Toshaan Bharvani
11 months ago
5 changed files with 294 additions and 10 deletions
@ -0,0 +1,38 @@ |
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diff --git a/compat.c b/compat.c |
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index 46dfe3a9c2e..478a9403eea 100644 |
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--- a/compat.c |
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+++ b/compat.c |
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@@ -190,26 +190,26 @@ compat_pkalg_proposal(struct ssh *ssh, char *pkalg_prop) |
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char * |
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compat_kex_proposal(struct ssh *ssh, char *p) |
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{ |
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- char *cp = NULL; |
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+ char *cp = NULL, *cp2 = NULL; |
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|
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if ((ssh->compat & (SSH_BUG_CURVE25519PAD|SSH_OLD_DHGEX)) == 0) |
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return xstrdup(p); |
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debug2_f("original KEX proposal: %s", p); |
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if ((ssh->compat & SSH_BUG_CURVE25519PAD) != 0) |
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- if ((p = match_filter_denylist(p, |
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+ if ((cp = match_filter_denylist(p, |
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"curve25519-sha256@libssh.org")) == NULL) |
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fatal("match_filter_denylist failed"); |
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if ((ssh->compat & SSH_OLD_DHGEX) != 0) { |
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- cp = p; |
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- if ((p = match_filter_denylist(p, |
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+ if ((cp2 = match_filter_denylist(cp ? cp : p, |
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"diffie-hellman-group-exchange-sha256," |
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"diffie-hellman-group-exchange-sha1")) == NULL) |
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fatal("match_filter_denylist failed"); |
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free(cp); |
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+ cp = cp2; |
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} |
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- debug2_f("compat KEX proposal: %s", p); |
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- if (*p == '\0') |
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+ if (cp == NULL || *cp == '\0') |
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fatal("No supported key exchange algorithms found"); |
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- return p; |
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+ debug2_f("compat KEX proposal: %s", cp); |
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+ return cp; |
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} |
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@ -0,0 +1,100 @@ |
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diff -up openssh-8.7p1/compat.c.sshrsacheck openssh-8.7p1/compat.c |
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--- openssh-8.7p1/compat.c.sshrsacheck 2023-01-12 13:29:06.338710923 +0100 |
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+++ openssh-8.7p1/compat.c 2023-01-12 13:29:06.357711165 +0100 |
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@@ -43,6 +43,7 @@ void |
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compat_banner(struct ssh *ssh, const char *version) |
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{ |
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int i; |
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+ int forbid_ssh_rsa = 0; |
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static struct { |
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char *pat; |
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int bugs; |
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@@ -145,16 +146,21 @@ compat_banner(struct ssh *ssh, const cha |
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}; |
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|
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/* process table, return first match */ |
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+ forbid_ssh_rsa = (ssh->compat & SSH_RH_RSASIGSHA); |
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ssh->compat = 0; |
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for (i = 0; check[i].pat; i++) { |
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if (match_pattern_list(version, check[i].pat, 0) == 1) { |
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debug_f("match: %s pat %s compat 0x%08x", |
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version, check[i].pat, check[i].bugs); |
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ssh->compat = check[i].bugs; |
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+ if (forbid_ssh_rsa) |
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+ ssh->compat |= SSH_RH_RSASIGSHA; |
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return; |
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} |
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} |
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debug_f("no match: %s", version); |
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+ if (forbid_ssh_rsa) |
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+ ssh->compat |= SSH_RH_RSASIGSHA; |
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} |
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|
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/* Always returns pointer to allocated memory, caller must free. */ |
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diff -up openssh-8.7p1/compat.h.sshrsacheck openssh-8.7p1/compat.h |
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--- openssh-8.7p1/compat.h.sshrsacheck 2021-08-20 06:03:49.000000000 +0200 |
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+++ openssh-8.7p1/compat.h 2023-01-12 13:29:06.358711178 +0100 |
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@@ -30,7 +30,7 @@ |
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#define SSH_BUG_UTF8TTYMODE 0x00000001 |
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#define SSH_BUG_SIGTYPE 0x00000002 |
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#define SSH_BUG_SIGTYPE74 0x00000004 |
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-/* #define unused 0x00000008 */ |
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+#define SSH_RH_RSASIGSHA 0x00000008 |
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#define SSH_OLD_SESSIONID 0x00000010 |
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/* #define unused 0x00000020 */ |
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#define SSH_BUG_DEBUG 0x00000040 |
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diff -up openssh-8.7p1/serverloop.c.sshrsacheck openssh-8.7p1/serverloop.c |
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--- openssh-8.7p1/serverloop.c.sshrsacheck 2023-01-12 14:57:08.118400073 +0100 |
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+++ openssh-8.7p1/serverloop.c 2023-01-12 14:59:17.330470518 +0100 |
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@@ -737,6 +737,10 @@ server_input_hostkeys_prove(struct ssh * |
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else if (ssh->kex->flags & KEX_RSA_SHA2_256_SUPPORTED) |
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sigalg = "rsa-sha2-256"; |
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} |
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+ if (ssh->compat & SSH_RH_RSASIGSHA && sigalg == NULL) { |
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+ sigalg = "rsa-sha2-512"; |
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+ debug3_f("SHA1 signature is not supported, falling back to %s", sigalg); |
