Re: [vdr] vdr-1.4.1: bug report and fix: ReadLink with relative targets

-- Patrick Cernko | mailto:errror@errror.org | http://www.errror.org "Hello, Tech Support? How do I set my laser printer to stun?" (anonym) --- vdr-1.4.1.orig/tools.c +++ vdr-1.4.1/tools.c @@ -478,6 +478,99 @@ return -1; } +// BEGIN: taken from coreutils-5.2.1: dir_name() & base_name() functions and helpers +#include <stddef.h> +#include <stdlib.h> +#include <string.h> + +#if FILESYSTEM_ACCEPTS_DRIVE_LETTER_PREFIX +# define FILESYSTEM_PREFIX_LEN(Filename) \ + ((Filename)[0] && (Filename)[1] == ':' ? 2 : 0) +#else +# define FILESYSTEM_PREFIX_LEN(Filename) 0 +#endif + +#if FILESYSTEM_BACKSLASH_IS_FILE_NAME_SEPARATOR +# define ISSLASH(C) ((C) == '/' || (C) == '\') +#else +# define ISSLASH(C) ((C) == '/') +#endif + +/* In general, we can't use the builtin `basename' function if available, + since it has different meanings in different environments. + In some environments the builtin `basename' modifies its argument. + + Return the address of the last file name component of NAME. If + NAME has no file name components because it is all slashes, return + NAME if it is empty, the address of its last slash otherwise. */ + +char * +base_name (char const *name) +{ + char const *base = name + FILESYSTEM_PREFIX_LEN (name); + char const *p; + + for (p = base; *p; p++) + { + if (ISSLASH (*p)) + { + /* Treat multiple adjacent slashes like a single slash. */ + do p++; + while (ISSLASH (*p)); + + /* If the file name ends in slash, use the trailing slash as + the basename if no non-slashes have been found. */ + if (! *p) + { + if (ISSLASH (*base)) + base = p - 1; + break; + } + + /* *P is a non-slash preceded by a slash. */ + base = p; + } + } + + return (char *) base; +} + +/* Return the length of `dirname (PATH)', or zero if PATH is + in the working directory. Works properly even if + there are trailing slashes (by effectively ignoring them). */ +size_t +dir_len (char const *path) +{ + size_t prefix_length = FILESYSTEM_PREFIX_LEN (path); + size_t length; + + /* Strip the basename and any redundant slashes before it. */ + for (length = base_name (path) - path; prefix_length < length; length--) + if (! ISSLASH (path[length - 1])) + return length; + + /* But don't strip the only slash from "/". */ + return prefix_length + ISSLASH (path[prefix_length]); +} + +/* Return the leading directories part of PATH, + allocated with xmalloc. + Works properly even if there are trailing slashes + (by effectively ignoring them). */ +char * +dir_name (char const *path) +{ + size_t length = dir_len (path); + int append_dot = (length == FILESYSTEM_PREFIX_LEN (path)); + char *newpath = (char*) malloc (length + append_dot + 1); + memcpy (newpath, path, length); + if (append_dot) + newpath[length++] = '.'; + newpath[length] = 0; + return newpath; +} +// END: taken from coreutils-5.2.1 + char *ReadLink(const char *FileName) { char RealName[PATH_MAX]; @@ -489,12 +582,26 @@ else // some other error occurred LOG_ERROR_STR(FileName); } - else if (n < int(sizeof(RealName))) { // got it! - RealName[n] = 0; - TargetName = RealName; - } - else - esyslog("ERROR: symlink's target name too long: %s", FileName); + else { + if (RealName[0] != '/') { // relative symlink, we must prepend the path of FileName + char* dirname = dir_name(FileName); + size_t dirnamelen = strlen(dirname); + char linkval[n+1]; + memcpy(linkval, RealName, n); + memcpy(RealName, dirname, dirnamelen); // first prepend the path of FileName + RealName[dirnamelen] = '/'; + memcpy(RealName+dirnamelen+1, linkval, n); // append the gotten n bytes from the link value + n += 1 + dirnamelen; + RealName[n] = 0; + free(dirname); + } + if (n < int(sizeof(RealName))) { // got it! + RealName[n] = 0; + TargetName = RealName; + } + else + esyslog("ERROR: symlink's target name too long: %s", FileName); + } return TargetName ? strdup(TargetName) : NULL; }