santa/Source/santad/SNTEventLog.m

/// Copyright 2015 Google Inc. All rights reserved.
///
/// Licensed under the Apache License, Version 2.0 (the "License");
/// you may not use this file except in compliance with the License.
/// You may obtain a copy of the License at
///
///    http://www.apache.org/licenses/LICENSE-2.0
///
///    Unless required by applicable law or agreed to in writing, software
///    distributed under the License is distributed on an "AS IS" BASIS,
///    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
///    See the License for the specific language governing permissions and
///    limitations under the License.

#import "SNTEventLog.h"

#include <sys/stat.h>
#include <sys/sysctl.h>

#import "SNTCachedDecision.h"
#import "SNTCertificate.h"
#import "SNTCommonEnums.h"
#import "SNTFileInfo.h"
#import "SNTKernelCommon.h"
#import "SNTLogging.h"

@interface SNTEventLog ()
@property NSMutableDictionary *detailStore;
@end

@implementation SNTEventLog

- (instancetype)init {
  self = [super init];
  if (self) {
    _detailStore = [NSMutableDictionary dictionaryWithCapacity:10000];
  }
  return self;
}

- (void)saveDecisionDetails:(SNTCachedDecision *)cd {
  self.detailStore[@(cd.vnodeId)] = cd;
}

- (void)logFileModification:(santa_message_t)message {
  NSString *action, *path, *newpath, *sha256, *outStr;

  path = @(message.path);

  switch (message.action) {
    case ACTION_NOTIFY_DELETE: {
      action = @"DELETE";
      break;
    }
    case ACTION_NOTIFY_EXCHANGE: {
      action = @"EXCHANGE";
      newpath = @(message.newpath);
      break;
    }
    case ACTION_NOTIFY_LINK: {
      action = @"LINK";
      newpath = @(message.newpath);
      break;
    }
    case ACTION_NOTIFY_RENAME: {
      action = @"RENAME";
      newpath = @(message.newpath);
      break;
    }
    case ACTION_NOTIFY_WRITE: {
      action = @"WRITE";
      struct stat filestat;
      stat(message.path, &filestat);

      if (filestat.st_size < 1024 * 1024) {
        SNTFileInfo *fileInfo = [[SNTFileInfo alloc] initWithPath:path];
        sha256 = fileInfo.SHA256;
      } else {
        sha256 = @"(too large)";
      }
      break;
    }
    default: action = @"UNKNOWN"; break;
  }

  outStr = [NSString stringWithFormat:@"action=%@|path=%@", action, [self sanitizeString:path]];
  if (newpath) {
    outStr = [outStr stringByAppendingFormat:@"|newpath=%@", [self sanitizeString:newpath]];
  }
  outStr = [outStr stringByAppendingFormat:@"|pid=%d|ppid=%d|uid=%d|gid=%d",
               message.pid, message.ppid, message.uid, message.gid];
  if (sha256) {
    outStr = [outStr stringByAppendingFormat:@"|sha256=%@", sha256];
  }

  LOGI(@"%@", outStr);
}

- (void)logDeniedExecution:(SNTCachedDecision *)cd withMessage:(santa_message_t)message {
  [self logExecution:message withDecision:cd];
}

- (void)logAllowedExecution:(santa_message_t)message {
  SNTCachedDecision *cd = self.detailStore[@(message.vnode_id)];
  [self logExecution:message withDecision:cd];
}

- (void)logExecution:(santa_message_t)message withDecision:(SNTCachedDecision *)cd {
  NSString *d, *r, *args, *outLog;

