diff options
| -rw-r--r-- | Documentation/config.txt | 12 | ||||
| -rw-r--r-- | Documentation/git-receive-pack.txt | 19 | ||||
| -rw-r--r-- | Documentation/technical/pack-protocol.txt | 6 | ||||
| -rw-r--r-- | Documentation/technical/protocol-capabilities.txt | 7 | ||||
| -rw-r--r-- | builtin/receive-pack.c | 132 | ||||
| -rw-r--r-- | send-pack.c | 18 | ||||
| -rwxr-xr-x | t/t5534-push-signed.sh | 22 |
7 files changed, 187 insertions, 29 deletions
diff --git a/Documentation/config.txt b/Documentation/config.txt index 0d01e32888..dd6fd65e9f 100644 --- a/Documentation/config.txt +++ b/Documentation/config.txt @@ -2038,17 +2038,17 @@ rebase.autostash:: successful rebase might result in non-trivial conflicts. Defaults to false. -receive.acceptpushcert:: - By default, `git receive-pack` will advertise that it - accepts `git push --signed`. Setting this variable to - false disables it (this is a tentative variable that - will go away at the end of this series). - receive.autogc:: By default, git-receive-pack will run "git-gc --auto" after receiving data from git-push and updating refs. You can stop it by setting this variable to false. +receive.certnonceseed:: + By setting this variable to a string, `git receive-pack` + will accept a `git push --signed` and verifies it by using + a "nonce" protected by HMAC using this string as a secret + key. + receive.fsckObjects:: If it is set to true, git-receive-pack will check all received objects. It will abort in the case of a malformed object or a diff --git a/Documentation/git-receive-pack.txt b/Documentation/git-receive-pack.txt index e6df234926..2d4b45242c 100644 --- a/Documentation/git-receive-pack.txt +++ b/Documentation/git-receive-pack.txt @@ -72,6 +72,24 @@ the following environment variables: using the same mnemonic as used in `%G?` format of `git log` family of commands (see linkgit:git-log[1]). +`GIT_PUSH_CERT_NONCE`:: + The nonce string the process asked the signer to include + in the push certificate. If this does not match the value + recorded on the "nonce" header in the push certificate, it + may indicate that the certificate is a valid one that is + being replayed from a separate "git push" session. + +`GIT_PUSH_CERT_NONCE_STATUS`:: +`UNSOLICITED`;; + "git push --signed" sent a nonce when we did not ask it to + send one. +`MISSING`;; + "git push --signed" did not send any nonce header. +`BAD`;; + "git push --signed" sent a bogus nonce. +`OK`;; + "git push --signed" sent the nonce we asked it to send. + This hook is called before any refname is updated and before any fast-forward checks are performed. @@ -147,6 +165,7 @@ service: if test -n "${GIT_PUSH_CERT-}" && test ${GIT_PUSH_CERT_STATUS} = G then ( + echo expected nonce is ${GIT_PUSH_NONCE} git cat-file blob ${GIT_PUSH_CERT} ) | mail -s "push certificate from $GIT_PUSH_CERT_SIGNER" push-log@mydomain fi diff --git a/Documentation/technical/pack-protocol.txt b/Documentation/technical/pack-protocol.txt index 7b543dc311..dda120631e 100644 --- a/Documentation/technical/pack-protocol.txt +++ b/Documentation/technical/pack-protocol.txt @@ -485,6 +485,7 @@ references. PKT-LINE("certificate version 0.1" LF) PKT-LINE("pusher" SP ident LF) PKT-LINE("pushee" SP url LF) + PKT-LINE("nonce" SP nonce LF) PKT-LINE(LF) *PKT-LINE(command LF) *PKT-LINE(gpg-signature-lines LF) @@ -533,6 +534,11 @@ Currently, the following header fields are defined: authentication material) the user who ran `git push` intended to push into. +`nonce` nonce:: + The 'nonce' string the receiving repository asked the + pushing user to include in the