1 file changed, 60 insertions, 11 deletions
diff --git a/source/ui-snapshot.c b/source/ui-snapshot.c
index a9bf858..5f2d69d 100644
--- a/source/ui-snapshot.c
+++ b/source/ui-snapshot.c
@@ -15,6 +15,7 @@
 #include "cgit.h"
 #include "filter.h"
 #include "html.h"
+#include "shared.h"
 #include "ui-shared.h"
 #include "ui-snapshot.h"
 
@@ -61,6 +62,31 @@ static int write_zip_archive(const char *hex, const char *prefix)
 	return write_archive_format("--format=zip", hex, prefix);
 }
 
+static int program_on_path(const char *program)
+{
+	const char *path = getenv("PATH");
+	struct strbuf full = STRBUF_INIT;
+	int found = 0;
+
+	if (!path)
+		return 0;
+	while (!found) {
+		const char *end = strchrnul(path, ':');
+
+		strbuf_reset(&full);
+		strbuf_add(&full, path, end - path);
+		if (!full.len)
+			strbuf_addch(&full, '.');
+		strbuf_addf(&full, "/%s", program);
+		found = !access(full.buf, X_OK);
+		if (!*end)
+			break;
+		path = end + 1;
+	}
+	strbuf_release(&full);
+	return found;
+}
+
 static int write_compressed_tar_archive(const char *hex, const char *prefix, char *argv[])
 {
 	struct cgit_exec_filter filter;
@@ -76,24 +102,28 @@ static int write_compressed_tar_archive(const char *hex, const char *prefix, cha
 static int write_tar_gzip_archive(const char *hex, const char *prefix)
 {
 	char *argv[] = { "gzip", "-n", NULL };
+
 	return write_compressed_tar_archive(hex, prefix, argv);
 }
 
 static int write_tar_bzip2_archive(const char *hex, const char *prefix)
 {
 	char *argv[] = { "bzip2", NULL };
+
 	return write_compressed_tar_archive(hex, prefix, argv);
 }
 
 static int write_tar_lzip_archive(const char *hex, const char *prefix)
 {
 	char *argv[] = { "lzip", NULL };
+
 	return write_compressed_tar_archive(hex, prefix, argv);
 }
 
 static int write_tar_xz_archive(const char *hex, const char *prefix)
 {
 	char *argv[] = { "xz", NULL };
+
 	return write_compressed_tar_archive(hex, prefix, argv);
 }
 
@@ -102,20 +132,21 @@ static int write_tar_zstd_archive(const char *hex, const char *prefix)
 	// Single-threaded like the other compressors, since -T0 would let one
 	// request pin every core.
 	char *argv[] = { "zstd", NULL };
+
 	return write_compressed_tar_archive(hex, prefix, argv);
 }
 
 // ui-shared.c reads entry zero as the tar whose signature stands in for every
 // tar variant, so this order cannot change.
 const struct cgit_snapshot_format cgit_snapshot_formats[] = {
-	{ ".tar",	"application/x-tar",	write_tar_archive	},
-	{ ".tar.gz",	"application/gzip",	write_tar_gzip_archive	},
-	{ ".tar.bz2",	"application/x-bzip2",	write_tar_bzip2_archive	},
-	{ ".tar.lz",	"application/x-lzip",	write_tar_lzip_archive	},
-	{ ".tar.xz",	"application/x-xz",	write_tar_xz_archive	},
-	{ ".tar.zst",	"application/zstd",	write_tar_zstd_archive	},
-	{ ".zip",	"application/zip",	write_zip_archive	},
-	{ NULL }
+	{ ".tar",	"application/x-tar",	write_tar_archive,	NULL	},
+	{ ".tar.gz",	"application/gzip",	write_tar_gzip_archive,	"gzip"	},
+	{ ".tar.bz2",	"application/x-bzip2",	write_tar_bzip2_archive,	"bzip2"	},
+	{ ".tar.lz",	"application/x-lzip",	write_tar_lzip_archive,	"lzip"	},
+	{ ".tar.xz",	"application/x-xz",	write_tar_xz_archive,	"xz"	},
+	{ ".tar.zst",	"application/zstd",	write_tar_zstd_archive,	"zstd"	},
+	{ ".zip",	"application/zip",	write_zip_archive,	NULL	},
+	{ 0 }
 };
 
 // Each tree is read the first time a signature for that format is asked for,
@@ -142,7 +173,10 @@ static int resolves(const char *rev)
 {
 	struct object_id oid;
 
-	return repo_get_oid(the_repository, rev, &oid) == 0;
+	// The name goes no further than this lookup, so a leading dash is
+	// fine here, while the wider syntax is refused as in cgit_valid_rev.
+	return !check_refname_format(rev, REFNAME_ALLOW_ONELEVEL) &&
+		!repo_get_oid(the_repository, rev, &oid);
 }
 
 static const char *ref_from_filename(const struct cgit_repo *repo, const char *filename,
@@ -197,14 +231,23 @@ static int send_snapshot(const struct cgit_snapshot_format *format, const char *
 		return 1;
 	}
 	if (!lookup_commit_reference(the_repository, &oid)) {
-		cgit_print_error_page(400, "Bad Request", "Not a commit reference: %s", hex);
+		cgit_print_error_page(404, "Not Found", "Not a commit: %s", hex);
+		return 1;
+	}
+	// A compressor that cannot run only shows up as a broken pipe once
+	// the tar is under way, so it is looked for while a status can still
+	// say so.
+	if (format->program && !program_on_path(format->program)) {
+		cgit_print_error_page(500, "Internal Server Error", "Unable to run %s", format->program);
 		return 1;
 	}
 	ctx.page.mimetype = xstrdup(format->mimetype);
 	ctx.page.filename = xstrdup(filename);
 	cgit_print_http_headers();
 	init_archivers();
-	format->write_func(hex, prefix);
+	// The archiver reads its arguments as a command line, so it gets the
+	// resolved id and never the name.
+	format->write_func(oid_to_hex(&oid), prefix);
 	return 0;
 }
 
@@ -321,6 +364,12 @@ void cgit_print_snapshot(const char *head, const char *hex, const char *filename
 		return;
 	}
 
+	// The name becomes the prefix of every member of the archive, and a
+	// revision expression such as :/pattern could carry a path in it.
+	if (!hex && dwim && strchr(filename, '/')) {
+		cgit_print_error_page(404, "Not Found", "Not found");
+		return;
+	}
 	if (!hex && dwim) {
 		hex = ref_from_filename(ctx.repo, filename, f);
 		if (!hex) {