Bug#923486: CVE-2019-6111 not fixed, file transfer of unwanted files by malicious SSH server still possible
Hi
Attached the patch and debdiff for unstable which fixes this issue.
Colin, but please double check if this is enough. A server which sends
an additional malicious file is blocked by that (and the patch is not
following git-dpm workflow as I'm unfamiliar with it).
dummy@sid:~$ scp -P 2222 foo@localhost:test.txt .
The authenticity of host '[localhost]:2222 ([127.0.0.1]:2222)' can't be established.
RSA key fingerprint is SHA256:BCYLeKMU5zuQ/Xd2Xc8sur4Mp7pQTMHcpwQkfAAmeXM.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '[localhost]:2222' (RSA) to the list of known hosts.
foo@localhost's password:
test.txt 100% 32 0.7KB/s 00:00
protocol error: filename does not match request
dummy@sid:~$
Regards,
Salvatore
diff -Nru openssh-7.9p1/debian/changelog openssh-7.9p1/debian/changelog
--- openssh-7.9p1/debian/changelog 2019-02-28 20:31:49.000000000 +0100
+++ openssh-7.9p1/debian/changelog 2019-02-28 22:45:36.000000000 +0100
@@ -1,3 +1,11 @@
+openssh (1:7.9p1-8.1) unstable; urgency=medium
+
+ * Non-maintainer upload.
+ * When checking that filenames sent by the server side match what the client
+ requested (Closes: #923486)
+
+ -- Salvatore Bonaccorso <carnil@debian.org> Thu, 28 Feb 2019 22:45:36 +0100
+
openssh (1:7.9p1-8) unstable; urgency=medium
[ Colin Watson ]
diff -Nru openssh-7.9p1/debian/patches/series openssh-7.9p1/debian/patches/series
--- openssh-7.9p1/debian/patches/series 2019-02-28 11:37:30.000000000 +0100
+++ openssh-7.9p1/debian/patches/series 2019-02-28 22:45:36.000000000 +0100
@@ -30,3 +30,4 @@
check-filenames-in-scp-client.patch
fix-key-type-check.patch
request-rsa-sha2-cert-signatures.patch
+upstream-when-checking-that-filenames-sent-by-the-se.patch
diff -Nru openssh-7.9p1/debian/patches/upstream-when-checking-that-filenames-sent-by-the-se.patch openssh-7.9p1/debian/patches/upstream-when-checking-that-filenames-sent-by-the-se.patch
--- openssh-7.9p1/debian/patches/upstream-when-checking-that-filenames-sent-by-the-se.patch 1970-01-01 01:00:00.000000000 +0100
+++ openssh-7.9p1/debian/patches/upstream-when-checking-that-filenames-sent-by-the-se.patch 2019-02-28 22:45:36.000000000 +0100
@@ -0,0 +1,351 @@
+From: "djm@openbsd.org" <djm@openbsd.org>
+Date: Sun, 10 Feb 2019 11:15:52 +0000
+Subject: upstream: when checking that filenames sent by the server side
+Origin: https://anongit.mindrot.org/openssh.git/commit/?id=3d896c157c722bc47adca51a58dca859225b5874
+Bug-Debian: https://bugs.debian.org/923486
+
+match what the client requested, be prepared to handle shell-style brace
+alternations, e.g. "{foo,bar}".
+
+"looks good to me" millert@ + in snaps for the last week courtesy
+deraadt@
+
+OpenBSD-Commit-ID: 3b1ce7639b0b25b2248e3a30f561a548f6815f3e
+---
+ scp.c | 282 +++++++++++++++++++++++++++++++++++++++++++++++++++++++---
+ 1 file changed, 270 insertions(+), 12 deletions(-)
+
+diff --git a/scp.c b/scp.c
+index 96fc246cd9ba..80bc0e8b16d1 100644
+--- a/scp.c
++++ b/scp.c
+@@ -630,6 +630,253 @@ parse_scp_uri(const char *uri, char **userp, char **hostp, int *portp,
+ return r;
+ }
+
++/* Appends a string to an array; returns 0 on success, -1 on alloc failure */
++static int
++append(char *cp, char ***ap, size_t *np)
++{
++ char **tmp;
++
++ if ((tmp = reallocarray(*ap, *np + 1, sizeof(*tmp))) == NULL)
++ return -1;
++ tmp[(*np)] = cp;
++ (*np)++;
++ *ap = tmp;
++ return 0;
++}
++
++/*
++ * Finds the start and end of the first brace pair in the pattern.
