Merge pull request #5991 from gilles-peskine-arm/asn1write-0-fix-2.28

Backport 2.28: Improve ASN.1 write tests
Mbed-TLS · Jun 30, 2022 · 0ae1c1c · 0ae1c1c
2 parents eee5c8a + d97de55
commit 0ae1c1c
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Showing 4 changed files with 183 additions and 23 deletions.
diff --git a/ChangeLog.d/asn1write-0-fix b/ChangeLog.d/asn1write-0-fix
@@ -0,0 +1,2 @@
+Bugfix
+   * Fix mbedtls_asn1_write_mpi() writing an incorrect encoding of 0.
diff --git a/library/asn1write.c b/library/asn1write.c
@@ -133,6 +133,11 @@ int mbedtls_asn1_write_mpi( unsigned char **p, unsigned char *start, const mbedt
     //
     len = mbedtls_mpi_size( X );
 
+    /* DER represents 0 with a sign bit (0=nonnegative) and 7 value bits, not
+     * as 0 digits. We need to end up with 020100, not with 0200. */
+    if( len == 0 )
+        len = 1;
+
     if( *p < start || (size_t)( *p - start ) < len )
         return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
 

diff --git a/tests/suites/test_suite_asn1write.data b/tests/suites/test_suite_asn1write.data
@@ -91,38 +91,47 @@ mbedtls_asn1_write_enum:0x12345678:"0A0412345678"
 ASN.1 Write enum 2147483647
 mbedtls_asn1_write_enum:0x7fffffff:"0A047fffffff"
 
-#ASN.1 Write mpi 0
-#mbedtls_asn1_write_mpi:"00":"020100"
+ASN.1 Write mpi 0 (null)
+mbedtls_asn1_write_mpi:"":"020100"
+
+ASN.1 Write mpi 0 (1 limb)
+mbedtls_asn1_write_mpi:"00":"020100"
 
 ASN.1 Write mpi 1
 mbedtls_asn1_write_mpi:"01":"020101"
 
 ASN.1 Write mpi 0x7f
 mbedtls_asn1_write_mpi:"7f":"02017f"
 
-#ASN.1 Write mpi 0x80
-#mbedtls_asn1_write_mpi:"7f":"02020080"
+ASN.1 Write mpi 0x7f with leading 0 limb
+mbedtls_asn1_write_mpi:"00000000000000007f":"02017f"
+
+ASN.1 Write mpi 0x80
+mbedtls_asn1_write_mpi:"80":"02020080"
 
-#ASN.1 Write mpi 0xff
-#mbedtls_asn1_write_mpi:"7f":"020200ff"
+ASN.1 Write mpi 0x80 with leading 0 limb
+mbedtls_asn1_write_mpi:"000000000000000080":"02020080"
+
+ASN.1 Write mpi 0xff
+mbedtls_asn1_write_mpi:"ff":"020200ff"
 
 ASN.1 Write mpi 0x100
 mbedtls_asn1_write_mpi:"0100":"02020100"
 
 ASN.1 Write mpi, 127*8-1 bits
 mbedtls_asn1_write_mpi:"7f7b16e05c1537de7c41cef1a0985d6a3ced98aec28e091874cbad6b5e40a5c956258f18861c28bed8ba808259339ee34b2e509c4080149474d5d5b86093f90c475a6443fc87e1a293d4151be625d652f1c32a00a018bba10c8a2ae5b2b0ee4be64e053dce9d07ec7919526c9dfcf2ec9fc3db485caa8e5a68a2cd0a427de8":"027f7f7b16e05c1537de7c41cef1a0985d6a3ced98aec28e091874cbad6b5e40a5c956258f18861c28bed8ba808259339ee34b2e509c4080149474d5d5b86093f90c475a6443fc87e1a293d4151be625d652f1c32a00a018bba10c8a2ae5b2b0ee4be64e053dce9d07ec7919526c9dfcf2ec9fc3db485caa8e5a68a2cd0a427de8"
 
