Improve error message when package is missing required signature

When attempting to install a package (either via -S or -U) and the
signature is missing, the current error message "invalid or corrupted
package (PGP signature)" is very unclear.  Instead inform the user
that the package is missing the required signature.

Partial fix for FS#34741.

Signed-off-by: Allan McRae <allan@archlinux.org>

3 files changed, 8 insertions, 1 deletions

diff --git a/lib/libalpm/alpm.h b/lib/libalpm/alpm.h
index 2277a69c..806cd959 100644
--- a/lib/libalpm/alpm.h
+++ b/lib/libalpm/alpm.h
@@ -1267,6 +1267,7 @@ typedef enum _alpm_errno_t {
 	ALPM_ERR_PKG_INVALID,
 	ALPM_ERR_PKG_INVALID_CHECKSUM,
 	ALPM_ERR_PKG_INVALID_SIG,
+	ALPM_ERR_PKG_MISSING_SIG,
 	ALPM_ERR_PKG_OPEN,
 	ALPM_ERR_PKG_CANT_REMOVE,
 	ALPM_ERR_PKG_INVALID_NAME,
diff --git a/lib/libalpm/be_package.c b/lib/libalpm/be_package.c
index cfe5fb36..5a709680 100644
--- a/lib/libalpm/be_package.c
+++ b/lib/libalpm/be_package.c
@@ -323,9 +323,13 @@ int _alpm_pkg_validate_internal(alpm_handle_t *handle,
 	}
 
 	/* even if we don't have a sig, run the check code if level tells us to */
-	if(has_sig || level & ALPM_SIG_PACKAGE) {
+	if(level & ALPM_SIG_PACKAGE) {
 		const char *sig = syncpkg ? syncpkg->base64_sig : NULL;
 		_alpm_log(handle, ALPM_LOG_DEBUG, "sig data: %s\n", sig ? sig : "<from .sig>");
+		if(!has_sig && !(level & ALPM_SIG_PACKAGE_OPTIONAL)) {
+			handle->pm_errno = ALPM_ERR_PKG_MISSING_SIG;
+			return -1;
+		}
 		if(_alpm_check_pgp_helper(handle, pkgfile, sig,
 					level & ALPM_SIG_PACKAGE_OPTIONAL, level & ALPM_SIG_PACKAGE_MARGINAL_OK,
 					level & ALPM_SIG_PACKAGE_UNKNOWN_OK, sigdata)) {
diff --git a/lib/libalpm/error.c b/lib/libalpm/error.c
index a59f4fe1..86221807 100644
--- a/lib/libalpm/error.c
+++ b/lib/libalpm/error.c
@@ -111,6 +111,8 @@ const char SYMEXPORT *alpm_strerror(alpm_errno_t err)
 			return _("invalid or corrupted package (checksum)");
 		case ALPM_ERR_PKG_INVALID_SIG:
 			return _("invalid or corrupted package (PGP signature)");
+		case ALPM_ERR_PKG_MISSING_SIG:
+			return _("package missing required signature");
 		case ALPM_ERR_PKG_OPEN:
 			return _("cannot open package file");
 		case ALPM_ERR_PKG_CANT_REMOVE: