kiss: switch to blake3 checksums (#72)

As discussed in kiss-community/repo#100 and #39, we seem to be in favor of switching to blake3.

The following changes are made:
- All newly generated checksums are blake3
- The user is prompted to generate blake3 checksums if sha256 sums are present (maybe this should be automatic)
- For installed packages, we can fall back to sha256 to check etcsums

This includes a name change of the `checksums` and `etcsums` files -- I'm not sure of any better way to detect whether sha256 sums are in use, as blake3 sums are the same length.

Feedback is appreciated

Co-authored-by: Owen Rafferty <owen@owenrafferty.com>
Reviewed-on: https://codeberg.org/kiss-community/kiss/pulls/72

kiss

@@ -198,6 +198,41 @@ decompress() {
     esac < "$1"
 }
 
+b3() {
+    # Higher level blake3 function which filters out non-existent
+    # files (and also directories).
+    for f do shift
+        [ -d "$f" ] || [ ! -e "$f" ] || set -- "$@" "$f"
+    done
+
+    _b3 "$@"
+}
+
+_b3() {
+    unset hash
+
+    # Skip generation if no arguments.
+    ! equ "$#" 0 || return 0
+
+    IFS=$newline
+
+    # Generate checksums for all input files. This is a single
+    # call to the utility rather than one per file.
+    #
+    # The length of the checksum is set to 33 bytes to
+    # differentiate it from sha256 checksums.
+    _hash=$("$cmd_b3" -l 33 "$@") || die "Failed to generate checksums"
+
+    # Strip the filename from each element.
+    # '<checksum> ?<file>' -> '<checksum>'
+    for sum in $_hash; do
+        hash=$hash${hash:+"$newline"}${sum%% *}
+    done
+
+    printf '%s\n' "$hash"
+    unset IFS
+}
+
 sh256() {
     # Higher level sh256 function which filters out non-existent
     # files (and also directories).
@@ -896,7 +931,7 @@ pkg_etcsums() {
         set -- "$pkg_dir/$repo_name/$etc" "$@"
     esac done < manifest
 
-    sh256 "$@" > etcsums
+    b3 "$@" > etcsums
 }
 
 pkg_tar() {
@@ -1125,7 +1160,7 @@ pkg_checksum_gen() {
         esac
     done < "$repo_dir/sources"
 
-    _sh256 "$@"
+    _b3 "$@"
 }
 
 pkg_verify() {
@@ -1145,6 +1180,13 @@ pkg_verify() {
     # Check that the first column (separated by whitespace) match in both
     # checksum files. If any part of either file differs, mismatch. Abort.
     null "$1" || while read -r chk _ || ok "$1"; do
+        equ "${#chk}" 64 && {
+            log "$repo_name" "Detected sha256 checksums." ERROR
+            log "blake3 is the new checksum provider for kiss. Please run"
+            log "'kiss checksum $repo_name' to regenerate the checksums file."
+            return 1
+        }
+
         printf '%s\n%s\n' "- ${chk:-missing}" "+ ${1:-no source}"
 
         equ "$1-${chk:-null}" "$chk-$1" ||
@@ -1378,10 +1420,13 @@ pkg_remove_files() {
     # functions allows us to stop duplicating code.
     while read -r file; do
         case $file in /etc/?*[!/])
-            sh256 "$KISS_ROOT/$file" >/dev/null
-
             read -r sum_pkg <&3 ||:
 
+            case "${#sum_pkg}" in
+                64) sh256 "$KISS_ROOT/$file" >/dev/null ;;
+                66) b3    "$KISS_ROOT/$file" >/dev/null ;;
+            esac
+
             equ "$hash" "$sum_pkg" || {
                 printf 'Skipping %s (modified)\n' "$file"
                 continue
@@ -1413,13 +1458,16 @@ pkg_remove_files() {
 }
 
 pkg_etc() {
-    sh256 "$tar_dir/$_pkg$file" "$KISS_ROOT$file" >/dev/null
+    read -r sum_old <&3 2>/dev/null ||:
+
+    case "${#sum_old}" in
+        64) sh256 "$tar_dir/$_pkg$file" "$KISS_ROOT$file" >/dev/null ;;
+        66) b3    "$tar_dir/$_pkg$file" "$KISS_ROOT$file" >/dev/null ;;
+    esac
 
     sum_new=${hash%%"$newline"*}
     sum_sys=${hash#*"$newline"}
 
-    read -r sum_old <&3 2>/dev/null ||:
-
     # Compare the three checksums to determine what to do.
     case ${sum_old:-null}${sum_sys:-null}${sum_new} in
         # old = Y, sys = X, new = Y
@@ -2040,6 +2088,9 @@ main() {
         command -v llvm-readelf
     )"} || cmd_elf=ldd
 
+    # b3sum is, for now, the only supported blake3 digest utility.
+    cmd_b3=b3sum
+
     # Figure out which sha256 utility is available.
     cmd_sha=${KISS_CHK:-"$(
         command -v openssl   ||
@@ -2047,7 +2098,7 @@ main() {
         command -v sha256    ||
         command -v shasum    ||
         command -v digest
-    )"} || die "No sha256 utility found"
+    )"} || war "No sha256 utility found"
 
     # Figure out which download utility is available.
     cmd_get=${KISS_GET:-"$(