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A fundamental primer on exploit development on both Windows and Linux based OS’s. The classical classes of vulnerablilities: buffer overflow stack overflow heap overflow use after free out of bounds read Integer Overflow and NetBSD Considered concrete example in the NetBSD kernel, based on an incorrect coding style that is exposed to integer overflow during input validation. static int set_cursor(struct tfb_softc *sc, struct wsdisplay_cursor *p) { #define cc (&sc->sc_cursor) u_int v, index = 0, count = 0, icount = 0; uint8_t r[2], g[2], b[2], image[512], mask[512]; int error, s; v = p->which; if (v & WSDISPLAY_CURSOR_DOCMAP) { index = p->cmap.index; count = p->cmap.count; if (index >= 2 || (index + count) > 2) +++ integer overflow return (EINVAL); error = copyin(p->cmap.red, &r[index], count); if (error) return error; error = copyin(p->cmap.green, &g[index], count); if (error) return error; error = copyin(p->cmap.blue, &b[index], count); if (error) return error; Note the overflow, about 1/2 way down. Just imagine if index was a really large value that overflowed 32 bits. A more robust way to code the validation check, can be seen in the OpenBSD code: ...

The sequence of tasks undertaken that make digital signatures possible. This does have a slight XML flavour to it. A digital signature is a mathematical scheme for verifying the authenticity of digital messages. The concept of digital signature completely hinges on assymetric cryptography (such as DSA or RSA). To validate a signature First the message can be normalised, and in the case of XML will use something like the “Exclusive XML Canonicalization” (XML-C14N), so we’re comparing apples with apples. This will disgard things like usage of white space. Using the normalised representation, compute a hash (e.g. SHA1) of the timestamp (contained WS-Security header) and entire message payload (the SOAP body). Using the public key from the partner organisation certificate, RSA decrypt the hash computed by partner organisation. If the two hashes are identical, we know the message has not been tampered with. (optional) Validate the timestamp (TTL) defined by partner organisation (typically 7 minutes from the original transmission time by the sender). To mitigate possible damage caused by replay attacks. To create a signature Wraps the response message in a SOAP envelope, which includes some WS-Security related headers including a timestamp. The timestamp is set to a configurable number of minutes (e.g. 10 minutes) in the future. Normalises the message using the “Exclusive XML Canonicalization” (XML-C14N) Using the normalised message form, compute a (e.g. SHA1) hash of the timestamp (WS-Security header) and entire response message payload (e.g. the SOAP body). Uses the private key of signing certificate, RSA signs the computed hash, and stores the result in the relevant security header (the SignatureValue header). The message is then delivered to partner organisation. For the above to work, there needs to be some established agreement as to the specific cipher suites and canonicalisation method used. This is all ...

A quick tour of doing web with golang, all living off the land with Go’s built-in standard library. Packages Working example, where the web server and templating code in source file $GOPATH/src/github.com/bm4cs/gotime/web/server.go. It does lots of things, but exports function StartServer (upper case first character means publically exported). package web func StartServer() { ... } The main func in $GOPATH/src/github.com/bm4cs/gotime/myapp/app.go can import the web package: import ( "github.com/bm4cs/gotime/web" ) func main() { web.StartServer() } Handling Requests The http package from the standard library, provides a ton a out of the box functionality. Writing Web Applications on golang.org is a very pragmatic guide. ...

Some more advanced Elasticsearch wisdom I gleaned from Jason Wong and Mark Laney from Elastic. Contents Environment with Config X-Pack Security (the 1337 way) Roles Built-in Query Web UI (batteries included) Internals Lucene Segments Elasticsearch Indexing Transaction Log and Flushing Doc Values Caching Field Modelling Typing Denormalising Range Types Mapping Parameters Fixing Data Painless Reindexing API’s Picking up Mapping Changes Multi-fields Custom Marker (flag) Field Fixing Fields Advanced Search and Aggregations Patterns Wildcard Query Regexp Qury Null Script (painless) Query Script Field Performance Considerations Search Templates Aggregations Percentile Top Hits Scripted (painless) Aggregations Significant Terms Aggregation Pipeline Aggregations Cluster Management Dedicated Nodes Hot Warm Architecture Tags Verify Shard Allocation Forced Awareness Capacity Planning Shard Allocation Litmus Test Primary Shards Scaling with Indices Scaling with Replicas Resources Time Based Data API’s for Managing Indices Document Modelling Nested Objects Nested Aggregations Parent Child Relationships Argh Which Technique is Best? Kibana Considerations Monitoring Task Management API The cat API Performance Issues Thread Pool Queues hot_threads API Indexing Slow Log Search Slow Log The Profile API X-Pack Monitoring Alerting From Dev to Production Disabling Dynamic Indices Production Mode Best Practices Network Best Practices Storage Best Practices Hardware Selection Throttles JVM Poor Query Performance Always Filter Aggregating Too Many Docs Denormalise First Too many shards Unnecessary Scripting Cross Cluster Replication Upgrades Rolling Upgrade Environment with Config Can use environment variables within elasticsearch.yml: ...

