Binary Triage (Phase 1)

Purpose

Quick fingerprinting to establish baseline facts before deeper analysis. Runs in seconds, not minutes.

When to Use

•First contact with an unknown binary
•Need architecture/ABI info for tool selection
•Quick capability assessment
•Before committing to expensive analysis

Key Principle

Gather facts fast, defer analysis.

This phase identifies WHAT the binary is, not HOW it works.

Triage Sequence

Step 1: File Identification

bash

# Basic identification
file binary

# Expected output patterns:
# ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-armhf.so.3
# ELF 64-bit LSB pie executable, ARM aarch64, version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-aarch64.so.1

Extract:

•Architecture (ARM, ARM64, x86_64, MIPS)
•Bit width (32/64)
•Endianness (LSB/MSB)
•Link type (static/dynamic)
•Interpreter path (libc indicator)

Step 2: Structured Metadata (rabin2)

bash

# All metadata as JSON
rabin2 -q -j -I binary | jq .

# Key fields:
# .arch     - "arm", "x86", "mips"
# .bits     - 32 or 64
# .endian   - "little" or "big"
# .os       - "linux", "none"
# .machine  - "ARM", "AARCH64"
# .stripped - true/false
# .static   - true/false

Step 3: ABI Detection

bash

# Interpreter detection
readelf -p .interp binary 2>/dev/null

# Or via rabin2
rabin2 -I binary | grep interp

# ARM-specific: float ABI
readelf -A binary | grep "Tag_ABI_VFP_args"
# hard-float: "VFP registers"
# soft-float: missing or "compatible"

Interpreter → Libc mapping:

Interpreter	Libc	Notes
`/lib/ld-linux-armhf.so.3`	glibc	ARM hard-float
`/lib/ld-linux.so.3`	glibc	ARM soft-float
`/lib/ld-musl-arm.so.1`	musl	ARM 32-bit
`/lib/ld-musl-aarch64.so.1`	musl	ARM 64-bit
`/lib/ld-uClibc.so.0`	uClibc	Embedded
`/lib64/ld-linux-x86-64.so.2`	glibc	x86_64

Step 4: Dependencies

bash

# Library dependencies
rabin2 -q -j -l binary | jq '.libs[]'

# Common patterns:
# libcurl.so.* → HTTP client
# libssl.so.* → TLS/crypto
# libpthread.so.* → Threading
# libz.so.* → Compression
# libsqlite3.so.* → Local database

Step 5: Entry Points & Exports

bash

# Entry points
rabin2 -q -j -e binary | jq .

# Exports (for shared libraries)
rabin2 -q -j -E binary | jq '.exports[] | {name, vaddr}'

Step 6: Quick String Scan

bash

# All strings with metadata
rabin2 -q -j -zz binary | jq '.strings | length'  # Count first

# Filter interesting strings (URLs, paths, errors)
rabin2 -q -j -zz binary | jq '
  .strings[] |
  select(.length > 8) |
  select(.string | test("http|ftp|/etc|/var|error|fail|pass|key|token"; "i"))
'

Step 7: Import Analysis

bash

# All imports
rabin2 -q -j -i binary | jq '.imports[] | {name, lib}'

# Group by capability
rabin2 -q -j -i binary | jq '
  .imports | group_by(.lib) |
  map({lib: .[0].lib, functions: [.[].name]})
'

Capability Mapping

Import Pattern	Capability
`socket`, `connect`, `send`	Network client
`bind`, `listen`, `accept`	Network server
`open`, `read`, `write`	File I/O
`fork`, `exec*`, `system`	Process spawning
`pthread_*`	Multi-threading
`SSL_`, `EVP_`	Cryptography
`dlopen`, `dlsym`	Dynamic loading
`mmap`, `mprotect`	Memory manipulation

Output Format

After triage, record structured facts:

json

{
  "artifact": {
    "path": "/path/to/binary",
    "sha256": "abc123...",
    "size_bytes": 245760
  },
  "identification": {
    "arch": "arm",
    "bits": 32,
    "endian": "little",
    "os": "linux",
    "stripped": true,
    "static": false
  },
  "abi": {
    "interpreter": "/lib/ld-musl-arm.so.1",
    "libc": "musl",
    "float_abi": "hard"
  },
  "dependencies": [
    "libcurl.so.4",
    "libssl.so.1.1",
    "libz.so.1"
  ],
  "capabilities_inferred": [
    "network_client",
    "tls_encryption",
    "compression"
  ],
  "strings_of_interest": [
    {"value": "https://api.vendor.com/telemetry", "type": "url"},
    {"value": "/etc/config.json", "type": "path"}
  ],
  "complexity_estimate": {
    "functions": "unknown (stripped)",
    "strings": 847,
    "imports": 156
  }
}

Knowledge Journaling

After triage completes, record findings for episodic memory:

code

[BINARY-RE:triage] {filename} (sha256: {hash})

Identification:
  Architecture: {arch} {bits}-bit {endian}
  Libc: {glibc|musl|uclibc} ({interpreter_path})
  Stripped: {yes|no}
  Size: {bytes}

FACT: Links against {library} (source: rabin2 -l)
FACT: Contains {N} strings of interest (source: rabin2 -zz)
FACT: Imports {function} from {library} (source: rabin2 -i)

Capabilities inferred:
  - {capability_1} (evidence: {import/string})
  - {capability_2} (evidence: {import/string})

HYPOTHESIS: {what binary likely does} (confidence: {0.0-1.0})

QUESTION: {open unknown that needs investigation}

Next phase: {static-analysis|dynamic-analysis}
Sysroot needed: {path or "extract from device"}

Example Journal Entry

code

[BINARY-RE:triage] thermostat_daemon (sha256: a1b2c3d4...)

Identification:
  Architecture: ARM 32-bit LE
  Libc: musl (/lib/ld-musl-arm.so.1)
  Stripped: yes
  Size: 153,600 bytes

FACT: Links against libcurl.so.4 (source: rabin2 -l)
FACT: Links against libssl.so.1.1 (source: rabin2 -l)
FACT: Contains string "api.thermco.com" (source: rabin2 -zz)
FACT: Imports curl_easy_perform (source: rabin2 -i)

Capabilities inferred:
  - HTTP client (evidence: libcurl import)
  - TLS encryption (evidence: libssl import)
  - Network communication (evidence: URL string)

HYPOTHESIS: Telemetry client that reports to api.thermco.com (confidence: 0.6)

QUESTION: What data does it collect and transmit?

Next phase: static-analysis
Sysroot needed: musl ARM (extract from device or Alpine)

Decision Points

After triage, determine:

•Sysroot selection - Based on arch + libc
•Analysis tool chain - r2 vs Ghidra vs both
•Dynamic analysis feasibility - QEMU viability based on arch
•Initial hypotheses - What does this binary likely do?

Next Steps

→ Proceed to binary-re-static-analysis for function enumeration → Or binary-re-dynamic-analysis if behavior observation is priority