++ * returns 0 on success or -1 for invalid patterns.
++ */
++static int
++find_brace(const char *pattern, int *startp, int *endp)
++{
++ int i;
++ int in_bracket, brace_level;
++
++ *startp = *endp = -1;
++ in_bracket = brace_level = 0;
++ for (i = 0; i < INT_MAX && *endp < 0 && pattern[i] != '\0'; i++) {
++ switch (pattern[i]) {
++ case '\\':
++ /* skip next character */
++ if (pattern[i + 1] != '\0')
++ i++;
++ break;
++ case '[':
++ in_bracket = 1;
++ break;
++ case ']':
++ in_bracket = 0;
++ break;
++ case '{':
++ if (in_bracket)
++ break;
++ if (pattern[i + 1] == '}') {
++ /* Protect a single {}, for find(1), like csh */
++ i++; /* skip */
++ break;
++ }
++ if (*startp == -1)
++ *startp = i;
++ brace_level++;
++ break;
++ case '}':
++ if (in_bracket)
++ break;
++ if (*startp < 0) {
++ /* Unbalanced brace */
++ return -1;
++ }
++ if (--brace_level <= 0)
++ *endp = i;
++ break;
++ }
++ }
++ /* unbalanced brackets/braces */
++ if (*endp < 0 && (*startp >= 0 || in_bracket))
++ return -1;
++ return 0;
++}
++
++/*
++ * Assembles and records a successfully-expanded pattern, returns -1 on
++ * alloc failure.
++ */
++static int
++emit_expansion(const char *pattern, int brace_start, int brace_end,
++ int sel_start, int sel_end, char ***patternsp, size_t *npatternsp)
++{
++ char *cp;
++ int o = 0, tail_len = strlen(pattern + brace_end + 1);
++
++ if ((cp = malloc(brace_start + (sel_end - sel_start) +
++ tail_len + 1)) == NULL)
++ return -1;
++
++ /* Pattern before initial brace */
++ if (brace_start > 0) {
++ memcpy(cp, pattern, brace_start);
++ o = brace_start;
++ }
++ /* Current braced selection */
++ if (sel_end - sel_start > 0) {
++ memcpy(cp + o, pattern + sel_start,
++ sel_end - sel_start);
++ o += sel_end - sel_start;
++ }
++ /* Remainder of pattern after closing brace */
++ if (tail_len > 0) {
++ memcpy(cp + o, pattern + brace_end + 1, tail_len);
++ o += tail_len;
++ }
++ cp[o] = '\0';
++ if (append(cp, patternsp, npatternsp) != 0) {
++ free(cp);
++ return -1;
++ }
++ return 0;
++}
++
++/*
++ * Expand the first encountered brace in pattern, appending the expanded
++ * patterns it yielded to the *patternsp array.
++ *
++ * Returns 0 on success or -1 on allocation failure.
++ *
++ * Signals whether expansion was performed via *expanded and whether
++ * pattern was invalid via *invalid.
