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1 | /* |
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2 | * Generic SSH public-key handling operations. In particular, |
3 | * reading of SSH public-key files, and also the generic `sign' |
4 | * operation for ssh2 (which checks the type of the key and |
5 | * dispatches to the appropriate key-type specific function). |
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6 | */ |
7 | |
8 | #include <stdio.h> |
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9 | #include <stdlib.h> |
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10 | |
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11 | #include "ssh.h" |
12 | |
13 | #define GET_32BIT(cp) \ |
14 | (((unsigned long)(unsigned char)(cp)[0] << 24) | \ |
15 | ((unsigned long)(unsigned char)(cp)[1] << 16) | \ |
16 | ((unsigned long)(unsigned char)(cp)[2] << 8) | \ |
17 | ((unsigned long)(unsigned char)(cp)[3])) |
18 | |
19 | #define rsa_signature "SSH PRIVATE KEY FILE FORMAT 1.1\n" |
20 | |
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21 | #define BASE64_TOINT(x) ( (x)-'A'<26 ? (x)-'A'+0 :\ |
22 | (x)-'a'<26 ? (x)-'a'+26 :\ |
23 | (x)-'0'<10 ? (x)-'0'+52 :\ |
24 | (x)=='+' ? 62 : \ |
25 | (x)=='/' ? 63 : 0 ) |
26 | |
27 | static int loadrsakey_main(FILE *fp, struct RSAKey *key, |
28 | char **commentptr, char *passphrase) { |
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29 | unsigned char buf[16384]; |
30 | unsigned char keybuf[16]; |
31 | int len; |
32 | int i, j, ciphertype; |
33 | int ret = 0; |
34 | struct MD5Context md5c; |
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35 | char *comment; |
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36 | |
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37 | /* Slurp the whole file (minus the header) into a buffer. */ |
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38 | len = fread(buf, 1, sizeof(buf), fp); |
39 | fclose(fp); |
40 | if (len < 0 || len == sizeof(buf)) |
41 | goto end; /* file too big or not read */ |
42 | |
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43 | i = 0; |
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44 | |
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45 | /* |
46 | * A zero byte. (The signature includes a terminating NUL.) |
47 | */ |
48 | if (len-i < 1 || buf[i] != 0) |
49 | goto end; |
50 | i++; |
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51 | |
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52 | /* One byte giving encryption type, and one reserved uint32. */ |
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53 | if (len-i < 1) |
54 | goto end; |
55 | ciphertype = buf[i]; |
56 | if (ciphertype != 0 && ciphertype != SSH_CIPHER_3DES) |
57 | goto end; |
58 | i++; |
59 | if (len-i < 4) |
60 | goto end; /* reserved field not present */ |
61 | if (buf[i] != 0 || buf[i+1] != 0 || buf[i+2] != 0 || buf[i+3] != 0) |
62 | goto end; /* reserved field nonzero, panic! */ |
63 | i += 4; |
64 | |
65 | /* Now the serious stuff. An ordinary SSH 1 public key. */ |
66 | i += makekey(buf+i, key, NULL, 1); |
67 | if (len-i < 0) |
68 | goto end; /* overran */ |
69 | |
70 | /* Next, the comment field. */ |
71 | j = GET_32BIT(buf+i); |
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72 | i += 4; |
73 | if (len-i < j) goto end; |
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74 | comment = malloc(j+1); |
75 | if (comment) { |
76 | memcpy(comment, buf+i, j); |
77 | comment[j] = '\0'; |
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78 | } |
79 | i += j; |
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80 | if (commentptr) |
81 | *commentptr = comment; |
82 | if (key) |
83 | key->comment = comment; |
84 | if (!key) { |
85 | return ciphertype != 0; |
86 | } |
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87 | |
88 | /* |
89 | * Decrypt remainder of buffer. |
90 | */ |
91 | if (ciphertype) { |
92 | MD5Init(&md5c); |
93 | MD5Update(&md5c, passphrase, strlen(passphrase)); |
94 | MD5Final(keybuf, &md5c); |
95 | des3_decrypt_pubkey(keybuf, buf+i, (len-i+7)&~7); |
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96 | memset(keybuf, 0, sizeof(keybuf)); /* burn the evidence */ |
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97 | } |
98 | |
99 | /* |
100 | * We are now in the secret part of the key. The first four |
101 | * bytes should be of the form a, b, a, b. |
102 | */ |
103 | if (len-i < 4) goto end; |
104 | if (buf[i] != buf[i+2] || buf[i+1] != buf[i+3]) { ret = -1; goto end; } |
105 | i += 4; |
106 | |
107 | /* |
108 | * After that, we have one further bignum which is our |
109 | * decryption modulus, and then we're done. |
110 | */ |
111 | i += makeprivate(buf+i, key); |
112 | if (len-i < 0) goto end; |
113 | |
114 | ret = 1; |
115 | end: |
116 | memset(buf, 0, sizeof(buf)); /* burn the evidence */ |
117 | return ret; |
118 | } |
119 | |
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120 | int loadrsakey(char *filename, struct RSAKey *key, char *passphrase) { |
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121 | FILE *fp; |
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122 | unsigned char buf[64]; |
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123 | |
124 | fp = fopen(filename, "rb"); |
125 | if (!fp) |
126 | return 0; /* doesn't even exist */ |
127 | |
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128 | /* |
129 | * Read the first line of the file and see if it's a v1 private |
130 | * key file. |
131 | */ |
132 | if (fgets(buf, sizeof(buf), fp) && |
133 | !strcmp(buf, rsa_signature)) { |
134 | return loadrsakey_main(fp, key, NULL, passphrase); |
135 | } |
136 | |
137 | /* |
138 | * Otherwise, we have nothing. Return empty-handed. |
139 | */ |
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140 | fclose(fp); |
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141 | return 0; |
142 | } |
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143 | |
144 | /* |
145 | * See whether an RSA key is encrypted. Return its comment field as |
146 | * well. |
147 | */ |
148 | int rsakey_encrypted(char *filename, char **comment) { |
149 | FILE *fp; |
150 | unsigned char buf[64]; |
151 | |
152 | fp = fopen(filename, "rb"); |
153 | if (!fp) |
154 | return 0; /* doesn't even exist */ |
155 | |
156 | /* |
157 | * Read the first line of the file and see if it's a v1 private |
158 | * key file. |
159 | */ |
160 | if (fgets(buf, sizeof(buf), fp) && |
161 | !strcmp(buf, rsa_signature)) { |
162 | return loadrsakey_main(fp, NULL, comment, NULL); |
163 | } |
164 | return 0; /* wasn't the right kind of file */ |
165 | } |