From d74b1fd54fdbc45966d12ea907dece11e072fb2b Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Thu, 1 Dec 2022 15:45:44 +0100 Subject: attr: fix silently splitting up lines longer than 2048 bytes When reading attributes from a file we use fgets(3P) with a buffer size of 2048 bytes. This means that as soon as a line exceeds the buffer size we split it up into multiple parts and parse each of them as a separate pattern line. This is of course not what the user intended, and even worse the behaviour is inconsistent with how we read attributes from the index. Fix this bug by converting the code to use `strbuf_getline()` instead. This will indeed read in the whole line, which may theoretically lead to an out-of-memory situation when the gitattributes file is huge. We're about to reject any gitattributes files larger than 100MB in the next commit though, which makes this less of a concern. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano --- t/t0003-attributes.sh | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 't') diff --git a/t/t0003-attributes.sh b/t/t0003-attributes.sh index b660593c20..416386ce2f 100755 --- a/t/t0003-attributes.sh +++ b/t/t0003-attributes.sh @@ -339,4 +339,25 @@ test_expect_success 'query binary macro directly' ' test_cmp expect actual ' +test_expect_success 'large attributes line ignores trailing content in tree' ' + test_when_finished "rm .gitattributes" && + # older versions of Git broke lines at 2048 bytes; the 2045 bytes + # of 0-padding here is accounting for the three bytes of "a 1", which + # would knock "trailing" to the "next" line, where it would be + # erroneously parsed. + printf "a %02045dtrailing attribute\n" 1 >.gitattributes && + git check-attr --all trailing >actual 2>err && + test_must_be_empty err && + test_must_be_empty actual +' + +test_expect_success 'large attributes line ignores trailing content in index' ' + test_when_finished "git update-index --remove .gitattributes" && + blob=$(printf "a %02045dtrailing attribute\n" 1 | git hash-object -w --stdin) && + git update-index --add --cacheinfo 100644,$blob,.gitattributes && + git check-attr --cached --all trailing >actual 2>err && + test_must_be_empty err && + test_must_be_empty actual +' + test_done -- cgit v1.3 From dfa6b32b5e599d97448337ed4fc18dd50c90758f Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Thu, 1 Dec 2022 15:45:48 +0100 Subject: attr: ignore attribute lines exceeding 2048 bytes There are two different code paths to read gitattributes: once via a file, and once via the index. These two paths used to behave differently because when reading attributes from a file, we used fgets(3P) with a buffer size of 2kB. Consequentially, we silently truncate line lengths when lines are longer than that and will then parse the remainder of the line as a new pattern. It goes without saying that this is entirely unexpected, but it's even worse that the behaviour depends on how the gitattributes are parsed. While this is simply wrong, the silent truncation saves us with the recently discovered vulnerabilities that can cause out-of-bound writes or reads with unreasonably long lines due to integer overflows. As the common path is to read gitattributes via the worktree file instead of via the index, we can assume that any gitattributes file that had lines longer than that is already broken anyway. So instead of lifting the limit here, we can double down on it to fix the vulnerabilities. Introduce an explicit line length limit of 2kB that is shared across all paths that read attributes and ignore any line that hits this limit while printing a warning. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano --- attr.c | 5 +++++ attr.h | 6 ++++++ t/t0003-attributes.sh | 25 +++++++++++++++++++++++-- 3 files changed, 34 insertions(+), 2 deletions(-) (limited to 't') diff --git a/attr.c b/attr.c index 41657479ff..38ecd2fff3 100644 --- a/attr.c +++ b/attr.c @@ -344,6 +344,11 @@ static struct match_attr *parse_attr_line(const char *line, const char *src, return NULL; name = cp; + if (strlen(line) >= ATTR_MAX_LINE_LENGTH) { + warning(_("ignoring overly long attributes line %d"), lineno); + return NULL; + } + if (*cp == '"' && !unquote_c_style(&pattern, name, &states)) { name = pattern.buf; namelen = pattern.len; diff --git a/attr.h b/attr.h index 404548f028..df9a75da55 100644 --- a/attr.h +++ b/attr.h @@ -107,6 +107,12 @@ * - Free the `attr_check` struct by calling `attr_check_free()`. */ +/** + * The maximum line length for a gitattributes file. If the line exceeds this + * length we will ignore it. + */ +#define ATTR_MAX_LINE_LENGTH 2048 + struct index_state; /** diff --git a/t/t0003-attributes.sh b/t/t0003-attributes.sh index 416386ce2f..7d68e6a56e 100755 --- a/t/t0003-attributes.sh +++ b/t/t0003-attributes.sh @@ -339,6 +339,15 @@ test_expect_success 'query binary macro directly' ' test_cmp expect actual ' +test_expect_success 'large attributes line ignored in tree' ' + test_when_finished "rm .gitattributes" && + printf "path %02043d" 1 >.gitattributes && + git check-attr --all path >actual 2>err && + echo "warning: ignoring overly long attributes line 1" >expect && + test_cmp expect err && + test_must_be_empty actual +' + test_expect_success 'large attributes line ignores trailing content in tree' ' test_when_finished "rm .gitattributes" && # older versions of Git broke lines at 2048 bytes; the 2045 bytes @@ -347,7 +356,18 @@ test_expect_success 'large attributes line ignores trailing content in tree' ' # erroneously parsed. printf "a %02045dtrailing attribute\n" 1 >.gitattributes && git check-attr --all trailing >actual 2>err && - test_must_be_empty err && + echo "warning: ignoring overly long attributes line 1" >expect && + test_cmp expect err && + test_must_be_empty actual +' + +test_expect_success 'large attributes line ignored in index' ' + test_when_finished "git update-index --remove .gitattributes" && + blob=$(printf "path %02043d" 1 | git hash-object -w --stdin) && + git update-index --add --cacheinfo 100644,$blob,.gitattributes && + git check-attr --cached --all path >actual 2>err && + echo "warning: ignoring overly long attributes line 1" >expect && + test_cmp expect err && test_must_be_empty actual ' @@ -356,7 +376,8 @@ test_expect_success 'large attributes line ignores trailing content in index' ' blob=$(printf "a %02045dtrailing attribute\n" 1 | git hash-object -w --stdin) && git update-index --add --cacheinfo 100644,$blob,.gitattributes && git check-attr --cached --all trailing >actual 2>err && - test_must_be_empty err && + echo "warning: ignoring overly long attributes line 1" >expect && + test_cmp expect err && test_must_be_empty actual ' -- cgit v1.3 From 3c50032ff5289cc45659f21949c8d09e52164579 Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Thu, 1 Dec 2022 15:45:53 +0100 Subject: attr: ignore overly large gitattributes files Similar as with the preceding commit, start ignoring gitattributes files that are overly large to protect us against out-of-bounds reads and writes caused by integer overflows. Unfortunately, we cannot just define "overly large" in terms of any preexisting limits in the codebase. Instead, we choose a very conservative limit of 100MB. This is plenty of room for specifying gitattributes, and incidentally it is also the limit for blob sizes for GitHub. While we don't want GitHub to dictate limits here, it is still sensible to use this fact for an informed decision given that it is hosting a huge set of repositories. Furthermore, over at GitLab we scanned a subset of repositories for their root-level attribute files. We found that 80% of them have a gitattributes file smaller than 100kB, 99.99% have one smaller than 1MB, and only a single repository had one that was almost 3MB in size. So enforcing a limit of 100MB seems to give us ample of headroom. With this limit in place we can be reasonably sure that there is no easy way to exploit the gitattributes file via integer overflows anymore. Furthermore, it protects us against resource exhaustion caused by allocating the in-memory data structures required to represent the parsed attributes. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano --- attr.c | 24 ++++++++++++++++++++++-- attr.h | 6 ++++++ t/t0003-attributes.sh | 17 +++++++++++++++++ 3 files changed, 45 insertions(+), 2 deletions(-) (limited to 't') diff --git a/attr.c b/attr.c index 38ecd2fff3..f9316d14ba 100644 --- a/attr.c +++ b/attr.c @@ -708,10 +708,25 @@ static struct attr_stack *read_attr_from_file(const char *path, int macro_ok) FILE *fp = fopen_or_warn(path, "r"); struct attr_stack *res; int lineno = 0; + int fd; + struct stat st; if (!fp) return NULL; - res = xcalloc(1, sizeof(*res)); + + fd = fileno(fp); + if (fstat(fd, &st)) { + warning_errno(_("cannot fstat gitattributes file '%s'"), path); + fclose(fp); + return NULL; + } + if (st.st_size >= ATTR_MAX_FILE_SIZE) { + warning(_("ignoring overly large gitattributes file '%s'"), path); + fclose(fp); + return NULL; + } + + CALLOC_ARRAY(res, 1); while (strbuf_getline(&buf, fp) != EOF) { if (!lineno && starts_with(buf.buf, utf8_bom)) strbuf_remove(&buf, 0, strlen(utf8_bom)); @@ -730,13 +745,18 @@ static struct attr_stack *read_attr_from_index(const struct index_state *istate, struct attr_stack *res; char *buf, *sp; int lineno = 0; + size_t size; if (!istate) return NULL; - buf = read_blob_data_from_index(istate, path, NULL); + buf = read_blob_data_from_index(istate, path, &size); if (!buf) return NULL; + if (size >= ATTR_MAX_FILE_SIZE) { + warning(_("ignoring overly large gitattributes blob '%s'"), path); + return NULL; + } res = xcalloc(1, sizeof(*res)); for (sp = buf; *sp; ) { diff --git a/attr.h b/attr.h index df9a75da55..5970f930fd 100644 --- a/attr.h +++ b/attr.h @@ -113,6 +113,12 @@ */ #define ATTR_MAX_LINE_LENGTH 2048 + /** + * The maximum size of the giattributes file. If the file exceeds this size we + * will ignore it. + */ +#define ATTR_MAX_FILE_SIZE (100 * 1024 * 1024) + struct index_state; /** diff --git a/t/t0003-attributes.sh b/t/t0003-attributes.sh index 7d68e6a56e..9d9aa2855d 100755 --- a/t/t0003-attributes.sh +++ b/t/t0003-attributes.sh @@ -361,6 +361,14 @@ test_expect_success 'large attributes line ignores trailing content in tree' ' test_must_be_empty actual ' +test_expect_success EXPENSIVE 'large attributes file ignored in tree' ' + test_when_finished "rm .gitattributes" && + dd if=/dev/zero of=.gitattributes bs=101M count=1 2>/dev/null && + git check-attr --all path >/dev/null 2>err && + echo "warning: ignoring overly large gitattributes file ${SQ}.gitattributes${SQ}" >expect && + test_cmp expect err +' + test_expect_success 'large attributes line ignored in index' ' test_when_finished "git update-index --remove .gitattributes" && blob=$(printf "path %02043d" 1 | git hash-object -w --stdin) && @@ -381,4 +389,13 @@ test_expect_success 'large attributes line ignores trailing content in index' ' test_must_be_empty actual ' +test_expect_success EXPENSIVE 'large attributes file ignored in index' ' + test_when_finished "git update-index --remove .gitattributes" && + blob=$(dd if=/dev/zero bs=101M count=1 2>/dev/null | git hash-object -w --stdin) && + git update-index --add --cacheinfo 100644,$blob,.gitattributes && + git check-attr --cached --all path >/dev/null 2>err && + echo "warning: ignoring overly large gitattributes blob ${SQ}.gitattributes${SQ}" >expect && + test_cmp expect err +' + test_done -- cgit v1.3 From a244dc5b0a629290881641467c7a545de7508ab2 Mon Sep 17 00:00:00 2001 From: Carlo Marcelo Arenas Belón Date: Tue, 2 Nov 2021 15:46:06 +0000 Subject: test-lib: add prerequisite for 64-bit platforms MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Allow tests that assume a 64-bit `size_t` to be skipped in 32-bit platforms and regardless of the size of `long`. This imitates the `LONG_IS_64BIT` prerequisite. Signed-off-by: Carlo Marcelo Arenas Belón Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- t/test-lib.sh | 4 ++++ 1 file changed, 4 insertions(+) (limited to 't') diff --git a/t/test-lib.sh b/t/test-lib.sh index 9fa7c1d0f6..7d6e0f89d1 100644 --- a/t/test-lib.sh +++ b/t/test-lib.sh @@ -1686,6 +1686,10 @@ build_option () { sed -ne "s/^$1: //p" } +test_lazy_prereq SIZE_T_IS_64BIT ' + test 8 -eq "$(build_option sizeof-size_t)" +' + test_lazy_prereq LONG_IS_64BIT ' test 8 -le "$(build_option sizeof-long)" ' -- cgit v1.3 From 81dc898df9b4b4035534a927f3234a3839b698bf Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Thu, 1 Dec 2022 15:46:25 +0100 Subject: pretty: fix out-of-bounds write caused by integer overflow When using a padding specifier in the pretty format passed to git-log(1) we need to calculate the string length in several places. These string lengths are stored in `int`s though, which means that these can easily overflow when the input lengths exceeds 2GB. This can ultimately lead to an out-of-bounds write when these are used in a call to memcpy(3P): ==8340==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x7f1ec62f97fe at pc 0x7f2127e5f427 bp 0x7ffd3bd63de0 sp 0x7ffd3bd63588 WRITE of size 1 at 0x7f1ec62f97fe thread T0 #0 0x7f2127e5f426 in __interceptor_memcpy /usr/src/debug/gcc/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:827 #1 0x5628e96aa605 in format_and_pad_commit pretty.c:1762 #2 0x5628e96aa7f4 in format_commit_item pretty.c:1801 #3 0x5628e97cdb24 in strbuf_expand strbuf.c:429 #4 0x5628e96ab060 in repo_format_commit_message pretty.c:1869 #5 0x5628e96acd0f in pretty_print_commit pretty.c:2161 #6 0x5628e95a44c8 in show_log log-tree.c:781 #7 0x5628e95a76ba in log_tree_commit log-tree.c:1117 #8 0x5628e922bed5 in cmd_log_walk_no_free builtin/log.c:508 #9 0x5628e922c35b in cmd_log_walk builtin/log.c:549 #10 0x5628e922f1a2 in cmd_log builtin/log.c:883 #11 0x5628e9106993 in run_builtin git.c:466 #12 0x5628e9107397 in handle_builtin git.c:721 #13 0x5628e9107b07 in run_argv git.c:788 #14 0x5628e91088a7 in cmd_main git.c:923 #15 0x5628e939d682 in main common-main.c:57 #16 0x7f2127c3c28f (/usr/lib/libc.so.6+0x2328f) #17 0x7f2127c3c349 in __libc_start_main (/usr/lib/libc.so.6+0x23349) #18 0x5628e91020e4 in _start ../sysdeps/x86_64/start.S:115 0x7f1ec62f97fe is located 2 bytes to the left of 4831838265-byte region [0x7f1ec62f9800,0x7f1fe62f9839) allocated by thread T0 here: #0 0x7f2127ebe7ea in __interceptor_realloc /usr/src/debug/gcc/libsanitizer/asan/asan_malloc_linux.cpp:85 #1 0x5628e98774d4 in xrealloc wrapper.c:136 #2 0x5628e97cb01c in strbuf_grow strbuf.c:99 #3 0x5628e97ccd42 in strbuf_addchars strbuf.c:327 #4 0x5628e96aa55c in format_and_pad_commit pretty.c:1761 #5 0x5628e96aa7f4 in format_commit_item pretty.c:1801 #6 0x5628e97cdb24 in strbuf_expand strbuf.c:429 #7 0x5628e96ab060 in repo_format_commit_message pretty.c:1869 #8 0x5628e96acd0f in pretty_print_commit pretty.c:2161 #9 0x5628e95a44c8 in show_log log-tree.c:781 #10 0x5628e95a76ba in log_tree_commit log-tree.c:1117 #11 0x5628e922bed5 in cmd_log_walk_no_free builtin/log.c:508 #12 0x5628e922c35b in cmd_log_walk builtin/log.c:549 #13 0x5628e922f1a2 in cmd_log builtin/log.c:883 #14 0x5628e9106993 in run_builtin git.c:466 #15 0x5628e9107397 in handle_builtin git.c:721 #16 0x5628e9107b07 in run_argv git.c:788 #17 0x5628e91088a7 in cmd_main git.c:923 #18 0x5628e939d682 in main common-main.c:57 #19 0x7f2127c3c28f (/usr/lib/libc.so.6+0x2328f) #20 0x7f2127c3c349 in __libc_start_main (/usr/lib/libc.so.6+0x23349) #21 0x5628e91020e4 in _start ../sysdeps/x86_64/start.S:115 SUMMARY: AddressSanitizer: heap-buffer-overflow /usr/src/debug/gcc/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:827 in __interceptor_memcpy Shadow bytes around the buggy address: 0x0fe458c572a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0fe458c572b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0fe458c572c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0fe458c572d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0fe458c572e0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa =>0x0fe458c572f0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa[fa] 0x0fe458c57300: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0fe458c57310: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0fe458c57320: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0fe458c57330: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0fe458c57340: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 Shadow byte legend (one shadow byte represents 8 application bytes): Addressable: 00 Partially addressable: 01 02 03 04 05 06 07 Heap left redzone: fa Freed heap region: fd Stack left redzone: f1 Stack mid redzone: f2 Stack right redzone: f3 Stack after return: f5 Stack use after scope: f8 Global redzone: f9 Global init order: f6 Poisoned by user: f7 Container overflow: fc Array cookie: ac Intra object redzone: bb ASan internal: fe Left alloca redzone: ca Right alloca redzone: cb ==8340==ABORTING The pretty format can also be used in `git archive` operations via the `export-subst` attribute. So this is what in our opinion makes this a critical issue in the context of Git forges which allow to download an archive of user supplied Git repositories. Fix this vulnerability by using `size_t` instead of `int` to track the string lengths. Add tests which detect this vulnerability when Git is compiled with the address sanitizer. Reported-by: Joern Schneeweisz Original-patch-by: Joern Schneeweisz Modified-by: Taylor Blau Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano --- pretty.c | 11 ++++++----- t/t4205-log-pretty-formats.sh | 17 +++++++++++++++++ 2 files changed, 23 insertions(+), 5 deletions(-) (limited to 't') diff --git a/pretty.c b/pretty.c index 7a7708a0ea..a1a01492c1 100644 --- a/pretty.c +++ b/pretty.c @@ -1473,7 +1473,9 @@ static size_t format_and_pad_commit(struct strbuf *sb, /* in UTF-8 */ struct format_commit_context *c) { struct strbuf local_sb = STRBUF_INIT; - int total_consumed = 0, len, padding = c->padding; + size_t total_consumed = 0; + int len, padding = c->padding; + if (padding < 0) { const char *start = strrchr(sb->buf, '\n'); int occupied; @@ -1485,7 +1487,7 @@ static size_t format_and_pad_commit(struct strbuf *sb, /* in UTF-8 */ } while (1) { int modifier = *placeholder == 'C'; - int consumed = format_commit_one(&local_sb, placeholder, c); + size_t consumed = format_commit_one(&local_sb, placeholder, c); total_consumed += consumed; if (!modifier) @@ -1551,7 +1553,7 @@ static size_t format_and_pad_commit(struct strbuf *sb, /* in UTF-8 */ } strbuf_addbuf(sb, &local_sb); } else { - int sb_len = sb->len, offset = 0; + size_t sb_len = sb->len, offset = 0; if (c->flush_type == flush_left) offset = padding - len; else if (c->flush_type == flush_both) @@ -1574,8 +1576,7 @@ static size_t format_commit_item(struct strbuf *sb, /* in UTF-8 */ const char *placeholder, void *context) { - int consumed; - size_t orig_len; + size_t consumed, orig_len; enum { NO_MAGIC, ADD_LF_BEFORE_NON_EMPTY, diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh index 204c149d5a..fff3e05615 100755 --- a/t/t4205-log-pretty-formats.sh +++ b/t/t4205-log-pretty-formats.sh @@ -867,4 +867,21 @@ test_expect_success 'log --pretty=reference is colored appropriately' ' test_cmp expect actual ' +test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'log --pretty with huge commit message' ' + # We only assert that this command does not crash. This needs to be + # executed with the address sanitizer to demonstrate failure. + git log -1 --pretty="format:%>(2147483646)%x41%41%>(2147483646)%x41" >/dev/null +' + +test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'set up huge commit' ' + test-tool genzeros 2147483649 | tr "\000" "1" >expect && + huge_commit=$(git commit-tree -F expect HEAD^{tree}) +' + +test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'log --pretty with huge commit message' ' + git log -1 --format="%B%<(1)%x30" $huge_commit >actual && + echo 0 >>expect && + test_cmp expect actual +' + test_done -- cgit v1.3 From b49f309aa16febeddb65e82526640a91bbba3be3 Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Thu, 1 Dec 2022 15:46:30 +0100 Subject: pretty: fix out-of-bounds read when left-flushing with stealing With the `%>>()` pretty formatter, you can ask git-log(1) et al to steal spaces. To do so we need to look ahead of the next token to see whether there are spaces there. This loop takes into account ANSI sequences that end with an `m`, and if it finds any it will skip them until it finds the first space. While doing so it does not take into account the buffer's limits though and easily does an out-of-bounds read. Add a test that hits this behaviour. While we don't have an easy way to verify this, the test causes the following failure when run with `SANITIZE=address`: ==37941==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x603000000baf at pc 0x55ba6f88e0d0 bp 0x7ffc84c50d20 sp 0x7ffc84c50d10 READ of size 1 at 0x603000000baf thread T0 #0 0x55ba6f88e0cf in format_and_pad_commit pretty.c:1712 #1 0x55ba6f88e7b4 in format_commit_item pretty.c:1801 #2 0x55ba6f9b1ae4 in strbuf_expand strbuf.c:429 #3 0x55ba6f88f020 in repo_format_commit_message pretty.c:1869 #4 0x55ba6f890ccf in pretty_print_commit pretty.c:2161 #5 0x55ba6f7884c8 in show_log log-tree.c:781 #6 0x55ba6f78b6ba in log_tree_commit log-tree.c:1117 #7 0x55ba6f40fed5 in cmd_log_walk_no_free builtin/log.c:508 #8 0x55ba6f41035b in cmd_log_walk builtin/log.c:549 #9 0x55ba6f4131a2 in cmd_log builtin/log.c:883 #10 0x55ba6f2ea993 in run_builtin git.c:466 #11 0x55ba6f2eb397 in handle_builtin git.c:721 #12 0x55ba6f2ebb07 in run_argv git.c:788 #13 0x55ba6f2ec8a7 in cmd_main git.c:923 #14 0x55ba6f581682 in main common-main.c:57 #15 0x7f2d08c3c28f (/usr/lib/libc.so.6+0x2328f) #16 0x7f2d08c3c349 in __libc_start_main (/usr/lib/libc.so.6+0x23349) #17 0x55ba6f2e60e4 in _start ../sysdeps/x86_64/start.S:115 0x603000000baf is located 1 bytes to the left of 24-byte region [0x603000000bb0,0x603000000bc8) allocated by thread T0 here: #0 0x7f2d08ebe7ea in __interceptor_realloc /usr/src/debug/gcc/libsanitizer/asan/asan_malloc_linux.cpp:85 #1 0x55ba6fa5b494 in xrealloc wrapper.c:136 #2 0x55ba6f9aefdc in strbuf_grow strbuf.c:99 #3 0x55ba6f9b0a06 in strbuf_add strbuf.c:298 #4 0x55ba6f9b1a25 in strbuf_expand strbuf.c:418 #5 0x55ba6f88f020 in repo_format_commit_message pretty.c:1869 #6 0x55ba6f890ccf in pretty_print_commit pretty.c:2161 #7 0x55ba6f7884c8 in show_log log-tree.c:781 #8 0x55ba6f78b6ba in log_tree_commit log-tree.c:1117 #9 0x55ba6f40fed5 in cmd_log_walk_no_free builtin/log.c:508 #10 0x55ba6f41035b in cmd_log_walk builtin/log.c:549 #11 0x55ba6f4131a2 in cmd_log builtin/log.c:883 #12 0x55ba6f2ea993 in run_builtin git.c:466 #13 0x55ba6f2eb397 in handle_builtin git.c:721 #14 0x55ba6f2ebb07 in run_argv git.c:788 #15 0x55ba6f2ec8a7 in cmd_main git.c:923 #16 0x55ba6f581682 in main common-main.c:57 #17 0x7f2d08c3c28f (/usr/lib/libc.so.6+0x2328f) #18 0x7f2d08c3c349 in __libc_start_main (/usr/lib/libc.so.6+0x23349) #19 