[Libguestfs] [nbdkit PATCH v3 2/2] plugin: add and use nbdkit_realpath

Introduce a new helper function to resolve a path name, calling nbdkit_error on failure: other than doing what nbdkit_absolute_path does, it also checks that the file exists (and thus avoids errors later on). Apply it where an existing path is required, both in nbdkit itself and in plugins. Related to: https://bugzilla.redhat.com/show_bug.cgi?id=1527334 Signed-off-by: Pino Toscano <ptoscano(a)redhat.com&gt; --- docs/nbdkit-plugin.pod | 17 +++++++++++++++++ include/nbdkit-common.h | 1 + plugins/example2/example2.c | 2 +- plugins/file/file.c | 6 +----- plugins/gzip/gzip.c | 2 +- plugins/split/split.c | 2 +- plugins/vddk/vddk.c | 2 +- plugins/xz/xz.c | 2 +- src/plugins.c | 2 +- src/utils.c | 19 +++++++++++++++++++ 10 files changed, 44 insertions(+), 11 deletions(-) diff --git a/docs/nbdkit-plugin.pod b/docs/nbdkit-plugin.pod index 27a885e..0fb81b8 100644 --- a/docs/nbdkit-plugin.pod +++ b/docs/nbdkit-plugin.pod @@ -285,6 +285,23 @@ C<NULL>. Note that this function does not check that the file exists. The returned string must be freed by the caller. +=head2 C<nbdkit_realpath> + + char *nbdkit_realpath (const char *filename); + +The utility function C<nbdkit_realpath> converts any path to an +absolute path, resolving symlinks. Under the hood it uses the +C<realpath> function, and thus it fails if the path does not exist, +or it is not possible to access to any of the components of the path. + +Note that this function works I<only> when used in the C<.config>, and +C<.config_complete> callbacks. + +If the path resolution was not possible, this calls C<nbdkit_error> +and returns C<NULL>. + +The returned string must be freed by the caller. + =head1 CALLBACKS =head2 C<.name> diff --git a/include/nbdkit-common.h b/include/nbdkit-common.h index 851b890..47d2c47 100644 --- a/include/nbdkit-common.h +++ b/include/nbdkit-common.h @@ -67,6 +67,7 @@ extern void nbdkit_vdebug (const char *msg, va_list args); extern char *nbdkit_absolute_path (const char *path); extern int64_t nbdkit_parse_size (const char *str); extern int nbdkit_read_password (const char *value, char **password); +extern char *nbdkit_realpath (const char *path); #ifdef __cplusplus } diff --git a/plugins/example2/example2.c b/plugins/example2/example2.c index 5bc4f94..a2d6fca 100644 --- a/plugins/example2/example2.c +++ b/plugins/example2/example2.c @@ -78,7 +78,7 @@ example2_config (const char *key, const char *value) { if (strcmp (key, "file") == 0) { /* See FILENAMES AND PATHS in nbdkit-plugin(3). */ - filename = nbdkit_absolute_path (value); + filename = nbdkit_realpath (value); if (!filename) return -1; } diff --git a/plugins/file/file.c b/plugins/file/file.c index f8cb3d3..b6e33de 100644 --- a/plugins/file/file.c +++ b/plugins/file/file.c @@ -65,7 +65,7 @@ file_config (const char *key, const char *value) if (strcmp (key, "file") == 0) { /* See FILENAMES AND PATHS in nbdkit-plugin(3). */ free (filename); - filename = nbdkit_absolute_path (value); + filename = nbdkit_realpath (value); if (!filename) return -1; } @@ -90,10 +90,6 @@ file_config_complete (void) nbdkit_error ("you must supply the file=<FILENAME> parameter after the plugin name on the command line"); return -1; } - if (access (filename, F_OK) < 0) { - nbdkit_error ("access '%s': %m", filename); - return -1; - } return 0; } diff --git a/plugins/gzip/gzip.c b/plugins/gzip/gzip.c index e9dbfdb..09dd629 100644 --- a/plugins/gzip/gzip.c +++ b/plugins/gzip/gzip.c @@ -62,7 +62,7 @@ gzip_config (const char *key, const char *value) { if (strcmp (key, "file") == 0) { /* See FILENAMES AND PATHS in nbdkit-plugin(3). */ - filename = nbdkit_absolute_path (value); + filename = nbdkit_realpath (value); if (!filename) return -1; } diff --git a/plugins/split/split.c b/plugins/split/split.c index 47c366d..bdcdcf7 100644 --- a/plugins/split/split.c +++ b/plugins/split/split.c @@ -76,7 +76,7 @@ split_config (const char *key, const char *value) return -1; } filenames = new_filenames; - filenames[nr_files] = nbdkit_absolute_path (value); + filenames[nr_files] = nbdkit_realpath (value); if (filenames[nr_files] == NULL) return -1; nr_files++; diff --git a/plugins/vddk/vddk.c b/plugins/vddk/vddk.c index 1c15127..8bc1517 100644 --- a/plugins/vddk/vddk.c +++ b/plugins/vddk/vddk.c @@ -153,7 +153,7 @@ vddk_config (const char *key, const char *value) if (strcmp (key, "config") == 0) { /* See FILENAMES AND PATHS in nbdkit-plugin(3). */ free (config); - config = nbdkit_absolute_path (value); + config = nbdkit_realpath (value); if (!config) return -1; } diff --git a/plugins/xz/xz.c b/plugins/xz/xz.c index 437f798..f45e489 100644 --- a/plugins/xz/xz.c +++ b/plugins/xz/xz.c @@ -67,7 +67,7 @@ xz_config (const char *key, const char *value) { if (strcmp (key, "file") == 0) { /* See FILENAMES AND PATHS in nbdkit-plugin(3). */ - filename = nbdkit_absolute_path (value); + filename = nbdkit_realpath (value); if (!filename) return -1; } diff --git a/src/plugins.c b/src/plugins.c index 4ff4b20..23223b3 100644 --- a/src/plugins.c +++ b/src/plugins.c @@ -133,7 +133,7 @@ plugin_dump_fields (struct backend *b) struct backend_plugin *p = container_of (b, struct backend_plugin, backend); char *path; - path = nbdkit_absolute_path (p->filename); + path = nbdkit_realpath (p->filename); printf ("path=%s\n", path); free (path); diff --git a/src/utils.c b/src/utils.c index 63adbf1..9134579 100644 --- a/src/utils.c +++ b/src/utils.c @@ -227,3 +227,22 @@ nbdkit_read_password (const char *value, char **password) return 0; } + +char * +nbdkit_realpath (const char *path) +{ + char *ret; + + if (path == NULL || *path == '\0') { + nbdkit_error ("cannot resolve a null or empty path"); + return NULL; + } + + ret = realpath (path, NULL); + if (ret == NULL) { + nbdkit_error ("realpath(%s): %m", path); + return NULL; + } + + return ret; +} -- 2.14.3