sftp: add users-groups-by-id@openssh.com extension for client

Signed-off-by: Praneeth Sarode <praneethsarode@gmail.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Eshan Kelkar <eshankelkar@galorithm.com>

include/libssh/sftp.h

@@ -79,6 +79,7 @@ typedef struct sftp_status_message_struct* sftp_status_message;
 typedef struct sftp_statvfs_struct* sftp_statvfs_t;
 typedef struct sftp_limits_struct* sftp_limits_t;
 typedef struct sftp_aio_struct* sftp_aio;
+typedef struct sftp_name_id_map_struct *sftp_name_id_map;
 
 struct sftp_session_struct {
     ssh_session session;
@@ -213,6 +214,22 @@ struct sftp_limits_struct {
     uint64_t max_open_handles;    /** maximum number of active handles allowed by server */
 };
 
+/**
+ * @brief SFTP names map structure to store the mapping between ids and names.
+ *
+ * This is mainly for the use of sftp_get_users_groups_by_id() function.
+ */
+struct sftp_name_id_map_struct {
+    /** @brief Count of name-id pairs in the map */
+    uint32_t count;
+
+    /** @brief Array of ids, ids[i] mapped to names[i] */
+    uint32_t *ids;
+
+    /** @brief Array of names, names[i] mapped to ids[i] */
+    char **names;
+};
+
 /**
  * @brief Creates a new sftp session.
  *
@@ -1194,6 +1211,58 @@ LIBSSH_API char *sftp_expand_path(sftp_session sftp, const char *path);
  */
 LIBSSH_API char *sftp_home_directory(sftp_session sftp, const char *username);
 
+/**
+ * @brief Create a new sftp_name_id_map struct.
+ *
+ * @param count         The number of ids/names to store in the map.
+ *
+ * @return              A pointer to the newly allocated sftp_name_id_map
+ * struct.
+ */
+LIBSSH_API sftp_name_id_map sftp_name_id_map_new(uint32_t count);
+
+/**
+ * @brief Free the memory of an allocated `sftp_name_id_map` struct.
+ *
+ * @param  map          A pointer to the `sftp_name_id_map` struct to free.
+ */
+LIBSSH_API void sftp_name_id_map_free(sftp_name_id_map map);
+
+/**
+ * @brief Retrieves usernames and group names based on provided user and group
+ *        IDs.
+ *
+ * The retrieved names are stored in the `names` field of the
+ * `sftp_name_id_map` structure. In case a uid or gid is not found, an empty
+ * string is stored.
+ *
+ * This calls the "users-groups-by-id@openssh.com" extension.
+ * You should check if the extension is supported using:
+ *
+ * @code
+ * int supported = sftp_extension_supported(sftp,
+ * "users-groups-by-id@openssh.com", "1");
+ * @endcode
+ *
+ * @param sftp           The SFTP session handle.
+ *
+ * @param users_map      A pointer to a `sftp_name_id_map` struct with the user
+ *                       IDs. Can be NULL if only group names are needed.
+ *
+ * @param groups_map     A pointer to a `sftp_name_id_map` struct with the group
+ *                       IDs. Can be NULL if only user names are needed.
+ *
+ * @return               0 on success, < 0 on error with ssh and sftp error set.
+ *
+ * @note                 The caller needs to free the memory used for
+ *                       the maps later using `sftp_name_id_map_free()`.
+ *
+ * @see sftp_get_error()
+ */
+LIBSSH_API int sftp_get_users_groups_by_id(sftp_session sftp,
+                                           sftp_name_id_map users_map,
+                                           sftp_name_id_map groups_map);
+
 #ifdef WITH_SERVER
 /**
  * @brief Create a new sftp server session.

src/libssh.map

@@ -481,3 +481,11 @@ LIBSSH_4_10_0    # Released
         ssh_pki_export_privkey_file_format;
         ssh_request_no_more_sessions;
 } LIBSSH_4_9_0;
+
+LIBSSH_AFTER_4_10_0
+{
+    global:
+        sftp_get_users_groups_by_id;
+        sftp_name_id_map_free;
+        sftp_name_id_map_new;
+} LIBSSH_4_10_0;

src/sftp.c

@@ -3305,4 +3305,216 @@ sftp_home_directory(sftp_session sftp, const char *username)
     return NULL;
 }
 