++ */
++static int
++brace_expand_one(const char *pattern, char ***patternsp, size_t *npatternsp,
++ int *expanded, int *invalid)
++{
++ int i;
++ int in_bracket, brace_start, brace_end, brace_level;
++ int sel_start, sel_end;
++
++ *invalid = *expanded = 0;
++
++ if (find_brace(pattern, &brace_start, &brace_end) != 0) {
++ *invalid = 1;
++ return 0;
++ } else if (brace_start == -1)
++ return 0;
++
++ in_bracket = brace_level = 0;
++ for (i = sel_start = brace_start + 1; i < brace_end; i++) {
++ switch (pattern[i]) {
++ case '{':
++ if (in_bracket)
++ break;
++ brace_level++;
++ break;
++ case '}':
++ if (in_bracket)
++ break;
++ brace_level--;
++ break;
++ case '[':
++ in_bracket = 1;
++ break;
++ case ']':
++ in_bracket = 0;
++ break;
++ case '\\':
++ if (i < brace_end - 1)
++ i++; /* skip */
++ break;
++ }
++ if (pattern[i] == ',' || i == brace_end - 1) {
++ if (in_bracket || brace_level > 0)
++ continue;
++ /* End of a selection, emit an expanded pattern */
++
++ /* Adjust end index for last selection */
++ sel_end = (i == brace_end - 1) ? brace_end : i;
++ if (emit_expansion(pattern, brace_start, brace_end,
++ sel_start, sel_end, patternsp, npatternsp) != 0)
++ return -1;
++ /* move on to the next selection */
++ sel_start = i + 1;
++ continue;
++ }
++ }
++ if (in_bracket || brace_level > 0) {
++ *invalid = 1;
++ return 0;
++ }
++ /* success */
++ *expanded = 1;
++ return 0;
++}
++
++/* Expand braces from pattern. Returns 0 on success, -1 on failure */
++static int
++brace_expand(const char *pattern, char ***patternsp, size_t *npatternsp)
++{
++ char *cp, *cp2, **active = NULL, **done = NULL;
++ size_t i, nactive = 0, ndone = 0;
++ int ret = -1, invalid = 0, expanded = 0;
++
++ *patternsp = NULL;
++ *npatternsp = 0;
++
++ /* Start the worklist with the original pattern */
++ if ((cp = strdup(pattern)) == NULL)
++ return -1;
++ if (append(cp, &active, &nactive) != 0) {
++ free(cp);
++ return -1;
++ }
++ while (nactive > 0) {
++ cp = active[nactive - 1];
++ nactive--;
++ if (brace_expand_one(cp, &active, &nactive,
++ &expanded, &invalid) == -1) {
++ free(cp);
++ goto fail;
++ }
++ if (invalid)
++ fatal("%s: invalid brace pattern \"%s\"", __func__, cp);
++ if (expanded) {
++ /*
++ * Current entry expanded to new entries on the
++ * active list; discard the progenitor pattern.
++ */
++ free(cp);
++ continue;
++ }
++ /*
++ * Pattern did not expand; append the finename component to
++ * the completed list
++ */
++ if ((cp2 = strrchr(cp, '/')) != NULL)
++ *cp2++ = '\0';
++ else
++ cp2 = cp;
++ if (append(xstrdup(cp2), &done, &ndone) != 0) {
++ free(cp);
++ goto fail;
++ }
++ free(cp);
++ }
++ /* success */
++ *patternsp = done;
++ *npatternsp = ndone;
++ done = NULL;
++ ndone = 0;
++ ret = 0;
++ fail:
++ for (i = 0; i < nactive; i++)
++ free(active[i]);
++ free(active);
++ for (i = 0; i < ndone; i++)
++ free(done[i]);
++ free(done);
++ return ret;
++}
++
+ void
+ toremote(int argc, char **argv)
+ {
+@@ -993,7 +1240,8 @@ sink(int argc, char **argv, const char *src)
+ unsigned long long ull;
+ int setimes, targisdir, wrerrno = 0;
+ char ch, *cp, *np, *targ, *why, *vect[1], buf[2048], visbuf[2048];
+- char *src_copy = NULL, *restrict_pattern = NULL;
++ char **patterns = NULL;
++ size_t n, npatterns = 0;
+ struct timeval tv[2];
+
+ #define atime tv[0]
+@@ -1023,16 +1271,13 @@ sink(int argc, char **argv, const char *src)
+ * Prepare to try to restrict incoming filenames to match
+ * the requested destination file glob.