-#ASN.1 Write mpi, 127*8 bits
-#mbedtls_asn1_write_mpi:"e77b16e05c1537de7c41cef1a0985d6a3ced98aec28e091874cbad6b5e40a5c956258f18861c28bed8ba808259339ee34b2e509c4080149474d5d5b86093f90c475a6443fc87e1a293d4151be625d652f1c32a00a018bba10c8a2ae5b2b0ee4be64e053dce9d07ec7919526c9dfcf2ec9fc3db485caa8e5a68a2cd0a427de8":"028180e77b16e05c1537de7c41cef1a0985d6a3ced98aec28e091874cbad6b5e40a5c956258f18861c28bed8ba808259339ee34b2e509c4080149474d5d5b86093f90c475a6443fc87e1a293d4151be625d652f1c32a00a018bba10c8a2ae5b2b0ee4be64e053dce9d07ec7919526c9dfcf2ec9fc3db485caa8e5a68a2cd0a427de8"
+ASN.1 Write mpi, 127*8 bits
+mbedtls_asn1_write_mpi:"e77b16e05c1537de7c41cef1a0985d6a3ced98aec28e091874cbad6b5e40a5c956258f18861c28bed8ba808259339ee34b2e509c4080149474d5d5b86093f90c475a6443fc87e1a293d4151be625d652f1c32a00a018bba10c8a2ae5b2b0ee4be64e053dce9d07ec7919526c9dfcf2ec9fc3db485caa8e5a68a2cd0a427de8":"02818000e77b16e05c1537de7c41cef1a0985d6a3ced98aec28e091874cbad6b5e40a5c956258f18861c28bed8ba808259339ee34b2e509c4080149474d5d5b86093f90c475a6443fc87e1a293d4151be625d652f1c32a00a018bba10c8a2ae5b2b0ee4be64e053dce9d07ec7919526c9dfcf2ec9fc3db485caa8e5a68a2cd0a427de8"
 
 ASN.1 Write mpi, 127*8+1 bits
-mbedtls_asn1_write_mpi:"108446d68934cc1af23c4cd909884d4bd737a1890e12f5ef8bf3d807d72feffa63c0bf2633345f8b8418d144617c871a7a0277ac0150eed4b3db7f9dff21114cd0d7f282400f03c931cb00c367550e374a1ed3762a1801ca714cfc8d5aac69707ca81e0661400ed0014d97cba48f94d835dd681fc3053c51958afbf7583cf49c":"028180108446d68934cc1af23c4cd909884d4bd737a1890e12f5ef8bf3d807d72feffa63c0bf2633345f8b8418d144617c871a7a0277ac0150eed4b3db7f9dff21114cd0d7f282400f03c931cb00c367550e374a1ed3762a1801ca714cfc8d5aac69707ca81e0661400ed0014d97cba48f94d835dd681fc3053c51958afbf7583cf49c"
+mbedtls_asn1_write_mpi:"018446d68934cc1af23c4cd909884d4bd737a1890e12f5ef8bf3d807d72feffa63c0bf2633345f8b8418d144617c871a7a0277ac0150eed4b3db7f9dff21114cd0d7f282400f03c931cb00c367550e374a1ed3762a1801ca714cfc8d5aac69707ca81e0661400ed0014d97cba48f94d835dd681fc3053c51958afbf7583cf49c":"028180018446d68934cc1af23c4cd909884d4bd737a1890e12f5ef8bf3d807d72feffa63c0bf2633345f8b8418d144617c871a7a0277ac0150eed4b3db7f9dff21114cd0d7f282400f03c931cb00c367550e374a1ed3762a1801ca714cfc8d5aac69707ca81e0661400ed0014d97cba48f94d835dd681fc3053c51958afbf7583cf49c"
 
 ASN.1 Write mpi, 255*8-1 bits
 mbedtls_asn1_write_mpi:"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":"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"
 
-#ASN.1 Write mpi, 255*8 bits
-#mbedtls_asn1_write_mpi:"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":"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"
+ASN.1 Write mpi, 255*8 bits
+mbedtls_asn1_write_mpi:"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":"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"
 
 ASN.1 Write mpi, 256*8-1 bits
 mbedtls_asn1_write_mpi:"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":"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"
@@ -191,7 +200,7 @@ ASN.1 Write OID: length=1
 mbedtls_asn1_write_string:MBEDTLS_ASN1_OID:"41":"060141"
 
 ASN.1 Write AlgorithmIdentifier, null parameters
-mbedtls_asn1_write_algorithm_identifier:"4f4944":8:"300d06034f4944"
+mbedtls_asn1_write_algorithm_identifier:"4f4944":0:"300706034f49440500"
 
 ASN.1 Write AlgorithmIdentifier, parameters (8 bytes)
 mbedtls_asn1_write_algorithm_identifier:"4f4944":8:"300d06034f4944"