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Hash SSIDs before logging them. #37524

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Hash SSIDs before logging them. #37524

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16 changes: 14 additions & 2 deletions src/darwin/Framework/CHIP/MTRCommissioningParameters.mm
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,10 @@

#import "MTRCommissioningParameters.h"

#import <CommonCrypto/CommonDigest.h>

#include <lib/support/BytesToHex.h>

NS_ASSUME_NONNULL_BEGIN

@implementation MTRCommissioningParameters : NSObject
Expand Down Expand Up @@ -47,10 +51,18 @@ - (void)setFailSafeExpiryTimeoutSecs:(NSNumber * _Nullable)failSafeExpiryTimeout

- (NSString *)description
{
// SSID is not required to be UTF-8, but almost always is.
NSString * ssidString;
if (self.wifiSSID) {
ssidString = [[NSString alloc] initWithData:self.wifiSSID encoding:NSUTF8StringEncoding];
// We want to log the SSID, but hash it, so that the actual SSID cannot be
// recovered from the log.
uint8_t hashedValue[CC_SHA256_DIGEST_LENGTH];
CC_SHA256(self.wifiSSID.bytes, static_cast<CC_LONG>(self.wifiSSID.length), hashedValue);

char hexValue[sizeof(hashedValue) * 2];
chip::Encoding::BytesToHex(hashedValue, sizeof(hashedValue), hexValue, sizeof(hexValue), chip::Encoding::HexFlags::kUppercase);
ssidString = [[NSString alloc] initWithBytes:hexValue
length:sizeof(hexValue)
encoding:NSUTF8StringEncoding];
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Why not just [string hash] per discussion? This is awfully complicated/expensive (not that the cost matters), what's the value here?

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As I said in the discussion if you do [string hash] then to check whether a given SSID is the one that went through this code you have to run [string hash] on the exact same operating system version of the same operating system as the one that created the log, no?

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Yup, which is fine.

} else {
ssidString = nil;
}
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