Rewrite internal function app_uninstall_remove_early_rules()

[Issue#]       SSDWSSP-372
[Bug]          Old code prone to errors, with implementation problems.
[Cause]        Fragile file parsing. Using temporary file. Unneeded semaphore, with wrong permissions.
[Solution]     Write more robust function, copying the file in place.
[Verification] Run libprivilege-control-tests.

Change-Id: I12f89f1c1c0c4bc43ffbb69db84cfb88b98c821b

diff --git a/include/common.h b/include/common.h
index b3de866..a0a8a76 100644 (file)
--- a/include/common.h
+++ b/include/common.h
@@ -26,7 +26,6 @@
 #include <dlog.h>
 #include <fts.h>
 #include <stdbool.h>
-#include <semaphore.h>
 
 #ifdef LOG_TAG
     #undef LOG_TAG
@@ -88,17 +87,9 @@ void fts_closep(FTS **f);
 #define AUTO_FTS_CLOSE  __attribute__ ((cleanup(fts_closep)))   = NULL
 
 #define SMACK_RULES_DIR          "/opt/etc/smack-app/accesses.d/"
-
-/*
- * TODO It should be a directory (/opt/etc/smack-app-early/accesses.d/) containing
- * rules to be loaded for each privilege. In the beginning there will be only
- * one file for all WRT apps.
- */
-#define SMACK_STARTUP_RULES_FILE "/opt/etc/smack-app-early/accesses.d/WRT"
+#define SMACK_STARTUP_RULES_FILE "/opt/etc/smack-app-early/accesses.d/rules"
 #define SMACK_LOADED_APP_RULES   "/var/run/smack-app/"
 
-#define PRIVILEGE_CONTROL_UNINSTALL_SEM "privilege-control-app-uninstall-semaphore"
-
 int smack_label_is_valid(const char* smack_label);
 
 int load_smack_from_file(const char* app_id, struct smack_accesses** smack, int *fd, char** path);

diff --git a/src/privilege-control.c b/src/privilege-control.c
index c1a515d..bd990b1 100644 (file)
--- a/src/privilege-control.c
+++ b/src/privilege-control.c
@@ -38,6 +38,7 @@
 #include <sys/smack.h>
 #include <linux/capability.h>
 #include <sys/capability.h>
+#include <sys/mman.h>
 #include <stdbool.h>
 #include <search.h>
 #include <iri.h>
@@ -1507,115 +1508,85 @@ int smack_get_access_new(const char* subject, const char* object, char** label)
 
 static int app_uninstall_remove_early_rules(const char *app_id)
 {
-       C_LOGD("Enter function: %s", __func__);
+       C_LOGD("Enter function: %s(%s)", __func__, app_id);
 
-       int ret = PC_OPERATION_SUCCESS;
-       FILE *file AUTO_FCLOSE;
-       FILE *file_new AUTO_FCLOSE;
-       char *tmp_filename AUTO_FREE;
-       char *single_line_format AUTO_FREE;
+       int ret;
+       int fd AUTO_CLOSE;
+       int size;
+       char tmp;
+       char *data, *data_end;
+       char *line_begin, *line_end, *write_pos;
        char subject[SMACK_LABEL_LEN + 1];
        char object[SMACK_LABEL_LEN + 1];
-       char rule_add[6];    // "rwxat" + '\0'
-       char rule_remove[6]; // "rwxat" + '\0'
-       sem_t *sem = NULL;
-
-       subject[SMACK_LABEL_LEN] = '\0';
-       object[SMACK_LABEL_LEN] = '\0';
-       rule_add[5] = '\0';
-       rule_remove[5] = '\0';
-
-       // Creating (opening) and waiting for semaphore
-       sem = sem_open(PRIVILEGE_CONTROL_UNINSTALL_SEM, O_CREAT, S_IRWXU | S_IRWXU | S_IRWXO, 1);
-       if (sem == SEM_FAILED) {
-               C_LOGE("sem_open failed, error: %s", strerror(errno));
-               ret = PC_ERR_INVALID_OPERATION;
-               goto out;
-       }
-       C_LOGD("Waiting for semaphore");
-       ret = sem_wait(sem);
-       if (ret < 0) {
-               C_LOGE("sem_wait failed, error: %s", strerror(errno));
-               ret = PC_ERR_INVALID_OPERATION;
-               goto out;
-       }
 
-       ret = asprintf(&single_line_format, "%%%ds %%%ds %%5s %%5s\\n", SMACK_LABEL_LEN, SMACK_LABEL_LEN);
-       if (ret < 0) {
-               C_LOGE("asprintf failed");
-               ret = PC_ERR_MEM_OPERATION;
-               goto out;
+       fd = open(SMACK_STARTUP_RULES_FILE, O_RDWR);
+       if (fd < 0) {
+               C_LOGE("Unable to open file %s: %s", SMACK_STARTUP_RULES_FILE, strerror(errno));
+               return PC_ERR_FILE_OPERATION;
        }
 