certificate, to prevent + replay attacks. + The GPG signature lines are a detached signature for the contents recorded in the push certificate before the signature block begins. The detached signature is used to certify that the commands were diff --git a/Documentation/technical/protocol-capabilities.txt b/Documentation/technical/protocol-capabilities.txt index a478cc4135..0c92deebcc 100644 --- a/Documentation/technical/protocol-capabilities.txt +++ b/Documentation/technical/protocol-capabilities.txt @@ -251,10 +251,11 @@ If the upload-pack server advertises this capability, fetch-pack may send "want" lines with SHA-1s that exist at the server but are not advertised by upload-pack. -push-cert ---------- +push-cert=<nonce> +----------------- The receive-pack server that advertises this capability is willing -to accept a signed push certificate. A send-pack client MUST NOT +to accept a signed push certificate, and asks the <nonce> to be +included in the push certificate. A send-pack client MUST NOT send a push-cert packet unless the receive-pack server advertises this capability. diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c index 431af39335..91d1a6f59d 100644 --- a/builtin/receive-pack.c +++ b/builtin/receive-pack.c @@ -48,10 +48,17 @@ static void *head_name_to_free; static int sent_capabilities; static int shallow_update; static const char *alt_shallow_file; -static int accept_push_cert = 1; static struct strbuf push_cert = STRBUF_INIT; static unsigned char push_cert_sha1[20]; static struct signature_check sigcheck; +static const char *push_cert_nonce; +static const char *cert_nonce_seed; + +static const char *NONCE_UNSOLICITED = "UNSOLICITED"; +static const char *NONCE_BAD = "BAD"; +static const char *NONCE_MISSING = "MISSING"; +static const char *NONCE_OK = "OK"; +static const char *nonce_status; static enum deny_action parse_deny_action(const char *var, const char *value) { @@ -135,10 +142,8 @@ static int receive_pack_config(const char *var, const char *value, void *cb) return 0; } - if (strcmp(var, "receive.acceptpushcert") == 0) { - accept_push_cert = git_config_bool(var, value); - return 0; - } + if (strcmp(var, "receive.certnonceseed") == 0) + return git_config_string(&cert_nonce_seed, var, value); return git_default_config(var, value, cb); } @@ -157,8 +162,8 @@ static void show_ref(const char *path, const unsigned char *sha1) "report-status delete-refs side-band-64k quiet"); if (prefer_ofs_delta) strbuf_addstr(&cap, " ofs-delta"); - if (accept_push_cert) - strbuf_addstr(&cap, " push-cert"); + if (push_cert_nonce) + strbuf_addf(&cap, " push-cert=%s", push_cert_nonce); strbuf_addf(&cap, " agent=%s", git_user_agent_sanitized()); packet_write(1, "%s %s%c%s\n", sha1_to_hex(sha1), path, 0, cap.buf); @@ -271,6 +276,110 @@ static int copy_to_sideband(int in, int out, void *arg) return 0; } +#define HMAC_BLOCK_SIZE 64 + +static void hmac_sha1(unsigned char out[20], + const char *key_in, size_t key_len, + const char *text, size_t text_len) +{ + unsigned char key[HMAC_BLOCK_SIZE]; + unsigned char k_ipad[HMAC_BLOCK_SIZE]; + unsigned char k_opad[HMAC_BLOCK_SIZE]; + int i; + git_SHA_CTX ctx; + + /* RFC 2104 2. (1) */ + memset(key, '\0', HMAC_BLOCK_SIZE); + if (HMAC_BLOCK_SIZE < key_len) { + git_SHA1_Init(&ctx); + git_SHA1_Update(&ctx, key_in, key_len); + git_SHA1_Final(key, &ctx); + } else { + memcpy(key, key_in, key_len); + } + + /* RFC 2104 2. (2) & (5) */ + for (i = 0; i < sizeof(key); i++) { + k_ipad[i] = key[i] ^ 0x36; + k_opad[i] = key[i] ^ 0x5c; + } + + /* RFC 2104 2. (3) & (4) */ + git_SHA1_Init(&ctx); + git_SHA1_Update(&ctx, k_ipad, sizeof(k_ipad)); + git_SHA1_Update(&ctx, text, text_len); + git_SHA1_Final(out, &ctx); + + /* RFC 2104 2. (6) & (7) */ + git_SHA1_Init(&ctx); + git_SHA1_Update(&ctx, k_opad, sizeof(k_opad)); + git_SHA1_Update(&ctx, out, sizeof(out)); + git_SHA1_Final(out, &ctx); +} + +static char *prepare_push_cert_nonce(const char *path, unsigned long stamp) +{ + struct strbuf buf = STRBUF_INIT; + unsigned char sha1[20]; + + strbuf_addf(&buf, "%s:%lu", path, stamp); + hmac_sha1(sha1, buf.buf, buf.len, cert_nonce_seed, strlen(cert_nonce_seed));; + strbuf_release(&buf); + + /* RFC 2104 5. HMAC-SHA1-80 */ + strbuf_addf(&buf, "%lu-%.*s", stamp, 20, sha1_to_hex(sha1)); + return strbuf_detach(&buf, NULL); +} + +/* + * NEEDSWORK: reuse find_commit_header() from jk/commit-author-parsing + * after dropping "_commit" from its name and possibly moving it out + * of commit.c + */ +static char *find_header(const char *msg, size_t len, const char *key) +{ + int key_len = strlen(key); + const char *line = msg; + + while (line && line < msg + len) { + const char *eol = strchrnul(line, '\n'); + + if ((msg + len <= eol) || line == eol) + return NULL; + if (line + key_len < eol && + !memcmp(line, key, key_len) && line[key_len] == ' ') { + int offset = key_len + 1; + return xmemdupz(line + offset, (eol - line) - offset); + } + line = *eol ? eol + 1 : NULL; + } + return NULL; +} + +static const char *check_nonce(const char *buf, size_t len) +{ + char *nonce = find_header(buf, len, "nonce"); + const char *retval = NONCE_BAD; + + if (!nonce) { + retval = NONCE_MISSING; + goto leave; + } else if (!push_cert_nonce) { + retval = NONCE_UNSOLICITED; + goto leave; + } else if (!strcmp(push_cert_nonce, nonce)) { + retval = NONCE_OK; + goto leave; + } + + /* returned nonce MUST match what we gave out earlier */ + retval = NONCE_BAD; + +leave: + free(nonce); + return retval; +} + static void prepare_push_cert_sha1(struct child_process *proc) { static int already_done; @@ -305,6 +414,7 @@ static void prepare_push_cert_sha1(struct child_process *proc) strbuf_release(&gpg_output); strbuf_release(&gpg_status); + nonce_status = check_nonce(push_cert.buf, bogs); } if (!is_null_sha1(push_cert_sha1)) { argv_array_pushf(&env, "GIT_PUSH_CERT=%s", sha1_to_hex(push_cert_sha1)); @@ -313,7 +423,10 @@ static void prepare_push_cert_sha1(struct child_process *proc) argv_array_pushf(&env, "GIT_PUSH_CERT_KEY=%s", sigcheck.key ? sigcheck.key : ""); argv_array_pushf(&env, "GIT_PUSH_CERT_STATUS=%c", sigcheck.result); - + if (push_cert_nonce) { + argv_array_pushf(&env, "GIT_PUSH_CERT_NONCE=%s", push_cert_nonce); + argv_array_pushf(&env, "GIT_PUSH_CERT_NONCE_STATUS=%s", nonce_status); + } proc->env = env.argv; } } @@ -1296,6 +1409,8 @@ int cmd_receive_pack(int argc, const char **argv, const char *prefix) die("'%s' does not appear to be a git repository", dir); git_config(receive_pack_config, NULL); + if (cert_nonce_seed) + push_cert_nonce = prepare_push_cert_nonce(dir, time(NULL)); if (0 <= transfer_unpack_limit) unpack_limit = transfer_unpack_limit; @@ -1340,5 +1455,6 @@ int cmd_receive_pack(int argc, const char **argv, const char *prefix) packet_flush(1); sha1_array_clear(&shallow); sha1_array_clear(&ref); + free((void *)push_cert_nonce); return 0; } diff --git a/send-pack.c b/send-pack.c index 9c2c64966d..7ad1a5968b 100644 --- a/send-pack.c +++ b/send-pack.c @@ -228,7 +228,8 @@ static const char *next_line(const char *line, size_t len) static int generate_push_cert(struct strbuf *req_buf, const struct ref *remote_refs, struct send_pack_args *args, - const char *cap_string) + const char *cap_string, + const char *push_cert_nonce) { const struct ref *ref; char stamp[60]; @@ -245,6 +246,8 @@ static int generate_push_cert(struct strbuf *req_buf, strbuf_addf(&cert, "pushee %s\n", anon_url); free(anon_url); } + if (push_cert_nonce[0]) + strbuf_addf(&cert, "nonce %s\n", push_cert_nonce); strbuf_addstr(&cert, "\n"); for (ref = remote_refs; ref; ref = ref->next) { @@ -295,6 +298,7 @@ int send_pack(struct send_pack_args *args, unsigned cmds_sent = 0; int ret; struct async demux; + const char *push_cert_nonce = NULL; /* Does the other end support the reporting? */ if (server_supports("report-status")) @@ -311,8 +315,14 @@ int send_pack(struct send_pack_args *args, agent_supported = 1; if (server_supports("no-thin")) args->use_thin_pack = 0; - if (args->push_cert && !server_supports("push-cert")) - die(_("the receiving end does not support --signed push")); + if (args->push_cert) { + int len; + + push_cert_nonce = server_feature_value("push-cert", &len); + if (!push_cert_nonce) + die(_("the receiving end does not support --signed push")); + push_cert_nonce = xmemdupz(push_cert_nonce, len); + } if (!remote_refs) { fprintf(stderr, "No refs in common and none specified; doing nothing.\n" @@ -343,7 +353,7 @@ int send_pack(struct send_pack_args *args, if (!args->dry_run && args->push_cert) cmds_sent = generate_push_cert(&req_buf, remote_refs, args, - cap_buf.buf); + cap_buf.buf, push_cert_nonce); /* * Clear the status for each ref and see if we need to send diff --git a/t/t5534-push-signed.sh b/t/t5534-push-signed.sh index 2f4b74ed83..2786346f9a 100755 --- a/t/t5534-push-signed.sh +++ b/t/t5534-push-signed.sh @@ -50,7 +50,6 @@ test_expect_success 'unsigned push does not send push certificate' ' test_expect_success 'talking with a receiver without push certificate support' ' prepare_dst && mkdir -p dst/.git/hooks && - git -C dst config receive.acceptpushcert no && write_script dst/.git/hooks/post-receive <<-\EOF && # discard the update list cat >/dev/null @@ -68,7 +67,6 @@ test_expect_success 'talking with a receiver without push certificate support' ' test_expect_success 'push --signed fails with a receiver without push certificate support' ' prepare_dst && mkdir -p dst/.git/hooks && - git -C dst config receive.acceptpushcert no && test_must_fail git push --signed dst noop ff +noff 2>err && test_i18ngrep "the receiving end does not support" err ' @@ -89,6 +87,7 @@ test_expect_success GPG 'no certificate for a signed push with no update' ' test_expect_success GPG 'signed push sends push certificate' ' prepare_dst && mkdir -p dst/.git/hooks && + git -C dst config receive.certnonceseed sekrit && write_script dst/.git/hooks/post-receive <<-\EOF && # discard the update list cat >/dev/null @@ -102,17 +101,24 @@ test_expect_success GPG 'signed push sends push certificate' ' SIGNER=${GIT_PUSH_CERT_SIGNER-nobody} KEY=${GIT_PUSH_CERT_KEY-nokey} STATUS=${GIT_PUSH_CERT_STATUS-nostatus} + NONCE_STATUS=${GIT_PUSH_CERT_NONCE_STATUS-nononcestatus} + NONCE=${GIT_PUSH_CERT_NONCE-nononce} E_O_F EOF - cat >expect <<-\EOF && - SIGNER=C O Mitter <committer@example.com> - KEY=13B6F51ECDDE430D - STATUS=G - EOF - git push --signed dst noop ff +noff && + + ( + cat <<-\EOF && + SIGNER=C O Mitter <committer@example.com> + KEY=13B6F51ECDDE430D + STATUS=G + NONCE_STATUS=OK + EOF + sed -n -e "s/^nonce /NONCE=/p" -e "/^$/q" dst/push-cert + ) >expect && + grep "$(git rev-parse noop ff) refs/heads/ff" dst/push-cert && grep "$(git rev-parse noop noff) refs/heads/noff" dst/push-cert && test_cmp expect dst/push-cert-status |