diff --git a/0001-Merge-pull-request-from-GHSA-gpxc-v2m8-fr3x.patch b/0001-Merge-pull-request-from-GHSA-gpxc-v2m8-fr3x.patch new file mode 100644 index 0000000..7d42aad --- /dev/null +++ b/0001-Merge-pull-request-from-GHSA-gpxc-v2m8-fr3x.patch @@ -0,0 +1,215 @@ +From 8f274035756c04efeb77eb654e9d4c4447287d65 Mon Sep 17 00:00:00 2001 +From: Till Kamppeter +Date: Wed, 17 May 2023 11:12:37 +0200 +Subject: [PATCH] Merge pull request from GHSA-gpxc-v2m8-fr3x + +* beh backend: Use execv() instead of system() - CVE-2023-24805 + +With execv() command line arguments are passed as separate strings and +not the full command line in a single string. This prevents arbitrary +command execution by escaping the quoting of the arguments in a job +with forged job title. + +* beh backend: Extra checks against odd/forged input - CVE-2023-24805 + +- Do not allow '/' in the scheme of the URI (= backend executable + name), to assure that only backends inside /usr/lib/cups/backend/ + are used. + +- Pre-define scheme buffer to empty string, to be defined for case of + uri being NULL. + +- URI must have ':', to split off scheme, otherwise error. + +- Check return value of snprintf() to create call path for backend, to + error out on truncation of a too long scheme or on complete failure + due to a completely odd scheme. + +* beh backend: Further improvements - CVE-2023-24805 + +- Use strncat() instead of strncpy() for getting scheme from URI, the latter + does not require setting terminating zero byte in case of truncation. + +- Also exclude "." or ".." as scheme, as directories are not valid CUPS + backends. + +- Do not use fprintf() in sigterm_handler(), to not interfere with a + fprintf() which could be running in the main process when + sigterm_handler() is triggered. + +- Use "static volatile int" for global variable job_canceled. +--- + backend/beh.c | 109 ++++++++++++++++++++++++++++++++++++++------------ + 1 file changed, 84 insertions(+), 25 deletions(-) + +diff --git a/backend/beh.c b/backend/beh.c +index 7e588c2e3..121e64905 100644 +--- a/backend/beh.c ++++ b/backend/beh.c +@@ -26,13 +26,14 @@ + #include + #include + #include ++#include + + + // + // Local globals... + // + +-static int job_canceled = 0; // Set to 1 on SIGTERM ++static volatile int job_canceled = 0; // Set to 1 on SIGTERM + + + // +@@ -237,21 +238,44 @@ call_backend(char *uri, // I - URI of final destination + char *filename) // I - File name of input data + { + const char *cups_serverbin; // Location of programs ++ char *backend_argv[8]; // Arguments for called CUPS backend + char scheme[1024], // Scheme from URI + *ptr, // Pointer into scheme +- cmdline[65536]; // Backend command line +- int retval; ++ backend_path[2048]; // Backend path ++ int pid, ++ wait_pid, ++ wait_status, ++ retval = 0; ++ int bytes; ++ + + // + // Build the backend command line... + // + +- strncpy(scheme, uri, sizeof(scheme) - 1); +- if (strlen(uri) > 1023) +- scheme[1023] = '\0'; ++ scheme[0] = '\0'; ++ strncat(scheme, uri, sizeof(scheme) - 1); + if ((ptr = strchr(scheme, ':')) != NULL) + *ptr = '\0'; +- ++ else ++ { ++ fprintf(stderr, ++ "ERROR: beh: Invalid URI, no colon (':') to mark end of scheme part.\n"); ++ exit (CUPS_BACKEND_FAILED); ++ } ++ if (strchr(scheme, '/')) ++ { ++ fprintf(stderr, ++ "ERROR: beh: Invalid URI, scheme contains a slash ('/').\n"); ++ exit (CUPS_BACKEND_FAILED); ++ } ++ if (!strcmp(scheme, ".") || !strcmp(scheme, "..")) ++ { ++ fprintf(stderr, ++ "ERROR: beh: Invalid URI, scheme (\"%s\") is a directory.\n", ++ scheme); ++ exit (CUPS_BACKEND_FAILED); ++ } + if ((cups_serverbin = getenv("CUPS_SERVERBIN")) == NULL) + cups_serverbin = CUPS_SERVERBIN; + +@@ -261,16 +285,25 @@ call_backend(char *uri, // I - URI of final destination + "ERROR: beh: Direct output into a file not supported.