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+ } |
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debug3_f("sign %s key (index %d) using sigalg %s", |
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sshkey_type(key), ndx, sigalg == NULL ? "default" : sigalg); |
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if ((r = sshbuf_put_cstring(sigbuf, |
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diff -up openssh-8.7p1/sshd.c.sshrsacheck openssh-8.7p1/sshd.c |
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--- openssh-8.7p1/sshd.c.sshrsacheck 2023-01-12 13:29:06.355711140 +0100 |
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+++ openssh-8.7p1/sshd.c 2023-01-12 13:29:06.358711178 +0100 |
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@@ -1640,6 +1651,7 @@ main(int ac, char **av) |
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int keytype; |
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Authctxt *authctxt; |
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struct connection_info *connection_info = NULL; |
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+ int forbid_ssh_rsa = 0; |
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#ifdef HAVE_SECUREWARE |
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(void)set_auth_parameters(ac, av); |
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@@ -1938,6 +1950,19 @@ main(int ac, char **av) |
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key = NULL; |
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continue; |
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} |
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+ if (key && (sshkey_type_plain(key->type) == KEY_RSA || sshkey_type_plain(key->type) == KEY_RSA_CERT)) { |
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+ size_t sign_size = 0; |
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+ u_char *tmp = NULL; |
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+ u_char data[] = "Test SHA1 vector"; |
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+ int res; |
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+ |
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+ res = ssh_rsa_sign(key, &tmp, &sign_size, data, sizeof(data), NULL); |
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+ free(tmp); |
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+ if (res == SSH_ERR_LIBCRYPTO_ERROR) { |
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+ logit_f("sshd: ssh-rsa algorithm is disabled"); |
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+ forbid_ssh_rsa = 1; |
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+ } |
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+ } |
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if (sshkey_is_sk(key) && |
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key->sk_flags & SSH_SK_USER_PRESENCE_REQD) { |
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debug("host key %s requires user presence, ignoring", |
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@@ -2275,6 +2306,9 @@ main(int ac, char **av) |
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check_ip_options(ssh); |
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+ if (forbid_ssh_rsa) |
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+ ssh->compat |= SSH_RH_RSASIGSHA; |
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+ |
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/* Prepare the channels layer */ |
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channel_init_channels(ssh); |
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channel_set_af(ssh, options.address_family); |
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@ -0,0 +1,57 @@ |
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diff --git a/ssh-keyscan.c b/ssh-keyscan.c |
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index d29a03b4..d7283136 100644 |
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--- a/ssh-keyscan.c |
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+++ b/ssh-keyscan.c |
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@@ -490,6 +490,15 @@ congreet(int s) |
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return; |
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} |
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+ /* |
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+ * Read the server banner as per RFC4253 section 4.2. The "SSH-" |
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+ * protocol identification string may be preceeded by an arbitarily |
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+ * large banner which we must read and ignore. Loop while reading |
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+ * newline-terminated lines until we have one starting with "SSH-". |
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+ * The ID string cannot be longer than 255 characters although the |
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+ * preceeding banner lines may (in which case they'll be discarded |
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+ * in multiple iterations of the outer loop). |
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+ */ |
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for (;;) { |
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memset(buf, '\0', sizeof(buf)); |
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bufsiz = sizeof(buf); |
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@@ -517,6 +526,11 @@ congreet(int s) |
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conrecycle(s); |
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return; |
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} |
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+ if (cp >= buf + sizeof(buf)) { |
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+ error("%s: greeting exceeds allowable length", c->c_name); |
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+ confree(s); |
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+ return; |
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+ } |
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if (*cp != '\n' && *cp != '\r') { |
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error("%s: bad greeting", c->c_name); |
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confree(s); |
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diff --git a/sshsig.c b/sshsig.c |
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index 1e3b6398..eb2a931e 100644 |
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--- a/sshsig.c |
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+++ b/sshsig.c |
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@@ -491,7 +491,7 @@ hash_file(int fd, const char *hashalg, struct sshbuf **bp) |
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{ |
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char *hex, rbuf[8192], hash[SSH_DIGEST_MAX_LENGTH]; |
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ssize_t n, total = 0; |
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- struct ssh_digest_ctx *ctx; |
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+ struct ssh_digest_ctx *ctx = NULL; |
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int alg, oerrno, r = SSH_ERR_INTERNAL_ERROR; |
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struct sshbuf *b = NULL; |
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@@ -549,9 +548,11 @@ hash_file(int fd, const char *hashalg, struct sshbuf **bp) |
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/* success */ |
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r = 0; |
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out: |
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+ oerrno = errno; |
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sshbuf_free(b); |
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ssh_digest_free(ctx); |
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explicit_bzero(hash, sizeof(hash)); |
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+ errno = oerrno; |
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return r; |
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} |
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