| From bdd058a0e676d2f013027fcfb2b344c313112a50 Mon Sep 17 00:00:00 2001 |
| From: Qualys Security Advisory <qsa@qualys.com> |
| Date: Thu, 1 Jan 1970 00:00:00 +0000 |
| Subject: [PATCH 074/126] proc/readproc.c: Fix bugs and overflows in |
| file2strvec(). |
| |
| Note: this is by far the most important and complex patch of the whole |
| series, please review it carefully; thank you very much! |
| |
| For this patch, we decided to keep the original function's design and |
| skeleton, to avoid regressions and behavior changes, while fixing the |
| various bugs and overflows. And like the "Harden file2str()" patch, this |
| patch does not fail when about to overflow, but truncates instead: there |
| is information available about this process, so return it to the caller; |
| also, we used INT_MAX as a limit, but a lower limit could be used. |
| |
| The easy changes: |
| |
| - Replace sprintf() with snprintf() (and check for truncation). |
| |
| - Replace "if (n == 0 && rbuf == 0)" with "if (n <= 0 && tot <= 0)" and |
| do break instead of return: it simplifies the code (only one place to |
| handle errors), and also guarantees that in the while loop either n or |
| tot is > 0 (or both), even if n is reset to 0 when about to overflow. |
| |
| - Remove the "if (n < 0)" block in the while loop: it is (and was) dead |
| code, since we enter the while loop only if n >= 0. |
| |
| - Rewrite the missing-null-terminator detection: in the original |
| function, if the size of the file is a multiple of 2047, a null- |
| terminator is appended even if the file is already null-terminated. |
| |
| - Replace "if (n <= 0 && !end_of_file)" with "if (n < 0 || tot <= 0)": |
| originally, it was equivalent to "if (n < 0)", but we added "tot <= 0" |
| to handle the first break of the while loop, and to guarantee that in |
| the rest of the function tot is > 0. |
| |
| - Double-force ("belt and suspenders") the null-termination of rbuf: |
| this is (and was) essential to the correctness of the function. |
| |
| - Replace the final "while" loop with a "for" loop that behaves just |
| like the preceding "for" loop: in the original function, this would |
| lead to unexpected results (for example, if rbuf is |\0|A|\0|, this |
| would return the array {"",NULL} but should return {"","A",NULL}; and |
| if rbuf is |A|\0|B| (should never happen because rbuf should be null- |
| terminated), this would make room for two pointers in ret, but would |
| write three pointers to ret). |
| |
| The hard changes: |
| |
| - Prevent the integer overflow of tot in the while loop, but unlike |
| file2str(), file2strvec() cannot let tot grow until it almost reaches |
| INT_MAX, because it needs more space for the pointers: this is why we |
| introduced ARG_LEN, which also guarantees that we can add "align" and |
| a few sizeof(char*)s to tot without overflowing. |
| |
| - Prevent the integer overflow of "tot + c + align": when INT_MAX is |
| (almost) reached, we write the maximal safe amount of pointers to ret |
| (ARG_LEN guarantees that there is always space for *ret = rbuf and the |
| NULL terminator). |
| [carnil: backport for 3.3.9: Add include for limits.h and use of MAX_INT] |
| |
| CVE: CVE-2018-1124 |
| Upstream-Status: Backport [https://gitlab.com/procps-ng/procps/commit/36c350f07c75aabf747fb833f52a234ae5781b20] |
| |
| Signed-off-by: Jagadeesh Krishnanjanappa <jkrishnanjanappa@mvista.com> |
| --- |
| proc/readproc.c | 53 ++++++++++++++++++++++++++++++++--------------------- |
| 1 file changed, 32 insertions(+), 21 deletions(-) |
| |
| diff -Naurp procps-ng-3.3.12_org/proc/readproc.c procps-ng-3.3.12/proc/readproc.c |
| --- procps-ng-3.3.12_org/proc/readproc.c 2016-07-09 14:49:25.825306872 -0700 |
| +++ procps-ng-3.3.12/proc/readproc.c 2018-07-24 00:46:49.366202531 -0700 |
| @@ -37,6 +37,7 @@ |
| #include <dirent.h> |
| #include <sys/types.h> |