\n"); + exit (CUPS_BACKEND_FAILED); + } +- else +- snprintf(cmdline, sizeof(cmdline), +- "%s/backend/%s '%s' '%s' '%s' '%s' '%s' %s", +- cups_serverbin, scheme, argv[1], argv[2], argv[3], +- // Apply number of copies only if beh was called with a +- // file name and not with the print data in stdin, as +- // backends should handle copies only if they are called +- // with a file name +- (argc == 6 ? "1" : argv[4]), +- argv[5], filename); ++ ++ backend_argv[0] = uri; ++ backend_argv[1] = argv[1]; ++ backend_argv[2] = argv[2]; ++ backend_argv[3] = argv[3]; ++ backend_argv[4] = (argc == 6 ? "1" : argv[4]); ++ backend_argv[5] = argv[5]; ++ backend_argv[6] = filename; ++ backend_argv[7] = NULL; ++ ++ bytes = snprintf(backend_path, sizeof(backend_path), ++ "%s/backend/%s", cups_serverbin, scheme); ++ if (bytes < 0 || bytes >= sizeof(backend_path)) ++ { ++ fprintf(stderr, ++ "ERROR: beh: Invalid scheme (\"%s\"), could not determing backend path.\n", ++ scheme); ++ exit (CUPS_BACKEND_FAILED); ++ } + + // + // Overwrite the device URI and run the actual backend... +@@ -279,17 +312,41 @@ call_backend(char *uri, // I - URI of final destination + setenv("DEVICE_URI", uri, 1); + + fprintf(stderr, +- "DEBUG: beh: Executing backend command line \"%s\"...\n", +- cmdline); ++ "DEBUG: beh: Executing backend command line \"%s '%s' '%s' '%s' '%s' '%s'%s%s\"...\n", ++ backend_path, backend_argv[1], backend_argv[2], backend_argv[3], ++ backend_argv[4], backend_argv[5], ++ (backend_argv[6] && backend_argv[6][0] ? " " : ""), ++ (backend_argv[6] && backend_argv[6][0] ? backend_argv[6] : "")); + fprintf(stderr, + "DEBUG: beh: Using device URI: %s\n", + uri); + +- retval = system(cmdline) >> 8; ++ if ((pid = fork()) == 0) ++ { ++ retval = execv(backend_path, backend_argv); + +- if (retval == -1) +- fprintf(stderr, "ERROR: Unable to execute backend command line: %s\n", +- strerror(errno)); ++ if (retval == -1) ++ fprintf(stderr, "ERROR: Unable to execute backend: %s\n", ++ strerror(errno)); ++ exit (CUPS_BACKEND_FAILED); ++ } ++ else if (pid < 0) ++ { ++ fprintf(stderr, "ERROR: Unable to fork for backend\n"); ++ return (CUPS_BACKEND_FAILED); ++ } ++ ++ while ((wait_pid = wait(&wait_status)) < 0 && errno == EINTR); ++ ++ if (wait_pid >= 0 && wait_status) ++ { ++ if (WIFEXITED(wait_status)) ++ retval = WEXITSTATUS(wait_status); ++ else if (WTERMSIG(wait_status) != SIGTERM) ++ retval = WTERMSIG(wait_status); ++ else ++ retval = 0; ++ } + + return (retval); + } +@@ -304,8 +361,10 @@ sigterm_handler(int sig) // I - Signal number (unused) + { + (void)sig; + +- fprintf(stderr, +- "DEBUG: beh: Job canceled.\n"); ++ const char * const msg = "DEBUG: beh: Job canceled.\n"; ++ // The if() is to eliminate the return value and silence the warning ++ // about an unused return value. ++ if (write(2, msg, strlen(msg))); + + if (job_canceled) + _exit(CUPS_BACKEND_OK); +-- +2.40.1 + diff --git a/cups-filters.spec b/cups-filters.spec index e998aeb..7358fde 100644 --- a/cups-filters.spec +++ b/cups-filters.spec @@ -15,7 +15,7 @@ Summary: OpenPrinting CUPS filters and backends for CUPS 2.X Name: cups-filters Epoch: 1 Version: 2.0~rc1 -Release: 1%{?dist} +Release: 2%{?dist} # the CUPS exception text is the same as LLVM exception, so using that name with # agreement from legal team @@ -27,6 +27,7 @@ Source0: %{URL}/releases/download/%{upstream_version}/%{name}-%{upstream_version # Patches +Patch0001: 0001-Merge-pull-request-from-GHSA-gpxc-v2m8-fr3x.patch # autogen.sh @@ -176,6 +177,9 @@ make check %changelog +* Wed May 17 2023 Zdenek Dohnal - 1:2.0~rc1-2 +- 2207970 - CVE-2023-24805 cups-filters: remote code execution in cups-filters, beh CUPS backend + * Thu Apr 27 2023 Zdenek Dohnal - 1:2.0~rc1-1 - 2.0rc1