+ */
+- if ((src_copy = strdup(src)) == NULL)
+- fatal("strdup failed");
+- if ((restrict_pattern = strrchr(src_copy, '/')) != NULL) {
+- *restrict_pattern++ = '\0';
+- }
++ if (brace_expand(src, &patterns, &npatterns) != 0)
++ fatal("%s: could not expand pattern", __func__);
+ }
+ for (first = 1;; first = 0) {
+ cp = buf;
+ if (atomicio(read, remin, cp, 1) != 1)
+- return;
++ goto done;
+ if (*cp++ == '\n')
+ SCREWUP("unexpected <newline>");
+ do {
+@@ -1058,7 +1303,7 @@ sink(int argc, char **argv, const char *src)
+ }
+ if (buf[0] == 'E') {
+ (void) atomicio(vwrite, remout, "", 1);
+- return;
++ goto done;
+ }
+ if (ch == '\n')
+ *--cp = 0;
+@@ -1133,9 +1378,14 @@ sink(int argc, char **argv, const char *src)
+ run_err("error: unexpected filename: %s", cp);
+ exit(1);
+ }
+- if (restrict_pattern != NULL &&
+- fnmatch(restrict_pattern, cp, 0) != 0)
+- SCREWUP("filename does not match request");
++ if (npatterns > 0) {
++ for (n = 0; n < npatterns; n++) {
++ if (fnmatch(patterns[n], cp, 0) == 0)
++ break;
++ }
++ if (n >= npatterns)
++ SCREWUP("filename does not match request");
++ }
+ if (targisdir) {
+ static char *namebuf;
+ static size_t cursize;
+@@ -1294,7 +1544,15 @@ bad: run_err("%s: %s", np, strerror(errno));
+ break;
+ }
+ }
++done:
++ for (n = 0; n < npatterns; n++)
++ free(patterns[n]);
++ free(patterns);
++ return;
+ screwup:
++ for (n = 0; n < npatterns; n++)
++ free(patterns[n]);
++ free(patterns);
+ run_err("protocol error: %s", why);
+ exit(1);
+ }
+--
+2.20.1
+
From: "djm@openbsd.org" <djm@openbsd.org>
Date: Sun, 10 Feb 2019 11:15:52 +0000
Subject: upstream: when checking that filenames sent by the server side
Origin: https://anongit.mindrot.org/openssh.git/commit/?id=3d896c157c722bc47adca51a58dca859225b5874
Bug-Debian: https://bugs.debian.org/923486
match what the client requested, be prepared to handle shell-style brace
alternations, e.g. "{foo,bar}".
"looks good to me" millert@ + in snaps for the last week courtesy
deraadt@
OpenBSD-Commit-ID: 3b1ce7639b0b25b2248e3a30f561a548f6815f3e
---
scp.c | 282 +++++++++++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 270 insertions(+), 12 deletions(-)
diff --git a/scp.c b/scp.c
index 96fc246cd9ba..80bc0e8b16d1 100644
--- a/scp.c
+++ b/scp.c
@@ -630,6 +630,253 @@ parse_scp_uri(const char *uri, char **userp, char **hostp, int *portp,
return r;
}
+/* Appends a string to an array; returns 0 on success, -1 on alloc failure */
+static int
+append(char *cp, char ***ap, size_t *np)
+{
+ char **tmp;
+
+ if ((tmp = reallocarray(*ap, *np + 1, sizeof(*tmp))) == NULL)
+ return -1;
+ tmp[(*np)] = cp;
+ (*np)++;
+ *ap = tmp;
+ return 0;
+}
+
+/*
+ * Finds the start and end of the first brace pair in the pattern.
+ * returns 0 on success or -1 for invalid patterns.
+ */
+static int
+find_brace(const char *pattern, int *startp, int *endp)
+{
+ int i;
+ int in_bracket, brace_level;
+
+ *startp = *endp = -1;
+ in_bracket = brace_level = 0;
+ for (i = 0; i < INT_MAX && *endp < 0 && pattern[i] != '\0'; i++) {
+ switch (pattern[i]) {
+ case '\\':
+ /* skip next character */
+ if (pattern[i + 1] != '\0')
+ i++;
+ break;
+ case '[':
+ in_bracket = 1;
+ break;
+ case ']':
+ in_bracket = 0;
+ break;
+ case '{':
+ if (in_bracket)
+ break;
+ if (pattern[i + 1] == '}') {
+ /* Protect a single {}, for find(1), like csh */
+ i++; /* skip */
+ break;
+ }
+ if (*startp == -1)
+ *startp = i;
+ brace_level++;
+ break;
+ case '}':
+ if (in_bracket)
+ break;
+ if (*startp < 0) {
+ /* Unbalanced brace */
+ return -1;
+ }
+ if (--brace_level <= 0)
+ *endp = i;
+ break;
+ }
+ }
+ /* unbalanced brackets/braces */
+ if (*endp < 0 && (*startp >= 0 || in_bracket))
+ return -1;
+ return 0;
+}
+
+/*
+ * Assembles and records a successfully-expanded pattern, returns -1 on
+ * alloc failure.