0x55ba6f2e60e4 in _start ../sysdeps/x86_64/start.S:115 SUMMARY: AddressSanitizer: heap-buffer-overflow pretty.c:1712 in format_and_pad_commit Shadow bytes around the buggy address: 0x0c067fff8120: fa fa fd fd fd fa fa fa fd fd fd fa fa fa fd fd 0x0c067fff8130: fd fd fa fa fd fd fd fd fa fa fd fd fd fa fa fa 0x0c067fff8140: fd fd fd fa fa fa fd fd fd fa fa fa fd fd fd fa 0x0c067fff8150: fa fa fd fd fd fd fa fa 00 00 00 fa fa fa fd fd 0x0c067fff8160: fd fa fa fa fd fd fd fa fa fa fd fd fd fa fa fa =>0x0c067fff8170: fd fd fd fa fa[fa]00 00 00 fa fa fa 00 00 00 fa 0x0c067fff8180: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c067fff8190: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c067fff81a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c067fff81b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c067fff81c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa Shadow byte legend (one shadow byte represents 8 application bytes): Addressable: 00 Partially addressable: 01 02 03 04 05 06 07 Heap left redzone: fa Freed heap region: fd Stack left redzone: f1 Stack mid redzone: f2 Stack right redzone: f3 Stack after return: f5 Stack use after scope: f8 Global redzone: f9 Global init order: f6 Poisoned by user: f7 Container overflow: fc Array cookie: ac Intra object redzone: bb ASan internal: fe Left alloca redzone: ca Right alloca redzone: cb Luckily enough, this would only cause us to copy the out-of-bounds data into the formatted commit in case we really had an ANSI sequence preceding our buffer. So this bug likely has no security consequences. Fix it regardless by not traversing past the buffer's start. Reported-by: Patrick Steinhardt Reported-by: Eric Sesterhenn Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano --- pretty.c | 2 +- t/t4205-log-pretty-formats.sh | 6 ++++++ 2 files changed, 7 insertions(+), 1 deletion(-) (limited to 't') diff --git a/pretty.c b/pretty.c index a1a01492c1..692a6382a1 100644 --- a/pretty.c +++ b/pretty.c @@ -1514,7 +1514,7 @@ static size_t format_and_pad_commit(struct strbuf *sb, /* in UTF-8 */ if (*ch != 'm') break; p = ch - 1; - while (ch - p < 10 && *p != '\033') + while (p > sb->buf && ch - p < 10 && *p != '\033') p--; if (*p != '\033' || ch + 1 - p != display_mode_esc_sequence_len(p)) diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh index fff3e05615..126dc20f23 100755 --- a/t/t4205-log-pretty-formats.sh +++ b/t/t4205-log-pretty-formats.sh @@ -867,6 +867,12 @@ test_expect_success 'log --pretty=reference is colored appropriately' ' test_cmp expect actual ' +test_expect_success 'log --pretty with space stealing' ' + printf mm0 >expect && + git log -1 --pretty="format:mm%>>|(1)%x30" >actual && + test_cmp expect actual +' + test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'log --pretty with huge commit message' ' # We only assert that this command does not crash. This needs to be # executed with the address sanitizer to demonstrate failure. -- cgit v1.3 From f6e0b9f38987ad5e47bab551f8760b70689a5905 Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Thu, 1 Dec 2022 15:46:34 +0100 Subject: pretty: fix out-of-bounds read when parsing invalid padding format An out-of-bounds read can be triggered when parsing an incomplete padding format string passed via `--pretty=format` or in Git archives when files are marked with the `export-subst` gitattribute. This bug exists since we have introduced support for truncating output via the `trunc` keyword a7f01c6b4d (pretty: support truncating in %>, %< and %><, 2013-04-19). Before this commit, we used to find the end of the formatting string by using strchr(3P). This function returns a `NULL` pointer in case the character in question wasn't found. The subsequent check whether any character was found thus simply checked the returned pointer. After the commit we switched to strcspn(3P) though, which only returns the offset to the first found character or to the trailing NUL byte. As the end pointer is now computed by adding the offset to the start pointer it won't be `NULL` anymore, and as a consequence the check doesn't do anything anymore. The out-of-bounds data that is being read can in fact end up in the formatted string. As a consequence, it is possible to leak memory contents either by calling git-log(1) or via git-archive(1) when any of the archived files is marked with the `export-subst` gitattribute. ==10888==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000000398 at pc 0x7f0356047cb2 bp 0x7fff3ffb95d0 sp 0x7fff3ffb8d78 READ of size 1 at 0x602000000398 thread T0 #0 0x7f0356047cb1 in __interceptor_strchrnul /usr/src/debug/gcc/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:725 #1 0x563b7cec9a43 in strbuf_expand strbuf.c:417 #2 0x563b7cda7060 in repo_format_commit_message pretty.c:1869 #3 0x563b7cda8d0f in pretty_print_commit pretty.c:2161 #4 0x563b7cca04c8 in show_log log-tree.c:781 #5 0x563b7cca36ba in log_tree_commit log-tree.c:1117 #6 0x563b7c927ed5 in cmd_log_walk_no_free builtin/log.c:508 #7 0x563b7c92835b in cmd_log_walk builtin/log.c:549 #8 0x563b7c92b1a2 in cmd_log builtin/log.c:883 #9 0x563b7c802993 in run_builtin git.c:466 #10 0x563b7c803397 in handle_builtin git.c:721 #11 0x563b7c803b07 in run_argv git.c:788 #12 0x563b7c8048a7 in cmd_main git.c:923 #13 0x563b7ca99682 in main common-main.c:57 #14 0x7f0355e3c28f (/usr/lib/libc.so.6+0x2328f) #15 0x7f0355e3c349 in __libc_start_main (/usr/lib/libc.so.6+0x23349) #16 0x563b7c7fe0e4 in _start ../sysdeps/x86_64/start.S:115 0x602000000398 is located 0 bytes to the right of 8-byte region [0x602000000390,0x602000000398) allocated by thread T0 here: #0 0x7f0356072faa in __interceptor_strdup /usr/src/debug/gcc/libsanitizer/asan/asan_interceptors.cpp:439 #1 0x563b7cf7317c in xstrdup wrapper.c:39 #2 0x563b7cd9a06a in save_user_format pretty.c:40 #3 0x563b7cd9b3e5 in get_commit_format pretty.c:173 #4 0x563b7ce54ea0 in handle_revision_opt revision.c:2456 #5 0x563b7ce597c9 in setup_revisions revision.c:2850 #6 0x563b7c9269e0 in cmd_log_init_finish builtin/log.c:269 #7 0x563b7c927362 in cmd_log_init builtin/log.c:348 #8 0x563b7c92b193 in cmd_log builtin/log.c:882 #9 0x563b7c802993 in run_builtin git.c:466 #10 0x563b7c803397 in handle_builtin git.c:721 #11 0x563b7c803b07 in run_argv git.c:788 #12 0x563b7c8048a7 in cmd_main git.c:923 #13 0x563b7ca99682 in main common-main.c:57 #14 0x7f0355e3c28f (/usr/lib/libc.so.6+0x2328f) #15 0x7f0355e3c349 in __libc_start_main (/usr/lib/libc.so.6+0x23349) #16 0x563b7c7fe0e4 in _start ../sysdeps/x86_64/start.S:115 SUMMARY: AddressSanitizer: heap-buffer-overflow /usr/src/debug/gcc/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:725 in __interceptor_strchrnul Shadow bytes around the buggy address: 0x0c047fff8020: fa fa fd fd fa fa 00 06 fa fa 05 fa fa fa fd fd 0x0c047fff8030: fa fa 00 02 fa fa 06 fa fa fa 05 fa fa fa fd fd 0x0c047fff8040: fa fa 00 07 fa fa 03 fa fa fa fd fd fa fa 00 00 0x0c047fff8050: fa fa 00 01 fa fa fd fd fa fa 00 00 fa fa 00 01 0x0c047fff8060: fa fa 00 06 fa fa 00 06 fa fa 05 fa fa fa 05 fa =>0x0c047fff8070: fa fa 00[fa]fa fa fd fa fa fa fd fd fa fa fd fd 0x0c047fff8080: fa fa fd fd fa fa 00 00 fa fa 00 fa fa fa fd fa 0x0c047fff8090: fa fa fd fd fa fa 00 00 fa fa fa fa fa fa fa fa 0x0c047fff80a0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c047fff80b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c047fff80c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa Shadow byte legend (one shadow byte represents 8 application bytes): Addressable: 00 Partially addressable: 01 02 03 04 05 06 07 Heap left redzone: fa Freed heap region: fd Stack left redzone: f1 Stack mid redzone: f2 Stack right redzone: f3 Stack after return: f5 Stack use after scope: f8 Global redzone: f9 Global init order: f6 Poisoned by user: f7 Container overflow: fc Array cookie: ac Intra object redzone: bb ASan internal: fe Left alloca redzone: ca Right alloca redzone: cb ==10888==ABORTING Fix this bug by checking whether `end` points at the trailing NUL byte. Add a test which catches this out-of-bounds read and which demonstrates that we used to write out-of-bounds data into the formatted message. Reported-by: Markus Vervier Original-patch-by: Markus Vervier Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano --- pretty.c | 2 +- t/t4205-log-pretty-formats.sh | 6 ++++++ 2 files changed, 7 insertions(+), 1 deletion(-) (limited to 't') diff --git a/pretty.c b/pretty.c index 692a6382a1..d55b88607a 100644 --- a/pretty.c +++ b/pretty.c @@ -1041,7 +1041,7 @@ static size_t parse_padding_placeholder(const char *placeholder, const char *end = start + strcspn(start, ",)"); char *next; int width; - if (!end || end == start) + if (!