  switch (cd.decision) {
    case EVENTSTATE_ALLOW_BINARY:
      d = @"ALLOW"; r = @"BINARY"; args = [self argsForPid:message.pid]; break;
    case EVENTSTATE_ALLOW_CERTIFICATE:
      d = @"ALLOW"; r = @"CERTIFICATE"; args = [self argsForPid:message.pid]; break;
    case EVENTSTATE_ALLOW_SCOPE:
      d = @"ALLOW"; r = @"SCOPE"; args = [self argsForPid:message.pid]; break;
    case EVENTSTATE_ALLOW_UNKNOWN:
      d = @"ALLOW"; r = @"UNKNOWN"; args = [self argsForPid:message.pid]; break;
    case EVENTSTATE_BLOCK_BINARY:
      d = @"DENY"; r = @"BINARY"; break;
    case EVENTSTATE_BLOCK_CERTIFICATE:
      d = @"DENY"; r = @"CERT"; break;
    case EVENTSTATE_BLOCK_SCOPE:
      d = @"DENY"; r = @"SCOPE"; break;
    case EVENTSTATE_BLOCK_UNKNOWN:
      d = @"DENY"; r = @"UNKNOWN"; break;
    default:
      d = @"ALLOW"; r = @"NOTRUNNING"; args = [self argsForPid:message.pid]; break;
  }

  outLog = [NSString stringWithFormat:@"action=EXEC|decision=%@|reason=%@", d, r];

  if (cd.decisionExtra) {
    outLog = [outLog stringByAppendingFormat:@"|explain=%@", cd.decisionExtra];
  }

  outLog = [outLog stringByAppendingFormat:@"|sha256=%@|path=%@|args=%@",
               cd.sha256, [self sanitizeString:@(message.path)], [self sanitizeString:args]];

  if (cd.certSHA256) {
    outLog = [outLog stringByAppendingFormat:@"|cert_sha256=%@|cert_cn=%@",
                 cd.certSHA256, [self sanitizeString:cd.certCommonName]];
  }

  outLog = [outLog stringByAppendingFormat:@"|pid=%d|ppid=%d|uid=%d|gid=%d",
               message.pid, message.ppid, message.uid, message.gid];

  LOGI(@"%@", outLog);
}

#pragma mark Helpers

- (NSString *)sanitizeString:(NSString *)inStr {
  inStr = [inStr stringByReplacingOccurrencesOfString:@"|" withString:@"<pipe>"];
  inStr = [inStr stringByReplacingOccurrencesOfString:@"\n" withString:@"\\n"];
  inStr = [inStr stringByReplacingOccurrencesOfString:@"\r" withString:@"\\r"];
  return inStr;
}

- (NSString *)argsForPid:(pid_t)pid {
  int mib[3];

  // Get size of buffer required to store process arguments.
  mib[0] = CTL_KERN;
  mib[1] = KERN_ARGMAX;
  int argmax;
  size_t size = sizeof(argmax);

  if (sysctl(mib, 2, &argmax, &size, NULL, 0) == -1) return nil;

  // Create buffer to store args
  NSMutableData *argsdata = [NSMutableData dataWithCapacity:argmax];
  char *argsdatabytes = (char *)argsdata.mutableBytes;

  // Fetch args
  mib[0] = CTL_KERN;
  mib[1] = KERN_PROCARGS2;
  mib[2] = pid;
  size = (size_t)argmax;
  if (sysctl(mib, 3, argsdatabytes, &size, NULL, 0) == -1) return nil;

  // Get argc
  int argc;
  memcpy(&argc, argsdatabytes, sizeof(argc));

  // Get pointer to beginning of string space
  char *cp;
  cp = (char *) argsdatabytes + sizeof(argc);

  // Skip over exec_path
  for (; cp < &argsdatabytes[size]; cp++) {
    if (*cp == '\0') {
      cp++;
      break;
    }
  }

  // Skip trailing NULL bytes
  for (; cp < &argsdatabytes[size]; cp++) if (*cp != '\0') break;

  // Loop over the argv array, stripping newlines in each arg and putting in a new array.
  NSMutableArray *args = [NSMutableArray arrayWithCapacity:argc];
  for (int i = 0; i < argc; i++) {
    NSString *arg = @(cp);
    [args addObject:arg];

    // Move the pointer past this string and the terminator at the end.
    cp += strlen(cp) + 1;
  }

  // Return the args as a space-separated list
  return [args componentsJoinedByString:@" "];
}

@end