aria2c_dl.sh

#!/bin/sh
set -eu

# Mirror IP addresses for updates.cdn-apple.com
MIRRORS="
17.253.53.35
17.253.53.203
17.253.53.202
37.143.84.100
37.143.84.113
91.241.30.48
"

STAT_FILE="$HOME/.aria2-cdn-stats"
touch "$STAT_FILE"
URL="${1:?Usage: $0 <URL>}"
FILENAME="${URL##*/}"

# Fetch the expected SHA-256 hash from the header
printf 'Fetching SHA-256 hash...\n'
EXPECTED_HASH=$(curl -sI "$URL" | tr -d '\r' | awk -F': ' 'tolower($1) == "x-amz-meta-digest-sha256" {print $2}')

if [ -z "$EXPECTED_HASH" ]; then
  printf 'Error: could not retrieve x-amz-meta-digest-sha256 header.\n' >&2
  exit 1
fi
printf 'Expected SHA-256: %s\n' "$EXPECTED_HASH"

# Build the list of mirror URIs by replacing the hostname with each IP
URIS=""
COUNT=0
for IP in $MIRRORS; do
  URI=$(printf '%s' "$URL" | sed "s|updates\.cdn-apple\.com|${IP}|")
  URIS="${URIS} ${URI}"
  COUNT=$((COUNT + 1))
done

SPLIT=12

# Download using aria2c
printf 'Downloading with %d mirrors (%d connections)...\n' "$COUNT" "$SPLIT"
aria2c \
  --check-certificate=false \
  --file-allocation=falloc \
  --header='Host: updates.cdn-apple.com' \
  --split="$SPLIT" \
  --max-connection-per-server=12 \
  --uri-selector=adaptive \
  --server-stat-if="$STAT_FILE" \
  --server-stat-of="$STAT_FILE" \
  --out="$FILENAME" \
  $URIS

# Verify the downloaded file
printf 'Verifying SHA-256...\n'
ACTUAL_HASH=$(openssl dgst -sha256 "$FILENAME" | awk '{print $NF}')

if [ "$ACTUAL_HASH" = "$EXPECTED_HASH" ]; then
  printf 'OK: hash matches.\n'
else
  printf 'MISMATCH!\n  expected: %s\n  actual:   %s\n' "$EXPECTED_HASH" "$ACTUAL_HASH" >&2
  exit 1
fi