*end || end == start) return 0; width = strtol(start, &next, 10); if (next == start || width == 0) diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh index 126dc20f23..cdde37d325 100755 --- a/t/t4205-log-pretty-formats.sh +++ b/t/t4205-log-pretty-formats.sh @@ -873,6 +873,12 @@ test_expect_success 'log --pretty with space stealing' ' test_cmp expect actual ' +test_expect_success 'log --pretty with invalid padding format' ' + printf "%s%%<(20" "$(git rev-parse HEAD)" >expect && + git log -1 --pretty="format:%H%<(20" >actual && + test_cmp expect actual +' + test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'log --pretty with huge commit message' ' # We only assert that this command does not crash. This needs to be # executed with the address sanitizer to demonstrate failure. -- cgit v1.3 From 1de69c0cdd388b0a5b7bdde0bfa0bda514a354b0 Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Thu, 1 Dec 2022 15:46:39 +0100 Subject: pretty: fix adding linefeed when placeholder is not expanded When a formatting directive has a `+` or ` ` after the `%`, then we add either a line feed or space if the placeholder expands to a non-empty string. In specific cases though this logic doesn't work as expected, and we try to add the character even in the case where the formatting directive is empty. One such pattern is `%w(1)%+d%+w(2)`. `%+d` expands to reference names pointing to a certain commit, like in `git log --decorate`. For a tagged commit this would for example expand to `\n (tag: v1.0.0)`, which has a leading newline due to the `+` modifier and a space added by `%d`. Now the second wrapping directive will cause us to rewrap the text to `\n(tag:\nv1.0.0)`, which is one byte shorter due to the missing leading space. The code that handles the `+` magic now notices that the length has changed and will thus try to insert a leading line feed at the original posititon. But as the string was shortened, the original position is past the buffer's boundary and thus we die with an error. Now there are two issues here: 1. We check whether the buffer length has changed, not whether it has been extended. This causes us to try and add the character past the string boundary. 2. The current logic does not make any sense whatsoever. When the string got expanded due to the rewrap, putting the separator into the original position is likely to put it somewhere into the middle of the rewrapped contents. It is debatable whether `%+w()` makes any sense in the first place. Strictly speaking, the placeholder never expands to a non-empty string, and consequentially we shouldn't ever accept this combination. We thus fix the bug by simply refusing `%+w()`. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano --- pretty.c | 14 +++++++++++++- t/t4205-log-pretty-formats.sh | 8 ++++++++ 2 files changed, 21 insertions(+), 1 deletion(-) (limited to 't') diff --git a/pretty.c b/pretty.c index d55b88607a..c6c757c0ce 100644 --- a/pretty.c +++ b/pretty.c @@ -1597,9 +1597,21 @@ static size_t format_commit_item(struct strbuf *sb, /* in UTF-8 */ default: break; } - if (magic != NO_MAGIC) + if (magic != NO_MAGIC) { placeholder++; + switch (placeholder[0]) { + case 'w': + /* + * `%+w()` cannot ever expand to a non-empty string, + * and it potentially changes the layout of preceding + * contents. We're thus not able to handle the magic in + * this combination and refuse the pattern. + */ + return 0; + }; + } + orig_len = sb->len; if (((struct format_commit_context *)context)->flush_type != no_flush) consumed = format_and_pad_commit(sb, placeholder, context); diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh index cdde37d325..1d768f7244 100755 --- a/t/t4205-log-pretty-formats.sh +++ b/t/t4205-log-pretty-formats.sh @@ -879,6 +879,14 @@ test_expect_success 'log --pretty with invalid padding format' ' test_cmp expect actual ' +test_expect_success 'log --pretty with magical wrapping directives' ' + commit_id=$(git commit-tree HEAD^{tree} -m "describe me") && + git tag describe-me $commit_id && + printf "\n(tag:\ndescribe-me)%%+w(2)" >expect && + git log -1 --pretty="format:%w(1)%+d%+w(2)" $commit_id >actual && + test_cmp expect actual +' + test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'log --pretty with huge commit message' ' # We only assert that this command does not crash. This needs to be # executed with the address sanitizer to demonstrate failure. -- cgit v1.3 From 48050c42c73c28b0c001d63d11dffac7e116847b Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Thu, 1 Dec 2022 15:46:49 +0100 Subject: pretty: fix integer overflow in wrapping format The `%w(width,indent1,indent2)` formatting directive can be used to rewrap text to a specific width and is designed after git-shortlog(1)'s `-w` parameter. While the three parameters are all stored as `size_t` internally, `strbuf_add_wrapped_text()` accepts integers as input. As a result, the casted integers may overflow. As these now-negative integers are later on passed to `strbuf_addchars()`, we will ultimately run into implementation-defined behaviour due to casting a negative number back to `size_t` again. On my platform, this results in trying to allocate 9000 petabyte of memory. Fix this overflow by using `cast_size_t_to_int()` so that we reject inputs that cannot be represented as an integer. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano --- git-compat-util.h | 8 ++++++++ pretty.c | 4 +++- t/t4205-log-pretty-formats.sh | 12 ++++++++++++ 3 files changed, 23 insertions(+), 1 deletion(-) (limited to 't') diff --git a/git-compat-util.h b/git-compat-util.h index f505f817d5..0ac1b7f560 100644 --- a/git-compat-util.h +++ b/git-compat-util.h @@ -918,6 +918,14 @@ static inline size_t st_sub(size_t a, size_t b) return a - b; } +static inline int cast_size_t_to_int(size_t a) +{ + if (a > INT_MAX) + die("number too large to represent as int on this platform: %"PRIuMAX, + (uintmax_t)a); + return (int)a; +} + #ifdef HAVE_ALLOCA_H # include # define xalloca(size) (alloca(size)) diff --git a/pretty.c b/pretty.c index c6c757c0ce..7e649b1cec 100644 --- a/pretty.c +++ b/pretty.c @@ -915,7 +915,9 @@ static void strbuf_wrap(struct strbuf *sb, size_t pos, if (pos) strbuf_add(&tmp, sb->buf, pos); strbuf_add_wrapped_text(&tmp, sb->buf + pos, - (int) indent1, (int) indent2, (int) width); + cast_size_t_to_int(indent1), + cast_size_t_to_int(indent2), + cast_size_t_to_int(width)); strbuf_swap(&tmp, sb); strbuf_release(&tmp); } diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh index 1d768f7244..c88b64d08b 100755 --- a/t/t4205-log-pretty-formats.sh +++ b/t/t4205-log-pretty-formats.sh @@ -887,6 +887,18 @@ test_expect_success 'log --pretty with magical wrapping directives' ' test_cmp expect actual ' +test_expect_success SIZE_T_IS_64BIT 'log --pretty with overflowing wrapping directive' ' + cat >expect <<-EOF && + fatal: number too large to represent as int on this platform: 2147483649 + EOF + test_must_fail git log -1 --pretty="format:%w(2147483649,1,1)%d" 2>error && + test_cmp expect error && + test_must_fail git log -1 --pretty="format:%w(1,2147483649,1)%d" 2>error && + test_cmp expect error && + test_must_fail git log -1 --pretty="format:%w(1,1,2147483649)%d" 2>error && + test_cmp expect error +' + test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'log --pretty with huge commit message' ' # We only assert that this command does not crash. This needs to be # executed with the address sanitizer to demonstrate failure. -- cgit v1.3 From 17d23e8a3812a5ca3dd6564e74d5250f22e5d76d Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Thu, 1 Dec 2022 15:47:00 +0100 Subject: utf8: fix returning negative string width The `utf8_strnwidth()` function calls `utf8_width()` in a loop and adds its returned width to the end result. `utf8_width()` can return `-1` though in case it reads a control character, which means that the computed string width is going to be wrong. In the worst case where there are more control characters than non-control characters, we may even return a negative string width. Fix this bug by treating control characters as having zero width. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano --- t/t4205-log-pretty-formats.sh | 6 ++++++ utf8.c | 8 ++++++-- 2 files changed, 12 insertions(+), 2 deletions(-) (limited to 't') diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh index c88b64d08b..e3905baa3c 100755 --- a/t/t4205-log-pretty-formats.sh +++ b/t/t4205-log-pretty-formats.sh @@ -899,6 +899,12 @@ test_expect_success SIZE_T_IS_64BIT 'log --pretty with overflowing wrapping dire test_cmp expect error ' +test_expect_success 'log --pretty with padding and preceding control chars' ' + printf "\20\20 0" >expect && + git log -1 --pretty="format:%x10%x10%>|(4)%x30" >actual && + test_cmp expect actual +' + test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'log --pretty with huge commit message' ' # We only assert that this command does not crash. This needs to be # executed with the address sanitizer to demonstrate failure. diff --git a/utf8.c b/utf8.c index 504e517c34..6a21fd6a7b 100644 --- a/utf8.c +++ b/utf8.c @@ -212,11 +212,15 @@ int utf8_strnwidth(const char *string, size_t len, int skip_ansi) const char *orig = string; while (string && string < orig + len) { - int skip; + int glyph_width, skip; + while (skip_ansi && (skip = display_mode_esc_sequence_len(string)) != 0) string += skip; - width += utf8_width(&string, NULL); + + glyph_width = utf8_width(&string, NULL); + if (glyph_width > 0) + width += glyph_width; } return string ? width : len; } -- cgit v1.3 From 937b71cc8b5b998963a7f9a33312ba3549d55510 Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Thu, 1 Dec 2022 15:47:04 +0100 Subject: utf8: fix overflow when returning string width The return type of both `utf8_strwidth()` and `utf8_strnwidth()` is `int`, but we operate on string lengths which are typically of type `size_t`. This means that when the string is longer than `INT_MAX`, we will overflow and thus return a negative result. This can lead to an out-of-bounds write with `--pretty=format:%<1)%B` and a commit message that is 2^31+1 bytes long: ================================================================= ==26009==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x603000001168 at pc 0x7f95c4e5f427 bp 0x7ffd8541c900 sp 0x7ffd8541c0a8 WRITE of size 2147483649 at 0x603000001168 thread T0 #0 0x7f95c4e5f426 in __interceptor_memcpy /usr/src/debug/gcc/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:827 #1 0x5612bbb1068c in format_and_pad_commit pretty.c:1763 #2 0x5612bbb1087a in format_commit_item pretty.c:1801 #3 0x5612bbc33bab in strbuf_expand strbuf.c:429 #4 0x5612bbb110e7 in repo_format_commit_message pretty.c:1869 #5 0x5612bbb12d96 in pretty_print_commit pretty.c:2161 #6 0x5612bba0a4d5 in show_log log-tree.c:781 #7 0x5612bba0d6c7 in log_tree_commit log-tree.c:1117 #8 0x5612bb691ed5 in cmd_log_walk_no_free builtin/log.c:508 #9 0x5612bb69235b in cmd_log_walk builtin/log.c:549 #10 0x5612bb6951a2 in cmd_log builtin/log.c:883 #11 0x5612bb56c993 in run_builtin git.c:466 #12 0x5612bb56d397 in handle_builtin git.c:721 #13 0x5612bb56db07 in run_argv git.c:788 #14 0x5612bb56e8a7 in cmd_main git.c:923 #15 0x5612bb803682 in main common-main.c:57 #16 0x7f95c4c3c28f (/usr/lib/libc.so.6+0x2328f) #17 0x7f95c4c3c349 in __libc_start_main (/usr/lib/libc.so.6+0x23349) #18 0x5612bb5680e4 in _start ../sysdeps/x86_64/start.S:115 0x603000001168 is located 0 bytes to the right of 24-byte region [0x603000001150,0x603000001168) allocated by thread T0 here: #0 0x7f95c4ebe7ea in __interceptor_realloc /usr/src/debug/gcc/libsanitizer/asan/asan_malloc_linux.cpp:85 #1 0x5612bbcdd556 in xrealloc wrapper.c:136 #2 0x5612bbc310a3 in strbuf_grow strbuf.c:99 #3 0x5612bbc32acd in strbuf_add strbuf.c:298 #4 0x5612bbc33aec in strbuf_expand strbuf.c:418 #5 0x5612bbb110e7 in repo_format_commit_message pretty.c:1869 #6 0x5612bbb12d96 in pretty_print_commit pretty.c:2161 #7 0x5612bba0a4d5 in show_log log-tree.c:781 #8 0x5612bba0d6c7 in log_tree_commit log-tree.c:1117 #9 0x5612bb691ed5 in cmd_log_walk_no_free builtin/log.c:508 #10 0x5612bb69235b in cmd_log_walk builtin/log.c:549 #11 0x5612bb6951a2 in cmd_log builtin/log.c:883 #12 0x5612bb56c993 in run_builtin git.c:466 #13 0x5612bb56d397 in handle_builtin git.c:721 #14 0x5612bb56db07 in run_argv git.c:788 #15 0x5612bb56e8a7 in cmd_main git.c:923 #16 0x5612bb803682 in main common-main.c:57 #17 0x7f95c4c3c28f (/usr/lib/libc.so.6+0x2328f) SUMMARY: AddressSanitizer: heap-buffer-overflow /usr/src/debug/gcc/libsanitizer/sanitizer_common/sanitizer_common_interceptors.inc:827 in __interceptor_memcpy Shadow bytes around the buggy address: 0x0c067fff81d0: fd fd fd fa fa fa fd fd fd fa fa fa fd fd fd fa 0x0c067fff81e0: fa fa fd fd fd fd fa fa fd fd fd fd fa fa fd fd 0x0c067fff81f0: fd fa fa fa fd fd fd fa fa fa fd fd fd fa fa fa 0x0c067fff8200: fd fd fd fa fa fa fd fd fd fd fa fa 00 00 00 fa 0x0c067fff8210: fa fa fd fd fd fa fa fa fd fd fd fa fa fa fd fd =>0x0c067fff8220: fd fa fa fa fd fd fd fa fa fa 00 00 00[fa]fa fa 0x0c067fff8230: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c067fff8240: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c067fff8250: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c067fff8260: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c067fff8270: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa Shadow byte legend (one shadow byte represents 8 application bytes): Addressable: 00 Partially addressable: 01 02 03 04 05 06 07 Heap left redzone: fa Freed heap region: fd Stack left redzone: f1 Stack mid redzone: f2 Stack right redzone: f3 Stack after return: f5 Stack use after scope: f8 Global redzone: f9 Global init order: f6 Poisoned by user: f7 Container overflow: fc Array cookie: ac Intra object redzone: bb ASan internal: fe Left alloca redzone: ca Right alloca redzone: cb ==26009==ABORTING Now the proper fix for this would be to convert both functions to return an `size_t` instead of an `int`. But given that this commit may be part of a security release, let's instead do the minimal viable fix and die in case we see an overflow. Add a test that would have previously caused us to crash. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano --- t/t4205-log-pretty-formats.sh | 8 ++++++++ utf8.c | 12 +++++++++--- 2 files changed, 17 insertions(+), 3 deletions(-) (limited to 't') diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh index e3905baa3c..aac9e4ce6c 100755 --- a/t/t4205-log-pretty-formats.sh +++ b/t/t4205-log-pretty-formats.sh @@ -922,4 +922,12 @@ test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'log --pretty with huge commit mes test_cmp expect actual ' +test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'log --pretty with huge commit message does not cause allocation failure' ' + test_must_fail git log -1 --format="%<(1)%B" $huge_commit 2>error && + cat >expect <<-EOF && + fatal: number too large to represent as int on this platform: 2147483649 + EOF + test_cmp expect error +' + test_done diff --git a/utf8.c b/utf8.c index 6a21fd6a7b..30c7787cfa 100644 --- a/utf8.c +++ b/utf8.c @@ -208,11 +208,12 @@ int utf8_width(const char **start, size_t *remainder_p) */ int utf8_strnwidth(const char *string, size_t len, int skip_ansi) { - int width = 0; const char *orig = string; + size_t width = 0; while (string && string < orig + len) { - int glyph_width, skip; + int glyph_width; + size_t skip; while (skip_ansi && (skip = display_mode_esc_sequence_len(string)) != 0) @@ -222,7 +223,12 @@ int utf8_strnwidth(const char *string, size_t len, int skip_ansi) if (glyph_width > 0) width += glyph_width; } - return string ? width : len; + + /* + * TODO: fix the interface of this function and `utf8_strwidth()` to + * return `size_t` instead of `int`. + */ + return cast_size_t_to_int(string ? width : len); } int utf8_strwidth(const char *string) -- cgit v1.3 From 81c2d4c3a5ba0e6ab8c348708441fed170e63a82 Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Thu, 1 Dec 2022 15:47:10 +0100 Subject: utf8: fix checking for glyph width in `strbuf_utf8_replace()` In `strbuf_utf8_replace()`, we call `utf8_width()` to compute the width of the current glyph. If the glyph is a control character though it can be that `utf8_width()` returns `-1`, but because we assign this value to a `size_t` the conversion will cause us to underflow. This bug can easily be triggered with the following command: $ git log --pretty='format:xxx%<|(1,trunc)%x10' >From all I can see though this seems to be a benign underflow that has no security-related consequences. Fix the bug by using an `int` instead. When we see a control character, we now copy it into the target buffer but don't advance the current width of the string. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano --- t/t4205-log-pretty-formats.sh | 7 +++++++ utf8.c | 19 ++++++++++++++----- 2 files changed, 21 insertions(+), 5 deletions(-) (limited to 't') diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh index aac9e4ce6c..5c5b56596e 100755 --- a/t/t4205-log-pretty-formats.sh +++ b/t/t4205-log-pretty-formats.sh @@ -905,6 +905,13 @@ test_expect_success 'log --pretty with padding and preceding control chars' ' test_cmp expect actual ' +test_expect_success 'log --pretty truncation with control chars' ' + test_commit "$(printf "\20\20\20\20xxxx")" file contents commit-with-control-chars && + printf "\20\20\20\20x.." >expect && + git log -1 --pretty="format:%<(3,trunc)%s" commit-with-control-chars >actual && + test_cmp expect actual +' + test_expect_success EXPENSIVE,SIZE_T_IS_64BIT 'log --pretty with huge commit message' ' # We only assert that this command does not crash. This needs to be # executed with the address sanitizer to demonstrate failure. diff --git a/utf8.c b/utf8.c index 30c7787cfa..077daf4b20 100644 --- a/utf8.c +++ b/utf8.c @@ -377,6 +377,7 @@ void strbuf_utf8_replace(struct strbuf *sb_src, int pos, int width, dst = sb_dst.buf; while (src < end) { + int glyph_width; char *old; size_t n; @@ -390,21 +391,29 @@ void strbuf_utf8_replace(struct strbuf *sb_src, int pos, int width, break; old = src; - n = utf8_width((const char**)&src, NULL); - if (!src) /* broken utf-8, do nothing */ + glyph_width = utf8_width((const char**)&src, NULL); + if (!src) /* broken utf-8, do nothing */ goto out; - if (n && w >= pos && w < pos + width) { + + /* + * In case we see a control character we copy it into the + * buffer, but don't add it to the width. + */ + if (glyph_width < 0) + glyph_width = 0; + + if (glyph_width && w >= pos && w < pos + width) { if (subst) { memcpy(dst, subst, subst_len); dst += subst_len; subst = NULL; } - w += n; + w += glyph_width; continue; } memcpy(dst, old, src - old); dst += src - old; - w += n; + w += glyph_width; } strbuf_setlen(&sb_dst, dst - sb_dst.buf); strbuf_swap(sb_src, &sb_dst); -- cgit v1.3 From 304a50adff6480ede46b68f7545baab542cbfb46 Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Thu, 1 Dec 2022 15:47:23 +0100 Subject: pretty: restrict input lengths for padding and wrapping formats Both the padding and wrapping formatting directives allow the caller to specify an integer that ultimately leads to us adding this many chars to the result buffer. As a consequence, it is trivial to e.g. allocate 2GB of RAM via a single formatting directive and cause resource exhaustion on the machine executing this logic. Furthermore, it is debatable whether there are any sane usecases that require the user to pad data to 2GB boundaries or to indent wrapped data by 2GB. Restrict the input sizes to 16 kilobytes at a maximum to limit the amount of bytes that can be requested by the user. This is not meant as a fix because there are ways to trivially amplify the amount of data we generate via formatting directives; the real protection is achieved by the changes in previous steps to catch and avoid integer wraparound that causes us to under-allocate and access beyond the end of allocated memory reagions. But having such a limit significantly helps fuzzing the pretty format, because the fuzzer is otherwise quite fast to run out-of-memory as it discovers these formatters. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano --- pretty.c | 26 ++++++++++++++++++++++++++ t/t4205-log-pretty-formats.sh | 24 +++++++++++++++--------- 2 files changed, 41 insertions(+), 9 deletions(-) (limited to 't') diff --git a/pretty.c b/pretty.c index aae6e792bc..e2285572c4 100644 --- a/pretty.c +++ b/pretty.c @@ -13,6 +13,13 @@ #include "gpg-interface.h" #include "trailer.h" +/* + * The limit for formatting directives, which enable the caller to append + * arbitrarily many bytes to the formatted buffer. This includes padding + * and wrapping formatters. + */ +#define FORMATTING_LIMIT (16 * 1024) + static char *user_format; static struct cmt_fmt_map { const char *name; @@ -1046,6 +1053,15 @@ static size_t parse_padding_placeholder(const char *placeholder, if (!