Fix Coverity defects (#8579)

Fix Coverity CID355287 and CID355289: technically it is a false-positive but it is easier to put a pattern in the code that they can recognise as a sanitizer. The compiler will remove it during optimization. Fix CID353973: the security condition is unlikely to occur but we can avoid it completely. Fix resource leak from CID 355286 and CID 355288. Fixing new resource leak introduced by a previous commit (CID355449)

aclk/aclk_common.c

@@ -42,7 +42,7 @@ ACLK_PROXY_TYPE aclk_verify_proxy(const char *string)
     if (!string)
         return PROXY_TYPE_UNKNOWN;
 
-    while (*string == 0x20)
+    while (*string == 0x20 && *string!=0)   // Help coverity (compiler will remove)
         string++;
 
     if (!*string)

aclk/aclk_lws_https_client.c

@@ -176,6 +176,7 @@ int aclk_send_https_request(char *method, char *host, char *port, char *url, cha
     context = lws_create_context(&info);
     if (!context) {
         error("Error creating LWS context");
+        freez(data);
         return 1;
     }
 

aclk/agent_cloud_link.c

@@ -146,29 +146,16 @@ int cloud_to_agent_parse(JSON_ENTRY *e)
 static RSA *aclk_private_key = NULL;
 static int create_private_key()
 {
-    char filename[FILENAME_MAX + 1];    struct stat statbuf;
+    char filename[FILENAME_MAX + 1];
     snprintfz(filename, FILENAME_MAX, "%s/claim.d/private.pem", netdata_configured_user_config_dir);
 
-    if (lstat(filename, &statbuf) != 0) {
-        error("Claimed agent cannot establish ACLK - private key not found '%s' failed.", filename);
+    long bytes_read;
+    char *private_key = read_by_filename(filename, &bytes_read);
+    if (!private_key) {
+        error("Claimed agent cannot establish ACLK - unable to load private key '%s' failed.", filename);
         return 1;
     }
-    if (unlikely(statbuf.st_size == 0)) {
-        info("Claimed agent cannot establish ACLK - private key '%s' is empty.", filename);
-        return 1;
-    }
-
-    FILE *f = fopen(filename, "rt");
-    if (unlikely(f == NULL)) {
-        error("Claimed agent cannot establish ACLK - unable to open private key '%s'.", filename);
-        return 1;
-    }
-
-    char *private_key = callocz(1, statbuf.st_size + 1);
-    size_t bytes_read = fread(private_key, 1, statbuf.st_size, f);
-    private_key[bytes_read] = 0;
-    debug(D_ACLK, "Claimed agent loaded private key len=%zu bytes", bytes_read);
-    fclose(f);
+    debug(D_ACLK, "Claimed agent loaded private key len=%ld bytes", bytes_read);
 
     BIO *key_bio = BIO_new_mem_buf(private_key, -1);
     if (key_bio==NULL) {

claim/claim.c

@@ -51,15 +51,7 @@ void claim_agent(char *claiming_arguments)
     char command_buffer[CLAIMING_COMMAND_LENGTH + 1];
     FILE *fp;
 
-    char *cloud_base_hostname = NULL; // Initializers are over-written but prevent gcc complaining about clobbering.
-    char *cloud_base_port = NULL;
     char *cloud_base_url = config_get(CONFIG_SECTION_CLOUD, "cloud base url", DEFAULT_CLOUD_BASE_URL);
-    if( aclk_decode_base_url(cloud_base_url, &cloud_base_hostname, &cloud_base_port))
-    {
-        error("Configuration error - cannot decode \"cloud base url\"");
-        return;
-    }
-
     const char *proxy_str;
     ACLK_PROXY_TYPE proxy_type;
     char proxy_flag[CLAIMING_PROXY_LENGTH] = "-noproxy";
@@ -120,31 +112,14 @@ void load_claiming_state(void)
     }
 
     char filename[FILENAME_MAX + 1];
-    struct stat statbuf;
-
     snprintfz(filename, FILENAME_MAX, "%s/claim.d/claimed_id", netdata_configured_user_config_dir);
 
-    // check if the file exists
-    if (lstat(filename, &statbuf) != 0) {
-        info("lstat on File '%s' failed reason=\"%s\". Setting state to AGENT_UNCLAIMED.", filename, strerror(errno));
-        return;
-    }
-    if (unlikely(statbuf.st_size == 0)) {
-        info("File '%s' has no contents. Setting state to AGENT_UNCLAIMED.", filename);
+    long bytes_read;
+    claimed_id = read_by_filename(filename, &bytes_read);
+    if (!claimed_id) {
+        info("Unable to load '%s', setting state to AGENT_UNCLAIMED", filename);
         return;
     }
 
-    FILE *f = fopen(filename, "rt");
-    if (unlikely(f == NULL)) {
-        error("File '%s' cannot be opened. Setting state to AGENT_UNCLAIMED.", filename);
-        return;
-    }
-
-    claimed_id = callocz(1, statbuf.st_size + 1);
-    size_t bytes_read = fread(claimed_id, 1, statbuf.st_size, f);
-    claimed_id[bytes_read] = 0;
     info("File '%s' was found. Setting state to AGENT_CLAIMED.", filename);
-    fclose(f);
-
-    snprintfz(filename, FILENAME_MAX, "%s/claim.d/private.pem", netdata_configured_user_config_dir);
 }

libnetdata/libnetdata.c

@@ -1453,3 +1453,41 @@ void recursive_config_double_dir_load(const char *user_path, const char *stock_p
     freez(udir);
     freez(sdir);
 }
+
+// Returns the number of bytes read from the file if file_size is not NULL.
+// The actual buffer has an extra byte set to zero (not included in the count).
+char *read_by_filename(char *filename, long *file_size)
+{
+    FILE *f = fopen(filename, "r");
+    if (!f)
+        return NULL;
+    if (fseek(f, 0, SEEK_END) < 0) {
+        fclose(f);
+        return NULL;
+    }
+    long size = ftell(f);
+    if (size <= 0 || fseek(f, 0, SEEK_END) < 0) {
+        fclose(f);
+        return NULL;
+    }
+    char *contents = callocz(size + 1, 1);
+    if (!contents) {
+        fclose(f);
+        return NULL;
+    }
+    if (fseek(f, 0, SEEK_SET) < 0) {
+        fclose(f);
+        freez(contents);
+        return NULL;
+    }
+    size_t res = fread(contents, 1, size, f);
+    if ( res != (size_t)size) {
+        freez(contents);
+        fclose(f);
+        return NULL;
+    }
+    fclose(f);
+    if (file_size)
+        *file_size = size;
+    return contents;
+}

libnetdata/libnetdata.h

@@ -278,6 +278,7 @@ extern void recursive_config_double_dir_load(
         , void *data
         , size_t depth
 );
+extern char *read_by_filename(char *filename, long *file_size);
 
 /* fix for alpine linux */
 #ifndef RUSAGE_THREAD