Pierre-Olivier Mercier
70140bc289
Embed the IEEE OUI registry (~1MB pre-processed text file) and resolve the vendor for every station MAC. Locally administered MACs (U/L bit set, used by iOS/Android private addresses and virtual interfaces) are skipped so we don't return spurious matches against randomized prefixes. The vendor name shows up in the device card as a secondary line, and falls back to the title position when no DHCP hostname is available — "Apple" with the IP and MAC is far more useful than "Sans nom". The lookup table loads lazily (sync.Once) on the first call so the ~40k-entry parse only runs when the station discovery code is exercised.
98 lines
2.4 KiB
Go
98 lines
2.4 KiB
Go
package backend
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import (
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_ "embed"
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"strings"
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"sync"
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)
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// IEEE OUI registry as a compact text file: each line is 6 hex characters
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// (uppercase, no separators) followed immediately by the organization name.
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// Sourced from https://standards-oui.ieee.org/oui/oui.csv and pre-processed
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// to strip the address column and common corporate suffixes (Inc, Ltd, ...).
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//
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//go:embed oui_data.txt
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var ouiData string
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var (
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ouiOnce sync.Once
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ouiTable map[string]string
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)
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func loadOUITable() {
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ouiTable = make(map[string]string, 40000)
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for line := range strings.SplitSeq(ouiData, "\n") {
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if len(line) < 7 {
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continue
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}
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ouiTable[line[:6]] = line[6:]
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}
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}
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// LookupVendor returns the organization assigned to the OUI prefix of mac,
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// or an empty string when the prefix is unknown or mac is malformed. Locally
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// administered MACs (the U/L bit is set) are explicitly skipped — they are
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// randomized by the device, not assigned to a vendor, so any match would be
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// a false positive.
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func LookupVendor(mac string) string {
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ouiOnce.Do(loadOUITable)
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prefix := normalizeOUI(mac)
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if prefix == "" {
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return ""
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}
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return ouiTable[prefix]
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}
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// normalizeOUI extracts the 6-hex-char OUI from a MAC address (any of
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// "aa:bb:cc:...", "aa-bb-cc-...", "aabb.ccdd.eeff", "aabbcc...") and returns
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// it uppercased. Returns "" for randomized MACs (locally administered bit
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// set) or anything that doesn't parse.
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func normalizeOUI(mac string) string {
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var hex strings.Builder
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hex.Grow(12)
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for i := 0; i < len(mac) && hex.Len() < 6; i++ {
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c := mac[i]
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switch {
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case c >= '0' && c <= '9', c >= 'A' && c <= 'F':
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hex.WriteByte(c)
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case c >= 'a' && c <= 'f':
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hex.WriteByte(c - 32)
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}
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}
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if hex.Len() < 6 {
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return ""
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}
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out := hex.String()
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// Skip locally administered MACs. The U/L bit is bit 1 of the first
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// octet — when set, the MAC was generated by the device (private
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// address randomization on iOS/Android, virtual interfaces, ...), not
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// assigned by IEEE, so OUI lookup is meaningless.
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first, ok := hexByte(out[0], out[1])
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if !ok || first&0x02 != 0 {
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return ""
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}
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return out
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}
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func hexByte(hi, lo byte) (byte, bool) {
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h, ok1 := hexNibble(hi)
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l, ok2 := hexNibble(lo)
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if !ok1 || !ok2 {
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return 0, false
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}
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return h<<4 | l, true
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}
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func hexNibble(c byte) (byte, bool) {
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switch {
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case c >= '0' && c <= '9':
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return c - '0', true
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case c >= 'A' && c <= 'F':
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return c - 'A' + 10, true
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case c >= 'a' && c <= 'f':
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return c - 'a' + 10, true
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}
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return 0, false
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}
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