/* $OpenBSD: realpath3.c,v 1.4 2019/07/16 17:48:56 bluhm Exp $ */ /* * Copyright (c) 2003 Constantin S. Svintsoff * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. The names of the authors may not be used to endorse or promote * products derived from this software without specific prior written * permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #include #include #include #include #include #include /* * The OpenBSD 6.4 libc version of realpath(3), preserved to validate * an implementation of realpath(2). * As our kernel realpath(2) is heading towards to POSIX compliance, * some details in this version have changed. */ /* * char *realpath(const char *path, char resolved[PATH_MAX]); * * Find the real name of path, by removing all ".", ".." and symlink * components. Returns (resolved) on success, or (NULL) on failure, * in which case the path which caused trouble is left in (resolved). */ char * realpath3(const char *path, char *resolved) { const char *p; char *q; size_t left_len, resolved_len, next_token_len; unsigned symlinks; int serrno, mem_allocated; ssize_t slen; char left[PATH_MAX], next_token[PATH_MAX], symlink[PATH_MAX]; struct stat sb; if (path == NULL) { errno = EINVAL; return (NULL); } if (path[0] == '\0') { errno = ENOENT; return (NULL); } /* * POSIX demands ENOENT for non existing file. */ if (stat(path, &sb) == -1) return (NULL); /* * POSIX demands ENOTDIR for non directories ending in a "/". */ if (!S_ISDIR(sb.st_mode) && strchr(path, '/') != NULL && path[strlen(path) - 1] == '/') { errno = ENOTDIR; return (NULL); } serrno = errno; if (resolved == NULL) { resolved = malloc(PATH_MAX); if (resolved == NULL) return (NULL); mem_allocated = 1; } else mem_allocated = 0; symlinks = 0; if (path[0] == '/') { resolved[0] = '/'; resolved[1] = '\0'; if (path[1] == '\0') return (resolved); resolved_len = 1; left_len = strlcpy(left, path + 1, sizeof(left)); } else { if (getcwd(resolved, PATH_MAX) == NULL) { if (mem_allocated) free(resolved); else strlcpy(resolved, ".", PATH_MAX); return (NULL); } resolved_len = strlen(resolved); left_len = strlcpy(left, path, sizeof(left)); } if (left_len >= sizeof(left)) { errno = ENAMETOOLONG; goto err; } /* * Iterate over path components in `left'. */ while (left_len != 0) { /* * Extract the next path component and adjust `left' * and its length. */ p = strchr(left, '/'); next_token_len = p ? (size_t) (p - left) : left_len; memcpy(next_token, left, next_token_len); next_token[next_token_len] = '\0'; if (p != NULL) { left_len -= next_token_len + 1; memmove(left, p + 1, left_len + 1); } else { left[0] = '\0'; left_len = 0; } if (resolved[resolved_len - 1] != '/') { if (resolved_len + 1 >= PATH_MAX) { errno = ENAMETOOLONG; goto err; } resolved[resolved_len++] = '/'; resolved[resolved_len] = '\0'; } if (next_token[0] == '\0') continue; else if (strcmp(next_token, ".") == 0) continue; else if (strcmp(next_token, "..") == 0) { /* * Strip the last path component except when we have * single "/" */ if (resolved_len > 1) { resolved[resolved_len - 1] = '\0'; q = strrchr(resolved, '/') + 1; *q = '\0'; resolved_len = q - resolved; } continue; } /* * Append the next path component and readlink() it. If * readlink() fails we still can return successfully if * it exists but isn't a symlink, or if there are no more * path components left. */ resolved_len = strlcat(resolved, next_token, PATH_MAX); if (resolved_len >= PATH_MAX) { errno = ENAMETOOLONG; goto err; } slen = readlink(resolved, symlink, sizeof(symlink)); if (slen < 0) { switch (errno) { case EINVAL: /* not a symlink, continue to next component */ continue; case ENOENT: if (p == NULL) { errno = serrno; return (resolved); } /* FALLTHROUGH */ default: goto err; } } else if (slen == 0) { errno = EINVAL; goto err; } else if (slen == sizeof(symlink)) { errno = ENAMETOOLONG; goto err; } else { if (symlinks++ > SYMLOOP_MAX) { errno = ELOOP; goto err; } symlink[slen] = '\0'; if (symlink[0] == '/') { resolved[1] = 0; resolved_len = 1; } else { /* Strip the last path component. */ q = strrchr(resolved, '/') + 1; *q = '\0'; resolved_len = q - resolved; } /* * If there are any path components left, then * append them to symlink. The result is placed * in `left'. */ if (p != NULL) { if (symlink[slen - 1] != '/') { if (slen + 1 >= sizeof(symlink)) { errno = ENAMETOOLONG; goto err; } symlink[slen] = '/'; symlink[slen + 1] = 0; } left_len = strlcat(symlink, left, sizeof(symlink)); if (left_len >= sizeof(symlink)) { errno = ENAMETOOLONG; goto err; } } left_len = strlcpy(left, symlink, sizeof(left)); } } /* * Remove trailing slash except when the resolved pathname * is a single "/". */ if (resolved_len > 1 && resolved[resolved_len - 1] == '/') resolved[resolved_len - 1] = '\0'; return (resolved); err: if (mem_allocated) free(resolved); return (NULL); }