Some Elasticsearch wisdom I gleaned from Jason Wong and Mark Laney from Elastic. Contents Use cases Log stash vs Beats? Time Series vs Static Data Logstash Installation Starting and Stopping Elasticsearch Killing Communication Discovery module (networking) Security Read-only Enabling X-Pack (Elasticsearch Security) CRUD Ingestion Reading Search Query and Filter Contexts Mapping Inverted Index Multi Fields (keyword fields) Anatomy of an Analyzer Custom Analyzer The reindex API Node Types Cluster state Shards Anatomy of Search (Shards) Troubleshooting Configuration Responses Cluster and Shard Health Diagnosing Issues Improving Search Results Multi-field Search Boosting Fuzziness Exact Terms Sorting Paging Highlighting Aggregations Best Practices Index Aliases Index Templates Scroll Search Cluster Backup Use cases Search Logging Metrics - unlike logs, are typically not in a text format. Business analytics - the aggregation and analysis of patterns (e.g. bucketing aggregations, ML jobs) Security analytics - Log stash vs Beats? Beats are lightweight data shippers, but are not appropriate for ETL type stashing. Logstash on the other hand, can take handle these concerns. But requires a much heavier runtime (JVM). An official SIEM solution is currently under development. ...

Update 2019-05-26: While having some familarity with roff is useful, since the time of originally have discovered Pandoc which can convert between many document formats, such as from markdown to roff. Writing documentation in markdown is just hard to beat. As the first text formatting program built for UNIX in 1970 running on a PDP-7, roff was a port of the BCPL program RUNOFF. Over the years roff has evolved into troff and the excellent GNU version groff. Similar to other formatting systems, such as LaTeX, groff features a macro system, targetted at authoring certain types of text documents. In spite of its old age, roff is still in wide spread use today, for producing text such as UNIX manual pages, software books, system documentation and standards documents. ...

Intro Install Package (yum or deb) X-Pack Configuration Verify Index Patterns Intro Elastics node.js web frontend in the stack, and (by default) runs on port 5601. It’s wise to install Kibana on its own infrastructure (i.e. isolated from the Elasticsearch cluster). The node process is light (compared to the JVM anyway) consuming hundreds of MB. Install Package (yum or deb) While available as a tarball, the nicest option is to go with a package, takes care of plumbing such as systemd, and general system integration such as /etc/kibana for configuration, logs and data files. ...

An evolving list of resources around packet analysis tips and tricks. Terminology Cheat sheets Anatomy of a Packet OSI Model Layers Link Layer Ether Type Fields Network layer Transport layer Tools Wireshark (and tshark) tcpdump Useful switches Examples Real world use-cases netsniff-ng Analysis Terminology SOC, or Security Operations Center, is a central location composed of leading edge tools, technology and peeps (intel gatherers, analysts) that deals with security issues at an organisational and technical level. IDS, or Intrusion Detection System, is a device that monitors network traffic for threats to the environment, proactively alert the SOC analyst of potential problems. IPS, or an Intrusion Prevention System, is more sits inline, and can take active or passive mitigation actions. SIEM, or Security Information and Event Management, is all about the collection and aggregation of alerts and logs for event tracking, retention and correlation from multiple hosts. Cheat sheets SANS TCP/IP and tcpdump Pocket Reference Guide RFC 790 Assigned Internet Protocol Numbers RFC 791 Internet Protocol Anatomy of a Packet OSI Model Layers 7: application: HTTP, FTP, DNS 6: presentation: SSL, JPEG 5: session: SQL, SCP, NetBIOS, SOAP 4: transport: TCP, UDP 3: network: IPv4, IPv6, ICMP 2: data-link: PPP, ARP, CDP 1: physical: Ethernet, Bluetooth Layers 2-4 will be of primary interest. ...

Providing SSO by integrating Linux (or FreeBSD) with a directory service, like Microsoft Active Directory (AD), is no where as daunting as it once was, and highlights some fascinating subsystems that enable users to be defined from a variety of data sources (such as LDAP) other than just the traditional /etc/passwd file. Initial setup Kerberos Create service keytab on AD System Security Services Daemon (sssd) Name Service Switch (nss) PAM (Pluggable Authentication Module) Testing Listing Users Listing Groups id Troubleshooting Samba (smbd) Join Issues Clock Synchronisation Issues Clearing SSSD Cache End to end script (for Ansible) Initial setup Update /etc/resolv.conf to bind to the AD DNS server. This will enable realmd to discover and join the active directory domain (i.e. kerberos realm). ...

A quick walkthrough of Logstash, the ETL engine offered by the Elastic Stack. Logstash is an open source, server-side data processing pipeline that ingests data from a multitude of sources simultaneously, transforms it, and then sends it to your favorite stash Logstash gained its initial popularity with log and metric collection, such as log4j logs, Apache web logs and syslog. Its application has broadened, to all kinds of data sources like large scale event streams, webhooks, database and message queue integration. Once data is transformed and cleaned up is routed to a final destination (i.e. the stash), Elasticsearch is one option, but lots of other choices are there (mongo, S3, Nagios, IRC, email). ...