*end || end == start) return 0; width = strtol(start, &next, 10); + + /* + * We need to limit the amount of padding, or otherwise this + * would allow the user to pad the buffer by arbitrarily many + * bytes and thus cause resource exhaustion. + */ + if (width < -FORMATTING_LIMIT || width > FORMATTING_LIMIT) + return 0; + if (next == start || width == 0) return 0; if (width < 0) { @@ -1205,6 +1221,16 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */ if (*next != ')') return 0; } + + /* + * We need to limit the format here as it allows the + * user to prepend arbitrarily many bytes to the buffer + * when rewrapping. + */ + if (width > FORMATTING_LIMIT || + indent1 > FORMATTING_LIMIT || + indent2 > FORMATTING_LIMIT) + return 0; rewrap_message_tail(sb, c, width, indent1, indent2); return end - placeholder + 1; } else diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh index 5c5b56596e..84c61dfc48 100755 --- a/t/t4205-log-pretty-formats.sh +++ b/t/t4205-log-pretty-formats.sh @@ -888,15 +888,21 @@ test_expect_success 'log --pretty with magical wrapping directives' ' ' test_expect_success SIZE_T_IS_64BIT 'log --pretty with overflowing wrapping directive' ' - cat >expect <<-EOF && - fatal: number too large to represent as int on this platform: 2147483649 - EOF - test_must_fail git log -1 --pretty="format:%w(2147483649,1,1)%d" 2>error && - test_cmp expect error && - test_must_fail git log -1 --pretty="format:%w(1,2147483649,1)%d" 2>error && - test_cmp expect error && - test_must_fail git log -1 --pretty="format:%w(1,1,2147483649)%d" 2>error && - test_cmp expect error + printf "%%w(2147483649,1,1)0" >expect && + git log -1 --pretty="format:%w(2147483649,1,1)%x30" >actual && + test_cmp expect actual && + printf "%%w(1,2147483649,1)0" >expect && + git log -1 --pretty="format:%w(1,2147483649,1)%x30" >actual && + test_cmp expect actual && + printf "%%w(1,1,2147483649)0" >expect && + git log -1 --pretty="format:%w(1,1,2147483649)%x30" >actual && + test_cmp expect actual +' + +test_expect_success SIZE_T_IS_64BIT 'log --pretty with overflowing padding directive' ' + printf "%%<(2147483649)0" >expect && + git log -1 --pretty="format:%<(2147483649)%x30" >actual && + test_cmp expect actual ' test_expect_success 'log --pretty with padding and preceding control chars' ' -- cgit v1.3 From 27ab4784d5c9e24345b9f5b443609cbe527c51f9 Mon Sep 17 00:00:00 2001 From: Patrick Steinhardt Date: Thu, 1 Dec 2022 15:46:09 +0100 Subject: fsck: implement checks for gitattributes Recently, a vulnerability was reported that can lead to an out-of-bounds write when reading an unreasonably large gitattributes file. The root cause of this error are multiple integer overflows in different parts of the code when there are either too many lines, when paths are too long, when attribute names are too long, or when there are too many attributes declared for a pattern. As all of these are related to size, it seems reasonable to restrict the size of the gitattributes file via git-fsck(1). This allows us to both stop distributing known-vulnerable objects via common hosting platforms that have fsck enabled, and users to protect themselves by enabling the `fetch.fsckObjects` config. There are basically two checks: 1. We verify that size of the gitattributes file is smaller than 100MB. 2. We verify that the maximum line length does not exceed 2048 bytes. With the preceding commits, both of these conditions would cause us to either ignore the complete gitattributes file or blob in the first case, or the specific line in the second case. Now with these consistency checks added, we also grow the ability to stop distributing such files in the first place when `receive.fsckObjects` is enabled. Signed-off-by: Patrick Steinhardt Signed-off-by: Junio C Hamano --- fsck.c | 38 +++++++++++++++++++++++++++++++++++++- fsck.h | 12 ++++++++++++ t/t1450-fsck.sh | 24 ++++++++++++++++++++++++ 3 files changed, 73 insertions(+), 1 deletion(-) (limited to 't') diff --git a/fsck.c b/fsck.c index 3a7fb9ebba..614c776429 100644 --- a/fsck.c +++ b/fsck.c @@ -2,6 +2,7 @@ #include "object-store.h" #include "repository.h" #include "object.h" +#include "attr.h" #include "blob.h" #include "tree.h" #include "tree-walk.h" @@ -615,7 +616,10 @@ static int fsck_tree(const struct object_id *tree_oid, } if (is_hfs_dotgitattributes(name) || is_ntfs_dotgitattributes(name)) { - if (S_ISLNK(mode)) + if (!S_ISLNK(mode)) + oidset_insert(&options->gitattributes_found, + entry_oid); + else retval += report(options, tree_oid, OBJ_TREE, FSCK_MSG_GITATTRIBUTES_SYMLINK, ".gitattributes is a symlink"); @@ -1206,6 +1210,35 @@ static int fsck_blob(const struct object_id *oid, const char *buf, ret |= data.ret; } + if (oidset_contains(&options->gitattributes_found, oid)) { + const char *ptr; + + oidset_insert(&options->gitattributes_done, oid); + + if (!buf || size > ATTR_MAX_FILE_SIZE) { + /* + * A missing buffer here is a sign that the caller found the + * blob too gigantic to load into memory. Let's just consider + * that an error. + */ + return report(options, oid, OBJ_BLOB, + FSCK_MSG_GITATTRIBUTES_LARGE, + ".gitattributes too large to parse"); + } + + for (ptr = buf; *ptr; ) { + const char *eol = strchrnul(ptr, '\n'); + if (eol - ptr >= ATTR_MAX_LINE_LENGTH) { + ret |= report(options, oid, OBJ_BLOB, + FSCK_MSG_GITATTRIBUTES_LINE_LENGTH, + ".gitattributes has too long lines to parse"); + break; + } + + ptr = *eol ? eol + 1 : eol; + } + } + return ret; } @@ -1293,6 +1326,9 @@ int fsck_finish(struct fsck_options *options) ret |= fsck_blobs(&options->gitmodules_found, &options->gitmodules_done, FSCK_MSG_GITMODULES_MISSING, FSCK_MSG_GITMODULES_BLOB, options, ".gitmodules"); + ret |= fsck_blobs(&options->gitattributes_found, &options->gitattributes_done, + FSCK_MSG_GITATTRIBUTES_MISSING, FSCK_MSG_GITATTRIBUTES_BLOB, + options, ".gitattributes"); return ret; } diff --git a/fsck.h b/fsck.h index d07f7a2459..cc3379d4e9 100644 --- a/fsck.h +++ b/fsck.h @@ -55,6 +55,10 @@ enum fsck_msg_type { FUNC(GITMODULES_URL, ERROR) \ FUNC(GITMODULES_PATH, ERROR) \ FUNC(GITMODULES_UPDATE, ERROR) \ + FUNC(GITATTRIBUTES_MISSING, ERROR) \ + FUNC(GITATTRIBUTES_LARGE, ERROR) \ + FUNC(GITATTRIBUTES_LINE_LENGTH, ERROR) \ + FUNC(GITATTRIBUTES_BLOB, ERROR) \ /* warnings */ \ FUNC(BAD_FILEMODE, WARN) \ FUNC(EMPTY_NAME, WARN) \ @@ -129,6 +133,8 @@ struct fsck_options { struct oidset skiplist; struct oidset gitmodules_found; struct oidset gitmodules_done; + struct oidset gitattributes_found; + struct oidset gitattributes_done; kh_oid_map_t *object_names; }; @@ -136,18 +142,24 @@ struct fsck_options { .skiplist = OIDSET_INIT, \ .gitmodules_found = OIDSET_INIT, \ .gitmodules_done = OIDSET_INIT, \ + .gitattributes_found = OIDSET_INIT, \ + .gitattributes_done = OIDSET_INIT, \ .error_func = fsck_error_function \ } #define FSCK_OPTIONS_STRICT { \ .strict = 1, \ .gitmodules_found = OIDSET_INIT, \ .gitmodules_done = OIDSET_INIT, \ + .gitattributes_found = OIDSET_INIT, \ + .gitattributes_done = OIDSET_INIT, \ .error_func = fsck_error_function, \ } #define FSCK_OPTIONS_MISSING_GITMODULES { \ .strict = 1, \ .gitmodules_found = OIDSET_INIT, \ .gitmodules_done = OIDSET_INIT, \ + .gitattributes_found = OIDSET_INIT, \ + .gitattributes_done = OIDSET_INIT, \ .error_func = fsck_error_cb_print_missing_gitmodules, \ } diff --git a/t/t1450-fsck.sh b/t/t1450-fsck.sh index 5071ac63a5..9e0afe1fbf 100755 --- a/t/t1450-fsck.sh +++ b/t/t1450-fsck.sh @@ -865,4 +865,28 @@ test_expect_success 'detect corrupt index file in fsck' ' test_i18ngrep "bad index file" errors ' +test_expect_success 'fsck error on gitattributes with excessive line lengths' ' + blob=$(printf "pattern %02048d" 1 | git hash-object -w --stdin) && + test_when_finished "remove_object $blob" && + tree=$(printf "100644 blob %s\t%s\n" $blob .gitattributes | git mktree) && + test_when_finished "remove_object $tree" && + cat >expected <<-EOF && + error in blob $blob: gitattributesLineLength: .gitattributes has too long lines to parse + EOF + test_must_fail git fsck --no-dangling >actual 2>&1 && + test_cmp expected actual +' + +test_expect_success 'fsck error on gitattributes with excessive size' ' + blob=$(test-tool genzeros $((100 * 1024 * 1024 + 1)) | git hash-object -w --stdin) && + test_when_finished "remove_object $blob" && + tree=$(printf "100644 blob %s\t%s\n" $blob .gitattributes | git mktree) && + test_when_finished "remove_object $tree" && + cat >expected <<-EOF && + error in blob $blob: gitattributesLarge: .gitattributes too large to parse + EOF + test_must_fail git fsck --no-dangling >actual 2>&1 && + test_cmp expected actual +' + test_done -- cgit v1.3