x = BN_new();
BIGNUM *y = BN_new();
BIGNUM *x = NULL;
BIGNUM *y = NULL;
@try {
x = BN_new();
y = BN_new();
checkSecurityOperation(x != NULL && y != NULL, @"BN_new");
unsigned char* buf_x; size_t bufsize_x;
unsigned char* buf_y; size_t bufsize_y;
checkSecurityOperation(1 == EC_POINT_get_affine_coordinates_GFp(ec_group, ec_point, x, y, NULL), @"EC_POINT_get_affine_coordinates_GFp");
EC_POINT_get_affine_coordinates_GFp(ec_group, ec_point, x, y, NULL);
int len_x = BN_num_bytes(x);
int len_y = BN_num_bytes(y);
checkSecurityOperation(len_x >= 0 && len_x <= EC25_COORDINATE_LENGTH, @"BN_num_bytes(x)");
checkSecurityOperation(len_y >= 0 && len_y <= EC25_COORDINATE_LENGTH, @"BN_num_bytes(y)");
int unused_x = EC25_COORDINATE_LENGTH - len_x;
int unused_y = EC25_COORDINATE_LENGTH - len_y;
bufsize_x = [NumberUtil assertConvertIntToNSUInteger:BN_num_bytes(x)];
bufsize_y = [NumberUtil assertConvertIntToNSUInteger:BN_num_bytes(y)];
checkEvpNotNull( buf_x = OPENSSL_malloc(bufsize_x), @"ec_x_buffer");
checkEvpNotNull( buf_y = OPENSSL_malloc(bufsize_y), @"ec_y_buffer");
BN_bn2bin(x, buf_x);
BN_bn2bin(y, buf_y);
NSMutableData* data = [NSMutableData dataWithBytes:buf_x length:bufsize_x];
[data appendData:[NSData dataWithBytes:buf_y length:bufsize_y]];
OPENSSL_free(buf_x);
OPENSSL_free(buf_y);
BN_free(x);
BN_free(y);
return data;
NSMutableData* data = [NSMutableData dataWithLength:EC25_COORDINATE_LENGTH*2];
// We offset the writes to keep things constant sized.
// Leading zeroes have no effect on the deserialization because BN_bn2bin outputs the bytes in big-endian order.
int wrote_x = BN_bn2bin(x, data.mutableBytes + unused_x);
int wrote_y = BN_bn2bin(y, data.mutableBytes + EC25_COORDINATE_LENGTH + unused_y);
checkSecurityOperation(wrote_x == len_x && wrote_y == len_y, @"BN_bn2bin");
return data;
} @finally {
if (x != NULL) BN_free(x);
if (y != NULL) BN_free(y);
}
}
-(void) unpackEcCoordinatesFromBuffer:(const unsigned char*) buffer
ofSize:(size_t) bufsize
toEcPoint:(EC_POINT*) ecp
withEcGroup:(const EC_GROUP*) ecg {
ofSize:(size_t) bufsize
toEcPoint:(EC_POINT*) ecp
withEcGroup:(const EC_GROUP*) ecg {
checkOperation(2*EC25_COORDINATE_LENGTH == bufsize);

25
Signal/test/network/rtp/zrtp/EC25AgreerTest.m
View File

@ -3,17 +3,12 @@
#import "EC25KeyAgreementParticipant.h"
#import "EC25KeyAgreementProtocol.h"
@interface EC25AgreerTest : XCTestCase{
}
@interface EC25AgreerTest : XCTestCase
@end
@implementation EC25AgreerTest
-(void) testKeyExchange {
-(void) testKeyExchangeMatchesPeerButNotOthers {
EC25KeyAgreementProtocol* protocol = [EC25KeyAgreementProtocol protocol];
id<KeyAgreementParticipant> ec1 = [protocol generateParticipantWithNewKeys];
@ -33,4 +28,20 @@
test(![shared_3 isEqualToData:shared_1]);
}
-(void) testKeyExchangeSucceedsConsistently {
EC25KeyAgreementProtocol* protocol = [EC25KeyAgreementProtocol protocol];
for (int i = 0; i < 1000; i++) {
id<KeyAgreementParticipant> ec1 = [protocol generateParticipantWithNewKeys];
id<KeyAgreementParticipant> ec2 = [protocol generateParticipantWithNewKeys];
NSData* pub_1 = [ec1 getPublicKeyData];
NSData* pub_2 = [ec2 getPublicKeyData];
NSData* shared_1 = [ec1 calculateKeyAgreementAgainstRemotePublicKey:pub_2];
NSData* shared_2 = [ec2 calculateKeyAgreementAgainstRemotePublicKey:pub_1];
test([shared_1 isEqualToData:shared_2]);
}
}
@end