-       ret = asprintf(&tmp_filename, "%s.tmp", SMACK_STARTUP_RULES_FILE);
-       if (ret < 0) {
-               C_LOGE("asprintf failed");
-               ret = PC_ERR_MEM_OPERATION;
-               goto out;
+       if (flock(fd, LOCK_EX)) {
+               C_LOGE("flock failed, error %s", strerror(errno));
+               return PC_ERR_FILE_OPERATION;
        }
 
-       file = fopen(SMACK_STARTUP_RULES_FILE, "r");
-       if (NULL == file) {
-               C_LOGE("fopen failed on %s", SMACK_STARTUP_RULES_FILE);
-               ret = PC_ERR_FILE_OPERATION;
-               goto out;
+       size = lseek(fd, 0, SEEK_END);
+       if (size < 0) {
+               C_LOGE("Unable to read file %s: %s", SMACK_STARTUP_RULES_FILE, strerror(errno));
+               return PC_ERR_FILE_OPERATION;
        }
 
-       file_new = fopen(tmp_filename, "w");
-       if (NULL == file) {
-               C_LOGE("fopen failed on %s", tmp_filename);
-               ret = PC_ERR_FILE_OPERATION;
-               goto out;
+       if (size == 0)
+               return PC_OPERATION_SUCCESS;
+
+       data = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+       if (data == MAP_FAILED) {
+               C_LOGE("Unable to read file %s: %s", SMACK_STARTUP_RULES_FILE, strerror(errno));
+               return PC_ERR_FILE_OPERATION;
        }
+       data_end = data + size;
+
+       line_begin = write_pos = data;
+       while (line_begin < data_end) {
+               line_end = memchr(line_begin, '\n', data_end - line_begin);
+               if (line_end == NULL)
+                       line_end = data_end - 1;
 
-       while (fscanf(file, single_line_format, subject, object, rule_add, rule_remove) == 4) {
-               C_LOGD("Checking line \"%s %s %s %s\"", subject, object, rule_add, rule_remove);
+               tmp = *line_end;
+               *line_end = '\0';
+               C_LOGD("Considering early rule: %s", line_begin);
 
-               if ((strncmp(subject, app_id, SMACK_LABEL_LEN) == 0) || (strncmp(object, app_id, SMACK_LABEL_LEN) == 0)) {
-                       C_LOGD("app_id found - rule will be ignored");
-                       continue; // do not re-write this rule for new file
+               ret = sscanf(line_begin, "%" TOSTRING(SMACK_LABEL_LEN) "s %" TOSTRING(SMACK_LABEL_LEN) "s", subject, object);
+               if (ret != 2) {
+                       C_LOGD("Rule format is invalid, skipping it.");
+                       goto loop_next;
                }
 
-               if (0 > fprintf(file_new, "%s %s %s %s\n", subject, object, rule_add, rule_remove)) { // re-writing rule to new file
-                       C_LOGE("Write rule \"%s %s %s %s\" to file failed. %s", subject, object, rule_add, rule_remove, strerror(errno));
-                       // Should we return with error here?
-                       ret = PC_ERR_FILE_OPERATION;
-                       goto out;
+               if (!strcmp(subject, app_id) || !strcmp(object, app_id)) {
+                       C_LOGD("Rule belongs to an app being removed, skipping it.");
+                       goto loop_next;
                }
-       }
 
-       fclose(file);
-       file = NULL;
-       fclose(file_new);
-       file_new = NULL;
+               C_LOGD("Rule still needed, keeping it.");
+               *line_end = tmp;
+               if (write_pos != line_begin)
+                       memcpy(write_pos, line_begin, line_end - line_begin + 1);
+               write_pos += (line_end - line_begin + 1);
 
-       if (unlink(SMACK_STARTUP_RULES_FILE)) {
-               C_LOGE("unlink failed %s", strerror(errno));
-               ret = PC_ERR_FILE_OPERATION;
-               goto out;
+       loop_next:
+               *line_end = tmp;
+               line_begin = line_end + 1;
        }
 
-       if (rename(tmp_filename, SMACK_STARTUP_RULES_FILE)) {
-               C_LOGE("rename failed. %s", strerror(errno));
-               ret = PC_ERR_FILE_OPERATION;
-               goto out;
-       }
+       munmap(data, size);
+       ret = ftruncate(fd, write_pos - data);
+       if (ret < 0) {
+               C_LOGE("Unable to truncate file %s to %d bytes: %s", SMACK_STARTUP_RULES_FILE, write_pos, strerror(errno));
 
-       if (chmod(SMACK_STARTUP_RULES_FILE, 644)) {
-               C_LOGE("chmod failed on %s file. Error: %s", tmp_filename, strerror(errno));
-               ret = PC_ERR_FILE_OPERATION;
-               goto out;
+               return PC_ERR_FILE_OPERATION;
        }
 
-       ret = PC_OPERATION_SUCCESS;
-
-out:
-
-       if (sem)
-               sem_post(sem);
-       // Should we check unlink?
-       sem_unlink(PRIVILEGE_CONTROL_UNINSTALL_SEM);
-       return ret;
+       return PC_OPERATION_SUCCESS;
 }
 
 API int app_label_shared_dir(const char* app_label, const char* shared_label, const char* path)//deprecated