+sftp_name_id_map sftp_name_id_map_new(uint32_t count)
+{
+    sftp_name_id_map map = NULL;
+
+    map = calloc(1, sizeof(struct sftp_name_id_map_struct));
+    if (map == NULL) {
+        return NULL;
+    }
+
+    map->count = count;
+
+    map->ids = calloc(count, sizeof(uint32_t));
+    if (map->ids == NULL) {
+        SAFE_FREE(map);
+        return NULL;
+    }
+
+    map->names = calloc(count, sizeof(char *));
+    if (map->names == NULL) {
+        SAFE_FREE(map->ids);
+        SAFE_FREE(map);
+        return NULL;
+    }
+
+    return map;
+}
+
+void sftp_name_id_map_free(sftp_name_id_map map)
+{
+    if (map == NULL) {
+        return;
+    }
+
+    SAFE_FREE(map->ids);
+
+    if (map->names != NULL) {
+        for (uint32_t i = 0; i < map->count; i++) {
+            SAFE_FREE(map->names[i]);
+        }
+        SAFE_FREE(map->names);
+    }
+
+    SAFE_FREE(map);
+}
+
+static int sftp_buffer_add_ids(ssh_buffer buffer, sftp_name_id_map map)
+{
+    uint32_t id_count = map ? map->count : 0;
+    int rc;
+
+    rc = ssh_buffer_pack(buffer, "d", sizeof(uint32_t) * id_count);
+    if (rc != SSH_OK) {
+        return -1;
+    }
+
+    for (uint32_t i = 0; i < id_count; i++) {
+        rc = ssh_buffer_pack(buffer, "d", map->ids[i]);
+        if (rc != SSH_OK) {
+            return -1;
+        }
+    }
+
+    return 0;
+}
+
+static int sftp_parse_names(ssh_buffer buffer, sftp_name_id_map map)
+{
+    uint32_t name_buf_len = 0;
+    char *name = NULL;
+    uint32_t id_count = map ? map->count : 0;
+    int rc;
+
+    rc = ssh_buffer_unpack(buffer, "d", &name_buf_len);
+    if (rc != SSH_OK) {
+        return -1;
+    }
+
+    for (uint32_t i = 0; i < id_count; i++) {
+        rc = ssh_buffer_unpack(buffer, "s", &name);
+        if (rc != SSH_OK) {
+            return -1;
+        }
+
+        name_buf_len -= strlen(name) + sizeof(uint32_t);
+        map->names[i] = name;
+    }
+
+    if (name_buf_len != 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+int sftp_get_users_groups_by_id(sftp_session sftp,
+                                sftp_name_id_map users_map,
+                                sftp_name_id_map groups_map)
+{
+    sftp_status_message status = NULL;
+    sftp_message msg = NULL;
+    ssh_buffer buffer = NULL;
+    uint32_t id;
+    int rc;
+
+    if (sftp == NULL) {
+        return -1;
+    }
+
+    /* check if the user has provided the correct arguments */
+    if (users_map == NULL && groups_map == NULL) {
+        ssh_set_error(sftp->session,
+                      SSH_FATAL,
+                      "Both users map and groups map cannot be NULL");
+        sftp_set_error(sftp, SSH_FX_FAILURE);
+        return -1;
+    }
+
+    buffer = ssh_buffer_new();
+    if (buffer == NULL) {
+        ssh_set_error_oom(sftp->session);
+        sftp_set_error(sftp, SSH_FX_FAILURE);
+        return -1;
+    }
+
+    id = sftp_get_new_id(sftp);
+
+    rc = ssh_buffer_pack(buffer, "ds", id, "users-groups-by-id@openssh.com");
+    if (rc != SSH_OK) {
+        ssh_set_error_oom(sftp->session);
+        SSH_BUFFER_FREE(buffer);
+        sftp_set_error(sftp, SSH_FX_FAILURE);
+        return -1;
+    }
+
+    /* pack all uids */
+    rc = sftp_buffer_add_ids(buffer, users_map);
+    if (rc != SSH_OK) {
+        ssh_set_error_oom(sftp->session);
+        SSH_BUFFER_FREE(buffer);
+        sftp_set_error(sftp, SSH_FX_FAILURE);
+        return -1;
+    }
+
+    /* pack all gids */
+    rc = sftp_buffer_add_ids(buffer, groups_map);
+    if (rc != SSH_OK) {
+        ssh_set_error_oom(sftp->session);
+        SSH_BUFFER_FREE(buffer);
+        sftp_set_error(sftp, SSH_FX_FAILURE);
+        return -1;
+    }
+
+    rc = sftp_packet_write(sftp, SSH_FXP_EXTENDED, buffer);
+    SSH_BUFFER_FREE(buffer);
+    if (rc < 0) {
+        return -1;
+    }
+
+    rc = sftp_recv_response_msg(sftp, id, true, &msg);
+    if (rc != SSH_OK) {
+        return -1;
+    }
+
+    if (msg->packet_type == SSH_FXP_EXTENDED_REPLY) {
+        rc = sftp_parse_names(msg->payload, users_map);
+        if (rc != SSH_OK) {
+            ssh_set_error(sftp->session,
+                          SSH_ERROR,
+                          "Failed to parse usernames");
+            sftp_set_error(sftp, SSH_FX_FAILURE);
+            sftp_message_free(msg);
+            return -1;
+        }
+
+        rc = sftp_parse_names(msg->payload, groups_map);
+        if (rc != SSH_OK) {
+            ssh_set_error(sftp->session,
+                          SSH_ERROR,
+                          "Failed to parse groupnames");
+            sftp_set_error(sftp, SSH_FX_FAILURE);
+            sftp_message_free(msg);
+            return -1;
+        }
+
+        sftp_message_free(msg);
+        return 0;
+    } else if (msg->packet_type == SSH_FXP_STATUS) {
+        status = parse_status_msg(msg);
+        sftp_message_free(msg);
+        if (status == NULL) {
+            return -1;
+        }
+
+        sftp_set_error(sftp, status->status);
+        ssh_set_error(sftp->session,
+                      SSH_REQUEST_DENIED,
+                      "SFTP server: %s",
+                      status->errormsg);
+        status_msg_free(status);
+    } else {
+        ssh_set_error(sftp->session,
+                      SSH_FATAL,
+                      "Received message %d when attempting to get user and "
+                      "group names by id",
+                      msg->packet_type);
+        sftp_message_free(msg);
+        sftp_set_error(sftp, SSH_FX_BAD_MESSAGE);
+    }
+
+    return -1;
+}
+
 #endif /* WITH_SFTP */