+ */
+static int
+emit_expansion(const char *pattern, int brace_start, int brace_end,
+ int sel_start, int sel_end, char ***patternsp, size_t *npatternsp)
+{
+ char *cp;
+ int o = 0, tail_len = strlen(pattern + brace_end + 1);
+
+ if ((cp = malloc(brace_start + (sel_end - sel_start) +
+ tail_len + 1)) == NULL)
+ return -1;
+
+ /* Pattern before initial brace */
+ if (brace_start > 0) {
+ memcpy(cp, pattern, brace_start);
+ o = brace_start;
+ }
+ /* Current braced selection */
+ if (sel_end - sel_start > 0) {
+ memcpy(cp + o, pattern + sel_start,
+ sel_end - sel_start);
+ o += sel_end - sel_start;
+ }
+ /* Remainder of pattern after closing brace */
+ if (tail_len > 0) {
+ memcpy(cp + o, pattern + brace_end + 1, tail_len);
+ o += tail_len;
+ }
+ cp[o] = '\0';
+ if (append(cp, patternsp, npatternsp) != 0) {
+ free(cp);
+ return -1;
+ }
+ return 0;
+}
+
+/*
+ * Expand the first encountered brace in pattern, appending the expanded
+ * patterns it yielded to the *patternsp array.
+ *
+ * Returns 0 on success or -1 on allocation failure.
+ *
+ * Signals whether expansion was performed via *expanded and whether
+ * pattern was invalid via *invalid.
+ */
+static int
+brace_expand_one(const char *pattern, char ***patternsp, size_t *npatternsp,
+ int *expanded, int *invalid)
+{
+ int i;
+ int in_bracket, brace_start, brace_end, brace_level;
+ int sel_start, sel_end;
+
+ *invalid = *expanded = 0;
+
+ if (find_brace(pattern, &brace_start, &brace_end) != 0) {
+ *invalid = 1;
+ return 0;
+ } else if (brace_start == -1)
+ return 0;
+
+ in_bracket = brace_level = 0;
+ for (i = sel_start = brace_start + 1; i < brace_end; i++) {
+ switch (pattern[i]) {
+ case '{':
+ if (in_bracket)
+ break;
+ brace_level++;
+ break;
+ case '}':
+ if (in_bracket)
+ break;
+ brace_level--;
+ break;
+ case '[':
+ in_bracket = 1;
+ break;
+ case ']':
+ in_bracket = 0;
+ break;
+ case '\\':
+ if (i < brace_end - 1)
+ i++; /* skip */
+ break;
+ }
+ if (pattern[i] == ',' || i == brace_end - 1) {
+ if (in_bracket || brace_level > 0)
+ continue;
+ /* End of a selection, emit an expanded pattern */
+
+ /* Adjust end index for last selection */
+ sel_end = (i == brace_end - 1) ? brace_end : i;
+ if (emit_expansion(pattern, brace_start, brace_end,
+ sel_start, sel_end, patternsp, npatternsp) != 0)
+ return -1;
+ /* move on to the next selection */
+ sel_start = i + 1;
+ continue;
+ }
+ }
+ if (in_bracket || brace_level > 0) {
+ *invalid = 1;
+ return 0;
+ }
+ /* success */
+ *expanded = 1;
+ return 0;
+}
+
+/* Expand braces from pattern. Returns 0 on success, -1 on failure */
+static int
+brace_expand(const char *pattern, char ***patternsp, size_t *npatternsp)
+{
+ char *cp, *cp2, **active = NULL, **done = NULL;
+ size_t i, nactive = 0, ndone = 0;
+ int ret = -1, invalid = 0, expanded = 0;
+
+ *patternsp = NULL;
+ *npatternsp = 0;
+
+ /* Start the worklist with the original pattern */
+ if ((cp = strdup(pattern)) == NULL)
+ return -1;
+ if (append(cp, &active, &nactive) != 0) {
+ free(cp);
+ return -1;
+ }
+ while (nactive > 0) {
+ cp = active[nactive - 1];
+ nactive--;
+ if (brace_expand_one(cp, &active, &nactive,
+ &expanded, &invalid) == -1) {
+ free(cp);
+ goto fail;
+ }
+ if (invalid)
+ fatal("%s: invalid brace pattern \"%s\"", __func__, cp);
+ if (expanded) {
+ /*
+ * Current entry expanded to new entries on the
+ * active list; discard the progenitor pattern.