| #include <sys/stat.h> |
| +#include <limits.h> |
| #ifdef WITH_SYSTEMD |
| #include <systemd/sd-login.h> |
| #endif |
| --- a/proc/readproc.c |
| +++ b/proc/readproc.c |
| @@ -600,11 +601,12 @@ static int file2str(const char *director |
| |
| static char** file2strvec(const char* directory, const char* what) { |
| char buf[2048]; /* read buf bytes at a time */ |
| - char *p, *rbuf = 0, *endbuf, **q, **ret; |
| + char *p, *rbuf = 0, *endbuf, **q, **ret, *strp; |
| int fd, tot = 0, n, c, end_of_file = 0; |
| int align; |
| |
| - sprintf(buf, "%s/%s", directory, what); |
| + const int len = snprintf(buf, sizeof buf, "%s/%s", directory, what); |
| + if(len <= 0 || (size_t)len >= sizeof buf) return NULL; |
| fd = open(buf, O_RDONLY, 0); |
| if(fd==-1) return NULL; |
| |
| @@ -612,18 +614,23 @@ static char** file2strvec(const char* di |
| while ((n = read(fd, buf, sizeof buf - 1)) >= 0) { |
| if (n < (int)(sizeof buf - 1)) |
| end_of_file = 1; |
| - if (n == 0 && rbuf == 0) { |
| - close(fd); |
| - return NULL; /* process died between our open and read */ |
| + if (n <= 0 && tot <= 0) { /* nothing read now, nothing read before */ |
| + break; /* process died between our open and read */ |
| } |
| - if (n < 0) { |
| - if (rbuf) |
| - free(rbuf); |
| - close(fd); |
| - return NULL; /* read error */ |
| + /* ARG_LEN is our guesstimated median length of a command-line argument |
| + or environment variable (the minimum is 1, the maximum is 131072) */ |
| + #define ARG_LEN 64 |
| + if (tot >= INT_MAX / (ARG_LEN + (int)sizeof(char*)) * ARG_LEN - n) { |
| + end_of_file = 1; /* integer overflow: null-terminate and break */ |
| + n = 0; /* but tot > 0 */ |
| } |
| - if (end_of_file && (n == 0 || buf[n-1]))/* last read char not null */ |
| + #undef ARG_LEN |
| + if (end_of_file && |
| + ((n > 0 && buf[n-1] != '\0') || /* last read char not null */ |
| + (n <= 0 && rbuf[tot-1] != '\0'))) /* last read char not null */ |
| buf[n++] = '\0'; /* so append null-terminator */ |
| + |
| + if (n <= 0) break; /* unneeded (end_of_file = 1) but avoid realloc */ |
| rbuf = xrealloc(rbuf, tot + n); /* allocate more memory */ |
| memcpy(rbuf + tot, buf, n); /* copy buffer into it */ |
| tot += n; /* increment total byte ctr */ |
| @@ -631,29 +638,34 @@ static char** file2strvec(const char* di |
| break; |
| } |
| close(fd); |
| - if (n <= 0 && !end_of_file) { |
| + if (n < 0 || tot <= 0) { /* error, or nothing read */ |
| if (rbuf) free(rbuf); |
| return NULL; /* read error */ |
| } |
| + rbuf[tot-1] = '\0'; /* belt and suspenders (the while loop did it, too) */ |
| endbuf = rbuf + tot; /* count space for pointers */ |
| align = (sizeof(char*)-1) - ((tot + sizeof(char*)-1) & (sizeof(char*)-1)); |
| - for (c = 0, p = rbuf; p < endbuf; p++) { |
| - if (!*p || *p == '\n') |
| + c = sizeof(char*); /* one extra for NULL term */ |
| + for (p = rbuf; p < endbuf; p++) { |
| + if (!*p || *p == '\n') { |
| + if (c >= INT_MAX - (tot + (int)sizeof(char*) + align)) break; |
| c += sizeof(char*); |
| + } |
| if (*p == '\n') |
| *p = 0; |
| } |
| - c += sizeof(char*); /* one extra for NULL term */ |
| |
| rbuf = xrealloc(rbuf, tot + c + align); /* make room for ptrs AT END */ |
| endbuf = rbuf + tot; /* addr just past data buf */ |
| q = ret = (char**) (endbuf+align); /* ==> free(*ret) to dealloc */ |
| - *q++ = p = rbuf; /* point ptrs to the strings */ |
| - endbuf--; /* do not traverse final NUL */ |
| - while (++p < endbuf) |
| - if (!*p) /* NUL char implies that */ |
| - *q++ = p+1; /* next string -> next char */ |
| - |
| + for (strp = p = rbuf; p < endbuf; p++) { |
| + if (!*p) { /* NUL char implies that */ |
| + if (c < 2 * (int)sizeof(char*)) break; |
| + c -= sizeof(char*); |
| + *q++ = strp; /* point ptrs to the strings */ |
| + strp = p+1; /* next string -> next char */ |
| + } |
| + } |
| *q = 0; /* null ptr list terminator */ |
| return ret; |
| } |