+ */
+ free(cp);
+ continue;
+ }
+ /*
+ * Pattern did not expand; append the finename component to
+ * the completed list
+ */
+ if ((cp2 = strrchr(cp, '/')) != NULL)
+ *cp2++ = '\0';
+ else
+ cp2 = cp;
+ if (append(xstrdup(cp2), &done, &ndone) != 0) {
+ free(cp);
+ goto fail;
+ }
+ free(cp);
+ }
+ /* success */
+ *patternsp = done;
+ *npatternsp = ndone;
+ done = NULL;
+ ndone = 0;
+ ret = 0;
+ fail:
+ for (i = 0; i < nactive; i++)
+ free(active[i]);
+ free(active);
+ for (i = 0; i < ndone; i++)
+ free(done[i]);
+ free(done);
+ return ret;
+}
+
void
toremote(int argc, char **argv)
{
@@ -993,7 +1240,8 @@ sink(int argc, char **argv, const char *src)
unsigned long long ull;
int setimes, targisdir, wrerrno = 0;
char ch, *cp, *np, *targ, *why, *vect[1], buf[2048], visbuf[2048];
- char *src_copy = NULL, *restrict_pattern = NULL;
+ char **patterns = NULL;
+ size_t n, npatterns = 0;
struct timeval tv[2];
#define atime tv[0]
@@ -1023,16 +1271,13 @@ sink(int argc, char **argv, const char *src)
* Prepare to try to restrict incoming filenames to match
* the requested destination file glob.
*/
- if ((src_copy = strdup(src)) == NULL)
- fatal("strdup failed");
- if ((restrict_pattern = strrchr(src_copy, '/')) != NULL) {
- *restrict_pattern++ = '\0';
- }
+ if (brace_expand(src, &patterns, &npatterns) != 0)
+ fatal("%s: could not expand pattern", __func__);
}
for (first = 1;; first = 0) {
cp = buf;
if (atomicio(read, remin, cp, 1) != 1)
- return;
+ goto done;
if (*cp++ == '\n')
SCREWUP("unexpected <newline>");
do {
@@ -1058,7 +1303,7 @@ sink(int argc, char **argv, const char *src)
}
if (buf[0] == 'E') {
(void) atomicio(vwrite, remout, "", 1);
- return;
+ goto done;
}
if (ch == '\n')
*--cp = 0;
@@ -1133,9 +1378,14 @@ sink(int argc, char **argv, const char *src)
run_err("error: unexpected filename: %s", cp);
exit(1);
}
- if (restrict_pattern != NULL &&
- fnmatch(restrict_pattern, cp, 0) != 0)
- SCREWUP("filename does not match request");
+ if (npatterns > 0) {
+ for (n = 0; n < npatterns; n++) {
+ if (fnmatch(patterns[n], cp, 0) == 0)
+ break;
+ }
+ if (n >= npatterns)
+ SCREWUP("filename does not match request");
+ }
if (targisdir) {
static char *namebuf;
static size_t cursize;
@@ -1294,7 +1544,15 @@ bad: run_err("%s: %s", np, strerror(errno));
break;
}
}
+done:
+ for (n = 0; n < npatterns; n++)
+ free(patterns[n]);
+ free(patterns);
+ return;
screwup:
+ for (n = 0; n < npatterns; n++)
+ free(patterns[n]);
+ free(patterns);
run_err("protocol error: %s", why);
exit(1);
}
--
2.20.1
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